Bevel up planes and camber limitations (long and has math)

[Randy Klein]

I've been using LV's trio of BU planes for a few weeks now and I have some comments on limitations of the BU design.

I prescribe to Chris Schwarz's recommendation of after using powered jointer and planer to mill lumber, use a jointer plane to flatten/remove machine marks followed by a smoother for final surface prep. He also recommends cambered irons for the jointer and smoother plane, with the jointer having more camber (and the ability to take a thicker shaving) and the smoother having less camber (and obviously a finer shaving). But the BU design has a significant limitation to cambering. It has to do with the bed angle.

Using a cambered blade, you project the iron just far enough so the corners just disappear into the sole. This will eliminate planer tracks. So how far you can project your iron depends on the camber. And the projection determines the thickness of shaving.

So doing a little trig: On a standard angle plane with bed angle 45 degrees, if you want a 5-6 thou shaving (Chris' recommendation for a jointer plane), you need to have a camber of about 7-8.5 thou. This is coincidentally the amount Chris mentions on his video (that's a good sanity check on the math). However, on a BU plane, the bed angle is 12 degrees, which works out to be a 24-29 thou camber! That's huge.

It's not so bad on a smoother (max 1.5 thou shaving) though. The camber needed for a standard angle is just over 2 thou (again the same number Chris mentions). And for a BU, the camber is just over 7.

So what conclusions can I draw from this?

If you want to follow Chris's method and camber your jointer, a BD jointer would be better (my opinion) than BU.

The smoothers I'm undecided on. On one hand you have BU's ability to easily change angles with different blades (but of course you can use different blades with back bevels for the standard angle), you can close the mouth tighter since there's no chip breaker, and you can use a low angle iron for end grain work.

But how often do you use a smoother for end grain, especially if you have a block plane? And a sharp iron on a standard angle can easily handle end grain anyways.

Or if you like the BU design jointer, you can always not camber your iron and use your smoother to get rid of the plane tracks.

Final thoughts: In the BU vs BD debate, it always comes down to the universal answer: "It depends".

[Derek Cohen]

If you want to follow Chris's method and camber your jointer, a BD jointer would be better (my opinion) than BU.

Randy

It is all an illusion, done with mirrors ...

First off, you are correct - BU plane irons require greater camber than those of a BD plane.

So what?

Just do it. The result is the same.

In the picture below I have chosen to use a LV LA Jack - but I could just as easily used the LV BU Jointer. I am planing across the grain of a Cherry table top (for a sofa table) with a iron bevelled at 25 degrees. This gives me a low cutting angle - quite a bit lower than possible with a BD plane.

It is possible to start with a heavy cut ...

http://i13.photobucket.com/albums/a262/Derek50/Furniture/Humphreys%20sofa%20table/2Markandplaneacross.jpg

... and then follow it with a finer cut - look at the feathering of the shavings ...

http://i13.photobucket.com/albums/a262/Derek50/Furniture/Humphreys%20sofa%20table/5Fineshavings.jpg

I tend to keep a few blades for different purposes. One is a 25 degree straight bevel for a shooting board. Another is a cambered bevel for across grain planing, and I can switch it between the LAJ and BUJ.

... how often do you use a smoother for end grain, especially if you have a block plane?

With regard the LV BUS, again I agree with you, but I think that you are missing the point. The advantage of the BU design lies in the other direction, that is, a flexibility with high angles of attack. There is no reason to use this type of plane with a low cutting angle. I only use a 60 or 62 degree cutting angle.

I use both BD and BU planes about equally. Generally I prefer the low centre of gravity "feel" imparted by the BU configuration.

On the other hand, here is something that I have not as yet attempted with a BU plane - using a #7 (BD) jointer as a scraping plane. The iron is given a 45 degree bevel, with a slight camber, and used in a BU configuration.

