Clearance angle matters

[Larry Williams]

Metal workers have understood clearance angles for generations but they call it relief angle. They know things like tool life, surface quality and surface distortion require close attention to clearance behind a cutting edge.

I wonder when woodworkers and woodworking tool makers will figure this out but I have little doubt Konrad Sauer actually knows what is going on:

http://sauerandsteiner.blogspot.com/

[David Weaver]

Similar to my (and everyone else's) experience, i'm sure, and the reason I don't use low angle planes much anymore. That wear on a bevel down iron is on the side that's easier to work honing and you can go more than 12 degrees if you want.

It's nice to have 20 degrees of clearance when you can get it, if you can't, then the plane behaves funny when you go from softwoods to hardwoods (or the reverse).

Not that the BU low angle planes don't excel at some things, I just would rather not use them all the time and have to chase that long wear bevel.

Be interesting to see if anyone has the same opinion as the one on FWW last year where one of the posters mentioned that they had good experience with a plane with no clearance.

[Bob Strawn]

Similar to my (and everyone else's) experience, i'm sure, and the reason I don't use low angle planes much anymore. That wear on a bevel down iron is on the side that's easier to work honing and you can go more than 12 degrees if you want.

It's nice to have 20 degrees of clearance when you can get it, if you can't, then the plane behaves funny when you go from softwoods to hardwoods (or the reverse).

Not that the BU low angle planes don't excel at some things, I just would rather not use them all the time and have to chase that long wear bevel.

Be interesting to see if anyone has the same opinion as the one on FWW last year where one of the posters mentioned that they had good experience with a plane with no clearance.

I like and use a flush cut plane regularly. They are great for cleanup and close edge work. A Japanese style spear plane is also a very nice tool that can be used with zero clearance. They work surprisingly well and in a few ways are superior. For example, wood, never, ever, jams in the throat. Zero clearance is best for continuing with an already established plane. For removing wood below the established plane, a zero clearance plane is not the right tool for the job. For establishing a plane from a rough surface, again, a flush cut is not ideal for the job. For removing glue, a flush cut plane may be the ideal.

Bob

[Jonathan McCullough]

I'm curious about those Bob, especially the Japanese spear plane. I've seen the veritas flush plane but could you show us a picture of the Japanese spear plane?

[David Weaver]

google:

"yari-kanna"

Think of turning a spear flat on its side and making the spear point single bevel instead of double bevel.

Totally different than anything you will have seen before.

[Sandy Stanford]

Metal workers have understood clearance angles for generations but they call it relief angle. They know things like tool life, surface quality and surface distortion require close attention to clearance behind a cutting edge.

I wonder when woodworkers and woodworking tool makers will figure this out but I have little doubt Konrad Sauer actually knows what is going on:

http://sauerandsteiner.blogspot.com/

Oh gracious, no ruler-tricked back bevel. Howls from across the Pond?

[david charlesworth]

Sandy,

No howls, just the observation that the ruler trick removes metal from precisely the area of the back of the blade where the wear bevel occurs.

I think this would have saved Konrad a great deal of grinding.

There is really no sense in removing metal from and polishing a large area when a small area will do.

David Charlesworth

[Ron Hock]

Konrad's post, that Larry is referring to, is several down on his blog homepage. In case you didn't scroll down far enough: http://sauerandsteiner.blogspot.com/2010/07/up-down-bevels-that-it.html.

The wear bevel on the wood side of the blade is caused the extra abrasion from fiber rebound. If that's the bevel side (bevel-down -- "BD") it's easier to remove than if it happens on the flat "back" of the blade (bevel-up -- "BU"). Just grind the cutting bevel past the wear bevel and you're back in shape. But with a BU plane, if you're a stickler for an overall flat back, you have to re-flatten the whole thing to remove the wear bevel or grind the main bevel back all the way past the wear bevel on the back.

If, however, you adjust your thinking such that the "back" is simply the Very Shallow Bevel opposite the main bevel, re-sharpening gets easier. In this regard I agree with David about his "ruler trick", especially for BU blades, but also for BD blades.

I chatted with Konrad about all this recently. As a freehand honer (sounds like some kind of harmonica), he eschews back bevels. But I asked him to give it a try just to see how that would affect this whole issue. I hope he'll try it and report back.

