Thread: Sharpening BU planes - add a 13°+ to underside?

I could only suggest you try it & see, it's the best way to find out. But I will add that you need to be very careful adding a bevel to the flat side of a BU blade. If it's an "ultra low angle" job like a 65 1/2, there is only 12.5* of of 'relief' behind the cutting edge. My experience suggests going below 10* of relief with a wood-cutting blade is asking for increased drag & poorer cutting efficiency so bear in mind that you do need a goodly amount of relief. Besides all else, putting back bevels on either BU or BD blades is reducing the acuteness of the edge & increasing the force required for it to penetrate the substrate. I should declare I've never been a fan of back-bevels, the only time I've resorted to them is when I got sick & tired of trying to flatten a pitted or warped blade & the back-bevel seemed like an easy get-out-of-jail card ('tisn't, really, 'cos you still need a flat surface to mate with the cap-iron). As a general rule, I reckon you'll get further faster by using as acute a sharpening angle as the particular blade steel you are using will safely take. That's a matter for you to decide based on the planes you use, the blades you have, & the woods you plane.

I'll also out myself as not being a fan of BU planes in any case. They have their place in my tool kit, but it's a very small place, really. About the only situation where a BU plane can regularly beat a well-tuned 45* BD plane with a cap-iron is cutting across the grain. Depending on the wood, the BD may do a perfectly adequate job there as well, but if you pit a good low-angle BU against the BD over multiple wood types, the BU will do a better job more often, in my experience.

Not knocking BU planes, there are those as love 'em & those as hate 'em and a whole crowd in between who are indifferent. Viva la difference.

Cheers,

Originally Posted by woodPixel

I was reading this: Lie Neilsen or Veritas?

and pointed out this: Lie Neilsen or Veritas? with the video below explaining why the old bed angles were chosen as they were....

in which @D.W. seemed to suggest that both the thinking was old and the discussion done to death.

BUT, I was thinking.

I've many BU planes. For THESE planes, would it be worthwhile adding a secondary bevel to the flat side of the blade to stop the "dig in" effect of a blunt blade?

Would it not be better to sharpen the blade only using this "bed side" secondary bevel and not really touching the primary bevel at all?

This would make resharpening significantly faster, as one only needs to re-hone the very small 13°+ secondary bevel.

By making this secondary bevel simply greater than the bed angle (i.e. 13° or more) then it won't dig in, nor cause a hindrance to the function of the blade. For it it were less of an angle, it would act as a skid. I chose a 2mm wide secondary simply to make the diagram obvious. The relief is shown as a chop-away in my SketchUp. All the angles are accurate.

Second thought, would this secondary act in some ways as @D.W's "unicorn bevel"?

Does the fact that the "new" BLADE angle is 63° make any difference at all considering the FACE of the blade is still approaching the cut at the same 62° total effective cutting angle?



I hope all this makes sense!



These are pictures from Veritas' website:

05P3401D3.gif



see this blown up picture I did to highlight what I mean.....

plane blade - Scene 1.jpg

No, Brett. A very firm "no" ... do not go there.

BU planes have a 12 degree bed. Leonard Lee (father of Rob, and founder of Lee Valley) wrote many years ago that the minimum clearance angle is around 7 degrees.

What Terry Gordon mentions in his video, as I recall (I have not watched it in some years), along with many others (Terry has his information largely from Brent Beach), that BU plane blades wear (as well) from the underside. This is referred to as a "wear bevel". The larger the wear bevel, the duller the blade will feel. Basically, the blade is no longer biting into the wood.

Now if you deliberately add a back bevel, it will exacerbate this situation. A 13 degree back bevel and the plane will not cut - unless you reverse the laws of the Universe. David Charlesworth's Ruler Trick is different from a formal back bevel as it is minute, around 2/3 of one degree.

There is a similar issue with BD plane blades. On a 45 degree frog (= 45 degree cutting angle), if you grind a 30 degree bevel, the relief angle is 15 degrees. If you grind a 35 degree bevel angel, the relief angle is now 10 degrees ... and getting close to the limit for clearance.

Regards from Perth

Derek

Further to your question regarding the Unicorn bevel, the answer is again "no", not the same. The Unicorn method is a m-i-n-u-t-e rounding and high increase in the angle of the bevel. You can do this with BU plane blade. You can do it with any blade. However, I do not advise it with BU planes on Australian timber.

David has demonstrated working on US timber, but Oz timber is, as you know, very interlocked. High cutting angles are needed for BU planes here, and specific angles at that. The issue I have with the Unicorn method - unless you are pretty experienced - is that it is difficult to gauge the angle you add .... that is why sharpening with BU plane blades is generally with a honing guide.