Jarrah shavings with- or against the grain ...

http://i13.photobucket.com/albums/a262/Derek50/Planes/ScrapershavingsJarrah.jpg

Regards from Perth

Derek

[Randy Klein]

Derek,

I see what you mean by illusion as I can't see any of your pictures ;) but it's probably just the server at work...

[Wilbur Pan]

First off, you are correct - BU plane irons require greater camber than those of a BD plane.

So what?
Hi Derek,

Well, my thought was that with a bevel down plane, you'll have to grind away 3 times the amount of steel at the edges to get the amount of camber you need compared to a bevel up plane.

Of course, you could argue that once you establish the camber, you only need to maintain it. But with my crappy sharpening skills, I'd probably just flatten it out. It's only when I'm trying to put a flat edge on a blade that I get awesome cambers. ;)

[Bob Opsitos]

Derek, can you take a picture of the camber on your iron? Curious to see what the amount of camber your running look like?

My BU irons are slightly cambered, only what I get from finger pressure during sharpening. I'll have to check with a square to see how much that has gotten me. I bet it is extremely small.

thanks
bob

[Randy Klein]

If you want to follow Chris's method and camber your jointer, a BD jointer would be better (my opinion) than BU.

Randy

It is all an illusion, done with mirrors ...

First off, you are correct - BU plane irons require greater camber than those of a BD plane.

So what?

Just do it. The result is the same.


Derek, I'm not so sure the result will be the same and here's why. For the same iron width (nominally 2-1/4") cambered to produce 5 thou shaving, the more cambered iron will have a narrower profile since the camber forces it "fall" off to the side faster. So the end result will be a surface with more, but thinner, undulations. The less cambered iron, of course, is opposite. It will have a wider profile and will result in undulations of greater width.

Now, I'm not sure if this difference will actually make an aesthetic difference, but the anal retentive side of me thinks the wider undulations will be more pleasing.

And of course, a thinner profile will need to have more passes taken to cover the width of the piece.

[Randy Klein]

Derek (or anyone else for that matter),

Maybe you can help me figure this out. I was planing some hard maple today that had some reversing grain I wasn't really expecting and ended up with some nice tearout teasing me.

I was already using my LV BU planes with a 50 degree cutting angle and I've been keeping it sharp. So I rehoned a steeper micro bevel and ended up with a cutting angle of 64 degrees (I was actually shooting for 62, but I forgot to change Mk II micro bevel knob). When I started planing with the new angle, the tearout disappeared and the expected increase in force was definitely there.

However, and this is where I need help, the surface doesn't look as good. The other pieces that I planed at the lower angle are significantly more glass-like and smoother feeling. I'm at lost as to why, what to do about it, or even if it will matter after the finish is applied.

The only guess I have is that the angle was too steep and induced a Type III chip formation, that I've heard Rob Lee refer to, leaving a fuzzy appearance.

Any thoughts would be greatly appreciated.

[Derek Cohen]

Randy

I can take some photos of the cambers, but it will have to wait until the weekend.

With regard to the surface finish with a high- verses low cutting angle, it really depends on the wood as much as the plane. Softer woods will not plane as smoothly with high cutting angles (think of a scraper on soft woods - tearing rather than shearing the fibres).

Regards from Perth

Derek

[Randy Klein]

I guess I'll hone some angle in between those two and take a few more passes.

[Bob Opsitos]

Becuause I was curious, I drew the shapes up in CATIA (CAD program here at work) and indeed for a .005" shaving on a 12deg bed and 25 deg, 2-3/8" wide iron you need almost .030" of camber to feather the edges. With that said it really doesn't look ridiculously cambered by any means. it appears to be ~23.5" radius.

Bob

[Randy Klein]

Becuause I was curious, I drew the shapes up in CATIA (CAD program here at work) and indeed for a .005" shaving on a 12deg bed and 25 deg, 2-3/8" wide iron you need almost .030" of camber to feather the edges. With that said it really doesn't look ridiculously cambered by any means. it appears to be ~23.5" radius.

