Plane iron clearance angle study

[Normand Leblanc]

Hello,
About a month ago we had a discussion on clearance angle and I said that a study was coming. So here it is.

The following graph would be a nice resumé

339640
This graph is saying that a 17° clearance angle (CA) is the best and that the number of shavings is reduced linearly if the CA is reduced.
The full study can be found http://oldchips.blogspot.ca/2016/06/study-plane-iron-clearance-angle.html

I am quite sure that some people will want to argue the results because they are not sharpening at the right angle for years, just like me. Now that I know what's the proper angle, I'm going to have to adapt my sharpening method. I don't have to but it's not difficult to adjust my free hand technique.

[Mark Gibney]

Interesting study - and a lot of work. But thanks, I think this will be very useful.

Interested to read what those with more hand tool experience than me think.

[Howard Pollack]

Pardon my ignorance, but does the phrase "clearance angle" refer to? Thanks.
-Howard

[Jim Koepke]

Interested to read what those with more hand tool experience than me think.

I think it is great someone took the time to do such a test.


Pardon my ignorance, but does the phrase "clearance angle" refer to? Thanks.
-Howard

It is the angle formed between the side of the blade contacting the work at its point of contact to the work piece. As an example with a Stanley bevel down bench plane the blade is bedded at 45º. A bevel at 25º would leave a clearance of 20º.

jtk

[Steve Voigt]

Normand, I think it's a great study, and I salute you for doing it. Just one comment.

You have two variables: the sharpening angle and the clearance angle. The latter is dependent on the former. You assume that what matters most is the clearance angle, but I think that's an untested assumption, unless I've missed something in your data.

Let me give you two examples. In your tests, you find that a sharpening angle of 28° (which results in 17° clearance) is best. Suppose we change the bed angle to 50°. Do you think that a sharpening angle of 33°, which would still result in a 17° clearance angle, would be best? I don't know, but I suspect it would not. I suspect that a sharpening angle of around 28° would still be best, so your optimum clearance angle would be around 22°. In your test, a clearance angle of 20° is worse than 17°, but I strongly suspect that's because at CA = 20°, the fragility of the bevel (which is sharpened at 25°) overwhelms the increased clearance.

Second example: suppose we lower the bed to 38°, the lowest angle that's commonly used in BD planes. Would a clearance angle of 17°, resulting in a sharpening angle of 21°, still be optimum? I'm pretty sure it wouldn't, that the iron would fold almost immediately at 21°. I suspect that the optimum clearance angle would be higher, maybe around 10°, which would give a sharpening angle of (again) around 28°.

In other words, I suspect (but cannot prove!) that a sharpening angle of around 28° is going be optimum for a wide band of bed angles centered around 45°, and so the optimum clearance angle will vary with bed angle.

Don't get me wrong, I thing your study is really useful and important. After all, 45° is by far the most common bed angle for BD planes, so your results have important practical implications for the majority of BD users. The bottom line, that a sharpening angle of around 28° results in the most durable edge for a 45° bed in most situations, is clear. But whether that's due to the sharpening angle or the clearance angle, I think the jury's still out on that one.

Thanks again for doing this!

[Pat Barry]

I would like to understand your sharpening process and the resulting geometry a bit better if you don't mind. You described your sharpening process as :
"Sharpening:
- Grind the blade at a 22° angle.
- Primary bevel on rough stone at 23°.
- First micro-bevel at 24° on a fine India stone.
- Second micro-bevel à 25° on translucent Arkansas.
- Repeat the process for 28, 31, 34 and 37° (clearance angle of 20, 17, 14, 11 and 8).
- All sharpening were done with a back-bevel of 1°"

I'm having trouble understanding the resulting shape of all these micro-bevels.

Could you describe how wide these various micro-bevels are? If you don't mind providing a quick sketch of what you think the resulting combination bevel looks like it would be great. Is the final micro-bevel (25°) the one that you use to determine the clearance angle (therefore 20° in this example)?

[Derek Cohen]

If someone is to have a CA of 17°, as this study suggest, then a primary bevel of 25° would be recommended. This 25° with one or two micro-bevel will achieve around 28° at the cutting edge leaving a CA of 17°. It is believed that LeeValley should have their blade ground at 25° instead of 30°.

Hi Normand

I, too, applaud the creative thought that went into your study. Woodworking knowledge benefits from efforts such as yours. However, I echo Steve's comments, and would have made the same points.

The problem with specifying an optimum bevel angle for a plane, as noted in the quote from your web page, is that it ignores the properties of the steels involved. For example, most steels do not have the longevity at 25 degrees that they would have at 30 degrees. This is a factor known for many years, and one I have demonstrated in my own research. It applies to O1, A2 and PM-V11 steels alike. Indeed, David Charlesworth will argue that 35 degrees is the optimum angle for O1, based upon his years of experience.

So, while a smaller clearance angle may well reduce edge longevity, as demonstrated in your study, we usually can increase longevity again by other means (such as a higher bevel, harder or more abrasion-resistant steel, etc). As in many things, guidelines are really compromises to deal with the range of variables usually involved in a given situation. While an ideal situation may exist, it may not be practical for all purposes.

Regards from Perth

Derek

[Normand Leblanc]

Hi Steve,
There is only one variable here. I sharpen at an angle (25, 28, 31, 34, 37) which mathematically give the clearance angle (20, 17, 14, 11, 8).

As for a different bed angles, I don't know more than you or anyone else. It has to be tested. That being said and looking at the graph in the first post, a 25° sharpening angle is better than 31°. This bring me to believe that, if we were to test a bed of 38° then a 25° sharpening angle would be best. For a bed at 50° I would sharpen at around 30°.

Pat,
The width of those micro-bevels are not important. What's important is the last micro-bevel angle so, yes, a final micro-bevel of 25° will give a CA of 20°.

Derek,
I've tested many different types of steels and they all behave the same way. I think that this is the greatest find of the study. Even the hardest steel PM-V11 is much better at a sharpening angle of 28° compared to 35° just like all the other steel.

I have also look at your website and didn't find anything for you to say "I have demonstrated in my own research". I've found plenty of end grain study which is not the same as planing with the grain. Maybe I missed something so could you please give me a link to any study pointing toward sharpening angles of 30 or 35 degrees.

Normand

[Derek Cohen]

Derek,
I've tested many different types of steels and they all behave the same way. I think that this is the greatest find of the study. Even the hardest steel PM-V11 is much better at a sharpening angle of 28° compared to 35° just like all the other steel.

I have also look at your website and didn't find anything for you to say "I have demonstrated in my own research". I've found plenty of end grain study which is not the same as planing with the grain. Maybe I missed something so could you please give me a link to any study pointing toward sharpening angles of 30 or 35 degrees.

Hi Normand

The studies I did involved endgrain. The planes were shooting planes. One had a clearance angle of 12 degrees. The other had a clearance angle of 33 degrees. Both planes used A2 steel. The plane with the 12 degree demonstrated a significantly greater edge longevity than the plane with a 33 degree clearance angle, even when there was a higher bevel angle in the latter (30 degrees vs 25 degrees):

http://www.inthewoodshop.com/ToolReviews/LVShootingPlane.html

Issues of clearance angle on edge longevity should not be differentiated by the direction of the grain, only that the conditions are held constant.

In a follow up assessment, where only the BD plane with the 33 degree clearance angle was used, it was demonstrated that PM-V11 steel had a significantly greater edge longevity at 30 degrees than at 25 degrees:

http://www.inthewoodshop.com/ToolReviews/MoreAboutShootingPlanesandTheirBlades.html

Regards from Perth

Derek

[Normand Leblanc]

Hi Derek,
I have to disagree with you. Shooting end grain is, IMHO, a completely different ball game for a few reasons:

1. End grain involve a lot of impacts which are basically not present in planing with the grain.
2. Kato and Kawaii have shown that planing against the grain (not end grain) does not wear the blade on the bevel side. This is an indication that grain direction have to be accounted for.
3. End grain is hardly compressible. When planing such grain I think that a small clearance angle should be better because there is no or very little wood springback (this is why we need a clearance angle) and, a large sharpening angle, as you have demonstrated, reinforce the edge.