Regards from Perth

Derek

I think you should try it for yourself but I predict you will not find it a great idea. Adding a bevel to the flat side of a BU blade is not very practical for the reason Derek pointed out. Planes with 12 degree beds like the Veritas lot & the Stanley 60 & 65 1/2 (actually they're 12.5* iirc), already have only 12* of of 'relief' behind the cutting edge. My experience suggests going below 10* of relief with any wood-cutting blade is asking for increased drag & poorer cutting efficiency. You can get away with as little as 5* on a metal-cutting tool, but not with wood, you'll have poor penetration & more drag and a rather under-performing tool.

But beside this, think of the geometry. Putting back bevels on either BU or BD blades is reducing the acuteness of the edge & increasing the force required for it to penetrate the substrate. I should declare I've never been a fan of back-bevels on anything, the only time I've resorted to them is when I got sick & tired of trying to flatten a pitted or warped blade & the back-bevel seemed like an easy get-out-of-jail card ('tisn't, really, 'cos you still need a flat surface to mate with the cap-iron if it's a BD plane). As a general rule, I reckon you'll get further faster by using as acute a sharpening angle as the particular blade steel you are using will safely take. That's a matter for you to decide based on the planes you use, the blades you have, & the woods you plane.

That's my 2c, but as I said, one should always try ideas, even whacky ones, some good discoveries are made that way, even if it's just that it wasn't such a good idea....

Cheers,

Originally Posted by derekcohen

Further to your question regarding the Unicorn bevel, the answer is again "no", not the same. The Unicorn method is a m-i-n-u-t-e rounding and high increase in the angle of the bevel. You can do this with BU plane blade. You can do it with any blade. However, I do not advise it with BU planes on Australian timber.

David has demonstrated working on US timber, but Oz timber is, as you know, very interlocked. High cutting angles are needed for BU planes here, and specific angles at that. The issue I have with the Unicorn method - unless you are pretty experienced - is that it is difficult to gauge the angle you add .... that is why sharpening with BU plane blades is generally with a honing guide.

Regards from Perth

Derek

I demonstrated the unicorn with a vintage stanley blade that was underhardened on cocobolo (with silica) with specific gravity of 1.1 and on quartersawn bubinga. It's in video on YT. I later rehardened one of the stanley irons to find that stanley left a lot of hardness on the table with the early 9 1/2 and 18 irons, that the steel is probably water hardening, and that if someone wanted to reharden the irons now, they'd be as good as anything else for high hardness.

what I found when doing that was that the unicorn is worth about 5 degrees even though it's much steeper at the terminus. Testing that with a softer iron, I also found the poorly understood truth about edge durability and life - which is that the idea of adding extra hardness and alloying to a blade believing that an upgrade will lead to some huge multiple of edge life is just hiding what should've been corrected with geometry. Even soft irons can plane extremely hard wood, even with silica in it without taking damage as long as the edge is prepared in a way they can do it. Early failure on anything other than outright near unhardened irons is a matter of fixing the failure, not replacing the iron.

5 degrees simply means if you want a similar performance from a bevel up plane, unicorn on the *bevel* side on top of a medium honed edge that is 5 degrees short of where the final microbevel would have been with flat bevels. Or, if a wood is so bad that it needs 60 or 62 degrees in a single iron, then unicorn over a 55 or 57 degree medium honed angle. heavy hand on the unicorning.

If I would ever make a bevel up plane or buy a specialty smoother (I sold all of mine, they're not coming back), I would use a 20 degree bed. If there's some need for a BU for shooting a lot of boards, something is probably in order to do less shooting and everything else becomes much easier in a vise where the edge life is many times longer in feet in any wood.

also, the long wear bands that show up on a low angle BU plane don't appear at all on a 20 degree bed bevel up plane, and thus a I no longer have anything other than a single block plane bedded at 20 degrees. I could never find a long term use for bevel up bench planes, and I started early with them, and then tested with a LN 62 which was novel with the unicorn, but still inferior to a simple type 20 stanley once used comparably on the same wood mentioned above. I get that for people who have never used a plane or who use one every couple of months, having a bench plane sized block plane is simple and maybe that or the gordon types are the only things needed, but they also put a fence up to keep those folks from every getting any further.