I've posted before about back bevels and I believe they will gain acceptance as an option for all plane blades. The only objection I've heard that makes sense is that, in order to change a BD blade back, the whole back bevel must be ground off. But that's not different from what's touted as an advantage with BU planes: that the angle of attack can be changed by simply changing the cutting bevel angle. If you want to change it back on a BU blade, you have to grind off the same amount of steel. And somehow, it's considered acceptable, even desirable to own several blades for BU planes but not for BD planes (with different back bevels to achieve the same result.) Why is that? (Asks the blade maker...)

I wrote a bit more about this here: http://hocktools.wordpress.com/2010/01/04/back-bevels-and-plane-geometry/ including a diagram or two that I hope will illustrate what I'm talking about.

[Derek Cohen]

Hi David and Ron

I consider the Ruler Trick to be a great innovation. I was recommending it as a method for minimising the wear bevel effect with BU planes some years ago. I still consider it the way to go, however I do point out now that it will not suit all users.

Conrad and I have a common preference for freehand sharpening. This is an important consideration when it comes to both the RT and BU blades. With BD blades and chisels I hollow grind and freehand the blades on waterstones. While I will use a honing guide to create a micro secondary bevel on the bevel face of BU plane blades (because this is essential when planing at high cutting angles), I leave the back of the blade flat. It is my usual procedure to strop a blade on leather and green rouge as a way of extending an edge. It is nigh impossible to strop a microbevel without altering its angle. Consequently, I only strop the back of a BU plane blade. While not a perfect method, it is (a) good enough to return the edge to about 95% of its original sharpness, and (b) remove or minimise the wear bevel so that it does not intrude.

Perhaps because of the latter I have not experenced the negative effects of a wear bevel as reported by a few. I would also emphasise that the wear bevel depicted by Conrad was extremely unusual in my experience. In fact it was considered to be extremely unusual by members of the Ubeaut (Australian) woodwork forum, where hard and abrasive woods are the norm. I would also say that I consider the wear bevel issue to be overstated as one simply does not hear of thousands of users of BU planes complaining that their planes do not hold an edge long or pointing to wear on the backs that resembles Conrad's.

Returning to the original issue, I think that the Ruler Trick remains a good method for those that are concerned about possible wear bevel intrusion, but that it is one that suits those who use a honing guide rather than those who freehand their blades.

Regards from Perth

Derek

[Joel Goodman]

Question -- from one who has been using a honing guide and is thinking of switching to freehanding. Why is the ruler trick and freehanding incompatable? Yes, it's a sort of guide but you don't have to mount the blade in it and it really doesn't slow you down. Thoughts?

[David Weaver]

i don't think it is. you just have to remember to keep your ruler around.

I'm a bit confused about that, too. I quite like blades thick enough to fit in a honing guide and be turned over and ruler tricked without removal from the jig.

I have not ruler tricked a BU plane, though, mostly because I haven't needed to. Aggressive stones should take care if it fine as long as finger pressure is kept at the edge of the iron (to make sure you're doing work where you want to) on the finish stone.

I don't use a jig much now, except for a few smoothers sometimes, or if I really want to squeeze in a microbevel on an iron that has shown that its primary is too shallow (not often) via weak durability.

[David Keller NC]

I've posted before about back bevels and I believe they will gain acceptance as an option for all plane blades. The only objection I've heard that makes sense is that, in order to change a BD blade back, the whole back bevel must be ground off. But that's not different from what's touted as an advantage with BU planes: that the angle of attack can be changed by simply changing the cutting bevel angle. If you want to change it back on a BU blade, you have to grind off the same amount of steel. And somehow, it's considered acceptable, even desirable to own several blades for BU planes but not for BD planes (with different back bevels to achieve the same result.) Why is that? (Asks the blade maker...)

I wrote a bit more about this here: http://hocktools.wordpress.com/2010/01/04/back-bevels-and-plane-geometry/ including a diagram or two that I hope will illustrate what I'm talking about.