Normand

[Graham Haydon]

Hi Normad

Good work. Something else to add, did you work with fine shavings and light cuts or did you also take deep cuts too? My gut says in deeper cuts the edge could perform less well as the support is not as great.
Also did any of the work have hard dead knots often found in pine? The hardness of those knots and the speed that there are hit (often quick as the pine is so easy to work until you hit one) would make edges with a lot of clearance more likely to fail. Also, as mentioned about end grain a touch less clearance would be better as the work is more abrupt.
I think it's likely why the typical angle of 30 degrees is so popular as it hit the mark as a great all round edge for a wide variety of tasks rather than having lots of plane irons or planes set with different clearance angles.

[Derek Cohen]

Hi Derek,
I have to disagree with you. Shooting end grain is, IMHO, a completely different ball game for a few reasons:

1. End grain involve a lot of impacts which are basically not present in planing with the grain.
2. Kato and Kawaii have shown that planing against the grain (not end grain) does not wear the blade on the bevel side. This is an indication that grain direction have to be accounted for.
3. End grain is hardly compressible. When planing such grain I think that a small clearance angle should be better because there is no or very little wood springback (this is why we need a clearance angle) and, a large sharpening angle, as you have demonstrated, reinforce the edge.

Normand

Normand, the main difference between end grain and face grain planing is that there will be less springback with end grain (this is the end result of the lower compressibility of end grain). Is this relevant? I could go off on a huge tangent about wear bevels, etc and their impact on edge longevity. What is relevant was that the planing conditions were held constant for the two bevel angles (25- and 30 degrees on the 45-degree bevel down LN #51). The differences in edge longevity are therefore a result of the bevel angle differences. That was my point - to illustrate that bevel angle is one factor and clearance angle is another.

The relevance is that clearance angle and the bevel angle involve a compromise - a trade off - to obtain edge longevity.

I look forward to seeing further tests by you at different bed angles.

Regards from Perth

Derek

[Normand Leblanc]

Hi Graham,
All the shavings were 0.002" thick but it's possible that very heavy cuts would require a higher sharpening angle...
No knots at all in the wood used for this study. A knot is very hard and would require a high sharpening angle again. I seldom use wood with knots.
You're most likely right that 30° is a very good angle.

Have a good day,
Normand

[Brian Holcombe]

Normand, I think this is a great study. I apologize for being minorly critical but I think it is best described as a study of combination best clearance angle and blade angle with a given bed angle. I think it is possibly more useful in that context since that is the context we're all working in.

I don't believe it possible to decouple all of the components, only two of three at a time.

Your efforts are a wonderful contribution and thank you for taking the time and making the effort.

[Luke Dupont]

Hi Normad

Good work. Something else to add, did you work with fine shavings and light cuts or did you also take deep cuts too? My gut says in deeper cuts the edge could perform less well as the support is not as great.
Also did any of the work have hard dead knots often found in pine? The hardness of those knots and the speed that there are hit (often quick as the pine is so easy to work until you hit one) would make edges with a lot of clearance more likely to fail. Also, as mentioned about end grain a touch less clearance would be better as the work is more abrupt.
I think it's likely why the typical angle of 30 degrees is so popular as it hit the mark as a great all round edge for a wide variety of tasks rather than having lots of plane irons or planes set with different clearance angles.

Good point on knots. I usually sharpen 25ish degrees (Freehand, and a little convex, so the precise angle is hard to say, but if I put my plane iron or chisel bevel down to a flat piece of wood, it'll usually start to take shavings around 28 degrees). A week ago, however, I was planing some SYP from hell, which had the hardest knots I've ever encountered. Twice I sharpened, and twice chewed up my edge every time I hit a knot. I had to resharpen at 35 degrees just to get through that board.

As with most things, I suspect there's no "best" angle, and it probably depends quite a bit on the kind of wood you're working, bed angle, etc. etc.

Still, great work on collecting the data, though, and it probably offers a good starting point. I personally like to sharpen with a good bit of clearance, as I have actually had problems with too little clearance before. It would be interesting to see other factors tested, though gathering the data could be an endless quantity of work, ultimately.

[Nicholas Lawrence]

Well, the "body mechanics" topic was dying down. This ought to keep things lively for a while. . .

In all seriousness though, I found it very interesting for a number of reasons, and want to thank you for the time and effort, and for sharing your findings with us.

[Stewie Simpson]

Hi Derek,
I have to disagree with you. Shooting end grain is, IMHO, a completely different ball game for a few reasons:

1. End grain involve a lot of impacts which are basically not present in planing with the grain.
2. Kato and Kawaii have shown that planing against the grain (not end grain) does not wear the blade on the bevel side. This is an indication that grain direction have to be accounted for.
3. End grain is hardly compressible. When planing such grain I think that a small clearance angle should be better because there is no or very little wood springback (this is why we need a clearance angle) and, a large sharpening angle, as you have demonstrated, reinforce the edge.

Normand

I am in agreement with Normand; you cant compare the results of working end grain to long grain; the wood fibres are totally different; planning of end grain works best with a low angle approach.

Referring to David Charlesworth's recommendation for a 35* honing bevel on a 45* bed with 01 tool steel. That makes little sense to me; why would you run your clearance angle so tight, when precedent records a honing angle of 28 - 30* for 01 tool steel as being the ideal optimum range. From my limited understanding of pm-v11 tool steel, the optimum honing angle is in a similar range to 01 tool steel. A2 tool steel on the other hand, requires a slightly higher optimum honing angle within a range of 30 - 33* to maximise the longevity of the cutting edge. http://www.hocktools.com/tech-info/o1-vs-a2.html

Stewie;

[Derek Cohen]

I am in agreement with Normand; you cant compare the results of working end grain to long grain; the wood fibres are totally different; planning of end grain works best with a low angle approach.

Referring to David Charlesworth's recommendation for a 35* honing bevel on a 45* bed with 01 tool steel. That makes little sense to me; why would you run your clearance angle so tight, when precedent records a honing angle of 28 - 30* for 01 tool steel as being the ideal optimum range. From my limited understanding of pm-v11 tool steel, the optimum honing angle is in a similar range to 01 tool steel. A2 tool steel on the other hand, requires a slightly higher optimum honing angle within a range of 30 - 33* to maximise the longevity of the cutting edge. http://www.hocktools.com/tech-info/o1-vs-a2.html

Stewie;

One last time, since it is evident that comments are being taken out of context ..

It is irrelevant whether the grain is face, edge, side, long, short, curly, or end. What is relevant is that it can be demonstrated that a 30 degree bevel will outlast a 25 degree bevel, and that some experience that a bevel of 35 degrees lasts even longer. If you wish to obsess about the grain direction, and not the bevel angles, then you are missing the point (which I made in two separate posts), that is, that a bevel angle is chosen for reasons other than optimum with regard to clearance.

Hopefully David will comment on his preference for 35 degrees.

Regards from Perth

Derek

[Luke Dupont]

One last time, since it is evident that comments are being taken out of context ..

It is irrelevant whether the grain is face, edge, side, long, short, curly, or end. What is relevant is that it can be demonstrated that a 30 degree bevel will outlast a 25 degree bevel, and that some experience that a bevel of 35 degrees lasts even longer. If you wish to obsess about the grain direction, and not the bevel angles, then you are missing the point (which I made in two separate posts), that is, that a bevel angle is chosen for reasons other than optimum with regard to clearance.

Hopefully David will comment on his preference for 35 degrees.

Regards from Perth

Derek

Is it not conceivable that different materials will wear a blade in different manners? We are not planing some homogeneous block of MDF, and end grain fibers, as well as long grain, both with and against, and other possible orientations, do behave very differently, and are resultingly cut (or split out) differently depending on how the tool is presented to the work. There's also give, flex, and tension in the grain which may account for different wear patterns.

Am I misunderstanding you/not following some relevant context? Or do you have some reasoning as to why this isn't the case?

Edit: Reorganizing this last point, as it's not about grain, but actually bevel geometry:
Is it possible, perhaps, for an edge as it rolls to more likely (/quick) become a problem with less clearance, as it means you will find the blade riding the bevel that much sooner? For a while, I sharpened one of my planes with very little clearance, and I found that it would, rather quickly compared to other irons, start acting as if it were dull. When I reduced the angle that I sharpened it at, it appeared to stay sharp, biting and taking shavings, for about twice as long as previous.