All that said, I wouldn't add a back bevel to the face of any low angle BU plane and on bevel down, and on a 20 degree bed plane, I'd find no great reason to do it as BU planes are smoothers and not remotely close to BD planes for anything more coarse. I guess there's room to go there on a 20 degree bed, but all of he discussions about getting particular with that lead to using a bevel down plane instead because they imply someone will be spending time to get things just right and not just being as unskilled as possible getting a few passes done with a plane for fitting or something.

Correction -I went back and looked at the videos - I planed with the block plane on bubinga on the video only, and I guess cocobolo wasn't on the video. I used a low carbon buck brothers (new, hardware store) iron in a type 20 stanley plane to plane the cocobolo stick to prove that failure is addressed by geometry correction first, steel way later (or never if being practical).

I'll plane the cocobolo later today if I can remember. the results with the cheese block plane iron on bubinga were after unicorn that you would have sore hands and be wishing for a break to resharpen.

the unicorn article on wood central shows the value of buffing on difficult wood (same cocobolo piece here). It's not a matter of making the iron last, it's a matter of what that means for actually getting work done - as soon as an iron starts splitting shavings, productivity is lost and all of the clearance angles and acuteness is out the window by a factor of 10. Real productivity planing doesn't start until the iron can stay undamaged. If that's too short of an interval by edge life (it won't be) then sharpening needs to become a priority.

Sharpening seems to be one of the things that everyone loves to talk about at length and never spend literally just a half an hour adjusting what they do to make sure they're finishing it. It's universal - the shaving forums were full of people posting all kinds of problems (with a lot of confidence in their correctness) and refusing to look at the edge of their razors to address what was almost always not quickly finishing the actual razor edge while sharpening.

I would use the uni on a block plane in difficult wood for a simple reason - you can hone one angle on an iron 5 degrees less with one stone and use that stone to work the back, and then buff the edge and that's it until grinding is needed. The edge is finished and stropped in one step, the edge is stronger and the planing resistance through wood is not more than it is with a flat bevel, especially further into the wear cycle.

Hi David

I need to clarify what I wrote. I am cautious about recommending the Unicorn method to those who use BU planes who are beginners. Let them practice on chisels first. A too-high bevel on a BU plane will cause problems.

Early on, I recommended to you that block planes are good to go, but this was after I mastered chisels. You have been doing this quite some while, are very good at this method, and perhaps do not realise that it can be tricky for a novice.

Regards from Perth

Derek

Originally Posted by derekcohen

Hi David

I need to clarify what I wrote. I am cautious about recommending the Unicorn method to those who use BU planes who are beginners. Let them practice on chisels first. A too-high bevel on a BU plane will cause problems.

Early on, I recommended to you that block planes are good to go, but this was after I mastered chisels. You have been doing this quite some while, are very good at this method, and perhaps do not realise that it can be tricky for a novice.

Regards from Perth

Derek

it's tricky for a novice with a bevel down plane that has limited clearance. On a block plane, to hone one single secondary bevel and then buff heavily has the same forgiveness as chisels, and it also covers up the fact that most beginners don't finish the edge very well - with a medium cut/color buff bar, the buffer will finish the edge. On a BU plane, the unicorn has to be relatively heavy to get the +5 degree effect.

I would guess most users will never master buffing the bevel side on a bevel down plane without limiting the clearance, but that is why I never intended to put a plane iron to a buffer in the first place. Bill and Winston both pushed me to come up with a way to do it because they felt like people don't finish sharpening that well. The ability to plane through silica was an unexpected pleasant surprise, but it's probably better not to to plane wood with silica in the first place if possible. sometimes that's not possible if using a lot of mahogany or limba - both plane really easily, but destroy edges if they have silica in them.

In pleasant easy planing wood, I don't see the need for the buffer anywhere, or the advantage other than maybe very light stropping to finish an edge. No creating a unicorn profile as what wiley called the tangent buff to finish (buff both sides lightly) takes experimentation to find how little needs to be done to get the biting crispness that you get sharpening with really fine abrasives.

too much of this (we're past that) really goes over the head of beginners - but suffice it to say that the real issue is limiting clearance on the wood side of a blade with the buffer will shorten the time before clearance runs out, and you can feel it. It may still be an advantage if it limits depth, but planing a lot relies on nothing more than rotation from handle force to hold a plane down - as soon as a plane doesn't start intermittent cuts easily without bearing down on it, effort goes to sharpening before more planing.

Just about everything that can be done by hand is understood quickly if output is measured. People never do it. I took this all the way to things like shoveling dirt - things that we deem too difficult for an average person to do suddenly become pretty easy if you find the easy way to do it and the body position and movement so that everything is upright and the power comes from leaning toward or away from or pushing with a shoulder rather than arms and hands (rotating core). Leaning down on a plane beyond a trivial amount always feels like getting something for nothing, but it's getting less in return for giving more.