Ron - I suspect you already know this, but the "buy one bevel down plane and several blades" thing is a lot more about the fact that a BU plane of equivalent length and width is either a) way, way less expensive than an equivalent BD plane (generally expressed by newbs with sticker shock - "you mean that thing doesn't have a motor and it's over $200?!?), or b) a little less expensive than an equivalent BD plane (generally expressed by those of us that have realized that you generally buy a particular plane once-in-a-lifetime).

The BU thing is a lot more about cheap than it is a particular advantage of the design, of which the only one is the ability to use it as a very low angle end-grain slicer. The high-angle, highly figured wood configuration is, as you note, easily achievable with a BD plane.

[Derek Cohen]

The BU thing is a lot more about cheap than it is a particular advantage of the design, of which the only one is the ability to use it as a very low angle end-grain slicer. The high-angle, highly figured wood configuration is, as you note, easily achievable with a BD plane.

David, that is very simplistic. As one who uses an equal number of BU and BD planes with high cutting angles (60 degrees and greater), it is evident to Blind Neddy that, all variables held constant, the BU plane is easier to use and most definitely easier to push through hardwood. The low centre of effort of the BU plane is the issue here.

I will comment about other things you say later (I am at work).

Regards from Perth

Derek

[Derek Cohen]

Ron - I suspect you already know this, but the "buy one bevel down plane and several blades" thing is a lot more about the fact that a BU plane of equivalent length and width is either a) way, way less expensive than an equivalent BD plane (generally expressed by newbs with sticker shock - "you mean that thing doesn't have a motor and it's over $200?!?), or b) a little less expensive than an equivalent BD plane (generally expressed by those of us that have realized that you generally buy a particular plane once-in-a-lifetime).

It is my impression as well that many see the advantage of a BU plane to be its flexibility, that is, its ability to swap blades with different angles. However it will soon become apparent that most do not like to work with one plane and several blades because it is inconvenient. After a while we buy more planes, and these become increasingly specialistic in what they do.

There is a specific place for both BU and BD planes - they have advantages and disadvantages. It should never be a case of "either-or".

I see the advantage of a BU plane as working at the cutting angle extremes - the configuration from a 12 degree bed means that you can achieve a lower cutting angle for end grain (e.g. for use on a shooting board) or a higher cutting angle (e.g. for a smoother on interlocked grain). There is no problem using a BU plane in the middle range (45 - 50 degrees), but their advantage lies at the outer extremes.

This is likely to be different for others since I do not expect the average woodworker in the USA to deal with the challenges of very hard Australian wood. For those who do not need or use high cutting angles, and never work on anything other than straight grained wood, then frankly you do not need a complex plane to begin with. You will not discover the performance differences between cutting angles. This whole topic will flbe a non-starter.

The advantage of a BD plane for me lies in the middle range of cutting angles where sharpening issues are less intrusive. BD planes work with lower bevel angles, generally between 25 - 30 degrees, and this is easy enough to hollow grind and freehand to achieve the desired cutting angle. This also makes for easier blade cambering (as achievable on BU planes, but more complicated to do). So the medium angle range with greater cambers are the domain of the BD plane. For example, jacks, foreplanes, scrub planes, plus smoothers for straight grained wood.

More later.

Regards from Perth

Derek

[Derek Cohen]

Question -- from one who has been using a honing guide and is thinking of switching to freehanding. Why is the ruler trick and freehanding incompatable? Yes, it's a sort of guide but you don't have to mount the blade in it and it really doesn't slow you down. Thoughts?

Hi Joel

It is really about technique for me - I am quite happy to have someone show me a different method, so please do think that I am being adament here.

When doing the Ruler Trick, I am used to moving the blade back-and-forth on a waterstone. The waterstone surface is hard and the chances of dubbing the edge is small.

Here is a picture of David at it ..

http://i13.photobucket.com/albums/a262/Derek50/Sharpening/RulerTrick.jpg

If I tried this on a strop I am going to dub the edge as the leather does not have enough resilience ...

http://i13.photobucket.com/albums/a262/Derek50/Sharpening/Ruler%20Trick%20on%20Strop/RulerTrickonstrop1.jpg

Stropping the back of a flat BU blade on the same strop is easier and safer...

http://www.inthewoodshop.com/WoodworkTechniques/Stroppingwithgreenrougeversesdiamondpaste_html_m52 ff5653.gif

Regards from Perth

Derek

[Joel Goodman]

Derek,

When you use the "ruler trick" do you go "side to side" (like side sharpening) or do you go "on and off the stone" (like Charlesworth)? I agree that the leather strop and the "ruler trick" don't work together -- I guess stropping on wood or MDF would present issues as well.