[Derek Cohen]

Edit: Reorganizing this last point, as it's not about grain, but actually bevel geometry:
Is it possible, perhaps, for an edge as it rolls to more likely (/quick) become a problem with less clearance, as it means you will find the blade riding the bevel that much sooner? For a while, I sharpened one of my planes with very little clearance, and I found that it would, rather quickly compared to other irons, start acting as if it were dull. When I reduced the angle that I sharpened it at, it appeared to stay sharp, biting and taking shavings, for about twice as long as previous.

Luke, while the clearance angle does affect the longevity of a blade (as demonstrated by Normand's study), in practice we do not experience rapid failure, as you imply. Some steels will delay the wear longer than others. Very low angles accelerate the wear faster. But all else within a reasonable range work very nicely with a bevel angle chosen to suit the wood.

Regards from Perth

Derek

[Warren Mickley]

Hello,
About a month ago we had a discussion on clearance angle and I said that a study was coming. So here it is.

The following graph would be a nice resumé

339640
This graph is saying that a 17° clearance angle (CA) is the best and that the number of shavings is reduced linearly if the CA is reduced.
The full study can be found http://oldchips.blogspot.ca/2016/06/study-plane-iron-clearance-angle.html

I am quite sure that some people will want to argue the results because they are not sharpening at the right angle for years, just like me. Now that I know what's the proper angle, I'm going to have to adapt my sharpening method. I don't have to but it's not difficult to adjust my free hand technique.

Here are two plane configurations which both cut at 40 degrees. Based on your study, Normand, which would you predict would hold up better,
1) standard block plane, with 20 degree clearance and 20 degree bevel, or
2) low angle bock plane with 12 degree clearance and 28 degree bevel?

[Normand Leblanc]

Hi Stewie,
I wasn't aware that D. Charlesworth was recommanding 35° with O-1 steel. The closest angle tested is 34° and the best results are at 28°. Let's compare the two.




Fir at 34°
Fir at 28°
Cherry at 34°
Cherry at 28°


O-1 blade
63
98
70
138


Hock blade
148
365
120
255



If someone has the choice as for the steel, O-1 would be a bad choice it seems. An A-2 Hock blade at a proper 28° angle should do 6 times as many shaving as an O-1 at 34° using fir and 3-1/2 times using cherry.

[Normand Leblanc]

Hi Warren,

"Here are two plane configurations which both cut at 40 degrees. Based on your study, Normand, which would you predict would hold up better,
1) standard block plane, with 20 degree clearance and 20 degree bevel, or
2) low angle bock plane with 12 degree clearance and 28 degree bevel?"

My study didn't go as low as a 20 degree bevel so I don't really know. My best guess would be that the 2nd configuration would be best because the edge is much stronger even if the clearance angle is lower. This would be especially true for harder woods. It's only a guess.

Have a good day,
Normand

[Stewie Simpson]

Hi Normand; I am a bit old school so I will stick to what I know best, and that's 01 tool steel. For a 45* bd plane iron; I start with a grinding angle of 25*, and end with a honing angle that comes close to 28/30*. I don't use a honing guide; the results you posted on 01 steel at 28* reaffirms my own understanding.

Appreciate the work you are doing.

regards Stewie;

[Normand Leblanc]

I can see that there is a need for more information.

What this study show is a flat is being formed on the bevel facing the workpiece. This flat increase in size with the length planed. This is the result of the fibers springback. With end grain there no such thing as springback (or very little) so planing with the grain can not be compared to planing end grain.

This flat is a fact that has been studied before by Kato and Kawaii and William Tindall, Steve Elliott and Frederick Horne. Also, Kees van der Heiden has shown here http://planetuning.infillplane.com/html/mechanics_of_chipbreakers.html that the vertical force required keep rising linearly with distance planed implying a larger and larger flat.

Hope it's clear.

Normand

[Derek Cohen]

Normand and Stewie

I think that it is difficult to come up with a fixed rule to cover a complex area. For illustration, compare the result that Steve Elliott obtained here:

http://bladetest.infillplane.com/html/bevel_angles.html

Steve concluded that, with a bed angle of 47 1/2 degrees, the worst and best results could be summarised as following:

To determine how large a bevel angle was needed to prevent edge failure, I began my testing using angles as low as 25º. All of the blades showed serious chipping or deformation after even moderate use on soft woods. I increased the bevel angle until problems were minimal for most of the blades, which was at 34º.

Edit to add:

A decision is made to ignore the clearance angle to obtain the best planed surface - rather than better edge holding results. For example, Japanese planes commonly have a bed angle of 40 degrees, yet use a bevel angle of 30 degrees (i.e. 10 degrees of clearance). The smoother I mostly use is a Veritas Custom #4 with a 42 degree frog. The bevel angle is again 30 degrees (12 degrees of clearance). According to Steve's research we should use a 34 degree bevel, but of course this would reduce the clearance angle to a negligible amount (8 degrees), and the plane might not work. A 30 degrees bevel is the compromise. The edge will hold up pretty well, perhaps not as well as 34 degrees, but I'd rather be planing at 42 degrees than at 47 1/2 degrees. The resulting surface will be a little clearer.


Regards from Perth

Derek

[Pat Barry]

What this study show is a flat is being formed on the bevel facing the workpiece. This flat increase in size with the length planed. This is the result of the fibers springback.
I haven't studied your work of course Normand, but I seriously doubt that your statement about the development of the flat being a function of fiber springback is true. I would predict that what is happening as the planing takes place is the the very edge is being blunted and that the edge becomes worn down. The resultof this would be evident both on the face of the blade adn the bottom side as wear. Thus the edge becomes dull and the wear develops accordingly. The result is a dull edge and the inevitable increase in bottom side wear that inhibits penetration of the dge of the tool and engagement into the work. I am sure I have seen images that demonstrate this in SEM or other high magnification views.

[Patrick Chase]

I know this has been beaten into the ground, but once again: I think you need to make it more clear that your test assumes a completely nonrepresentative mode of use (pushing from the back of the sole, with no downforce).

Real planes are pushed from their totes and knobs, and there is ALWAYS some downforce. The optimum for that configuration will inevitably and necessarily be different, and will favor higher edge angles and lower clearance angles.

In other words, this is a nice science fair experiment that isn't relevant to how planes are used in the real world. I'll keep it in mind if I ever decide to plane by pushing exclusively from the heel of the sole, though.

[Patrick Chase]

Derek,
I've tested many different types of steels and they all behave the same way. I think that this is the greatest find of the study. Even the hardest steel PM-V11 is much better at a sharpening angle of 28° compared to 35° just like all the other steel.

This is a HUGE red flag w.r.t. your results. Wear bevel formation is principally an abrasion-driven process, whereas other edge failure modes have different mechanisms. Your statement here is equivalent to claiming that the ideal angle is independent of the steel's balance of abrasion resistance vs {toughness, hardness, etc}. The real world doesn't work that way.

[Patrick Chase]

It is irrelevant whether the grain is face, edge, side, long, short, curly, or end. What is relevant is that it can be demonstrated that a 30 degree bevel will outlast a 25 degree bevel, and that some experience that a bevel of 35 degrees lasts even longer. If you wish to obsess about the grain direction, and not the bevel angles, then you are missing the point (which I made in two separate posts), that is, that a bevel angle is chosen for reasons other than optimum with regard to clearance.

My experience is similar to yours. I think this divergence comes down to the "zero downforce" thing. I could easily see real-world plane use (with tote and knob) adding 7 degrees to the optimum.

[Patrick Chase]

Here are two plane configurations which both cut at 40 degrees. Based on your study, Normand, which would you predict would hold up better,
1) standard block plane, with 20 degree clearance and 20 degree bevel, or
2) low angle bock plane with 12 degree clearance and 28 degree bevel?

Pushing from the sole, or using it in the normal way? :-)

The results will be quite different, as I'm pretty sure you already know or else you wouldn't have posed the question.

Also you usually don't take 2-mil cuts with a block plane, so that will probably also shift the optimum...

[Jim Koepke]

I know this has been beaten into the ground, but once again: I think you need to make it more clear that your test assumes a completely nonrepresentative mode of use (pushing from the back of the sole, with no downforce).

Real planes are pushed from their totes and knobs, and there is ALWAYS some downforce. The optimum for that configuration will inevitably and necessarily be different, and will favor higher edge angles and lower clearance angles.