Bob
Bob, I was trying to draw the circles to correspond with the camber, but MS powerpoint is not so good. I did make an excel spreadsheet that has iron width, bed angle, thickness shaving as inputs and it spits out the required camber.

I wonder if anyone can plot these circles to scale on a CAD program. It would be nice to have as a reference as I hone to compare against.

And for my case, a 2-1/4" iron, bedded at 12 degrees and a desired shaving of 0.006", the camber needed has a radius of 22". Compare this to a bed angle of 45 degrees and the radius is 75". I haven't seen these as circles yet though, so may that huge disparity in radii is only slight.

[Randy Klein]

Derek, I'm not so sure the result will be the same and here's why. For the same iron width (nominally 2-1/4") cambered to produce 5 thou shaving, the more cambered iron will have a narrower profile since the camber forces it "fall" off to the side faster. So the end result will be a surface with more, but thinner, undulations. The less cambered iron, of course, is opposite. It will have a wider profile and will result in undulations of greater width.

Now, I'm not sure if this difference will actually make an aesthetic difference, but the anal retentive side of me thinks the wider undulations will be more pleasing.

And of course, a thinner profile will need to have more passes taken to cover the width of the piece.

I actually need to retract what I said here in the quote, since I figured out that I was mistaken. The profile will end up being the same, since the bed angle of the LA will "flatten out" the more cambered blade.

However, another issue I thought of: If you are cambering your jointer iron 28 thou, this means you need to project it 28 thou from the sole, in order to get the proper thickness of shaving. As opposed to the a normal plane where you only need to project it about 8 thou.

I was wondering if this larger projection has any affect, since the blade is unsupported. Or maybe the extra thickness of the iron takes care of this already.

[Bob Opsitos]

Very slight, I plotted them out 1:1 and I doubt you'd be able to tell the difference with only a 2.25" chord length (blade width) without a square/straight edge to compare them. The difference is only .517mm in camber. The two lines are blurred together on the screen at that point.

Attached is a 1:1 of the 22deg radius across a 2.25" blade width. You'll likely have to play with the printing scale to ensure it comes out correct.

Bob

[Wilbur Pan]

However, another issue I thought of: If you are cambering your jointer iron 28 thou, this means you need to project it 28 thou from the sole, in order to get the proper thickness of shaving. As opposed to the a normal plane where you only need to project it about 8 thou.

I was wondering if this larger projection has any affect, since the blade is unsupported. Or maybe the extra thickness of the iron takes care of this already.
I think that whether you use a standard angle or a low angle jointer, either one of them should be set up to take a 0.006" shaving. As you say, because of the differing angles, the low angle plane will need a greater degree of camber to achieve this.

However, the edge of that blade should still only project about 0.006" below the surface of the sole of the plane. The blade probably projects further out from the base of the frog, but because of the low angle, the downward projection is less.

[Wiley Horne]

Randy,

I don't believe blade support on a bevel-up plane is going to be an issue, even with the camber. Bear in mind that on a bevel-down plane, the entire primary bevel is cantilevered, though it is also pre-tensioned by the cap iron.

What is going to happen when you camber a 12-degree-bedded, bevel-up iron, is that the blade edge will need to be managed within tighter tolerances over time, than a bevel-down iron. In the situation you describe, each time you resharpen, you have two conditions to meet: maintain the camber of approx. 1/32", and maintain the final honing angle. And in doing this, you will want to remove enough metal with each sharpening to get beyond the wear on the back of the blade. This is manageable, and it's manageable on a hand-held basis, but will require more attention to tolerances than in the bevel-down situation.

In general, the bevel up plane has a blade geometry which is sensitive to changes occurring on the backside (clearance is affected), as well as changes on the bevel side (changes the attack angle). As long as you're aware of this as you resharpen over time, it's manageable.