Since unicorn on a block plane or bevel up plane never touches the back of the iron, all of this issue about effort and clearance goes out the window. Any beginner who wishes to simplfy the honing routine can just set the edge geometry with a middle stone on the bevel side, maintain camber that way and buff without much fear of ruining anything - the buffed bit always comes off easily again with the middle stone and is gone.

Such a simple thing, but hard to understand.

Here I was thinking I'd solved an intractable problem, only to be left with even more questions

You didn't take into account something called "clearance angle", the angle between the bottom of the cutting iron and the sole of the plane. Your suggestion would make that angle so shallow, it would probably make your plane stop working. I think the video you quoted mentions clearance angle.

Give your suggestion a try and see if it in fact breaks the plane. There's nothing like trying for yourself and actually finding out.

My diagram showed both the clearance and the part that would be taken "off".

Sounds like my idea is a no-go.

I already use "the ruler trick" and it seems to work very well indeed.

It seems I'm trying to find a solution to a problem that might not be important. I really don't mind sharpening and whipping out the blade periodically to hone it back up is trivial enough The Veritas BU planes are a doodle to fit the blade back in, as nothing moves as part of the disassembly

As promised, and only as a sideshow to this thread - block plane, unicorn.

cocobolo - quartered. This is one of the densest woods that I have, but not the hardest. I also have blanks of katalox and gombeira but they're newer and not dead quartered and not as hard to plane.

This is an unlisted video only because even by my low quality standards, it's not high enough to shoot out for a couple of hundred people to see.

This is the equal (or worse) of anything anyone is actually building with and planing in australia. Specific gravity is 1.1, and it's 50 years old, so it doesn't have the softness (oiliness) and smoothness that new cocobolo has - it's dry and powdery between the latewood.

unicoco stanley - YouTube



It doesn't quite plane perfectly even at about 65 degrees effective plus unicorn. It feels like another 5 degrees and it would be good.

It also has silica in it.

Personally, I think bevel up planes are easier with one bevel and the unicorn (nothing on the back - the ruler trick is OK, but you will get to a point with it where visual wear may be hard to chase totally out.

there are no flaws in the surface that wouldn't be addressed either by very short finish sanding, or by french polish finish, which deals with surface fuzziness that doesn't rise to the level of tearout well.

separate from this, katalox and gombeira are available here in quantity, so are a lot of other mexican woods. the determination of harder woods is a little spurious because everything varies a lot and the swarzias can reach 1.2 times the density of water *dry* equilibrium and at least one of them is stiffer than one of the woods claimed to be the hardest to bend in the world.

Both plane a little more easily than this cocobolo - actually, they can plane very nicely, you just won't be taking a deep jack shaving in them.


if you're a beginner, set the first angle with a guide.

Just for giggles, I used a stanley block plane iron (stock) that's very soft compared to boutique stuff, and then one of early-mid 1900s block plane irons from stanley that I rehardened. the rehardened iron is very plain steel, but it's as hard as anything marketed, showing that stanley left a little in the tank on earlier irons.

Buffing the finished edge after only one medium stone (and no treatment on the back of the iron) is actually a little more forgiving, and it's easy - more and more buffing seems to be a better balance for a smoother as I mixed up the irons and buffed the soft one longer than the hard one (wanted to do the other way around) resulting in a steeper edge, and that one was a little sweeter through the wood even though two identical irons with one harder than the other - the harder iron always has a little more sweetness. Or put another way, the extra "more buffing" on the soft iron made it work a little better here.

Watched your vid DW. That is amazing video quality on your phone.... really amazing.

I need some metal working slippers

That demo is highly convincing. Highly!

Originally Posted by woodPixel

Watched your vid DW. That is amazing video quality on your phone.... really amazing.

I need some metal working slippers

That demo is highly convincing. Highly!

Brian Holcombe used to make videos in a really clean shop with carpet where he wore nice clothes and a robe, and he's very fit - a striking fellow. And the work quality is there in spades - it's not just a show.

I wear filthy clothes gray with metal, am fat and wear some kind of brand name slipper that escapes me right now because they keep metal splinters from going into the bottoms of my feet and when metal splinters get in them, they're soft enough that they can't push in metal splinters from the insole into my foot, and won't leave me walking around in public in my "real shoes" with metal in them. (dearfoms or dearforms or something)

I get that the presentation (both of shop and self) is half of the convincing part. I'll leave that to the people who like that stuff...I'm descended from farmers.