Thanks for sharing your experience.

[Derek Cohen]

Hi Joel

The RT is back-and-forth not side-to-side (that would slice the leather).

Last night I had a thought, however, such an obvious idea ... Instead of using leather, "strop" on a 12000 Shapton-with-ruler.

Regards from Perth

Derek

[david charlesworth]

I think Ron's link above describes things perfectly. I hope he will be pleased to hear that I keep several blades for each of my favourite 5 1/2s. Different cambers and one back bevel. As his article points out the width of this need be no more than 1/64" so it is easily changed.

Brian Burns' pamphlet, available from Japan Woodworker is very good. The machine planer application is particularly useful and it was a well known machinist's trick in the past..

I have not yet been convinced of the advantage of 50 or 55 degree effective pitch but am absolutely certain about 60 & 70 degrees which will smooth any hard and dense timber.

I sharpen plane blades on two stones, a King 800 and King 10,000 and have not found a need to strop, tho I have nothing against this process.

Best wishes,
David

[Joel Goodman]

Derek,

Thanks for the advice and I didn't mean to hijack the thread!

Joel

[David Keller NC]

It is my impression as well that many see the advantage of a BU plane to be its flexibility, that is, its ability to swap blades with different angles. However it will soon become apparent that most do not like to work with one plane and several blades because it is inconvenient. After a while we buy more planes, and these become increasingly specialistic in what they do.

There is a specific place for both BU and BD planes - they have advantages and disadvantages. It should never be a case of "either-or".

I see the advantage of a BU plane as working at the cutting angle extremes - the configuration from a 12 degree bed means that you can achieve a lower cutting angle for end grain (e.g. for use on a shooting board) or a higher cutting angle (e.g. for a smoother on interlocked grain). There is no problem using a BU plane in the middle range (45 - 50 degrees), but their advantage lies at the outer extremes.


Derek - I should say up front that I'm not an anti-BU guy; I've several that see regular use, along with BD planes as well. But what I do see regularly on WW forums is an implied (or explicit) thought that the utility of having 2 or 3 blades with differently honed cutting angles to accomodate either regular planing, end grain planing, or highly-figured grain planing is the exclusive domain of BU planes, and that's just not true. It's certainly true that one cannot achieve a 35 degree planing angle on any (that I"m aware of) BD plane, so in my mind low-angle, end-grain planing is the one exclusive advantage of BU planes.

But - setting up for one plane with two or more blades to accomplish 45 degree, 55 degree and 62 degree (or some other combination) cutting angles is easily accomplished with a BD plane, presuming one has several different blades.

However, a BD plane from L-N, Lee Valley, or others in a similar quality range is a fair bit more expensive - usually around $75 - $150. I suspect this is partly why setting up a BD plane to plane at 55 degrees, 60, or higher is not often mentioned in a BU, buy-one-plane-and-several-blades threads.

Other than end-grain planing (and possibly the lower expense) however, I do not see an objective advantage to a BU plane. There are subjective reasons - some do prefer the BU designs of L-N and Lee Valley as aesthetically more pleasing, or better in the "feels right in my hand" department. However, from a purely engineering & physics point of view, the lower center of gravity of a typical BU plane doesn't significantly affect the planing force required with each stroke. Note that I said "significantly". Theoretically, one could calculate a very slight difference based on the different forward/perpendicular force vectors involved, but these would be very, very slight and would heavily depend on the particular user's style and preferences. The vast majority of the force required to push a plane through an efficient planing stroke depends on the width of the cut, how and how well the blade is sharpened, the length and width of the sole, whether the sole is lubricated or not, the hardness of the wood, the strength of the bonding between the fibers of the wood, whether the grain is interlocked, etc... etc...

This is why I conclude that there is simply no objective advantage to a BU plane vs an equivalent BD plane, other than those factors already mentioned of achieving a low cutting angle. Subjective preferences, of course, is another matter.