Similar considerations attend the sharpening of bevel-down irons over time, but the tolerances are usually greater. I say 'usually' because in certain situations, for example with Japanese planes bedded in the low-40's, maintaining the bevel requires great discipline, because clearance is limited and bevel-rounding due to sloppy sharpening will cause clearance problems fairly quickly.

Each different group of planes has blade and bedding geometries that impose discipline on the way we sharpen.

Wiley

[Randy Klein]

What is going to happen when you camber a 12-degree-bedded, bevel-up iron, is that the blade edge will need to be managed within tighter tolerances over time, than a bevel-down iron. In the situation you describe, each time you resharpen, you have two conditions to meet: maintain the camber of approx. 1/32", and maintain the final honing angle. And in doing this, you will want to remove enough metal with each sharpening to get beyond the wear on the back of the blade. This is manageable, and it's manageable on a hand-held basis, but will require more attention to tolerances than in the bevel-down situation.

That may be the problem I'm having then. The first camber I honed on a fresh blade cut beautifully. I was really impressed. Each subsequent honing seems to just make it worse and worse and now its cutting horrible unless I take such a thin shaving, that's it more like dust than shaving.

So I guess I need to hone longer on the 1000 grit? How do I know when I'm done though, I got a burr each time before, what do I look for now?

[Wiley Horne]

Randy,

It sounds like you've been losing clearance, and if you're now making dust, you've just run out of clearance. Have your planing windows been getting shorter with each subsequent sharpening? And are you having to push the plane down into the work to keep the blade in the cut and making a shaving? If so, that would indicate that the wear on the blade back is not being fully removed, but rather is building up over time.

If not, something other than clearance loss is going on.

Wiley

[Derek Cohen]

It sounds like you've been losing clearance, and if you're now making dust, you've just run out of clearance.

Wiley, I agree.

Randy, there was a thread on this a couple of weeks ago. Search it out.

Regards from Perth

Derek

[Randy Klein]

Randy,

It sounds like you've been losing clearance, and if you're now making dust, you've just run out of clearance. Have your planing windows been getting shorter with each subsequent sharpening? And are you having to push the plane down into the work to keep the blade in the cut and making a shaving? If so, that would indicate that the wear on the blade back is not being fully removed, but rather is building up over time.

That's exactly what is happening. I'll do the search on clearance angles and see if I can fix this. Thank you.

[Robert Trotter]

Hi Randy,

I haven't had this problem yet with my BU planes but expect to in the future. But you may want o check out a thread Derek did about a back bevle of sorts on the back of the blade. only enough to give you clearance and not too much as to make the blade not work.

There was a another thread or it may have been on another site (too much reading and I can't remember:) ) about the wear characteristices of BU planes. Just the fact of using the planes and the orientation of the bevel means that friction and hence wear on the back of the blade is inevitable.. You might want to check with Derek or try reading this thread http://www.sawmillcreek.org/showthread.php?t=46995

Robert

[Randy Klein]

I've read the site you referring to. I believe it's Brent Beach. He advocates a small back bevel or you'll have to hone away alot more metal to get to the wear bevel. However, there are other sites that mention a back bevel would only enlarge the wear bevel and make matters worse.

I guess I'll try a back bevel (using the ruler trick) and see how that goes.

[Mike K Wenzloff]

A properly maintained, very low back bevel on a BU plane is fine. It is the "maintained" part without a repeatable method which will lessen its effectiveness.

I respect Brent's research. Where I differ from him is in a practical shop environment where working wood is the goal verses the theoretical application of sharpening principles.

It is true that adding a back bevel on a BU plane will exacerbate the lower wear bevel. In fact, it provides two points of wear that must be removed in order to obtain a "new" cutting edge. For someone who is aware of good sharpening practice, is aware of the "problem" and how to rectify it, this is not a big deal (well, at that point, sharpening isn't a big deal). But it is something "else" to do.

Anything which takes more time than standard practice makes sharpening the goal or a great portion of the goal. Fine for planing demonstrations and contests--or research. Not so good for normal shop practice and getting back to work.