In other words, this is a nice science fair experiment that isn't relevant to how planes are used in the real world. I'll keep it in mind if I ever decide to plane by pushing exclusively from the heel of the sole, though.

And while you are at it, rig up some method of measuring the exact amount of downforce being applied.

You will need to include a lot more charts and graphs to include every possible kind of wood and grain combination, every possible bedding angle, different amounts of down force and every metal that was ever used to make a plane blade.

After all is said and done, some folks are just not able to see this as a guide or survey of blade wear in a common 45º bedded plane on wood without knots.

So instead of keeping something a simple guide, let us stir the pot and come up with something that would likely be even more confusing.

In the end, it will likely do nothing to convince me to change what has worked best for my needs over the years.

jtk

[Matthew Springer]

I volunteer to be the control group and keep sharpening at whatever random angle I end up setting the jig to at the time. That at least will give us a nice floor for bad results.

[Jim Koepke]

I volunteer to be the control group and keep sharpening at whatever random angle I end up setting the jig to at the time. That at least will give us a nice floor for bad results.

Speaking of floors for bad results, just come to my shop and look at all the scraps of mistakes laying on my floor. :eek:

Then consider those who make no mistakes seldom make anything else.

jtk

[Patrick Chase]

And while you are at it, rig up some method of measuring the exact amount of downforce being applied.

You will need to include a lot more charts and graphs to include every possible kind of wood and grain combination, every possible bedding angle, different amounts of down force and every metal that was ever used to make a plane blade.

After all is said and done, some folks are just not able to see this as a guide or survey of blade wear in a common 45º bedded plane on wood without knots.

To be clear, my objection isn't that Normand got the wrong answer. It's that there is no right answer.

His claim that "a 17 degree angle is best" (his wording) is at the very least not sufficiently qualified. A 45 deg bedded plane on soft/medium straight-grained wood are only the start of the (many) preconditions that must hold for the results of that experiment to be valid.

I pointed out zero downforce because it's the single biggest deviation from how planes are used in the real world. It is the nature of science that in order for an experimental result to be valid the researcher must show that all of the relevant parameters are representative and properly controlled. A reviewer need only demonstrate one significant exception to invalidate the whole mess. I chose downforce.

As you point out things like downforce and "acceptable resistance" (i.e. how high the cutting forces have to be before we decide the blade is dull) are individual preferences, so even a perfect experiment would only yield a valid result for one person.

[Patrick Chase]

I volunteer to be the control group and keep sharpening at whatever random angle I end up setting the jig to at the time. That at least will give us a nice floor for bad results.

Hehe. There's definitely a (wood-dependent) practical minimum below which the blade won't cut with any reasonable amount of downforce or other "user help". I've seen trouble at 5 deg on relatively soft wood.

There are folks (Sellars for example) who claim good cutting performance at even lower angles, though some of those people (Sellars again) also use continuously-varying convex bevels, so it's not clear to me how they even *know* what angle they're using.

[Normand Leblanc]

Stewie,

Hi Normand; I am a bit old school so I will stick to what I know best, and that's 01 tool steel. For a 45* bd plane iron; I start with a grinding angle of 25*, and end with a honing angle that comes close to 28/30*. I don't use a honing guide; the results you posted on 01 steel at 28* reaffirms my own understanding.

There is nothing wrong with O-1 and I've used that steel a lot. 28/30° is very close to what I'm saying.

Luke and Pat

Is it not conceivable that different materials will wear a blade in different manners?

Again, this has been shown by Kato and Kawai.
http://planetuning.infillplane.com/assets/images/fig7sm.jpg
With a raising grain, there is a visible wear on the bevel side. With plunging grain (negative angles) there is very little or no wear on the bevel.

Derek,
It seems that I had not seen that page on Steve website.


A decision is made to ignore the clearance angle to obtain the best planed surface - rather than better edge holding results

In my study I wasn't looking at the best planed surface at all. In fact, the 0.002" depth of cut that I used is ticker than what I would plane to get the best surface finish. For someone working with very hard wood like you, I'm sure that a higher sharpening angle is better.


Patrick,
You do not understand yet? Go back and read carefully the study then you can participate in this thread intelligently.

[Patrick Chase]

Patrick,
You do not understand yet? Go back and read carefully the study then you can participate in this thread intelligently.

In my experience ad hominem attacks are what people resort to when they have nothing else to say. Address the arguments, please.

Why do you think that pushing from the heel of the plane has any relevance to real-world use?

[Jim Koepke]

As you point out things like downforce and "acceptable resistance" (i.e. how high the cutting forces have to be before we decide the blade is dull) are individual preferences, so even a perfect experiment would only yield a valid result for one person.

Be what it may, I see it as an interesting starting point for consideration when one is sharpening a blade for what ever reason.

Didn't you at one time start a thread claiming to have found the 'perfect' clearance angle?

You stated:


I'm firmly of the opinion that extra clearance is nothing more than wasted blade life

This all reminds me of a radio host who told about an advertising sales representative who said, "nobody listens to AM radio."

It started a trend of people calling his program and saying, "high _____, I'm a nobody from _____." Millions of 'nobodys' listened to his program.

I believe it was you who also said, "nobody uses a block plane for a 0.002" shaving."

Well, I am a nobody on that count.

I guess I am also a nobody who pushes a smoother with as little a down force as possible across a surface for final passes.

To me, pushing from the heel of the plane "has real world use."

jtk

[Patrick Chase]

Be what it may, I see it as an interesting starting point for consideration when one is sharpening a blade for what ever reason.

Didn't you at one time start a thread claiming to have found the 'perfect' clearance angle?


No, I did not. (http://www.sawmillcreek.org/showthread.php?244074-Clearance-in-BD-plane)

I said that I'd accidentally used a 5 deg angle and run into severe issues on one wood (Alder) but not another (Maple). I made no claim that my results reflected an "ideal" or applied to any other situation. My exact words in the first post were "so here's one empirical point for the endless clearance debate" and "I'm going to continue to aim for ~10 deg". That's about as far as you can possibly get from claiming to have found a universal answer (as in this thread) or claiming that everybody should aim for that angle on all but the very hardest woods.

In later posts in the thread I also acknowledged that the cutting forces at the angles I use are slightly greater than at higher clearance angles (I think Kees' ~20% number from that thread is about right for typical hardwoods), and others might have different preferences as a result.

I do in fact think that excess clearance is simply wasted blade life. Acute angles wear faster than obtuse ones, so If you allow more clearance than you actually need (based on the woods you work, your technique, etc) then you're wasting time honing and throwing away perfectly good tool steel. Note however that I carefully acknowledged and left room for the fact that the threshold for "excess" is subjective.

It's called "nuance".

EDIT: Since you brought up [in]consistency, let's all remind ourselves of these results: http://www.sawmillcreek.org/showthread.php?244074-Clearance-in-BD-plane&p=2567525#post2567525.

If the same person can come up with data that differ by more than a factor of 100 for nominally the exact same thing, then that should tell you something very significant about the difficulty and validity of such experiments.

[Patrick Chase]

This is a HUGE red flag w.r.t. your results. Wear bevel formation is principally an abrasion-driven process, whereas other edge failure modes have different mechanisms. Your statement here is equivalent to claiming that the ideal angle is independent of the steel's balance of abrasion resistance vs {toughness, hardness, etc}. The real world doesn't work that way.

After re-rereading the study I think I understand this part.

Normand, in your study your only criterion for stopping was whether the plane would self-initiate a full-width shaving, correct?

It appears that you didn't consider things like surface quality, so that means that your chosen metric is insensitive to non-abrasion failure modes like chipping (at least not until it gets bad enough to prevent a full-width shaving). That may in turn would explain why you found the same optimum for steels with wildly different "balances" of hardness/toughness/abrasion-resistance. If your chosen metric only tests one attribute then its relation to the others is no longer a factor.

At the risk of reopening the "end grain sub-debate" this is exactly why Derek pares some end grain in pine every N strokes in his studies, to make sure that the blade is still cutting cleanly as opposed to just cutting. I think that would be a worthwhile process improvement here.

On a separate note, I'd suggest honing on diamond (film or paste) for experiments like this in the future. It can be spendy, but it cuts basically all tool steels well and therefore controls for stone<->steel incompatibility issues like the one you saw with PM-V11 on oilstones (or like what happened to Derek when he evaluated a CPM-10V chisel after honing on Shapton Pros).

