‘Back Bevels’ expanded…

Hello again Faithful Reader,

It would seem that my previous blog post here, “Why I put a ‘back bevel’ on plane blades” has attracted a few comments, actually more than a few and certainly more than is usual.

It’s surprising, and very encouraging to see the comments, and while it might seem like there’s a little disagreement going on, actually I don’t think that’s much of the case.

So, in no particular order…

David W, yeah, I know. Folks don’t like having their heart felt beliefs challenged even when presented with overwhelming evidence. That’s ok, but what I get disappointed with is when those same people tend to push others toward their beliefs. While few people will admit to have a ‘vested interest’ in these things, the truth of the matter is that most people do have a vested interest of sorts. Having someone else take up their torch and wave it gleefully is a vindication that they’re ‘right’, which everyone naturally wants to be, that is ‘right’.

For myself, I sell these things and the way I am wired means that if I sell something, I’m not comfortable if that ‘thing’ doesn’t do exactly what I say it will, which is why someone bought it in the first place from me. Typically, I’m very conservative with what I recommend, preferring to under promise-over deliver than the other way around.

I find doing so gets me my own torch bearers!

David C, I sharpen so many things with so many different sharpening devices I tend to forget that not everyone has the confidence I do now. I agree, a prop of some kind is important and do use a thin ruler more often than not, but still just ‘wave the back’ on the stone free hand. Because the bevel on the back is so small and shallow, I find it can be erased easily even if it’s slightly ‘steep’. I have used ‘feeler tape’ which is constant thickness steel strip used as a feeler gauge, you just cut off as much as you need when you need it.

The ruler I use is a 150mm Shinwa hardened Stainless Steel one, nothing special but it’s made in China and actually too short. I’m not convinced it’s the best thing, but a small ruler is cheap and it works. No point trying to re-invent the wheel.

(I have plenty of feeler tape though, so it gets used as well. Pity it rusts just as quickly as a feeler gauge does!)

Dave from VA, I too have, in the past, used a steep back bevel to raise the effective angle of attack of a plane’s blade. I don’t tend to do so now, finding that judicious use of chip breaker, experience in reading the wood and keeping both the blade sharp and the shaving thin seems to keep me out of trouble more often than not.

Regarding Japanese blades, funny you should mention that…

I was talking with Mr. Uozumi Snr. (Tsunesaburo II) about such things. Specifically I’d asked about changing the way in which their Stanley blades were prepared to help ensure that lusted after ‘flat back’. He said he’d look into it as his little project, but got back to me that changing the method did help, it still wasn’t quite good enough and added too much complication for not enough result, so back to the old way which makes the blades quite flat, but not dead flat. I simply told him that I personally tilt the back to get that edge sharp, and showed him with a ruler how I usually do it.

That spawned into a mildly animated discussion about what’s actually going on at edge there, at the back. I’ll go into detail at another time, but basically what we agreed upon is outlined in the original blog post. The steel does get damaged by scratches, corrosion and wear. It’s completely unavoidable, and all you can do is to try and make sure that every time the blade comes off the finishing stone that it’s left behind fresh metal. Japanese chisels allow this quite easily with the back hollow. Japanese plane blades allow this through regular tapping out, allowing that ‘defective’ metal to be removed (other reasons for tapping out too), the ‘Uradashifuyoh’ blades (no tapping out) allow it by design as the back is narrow and on Western plane blades, you get it with a small back bevel which replicates the effect of ‘uradashifuyoh’.

As I said, there’s more to it than just that, but the basic premise is that maintaining a flat back and simply ‘wiping off’ the burr isn’t a great idea. You’re hamstrung with a Western chisel to some extent, but chisels are usually narrower and it’s easy to keep that steel back clean and defect free.

And now, I don’t do back bevels to change the angle. I either make a plane for the job or order up a dai to suit. I’m not a fan of using an edge that’s not ‘sharp’, and anything less acute than 30° just twists my guts into knots. Yeah, I’m being a purist!

Archie, if that small bevel was simply maintained, then yes it would soon be pitted and scratched. The idea is that that small bevel on the back is constantly being put into fresh steel. It’s not a case of a ‘quick lick’ on the back to wipe off the burr, you do need to actually take off some metal each time. I don’t know about anyone else, but when I sharpen a blade I’ll use it, touch it up once or twice on the finest stone I’m using at the time, then drop down to a ‘middle’ stone to get that face bevel into fresh steel again, which also shrinks the back bevel. When I’m not longer happy with the edge, I drop down to a #1000 stone to make sure all evidence of the previous edge is eliminated and I start again.

It’s a blade, it’s meant to be used up. It’s a fool’s errand to preserve bad steel for the sake of ‘speed in sharpening’, because steel that’s not fresh and clean won’t get as sharp and won’t stay (less) sharp as long as good steel.

It’s funny, I used to follow what the ‘experts’ said with regard to sharpening, trying to get the time actually sharpening as short as possible and get to cutting wood again. When I was actually ‘cutting wood’ trying to put food in my kid’s mouths, I ended up paying less attention to the ‘experts’ and doing what I thought was right, which was pretty much re-build the edge almost every time the blade came out of the plane.

I can’t prove anything as I didn’t take pictures, didn’t record video and didn’t write anything down but I did feel that I could keep working for a lot longer and got better results when I made a fresh edge rather than ‘touching up’ the edge. The time spent was about the same in the end I think, and I didn’t spent much time solving problems with the planes, they just worked.

That pretty much all the professional planing folk I’ve talked to here ‘re-build’ their edges quite often adds some credibility to my thoughts, but that kind of talk is way too controversial to bring up in genteel woodworking circles.

And besides, it “uses up more steel and stones. I sell them so I must want you to buy them all from me so I can get even richer!”

I hope that covers everything, and because there’s a 2 week limit of comments here, this might allow the discussion to carry on without being cut off.

Thank you all for the comments and for reading. I can only hope that someone learns something new.

Stu.