Really, the whole issue of precision cambering falls into the same category.
It is more difficult to maintain a camber on a BU plane, as has been mentioned in this thread, because of the lower angle. Which is why I don't teach people to camber a BU plane. Yes, ease the corners. But full-on cambering? only if one wishes the continuing maintenance.

The best advice when using a BB is to simply hone frequently. If using a BB, use the same aid (ruler et al) to maintain the BB. Use the same projection else the angle will either grow steeper lowering the clearance or one will hit the heel of the BB and yet more steel has to be removed.

If one chooses not to use a BB on a BU plane, elect instead to not merely hone the edge when working to renew it, but rather begin at a coarse enough grit to quickly remove enough metal to deal with the lower wear bevel. Then advance to the finer stone(s). For class demonstrations, I used a 1k Shapton to quickly remove enough material at the primary bevel angle and then simply created a secondary micro bevel on an 8k stone. That was the fastest method of getting back to work.

Take care, Mike

[Randy Klein]

For class demonstrations, I used a 1k Shapton to quickly remove enough material at the primary bevel angle and then simply created a secondary micro bevel on an 8k stone. That was the fastest method of getting back to work.

Take care, Mike

How do you know when you're done on the 1k Shapton? Or is does it cut fast enough that you don't have to worry about it? I have a Norton 1k, will that cut fast enough as well?

[Mike K Wenzloff]

Hi Randy--it's easy once you've sharpened enough edges. What's hard is long-distance communication. Much easier in person.

Probably the easiest way to learn it is to just inspect the back edge of the blade, especially on a BU plane. One of the issues is that when doing the primary bevel, you will still feel a burr on the back even if the lower wear bevel isn't fully removed. Because one can feel the burr, one can assume the edge is indeed sharp and attempt to remove the burr by a few strokes on a fine stone. Often all that has happened (if the edge has not been honed far enough back) is that the wire edge has been straightened out, but it will fracture once the plane is used and the edge will dull prematurely.

OK. So how does one "know" that the lower wear bevel has been removed? Us a magnifier to look at the back of the blade after honing. Keep a rough track of how many strokes it takes to remove it fully. After a couple times of doing that it will become second nature--you'll just hone, strop or use a fine stone to do a secondary bevel or the entire primary and go back to work without inspecting again.

As for stones--the concrete in your garage is good enough. So once one has a stone you don't need to bend over <g>. A tongue in cheek way to say, use what you have. It'll work fine. Don't spend more money on different sharpening stuff.

Really. Other than my final smoother, I never sharpen past a 2k waterstone on the bench or joinery planes. I left the 2k stone on the back of my bench and frequently just hone while in use. I've since gone back to oil stones (you reading this Alf?) due to a warped sense of tool use and accumulation for building an 18th/19th century tool chest. But any means can be used for sharpening.

And I have used a concrete floor many times...

Take care, Mike

[Derek Cohen]

Hi Randy

Below is a copy of a post I made here a few weeks ago. I think that Mike and I are probably going along similar paths, and our advice is therefore complimentary.

For a while I was using David Charlesworth's Ruler Trick to create a micro backbevel. In the beginning David designed this strategy as a shortcut to honing blades with backs that were not flat. This is not a reason to use them on quality new blades since they will come from the factory in state almost ready to go. David had old Stanley/Record blades in mind. Then the technique became one of removing the wire edge, and this is the reason I incorporated it. In addition, the "upside down" bevel up blades were considered to wear on the backs more rapidly that those used in a BD configuration, so it was a case of killing two birds with one stone.