[Stewie Simpson]

Patrick; I have a terrific idea; since your never shy of offering advise to others; why don't you run your own independent tests and forward the results to the forum; with your expertise in mechanical engineering and computer skills, you would make the ideal candidate; you could call it "Cutting to the Chase".

regards Stewie;

[Patrick Chase]

Patrick; I have a terrific idea; since your never shy of offering advise to others; why don't you run your own independent tests and forward the results to the forum; with your expertise in mechanical engineering and computer skills, you would make the ideal candidate; you could call it "Cutting to the Chase".

regards Stewie;

Why on Earth would I waste my time like that?

My principal and consistent argument in this thread is that the optimum is driven by subjective preferences, both in terms of how to drive the plane (downforce etc) and in terms of what we consider "good" performance. That being the case, the results of my testing would only be valid for me.

Case in point: While I think that the "zero downforce" test condition is unrepresentative of all real-world use (unless somebody here actually does plane by pushing from the sole?) there would be no way to agree on how much downforce to use for a more representative test. It would instantaneously degenerate into a religious debate about bench height and/or tote angle, and we all know there is no single right answer to those.

Anticipating a likely reply: Even if you try to push directly forward on the tote of a plane alone (no knob), you are applying downforce. This is so because the tote is above the sole, so pushing on it always creates a forward/down moment. That moment must be cancelled by a normal force on the sole/blade, a.k.a. "downforce".

[James Waldron]

A very interesting and stimulating debate indeed.

On the other hand, it is worthy of note that the debate is about the conclusions to be drawn from the data and not about the data itself. I think that distinction is of some import. Viewed as a set of data, measuring what is (at least close to) a single variable test, it's meaning is contradictory to other testing that other folks have done (at least as I understand the history here and elsewhere).

As with any testing regime with multiple variables, only a relatively large number of tests varying multiple permutations of variables can provide an adequate dataset for the application of multivariate calculus to derive any truly solidly grounded results. Multivariable systems often produce unexpected conclusions when proper mathematical analysis is applied. In advance of such an undertaking, it is not possible to know with any fundamental certainty what hypotheses about the exiting data are correct or even reliable across a useful spectrum of usage.

In that context, "follow historic precedent" is one decent stop gap choice, "it works for me" is another, and so on. Interesting as these debates may be, no one should "bet the farm" on a single proposition hypothesized from these data or in light of others. The most we can realistically say is that exemplars that demonstrate failure may help us discern the boundaries of effectiveness. They do not lead us to optima.

I suggest that we need not "... rage, rage against the light ...." in debating this isolated dataset.

[Normand Leblanc]

Hi James,

My son, who is a data scientist, would tell me that I do not have enough data!

Many people here argue about the results of this study. May I suggest that you, or anybody interested, sharpen a blade at 28° and then test it. Then resharpen at 35° - or any other angle that you would be interested - and test it again. Doesn't take long - maybe faster than writing here.

I just found this website http://homepages.sover.net/~nichael/nlc-wood/chapters/caop.html where the clearance angle role is very well explained

"The clearance angle is the angle between the bevel on the back of the blade and the wood surface. It is the angle by which the blade clears the freshly cut surface (Fig.A-l:2). This clearance is required, for the following reason. The thrust as the blade moves forward distorts the wood a small amount, until the wood yields to the cutting action. Part of this distortion is a downward compression. As the blade moves on, the freshly cut wood springs back and would tend to lift the plane blade if it had no clearance. Greater downward pressure would be required for a smooth cut, and friction would increase."

[Patrick Chase]

Hi James,

My son, who is a data scientist, would tell me that I do not have enough data!

No amount of data can answer an unanswerable question. There is no ideal clearance angle, merely subjective tradeoffs.




Many people here argue about the results of this study. May I suggest that you, or anybody interested, sharpen a blade at 28° and then test it. Then resharpen at 35° - or any other angle that you would be interested - and test it again. Doesn't take long - maybe faster than writing here.

Derek has told you that he tried that and prefers 35 in at least some circumstances.
David has told you that he tried that and prefers 35 (same caveat).
I've told you that I've tried that and prefer 35 (same caveat).

Does that mean that 35 is "the ideal"? Absolutely not. But it should be a huge clue that individual working style and preference are factors here, and that there consequently is no ideal, period.

For that matter I told you in the other thread that I'd switched my 5 y/o son's plane to 30 deg because in his case a pound or two (probably less) of cutting force is a big enough deal to be worth sacrificing other attributes.



I just found this website http://homepages.sover.net/~nichael/nlc-wood/chapters/caop.html where the clearance angle role is very well explained

"The clearance angle is the angle between the bevel on the back of the blade and the wood surface. It is the angle by which the blade clears the freshly cut surface (Fig.A-l:2). This clearance is required, for the following reason. The thrust as the blade moves forward distorts the wood a small amount, until the wood yields to the cutting action. Part of this distortion is a downward compression. As the blade moves on, the freshly cut wood springs back and would tend to lift the plane blade if it had no clearance. Greater downward pressure would be required for a smooth cut, and friction would increase."

Sure, but nobody here is proposing a blade that "[has] no clearance" as posited by that quotation. All it says is that you need *some* amount of clearance.

Even if lower clearance does slightly increase cutting forces (as I've acknowledged repeatedly in this thread), why do you think that should trump all other concerns (edge life, surface quality, etc)? Like everything in life it's a tradeoff, and obsessively latching onto a single metric is problematic.

EDIT: Softened last para

[James Waldron]

Hi James,

My son, who is a data scientist, would tell me that I do not have enough data!

Many people here argue about the results of this study. May I suggest that you, or anybody interested, sharpen a blade at 28° and then test it. Then resharpen at 35° - or any other angle that you would be interested - and test it again. Doesn't take long - maybe faster than writing here.

I just found this website http://homepages.sover.net/~nichael/nlc-wood/chapters/caop.html where the clearance angle role is very well explained

"The clearance angle is the angle between the bevel on the back of the blade and the wood surface. It is the angle by which the blade clears the freshly cut surface (Fig.A-l:2). This clearance is required, for the following reason. The thrust as the blade moves forward distorts the wood a small amount, until the wood yields to the cutting action. Part of this distortion is a downward compression. As the blade moves on, the freshly cut wood springs back and would tend to lift the plane blade if it had no clearance. Greater downward pressure would be required for a smooth cut, and friction would increase."

I fully agree with your son. That is indeed one central point of my prior post.

I'm not proposing to do any testing. I've far too much else to demand my time to launch such a Promethean task as my prior post indicates. I wrote then and again now to suggest something far different: you work is not in any way false or even questioned, by any one here and certainly not by me; the effort is worthwhile, as it adds data we have not had before. What I have written to say, apparently unclearly and inadequately, is that your data are not sufficient to draw conclusions about optima, by you or by anyone else, because the feature you have explored is one of many variables in a complex system; you need more data and while you may choose to hold your conclusions dear, while the logic of your thought may seem compelling, and your defenses of your rationale may be eloquent, so too are those of voices raised in opposition to yours. None can be certainly correct, as all are drawing inferences that are inadequately supported by the limited data.

It is always good to remember that a thing may be logical and yet not be true.

But be of good cheer. Such a debate is fun, it may spark further experimentation and additional data for our contemplation, and no furry animals are harmed in the engagement. Unless someone takes it all too far. Taking it too far is the point of my prior post: a courteous and collegial debate is what is needed here and not an exchange of charges and counter-charges. Indeed, my prior post was address, in my intent, more to the somewhat adversarial tenor of some others on the thread, and I did not have you specifically in mind.

As to the language you quoted above, it falls short of validating your hypothesis of the optimum angle. It speaks only to your assertion of a specific physical basis for - in several steps - producing some supposed support for your inferences, although with no supporting data and a citation of an authority with unknown and uncertain provenance. Remember, you found it on the internet! It is, at best and even if totally true and correct, a "red herring."

In short, you and everyone else should take a breath. You're all beginning to "violate my safe space."

[Patrick Chase]

OK, I'm backing off, regardless of who replies.

I agree with James that Normand's work is valuable and that it established something that's useful to know (how to optimize clearance for longest cutting life at some unknown fixed downforce).

My objection was to the conclusion that it had demonstrated that some clearance angle "is the best" (exact words from #1).

[James Waldron]

OK, I'm backing off, regardless of who replies.

I agree with James that Normand's work is valuable and that it established something that's useful to know (how to optimize clearance for longest cutting life at some unknown fixed downforce).

My objection was to the conclusion that it had demonstrated that some clearance angle "is the best" (exact words from #1).

Whoa! Don't be backing off because of me! This latest post has a very nice tone and puts your point clearly and without question, is a reasonable and reasoned position. I don't want to stop the debate, just get it back to a less contentious level.

For example, it would interesting to consider your point made one more post back that: "No amount of data can answer an unanswerable question. There is no ideal clearance angle, merely subjective tradeoffs."

In one sense, you're right because even when the system is completely quantified with all the necessary data, there will be up-sides and down-sides to each peak in performance, and those are likely to differ. The choice of which properties to optimize and which to tolerate at less than best will ultimately introduce a subjective (or at least seemingly so) aspect to out several choices among several peaks of performance.

In another sense, you're wrong, in that any physical system that is fully explored and quantified for all the variables can be defined by the calculus to locate the peaks of performance (only rarely would there be a single peak of performance for all purposes). Then, in one way of looking at the possible choices, the seeming subjective choice of a particular peak would most often be dictated by the result we require of the system and is only subjective in that we thought we had a choice to make, but considering what we wish to achieve, there was a particular peak that best served our goals and dictated our choice after all.

On the other hand, planing wood with a hand plane is far from such quantification; there are so many variables and so few opportunities to test appropriately that we may never get 'er done. So for now and for the foreseeable future, we have broad guidelines we can follow based on empirical experience. And we can build fine furniture with that, so it may not matter a great deal to the craft that there is more to learn here. And we will learn more as the curious look again into the variables and generate additional, new results to debate and digest. Good on us all.

[Patrick Chase]

In one sense, you're right because even when the system is completely quantified with all the necessary data, there will be up-sides and down-sides to each peak in performance, and those are likely to differ. The choice of which properties to optimize and which to tolerate at less than best will ultimately introduce a subjective (or at least seemingly so) aspect to out several choices among several peaks of performance.

In another sense, you're wrong, in that any physical system that is fully explored and quantified for all the variables can be defined by the calculus to locate the peaks of performance (only rarely would there be a single peak of performance for all purposes).

There won't even be a single peak for the same purpose for different users, the reason being that there is no single definition of "performance".

Normand seems to care a lot about cutting force. I don't care at all as long as it's within, say, 20% of the minimum for the cutting angle. We will consequently never agree on a single "optimal" angle, even for the exact same application (wood, grain orientation, cut depth, plane, etc etc etc). As noted in a previous post my 5 y/o son's current optimum is closer to Normand's than to mine though.



Then, in one way of looking at the possible choices, the seeming subjective choice of a particular peak would most often be dictated by the result we require of the system and is only subjective in that we thought we had a choice to make, but considering what we wish to achieve, there was a particular peak that best served our goals and dictated our choice after all.

True, in theory with enough data you could quantify the tradeoffs to the point where each person could derive their individual optimum from a model. As you point out, planing is so complex as to make that potentially impracticable. In addition, that assumes that everybody accurately understands their own preferences, and in my experience that's seldom the case. I think that most people (me included) iterate their way to a preferred configuration without fully understanding why they got there.

[Matthew Springer]

One thing I've really enjoyed about this thread was thinking about the clearance angle at all. I was sharpening my BD bench planes at 40 deg (moar is better and 45 was to steep to fit in the jig). I also beleived myself brilliant for having "discovered" this.

Because I naively assumed that would be best for edge retention. Makes intuitive sense since that part of the blade isn't in contact with the wood. Right?

Except it's totally wrong. Yet another human endeavor where the simple, intuitive answer turns out to be too simple. It turns our reasoning by personal incredulity has issues; who knew?

[Patrick Chase]

One thing I've really enjoyed about this thread was thinking about the clearance angle at all. I was sharpening my BD bench planes at 40 deg and 45 was to steep to fit in the jig.

Because I naively assumed that would be best for retention. Makes intuitive sense since that part of the blade isn't in contact with the wood. Right?

Except it's totally wrong. Yet another human endeavor where the simple, intuitive answer turns out to be too simple.

Out of curiosity were you seeing serious cutting issues at 5 deg?

I'm asking because there seems to be wide diversity of opinion about where Really Bad Things (tm) start to happen. I've seen severe cutting issues at 5 deg on softer woods but not harder ones, while Sellars claims that a blade with 3 deg relief cuts "as well as" one with 15 (which I find hard to believe).

[Matthew Springer]

Out of curiosity were you seeing serious cutting issues at 5 deg?

Yes but I assumed it was me not getting things sharp enough or a host of other factors. I probalby didnt sharpen steeper than 38 in practice with micro bevels. The single biggest issue is that the plane is just really hard to push. (side note:Which also wouldn't make any sense unless the wood actually was in contact with the bevel side). It feels like you're taking much too thick a shaving even though they're pretty thin and they get really curly, so you back off and start to get more "dusty" shavings almost like a card scraper but backwards.

The problems were most manifest in the jointer plane (7) and jack (5-1/2) when I skewed the plane. I have a york pitch 4-1/2 so that was fine. I'd get really really bad tearout when I skewed, especially with the jointer. I was also experimenting with the chip breaker trick on some curly maple for a passthrough arch in the house so I thought that also might have something to do with it.

[Pat Barry]

A very interesting and stimulating debate indeed.

On the other hand, it is worthy of note that the debate is about the conclusions to be drawn from the data and not about the data itself. I think that distinction is of some import. Viewed as a set of data, measuring what is (at least close to) a single variable test, it's meaning is contradictory to other testing that other folks have done (at least as I understand the history here and elsewhere).

As with any testing regime with multiple variables, only a relatively large number of tests varying multiple permutations of variables can provide an adequate dataset for the application of multivariate calculus to derive any truly solidly grounded results. Multivariable systems often produce unexpected conclusions when proper mathematical analysis is applied. In advance of such an undertaking, it is not possible to know with any fundamental certainty what hypotheses about the exiting data are correct or even reliable across a useful spectrum of usage.

In that context, "follow historic precedent" is one decent stop gap choice, "it works for me" is another, and so on. Interesting as these debates may be, no one should "bet the farm" on a single proposition hypothesized from these data or in light of others. The most we can realistically say is that exemplars that demonstrate failure may help us discern the boundaries of effectiveness. They do not lead us to optima.

I suggest that we need not "... rage, rage against the light ...." in debating this isolated dataset.
This is too deep for me. Because of that I don't know if you have a point or are just stringing a line of nonsense.

[george wilson]

Is any of this kind of stuff going to make anyone a more SKILLED woodworker????? NO,NO,NAH.

[James Waldron]

This is too deep for me. Because of that I don't know if you have a point or are just stringing a line of nonsense.

Multivarient calculus is difficult for anyone and it's awfully hard for anyone to foresee what results it may produce. And since we don't have the data, it doesn't much matter. I was just trying to get everyone to realize that there were far too many angels dancing on the head of this pin and everyone needed to take a deep breath and stop arguing past one another. There were instances of folks not taking the trouble to assess and understand what others were saying.

I personally think this is a rich field for learning if we can swap our factual experiences (data) and not get too hung up on extrapolations and inferences from the data (opinions) which we can neither prove nor disprove beyond "it works for me" or "I tried it an I couldn't get it to work."

Maybe you could PM Patrick to ask his view privately. It seems he gets it. It seems he doesn't fully agree with my position about picking optimum setup, but he isn't too far from where I am. I'm sorry if you find it hard to deal with. Not everybody needs this. If it's a bit over the top, I apologize.

[Stewie Simpson]

Is any of this kind of stuff going to make anyone a more SKILLED woodworker????? NO,NO,NAH.

George; have a read of #53..

Stewie;

[Patrick Chase]

Multivarient calculus is difficult for anyone and it's awfully hard for anyone to foresee what results it may produce. And since we don't have the data, it doesn't much matter. I was just trying to get everyone to realize that there were far too many angels dancing on the head of this pin and everyone needed to take a deep breath and stop arguing past one another. There were instances of folks not taking the trouble to assess and understand what others were saying.

I suspect Pat did the full science/engineering calc sequence in his undergrad.