However ... I get quite lazy about honing. I have done so much experimentation that some might think I like the area. I do not. I am looking for quicker, more efficient honing strategies that do not compromise quality. So I increasingly return to freehand honing. This involves grinding a hollow and honing freehand on waterstones. Also, I like to touch up on strops in between honings (keeping the edge sharp). This method is not suited to the traditional BU method(if one could call it that with such a short history) that involves very specific microbevel angles via a honing guide. A micro backbevel gets in the way when stropping as it is important (very important!) that you do not exceed 5 degrees here so as to maintain at least 7 degrees of clearance. So I began to hone without a backbevel ... and found that it made no difference at all.

I mostly treat my BU blades in exactly the same way as I treat my BD blades. I grind the angle I seek on a 6" high speed dry grinder, and for the BU blades I make use of the Tormek angle setter. I can then freehand them on my Shaptons. I can freehand hone them on strops as I work. No backbevel. No need.

One edit that I must make to the above is to emphasize that the reason that I do not need a backbevel is because the edge is not permitted to get too worn owing to ongoing stropping.

You know that when the wear bevel has not been removed when you can feel a wire edge remains.

Regards from Perth

Derek

[Randy Klein]

the edge is not permitted to get too worn owing to ongoing stropping.

So on average and ball park, how many passes do you take before stropping?

[Derek Cohen]

Randy

It depends on the abrasiveness of the wood. As soon as I feel the plane is cutting less smoothly I strop the edge.

The picture below is a current project - a Cherry table top. The shaving in the background were from planing across the grain on both sides. I only recall stropping the blade of the LV LA Jack once throughout.

http://i13.photobucket.com/albums/a262/Derek50/Furniture/Humphreys%20sofa%20table/14Otherside.jpg

This amount with Jarrah would likely require about 4 lots of stropping.

Regards from Perth

Derek

[Wiley Horne]

Randy,

This is to pick up on Mike's point about planes and applications. Your bevel-up planes give you a fine set of smoother, panel plane, and jointer.

For the woods you're working--temperate zone hardwoods--and if you're trying to do stock preparation from roughsawn, try getting yourself a wooden jack to go crossgrain and get the cup out. 6" to 8" radius camber. Then go up and down the board with a wooden foreplane. Use about 1/64" of camber on it. 17" to 22" long. You'll think you died and went to heaven. Come in behind with your bevel-up planes for final finish.

Wiley

[Randy Klein]

Randy,

This is to pick up on Mike's point about planes and applications. Your bevel-up planes give you a fine set of smoother, panel plane, and jointer.

For the woods you're working--temperate zone hardwoods--and if you're trying to do stock preparation from roughsawn, try getting yourself a wooden jack to go crossgrain and get the cup out. 6" to 8" radius camber. Then go up and down the board with a wooden foreplane. Use about 1/64" of camber on it. 17" to 22" long. You'll think you died and went to heaven. Come in behind with your bevel-up planes for final finish.

Wiley

Wiley, I'm not there yet. I have a powered jointer and planer for milling. I'm using the jointer and smoother to clean up the imperfections left.

But one day, I have plans on doing at least one project all with hand planes. But I think I want to make the planes that can do that.

[Wiley Horne]

Randy,

Oh. I thought you were cambering your LV jointer in order to do surface prep. on rough stock. I.e., using your 22" plane as a try plane. If the stock is already flattened and thicknessed, do you think you need camber, beyond just ordinary relief of the blade edges?

Wiley

[Randy Klein]

Randy,

Oh. I thought you were cambering your LV jointer in order to do surface prep. on rough stock. I.e., using your 22" plane as a try plane. If the stock is already flattened and thicknessed, do you think you need camber, beyond just ordinary relief of the blade edges?

Wiley

According to Chris Schwarz you do. But not to say that is the right way, just one way. It's setup to take a 0.005 to 0.006 shaving that feathers at the ends. It takes care of snipe and planer ridges and further flattens the piece. Then the smoother takes care of the ridges left by the jointer plane. You could do it all with the smoother, but it would take many more passes with such a light cut.

[Randy Klein]

So I honed my irons once again and used a back bevel via the ruler trick. Since the iron had a camber, I had to arc the blade while doing the ruler trick, but it wasn't that hard at all.