If we're invoking multivariate calc (or worse still graduate-level mathematical physics - now THERE'S a good time) for something like this then it's a lost cause IMO. I understand where you're coming from, but I wouldn't attempt to apply that to myself much less advocate it for the "general population".

Stewie's basically right - the main value in a discussion like this is in learning what to avoid (5 deg clearance for example, which is ironically exactly where this all started (http://www.sawmillcreek.org/showthread.php?244074-Clearance-in-BD-plane)in the previous thread) so that you're not banging your head into a wall like Matthew. Optimizing is of far less importance.

[Pat Barry]

Multivarient calculus is difficult for anyone and it's awfully hard for anyone to foresee what results it may produce. And since we don't have the data, it doesn't much matter. I was just trying to get everyone to realize that there were far too many angels dancing on the head of this pin and everyone needed to take a deep breath and stop arguing past one another. There were instances of folks not taking the trouble to assess and understand what others were saying.

I personally think this is a rich field for learning if we can swap our factual experiences (data) and not get too hung up on extrapolations and inferences from the data (opinions) which we can neither prove nor disprove beyond "it works for me" or "I tried it an I couldn't get it to work."

Maybe you could PM Patrick to ask his view privately. It seems he gets it. It seems he doesn't fully agree with my position about picking optimum setup, but he isn't too far from where I am. I'm sorry if you find it hard to deal with. Not everybody needs this. If it's a bit over the top, I apologize.

I had enough multiVARIABLE calculus in college back in the day to know that there is no such thing as multvarient calculus. Beyond that though, seeing as how you have a good handle on the calculus, please humor us with the variable and equation set we can all use to analyze this problem. Please don't talk down to us though. Show us your data please. I suspect all we will get is a lot of words strung together but no real substance.

[Patrick Chase]

I had enough multiVARIABLE calculus in college back in the day to know that there is no such thing as multvarient calculus.

It's also called multivariate calculus depending on professor and institution. Never multivariant though AFAIK :-).

[Normand Leblanc]

Putting calculus aside for a moment, I believe there is a need to explain how this study was done. It's all written in my blog but some people don't seem to get it right. Just like most studies it's a long read and people usually jump from graphs to pictures without really reading what's there. The "no vertical force" that Patrick bring back all the time looks to be the main problem.

Description of a test after sharpening until complete:
1) plane 5 normal shavings applying whatever force is required (a normal planing)
2) check if the weight of the plane is enough to get a full shaving pushing by the sole. Yes then repeat 1. No, then test completed.

Step 2 could a be to check the blade with a microscope or something else.

By doing the check for step 2 with the weight of the plane I know that at this moment - when I cannot get a full shaving - the blade has been worn just enough so that a weight (the plane in this case but it could be 20 or 50 pounds or whatever you want) applied to the worn edge surface is not enough to engage a cut.

All the tests have been done with the same method. That means that each and every test is stopped when the same weight (the plane) cannot force the blade to take a shaving.

This study got me to realize that, when we stop planing, it's not really because the edge is dull but because the size of the flat under the blade requires that we put a lot of pressure to engage the blade - the blade skip. That flat is the real problem. If you think that it's not the case then you will have to explain why I got close to double the number of shaving at a sharpening angle of 28° compared to 34° all else being the same.

Also, can someone explain why all the old blades from Stanley, Record and Millers Falls are manufactured at 25° if the proper angle is 30-35°. I've never seen a higher angle written on any blade, did you? At the time, the whole world was using hand planes. I'm quite sure they knew what they were doing.

[Stewie Simpson]

The notion that there lacks any clear evidence to advocate a final honing angle of 28/30* is far from true; one need only refer to early western literature dating back to at least the start of the 19th century to highlight that inaccuracy. When discussing the optimum honing angle its important to identify the type of tool steel being referred too. From a historic perspective we can generally refer to it as being of 01 steel. With the advancement in modern metalurgy; A2 and PM-V11 have now entered the market in competition with the traditional choice of 01 steel. To be clear; I don't have a deep understanding of metallurgy; and as such rely heavily on the advise given by those who really should know; the likes of Ron Hock. The general consensus is that the optimum honing angle for PM-V11 is closely aligned to that of 01 steel; while A2 steel needs a higher honing angle of 2-3* above that determined by 01 and PM. For those that now suggest the optimum honing angle should be increased further to 35* or higher; I have not seen any change of advise from that mentioned previously; that would in anyway validate your line of argument.

It should noted:

Veritas bd plane irons (01;PM -V11;A2 tool steel) are supplied ready to use with a flat primary of 30*; and a 35* micro bevel. http://www.leevalley.com/US/wood/page.aspx?p=44751&cat=1,41182,48944&ap=1

Lie Nielson bd plane irons (A2 tool steel) are supplied with a flat primary bevel of 25*; with a recommendation to the user to hone a 30 - 35* secondary bevel; to increase the life of the cutting edge when working abrasive, and hardwoods. https://www.lie-nielsen.com/nodes/4065/bench-planes


Why Veritas chose to supply their bd plane irons with a 30* primary angle; let alone subscribing to the same honing angle of 35* on all 3 tool steels; is something I am personally at a loss to understand.

Stewie;

[James Waldron]

That's my point: we don't have the data to be defining much of substance beyond "this works for me" or "I tried that and I couldn't get it to work." There's no substance to any of the conclusions that attempt to define an optimum from the variance of a single variable here as the OP has attempted. Beyond that I have not gone.

And thanks Patrick for correcting my haste.

[Scott DelPorte]

Interesting study Normand.

So would your recommendation to BU bench plane makers be to increase the bed angle to get longer edge retention? I too notice the need to sharpen more often when using a BU smoother, but never attributed it to CA. It would be great if edge retention could be improved by a change like this. I think my plane has a 12 deg angle.

Thank you for doing all the work that this study represents.

[Patrick Chase]

Veritas bd plane irons (01;PM -V11;A2 tool steel) are supplied ready to use with a flat primary of 30*; and a 35* micro bevel. http://www.leevalley.com/US/wood/page.aspx?p=44751&cat=1,41182,48944&ap=1


Nit-picky, butt...

Yep, they do in fact ship their classic (non-custom) BD planes with 35-deg secondaries. To be honest that may be how I first came to try 10 deg clearance.

The newer custom BD planes ship with a 28-deg primary and no secondary. I think they did that because those planes can be configured with cutting angles as low as 40 deg, so they kept the primary low enough that you can do a 30 deg secondary and still maintain 10 deg clearance.

[Derek Cohen]

Interesting study Normand.

So would your recommendation to BU bench plane makers be to increase the bed angle to get longer edge retention? I too notice the need to sharpen more often when using a BU smoother, but never attributed it to CA. It would be great if edge retention could be improved by a change like this. I think my plane has a 12 deg angle.

Thank you for doing all the work that this study represents.

Scott, I did this a number of years ago, that is, built an infill BU smoother (http://www.inthewoodshop.com/ShopMadeTools/GalootSmootherII.html) with a 25 degree bed. The reason I did so was partly to explore the clearance/wear bevel issue, and partly to be able to use a hollow ground 35 degree bevel since this was easy to freehand (no need for a high secondary microbevel for a high cutting angle). The plane works extremely well, but I cannot say that it holds an edge better than the equivalent 12 degree bed BU with a 50 degree bevel. I do, however, believe that this is the ultimate set up for a dedicated BU smoother. It certainly is the answer for one that prefers freehanding smoothers with a camber.

The question you raise is another example of a singular solution for graded situation. What you have to keep in mind is that the cutting angle of a BU plane is the bed+bevel angle. So, increase the bed and you can lower the bevel angle (which is what I did). Nevertheless, the bevel angle is still much higher than for a BD plane (which may range between 25 - 35 degrees). For example, if you want a common angle (45 degrees) on a 20 degree bed, the bevel on the BU plane needs to be 25 degrees; on a 25 degree bed, you need a 20 degree bevel. This is moving in the wrong direction for edge retention for smoothers. As soon as you begin planing more demanding wood, the bevel angle needs to increase (since, unlike the BD plane, there is no chipbreaker to use). Back to square one here.

Regards from Perth

Derek

[Stewie Simpson]

Derek; I have never owned a Veritas bench plane; your a proponent of freehand sharpening; do you find the shorter length offered by Veritas a little more difficult to manage compared to the traditional length offered by Stanley and LN.

regards Stewie;

http://www.inthewoodshop.com/ToolReviews/LVShootingPlane.html

http://www.inthewoodshop.com/ToolReviews/LVShootingPlane_html_652b2db8.jpg

[Derek Cohen]

Hi Stewie

No real difference. I hold the blade below the slot. What lies above the slot is just extra weight. If anything, the shorter blades may easier to balance for that reason.

The same may be said for the Custom Plane blades. There is an illusion that the blades are shorter. However they are the same length below the slot ...

http://i13.photobucket.com/albums/a262/Derek50/Planes/LV%20Custom%20Plane/Changing-blades8_zpsfledgltp.jpg

Regards from Perth

Derek

[Scott DelPorte]

Hi Derek
I appreciate the benefit of all the experimenting you guys have done. And since the cutting angle on a BU is the bedding angle (= CA) plus the bevel grind, I understand how increasing the CA would necessitate reducing the grind angle for a given cutting angle.

One of the things I like about my BU plane is that I can configure it with a 62 deg cutting angle by changing to a blade supplied with 50 deg grind. I sometimes use this on difficult wood with interlocking grain, and can get better results than I can with any of my other planes which cannot go that high. While I share your experience of having no difficulty with sharpening due to the shorter length of the BU irons, I do find it more difficult to sharpen the blades with a higher grind angle because the length of the bevel gets shorter. I am a hollow grind and freehand sharpening guy.

Independent of any potential wear improvement due to a higher CA, a higher bed angle would be a benefit to me because I could use a lower grind angle (with easier sharpening) and still get a high cutting angle. Normand is showing a "sweet spot" in his data that indicates increasing the bedding angle of a BU plane to 17 degrees might improve the wear on irons. And since the increased bed angle would allow me to decrease the grind angle and still maintain a high cutting angle, I would perceive a benefit from that as well. However, Normand's data shows increased wear on the other side of 17 degrees too, although we are forced to extrapolate if we want to draw conclusions about the 25 deg you used in your prototype. If 17 deg is more or less a sweet spot in many of the conditions Normand tested, it seems plausible that the 25 deg bed angle might result in similar wear resistance to the 12 deg angle.

A higher bed angle on these planes might also result in a stiffer structure under the plane iron. Considering the stiffness of the BU blades itself, I am not sure how much it matters, but it cant hurt. Very interesting stuff, and I really appreciate all the work you guys do with experiments like these (making an infill BU smoother with a higher bedding angle), and sharing the results with the group.
Thanks
Scott

[Normand Leblanc]

That's my point: we don't have the data to be defining much of substance beyond "this works for me" or "I tried that and I couldn't get it to work." There's no substance to any of the conclusions that attempt to define an optimum from the variance of a single variable here as the OP has attempted. Beyond that I have not gone.

James,

I believe that the study goes beyond "this work for me". Just look at the various projects that woodworkers are doing with hand tools and the vast majority is being done on soft or medium-hard. Also, most hand planes (maybe 80%?) are bedded at 45°. For sure, very hard wood or end-grain haven't been tested but the study's results are for regular work with regular planes and they are applicable for many project.

Scott,
I freehand all my blades (convex bevel) except for BU when the sharpening angle is more than 40° where I need to use a guide.


So would your recommendation to BU bench plane makers be to increase the bed angle to get longer edge retention?

I wouldn't go that far because, the more I think about it, the more I believe that our BU planes are best for end grain or very very hard wood where the clearance angle is not really a concern. On the other hand, I recently built a large end grain cutting board using mostly 45° bedded planes. At the time, like I said earlier, my freehand sharpening technique got me an angle of anywhere between 30-35°. This board can be seen here http://oldchips.blogspot.ca/2016/04/a-huge-cutting-board.html

Looking at the resale market for old planes, one has to conclude that low angle type were not popular during a period where everyone was using a plane. It's a bit strange that today many of us are using more BU than BD.

Have a good day,
Normand

[John Schtrumpf]

... It's a bit strange that today many of us are using more BU than BD.

Have a good day,
Normand

BU planes are the gateway drug to the hand tool world :)

[Kees Heiden]

Having been off-grid for a few days, it seems like I missed a lot of fun!

First, congratulations with your research project. I know there goes a terrible amount of time, energy and money in a project like this (maybe not the last one as you seem to have found a cheap way of doing this). I think we can accept your results on face value. You didn't write how many repeats you did on various bits of wood. I think it might make a difference even within the same type of wood, depending on grain angle, hardness, silica content etc. Just the fact that you saw quite a bit of variation between the different species of wood, makes me think variation is the nature of the beast. But I do see a trend: more clearance is valuable, up to a point.

On a quick browsing of this thread I found some arguing about your conclusion, and I think they are right in saying your conclusion was too conclusive! In your data set a clearance angle of 17 degrees was obviously the one with the least amount of edge wear. But when I only look for the O1 steel data, I see almost a straight line between 20 and 14 degrees of clearance. Personally I am not interested in the newer steels. O1 and W1 come with the antique tools I love so much, so in my case I would see the optimum clearance angle would be anything above 14 degrees, and because I also love to work with knotty wood, I would like to avoid too shallow of a sharpening angle. So, I guess, my practice of striving for a 30 degree angle, is not such a bad one. But that is a conclusion valid only for my circumstances.

There is one big caveat, like mentioned by Patrick. Your test is only valid for pure abrassive wear. Other edge damage like chipping or folding is important too. I don't read anywhere in your report to see if you checked if these happened at all. According to David Weaver, the blades he likes best are wearing in a purely abrassive way only and he finds that treat in properly heat treated, old fashioned cast steel (close to W1 steel). Even when the edge is getting past its prime, he can still use it with a bit more down pressure, while a chipping blade immediately leaves evidence in the wood surface. To catch evidence of this kind of thing happening in an early phase, I think it is good to have a look with a microscope.

Chipping and folding in O1 and W1 type of steels can be managed through the sharpening angle or through the tempering of the blade. Rasing the sharpening angle helps to strengten the edge, but of course lowers the clearance angle. Looking at your data that might not be of much importance until you start to really go over 30 degrees. If the edge is prone to chipping, it helps to reduce the hardness a little. Some of the old plane blades, especially French ones, can be pretty soft. As long as you don't work very hard kinds of wood you might avoid the opposite of chipping: folding of the edge.

Regarding the idea that endgrain doesn't need clearance, I think this is a misconception. In my idea the wood fibers are indeed not very compressible in the end grain orientation, but they do bend over easilly, especially in softer kinds of wood. You see this very easilly when trying to cut endgrain with a dull edge. You see voids in the surface, where the fibers have bend over too much and have been seperated. When planing end grain with a fresh edge, the fibers are bend over and then spring back, because of the elasticity of the wood fibers. I think this effect is even stronger then the kind of spring back you see in long grain plaining.

[Normand Leblanc]

Hi Kees,
Ya! You missed all the fun.

Those tests took me way longer than expected but they did not cost very much. I'm left with a bunch of new blades... Every result is the average of two test.

Ok, ok. I agree that the wording used, especially in post #1 were too conclusive.

You're not the only one that seems to like O-1 and it gave me the idea to split the results between the soft and hard blades. Here are the results,

339842

It seems that softer steels don't require a very accurate sharpening angle when compared to harder steels. There is hardly a difference between 20, 17 and 14° for those.


There is one big caveat, like mentioned by Patrick. Your test is only valid for pure abrassive wear. Other edge damage like chipping or folding is important too. I don't read anywhere in your report to see if you checked if these happened at all
I wasn't looking for surface finish at all but except for one test where there was a small knot, I haven't seen anything to get me to believe that the blade was chipped or folded. It has to be remembered that I wasn't wearing down the blade. The blades, after that each test was completed, were still in a pretty good shapes.

Have a good day,
Normand

[Kees Heiden]

The difference between the classic steels and the modern ones is remarkable. No idea why! They sure seem to wear in a different way.

[Pat Barry]

Hi Normand,
The K&K images below are good references. It would be really interesting to see how your various blades show wear by comparison. You probably don't have access to a SEM but maybe you have high enough magnification to see what an O1 and PMV11 blade look like at the end of test. I wonder if they show much back side wear like for example, figures b, d, and e



http://planetuning.infillplane.com/assets/images/fig7sm.jpg