And that worked magic. No more huge downward pressure needed, no more dust. Nice clean shavings and a very smoother surface is what I have now.

Thanks for all your advice, it saved me. You don't know how close I was to giving up on hand planes and buying Festool sanders...

Now I need to re-smooth some of my previous pieces...

[Mike K Wenzloff]

If there was a clapping emoticon, I would insert it. Good on ya, Randy.

Nothing like a tool that is working, electrically powered or hand powered.

Take care, Mike

[Wiley Horne]

Randy!

One word for you: Congratulations!! (like Mike said) I somehow missed your 'success' posting, and so my last two posts were totally beside the point. Please disregard them. Have a good weekend.

Wiley

[Larry Williams]

... This method is not suited to the traditional BU method(if one could call it that with such a short history) that involves very specific microbevel angles via a honing guide. A micro backbevel gets in the way when stropping as it is important (very important!) that you do not exceed 5 degrees here so as to maintain at least 7 degrees of clearance....

I've been trying to find time to get involved in this thread and figure out what everyone was talking about. It figures that by the time I could spend a little time here, the thread would end. It seems Randy has solved his issues but stumped by the above.. I've seen it before but can't figure out its source.

Can someone tell me who or where this 7º clearance angle comes from?

Clearance angles are like relief angles in metal working. Maintaining adequate clearance is necessary in both wood and metal working because of something called visco-elastic deflection. This is deflection caused by resistance to the cut which results in materials being compressed and deformed ahead of the cutting edge. After the material is sheared, it returns to close to its original shape standing back up and growing slightly in height.

In metal working, if you're working with a single edge HSS cutting tool, the general rules for relief angles are: for hard/tough metals 6º to 8º; for medium to mild steels, cast iron etc. 8º to 12º; and for softer metals like copper, brass or aluminum 12º to 16º. These are taken from a recent (2000) Machinery's Handbook. These relief angles would be greater for A-2 or O-1 steel given the lower red hardness of these steels.

My own personal experience with wood and hand planes cutting at York or middle pitch indicates 20º of clearance is barely adequate unless you want your depth of cut severely limited to less than a couple thousands of an inch or so. I've confirmed this in designing and making special single edge tooling for machine work. I've worked a lot of metal and have no doubt that even aluminum deflects less than wood ahead of a cutting edge.

I'd sure like to see locate the source saying 7º is all that is necessary for a hand plane. I'd like to know what that is based on. I also once honed a 40º micro bevel on my own low angle bevel-up type smooth plane and tried to take a heavy cut. I couldn't. If I just let it ride on the surface the spring back from visco-elastic deflection made the depth of cut self limiting.

I was looking forward to seeing Derek's photos of his cambered BU irons. I was hoping I'd see them in the obtuse bevel angles some claim work so well on BU planes. I've been wondering if cambering obtuse BU irons on these planes would allow a deeper cut or just limit the width of cut.

[Derek Cohen]

I was looking forward to seeing Derek's photos of his cambered BU irons. I was hoping I'd see them in the obtuse bevel angles some claim work so well on BU planes. I've been wondering if cambering obtuse BU irons on these planes would allow a deeper cut or just limit the width of cut.

I was hoping to post photos yesterday but I just did not have the time (finishing off a table: http://www.woodcentral.com/cgi-bin/handtools.pl?noframes;read=112292 )

Also, it is not so easy to take images that convey the info in a clear manner since the surfaces are so reflective. I've done my best, and I hope it can be interpreted by others. In addition, my digital caliper's battery is dead, so I can only estimate the thickness of the shavings. That is not such an issue since you can see them for yourselves.

A little background. The blades I will display are those of my LV LA Jack. I have two that I use specifically with this plane. Both are bevelled (hollow ground) at 25 degrees so that I may hone them freehand on my Shaptons. The first has a straight bevel. This is for use on the shooting board. The second (and the subject under the spotlight) is cambered for use as a traditional jack plane. Actually, I have a third blade as well, and this is bevelled at 50 degrees so that the plane may be used as a high angle panel plane.

Aaahh - you all think that the LAJ cannot be used as a jack? Well, this is what I used when flattening the tabletop in the link above.

Here are two 25 degree blades, one straight and the other cambered:

http://i13.photobucket.com/albums/a262/Derek50/Sharpening/Cambered%20blade%20for%20LAJ/Camber-2blades1.jpg

http://i13.photobucket.com/albums/a262/Derek50/Sharpening/Cambered%20blade%20for%20LAJ/Camber-2blades2.jpg

As you can see, the amount of camber is almost too little to see with the eye. I estimate that the camber is about .002 at each side.

Here is another view. This one is used to assess camber as per David Charlesworth's method, that is, when dragging a wooden edge over the blade, I cannot make a shaving at the sides but I can make a .002 shaving at the centre.

http://i13.photobucket.com/albums/a262/Derek50/Sharpening/Cambered%20blade%20for%20LAJ/Camberedblade1.jpg

Working with a scrap of Tasmanian Oak, I begin a shallow cut across the grain:

http://i13.photobucket.com/albums/a262/Derek50/Sharpening/Cambered%20blade%20for%20LAJ/Camberedblade-fineacrossgrain1.jpg

Notice that the shaving forms only in the centre of the mouth.

Now a medium thick shaving. This is full width and tapered at the sides.

http://i13.photobucket.com/albums/a262/Derek50/Sharpening/Cambered%20blade%20for%20LAJ/Camberedblade-mediumacrossgrain1.jpg

Here is the same process, this time with the grain:

http://i13.photobucket.com/albums/a262/Derek50/Sharpening/Cambered%20blade%20for%20LAJ/Camberedblade-finewithgrain1.jpg

And this time a medium, full width shaving on a Pine board:

http://i13.photobucket.com/albums/a262/Derek50/Sharpening/Cambered%20blade%20for%20LAJ/Camberedblade-mediumwithgrain4.jpg

... and a close up ...

http://i13.photobucket.com/albums/a262/Derek50/Sharpening/Cambered%20blade%20for%20LAJ/Camberedblade-mediumwithgrain2.jpg

To obtain this camber I applied 25 extra strokes on the 1000 Shapton stone to each side of the bevel (then moved on to a few strokes on the 5000, 8000, and strop).

Regards from Perth

Derek

[Robert Trotter]

OK, nice thread but what is the consensus on a smoother?

It seems that a slight camber on the BU Jack or Jointer coul be useful. And many seem to say that a smoother should have a camber on it also.

But recently I have read a few post that have me a bit confused. They could have just been typos???? Some seem to think that a smoother doesn't need a camber at all, just a straight blade edge. Some say only to round or relieve the corners (straight blade with just corners rounded abit to reduce "tearing" the wood. And a lot say to camber the blade but it being only a small camber like in Derek's posts.

What is the concensus on a smoother. BU smoother and LA smoother (bother LV low angle BU planes).

And while we are here, anyone like to give a rundown on blade camber or stright for BU jointer, BU jack and the two smoothers from LV.:o

Rob

[Randy Klein]

Robert,

I don't think there is a consensus. You do whatever works for you. For me, I like to camber the smoother and jointer, simply that's the way I first saw it done (even if that was only a few months ago...). But those are all viable options since its the end result that is important and not the way you got there.

[Wendell Wilkerson]

Derek,

With the current camber you have on your LA jack blade, do you think you can pull a 5-6 thou shaving and still have the edge feather to nothing? Or would you need to increase the camber?

Wendell

[Randy Klein]

Derek,

With the current camber you have on your LA jack blade, do you think you can pull a 5-6 thou shaving and still have the edge feather to nothing? Or would you need to increase the camber?

Wendell

That's the thickness I get, but it requires a camber of 28 thousandths...