Flattening Bench Tools

[Jeff Zens]

How do you flatten your tool backs? Glass? Granite counter tops? In this blog post (http://wp.me/pmJHd-9z) I offer some thoughts (and urge some caution) about your choice, and offer suggestions that might save you some anguish and wasted effort.

[bridger berdel]

I use whatever seems right for the situation. I have started with hammer and anvil (ala tapping out a japanese blade), I have used a file on softer cutters, I have used an angle die grinder with a sandpaper disk and transfer color from a reference plate, I have used sandpaper on a flat surface, but I usually finish off with diamond stones then hard arkansas.

Bridger

[David Weaver]

Why not copy whatever your advice is into SMC so people can read it without being redirected to a different site?

The commentary about granite countertop scrap and how flat it may or may not be has been hashed out here many times before.

[Aaron Rappaport]

Bridger,

Have you ever tapped out a western blade? I'd never thought of it until I read your post just now. Might be just the thing for the frequent and annoying situation where one corner of the back, at the blade's edge, is low. I've always handled those situations by (1) lots of elbow grease and grumbling, often followed by (2) cutting the edge back to get around the bad spot.

Tapping sounds like it could be a better way. I once read on a japanese woodworking forum about "reverse" tapping out, where a piece of soft metal was placed against a high spot on the hard back and then tapped on with a hammer, so as to push the high spot in without shattering the brittle metal of the back. (Hope that's clear!)

[David Weaver]

I'm not bridger, but if you have enough soft backing metal and take it slow, you risk only cracking the blade - it's worth a shot. One of my books (i think) says that a hammer tapout method might mean several thousand taps (on the bevel) and none touching the cutting steel, obviously, or it will crack off. Most older western planes should be soft enough that they're a little more forgiving than a super hard white steel iron, though they do have a little bit to a lot less backing metal supporting the inlaid hard bit.

[Jessica Pierce-LaRose]

I can't comment on tapping out; but when I've had blades where an annoying bit on the corner or front edge isn't lapping out (and I'm sure that the surface I'm lapping with is true - I checked my granite piece when I got it a machinists edge and feeler gauges) I've taken a handheld grinding wheel and put a bit of a hollow in the center of the blade. Not much, but it makes the lapping go faster. This is also very, very helpful when you have a blade with a bit of a "belly" to the back - that blade may rock, and just like jointing an edge with a "hump" in it, it's easy to just make things worse if you aren't careful. Just enough grinding to get a couple of points resting on the lapping surface makes the piece much more stable and the lapping process work great. Garret Hack details this method in one of his books, which is where I picked it up.

[Aaron Rappaport]

For fun once, rather than lapping the back of a beater chisel I first put a series of 1/8" cylindrical grooves in its back using my 6" high speed grinder. Some trigonometry shows that these should be less than 0.001" deep. Then I lapped. The grooves went away really quickly from near the sharp end, suggesting that this is a good way to safely take a thousandth of an inch off the back of a blade at a time. I haven't tried it on any more valuable blades, partly because the residual grooves will wreck the blades resale value! More recently, as I've ground away (literally) hand lapping, I've wondered about the time-resale value trade off.

[Jessica Pierce-LaRose]

I should add that I grind very little, and tend to go back and forth between the grinding and lapping - seems to be safest way to not go too far. I stay away from the cutting edge and sides. I used one of those little 2-3" mounted grinding wheels you can use in a drill or a foredom type handpiece.

[Chris Vandiver]

Bridger,

Have you ever tapped out a western blade? I'd never thought of it until I read your post just now. Might be just the thing for the frequent and annoying situation where one corner of the back, at the blade's edge, is low. I've always handled those situations by (1) lots of elbow grease and grumbling, often followed by (2) cutting the edge back to get around the bad spot.

Tapping sounds like it could be a better way. I once read on a japanese woodworking forum about "reverse" tapping out, where a piece of soft metal was placed against a high spot on the hard back and then tapped on with a hammer, so as to push the high spot in without shattering the brittle metal of the back. (Hope that's clear!)

You can certainly tap out a vintage laminated western iron. There isn't much difference between those and a laminated Japanese iron, structurally. Tapping out is really just cold forging. If you try and tap out a solid tool steel blade(non-laminated) that has been hardened, you'll just end up breaking it.

[george wilson]

I most certainly agree,Chris. If you have a Western blade that can stand being hammered on,it is too soft to be a decent blade. I wouldn't even consider tapping any of my Western blades flat!!!!

[Aaron Rappaport]

I most certainly agree,Chris. If you have a Western blade that can stand being hammered on,it is too soft to be a decent blade. I wouldn't even consider tapping any of my Western blades flat!!!!

Wait, the Japanese woodworking list postings I referred to lead to my idea of tapping on a piece of soft metal (lead or tin) placed on top of the hard metal of the western blade, not tapping directly on the hard metal itself. The purpose of the soft metal being to take the place of the soft metal laminated to the very hard metal of a Japanese blade.

As we all know, users of Japanese tools tap on the soft metal part of the laminate routinely in order to remove a little bit of the hollow from the back of the blade. What was surprising in the list postings I referred to above (but can't find just now), it appears that some users of Japanese tools place soft metal over the *hard* metal side of their blades and tap on said soft metal to *intentionally create more hollow*, i.e. to intentionally create more low area on the backs of their blades. In that case, the hard metal is protected from hammer both by the soft metal placed between them, AND by the soft metal laminated to its other (non-hammer) side.

The question is whether this will work with the somewhat softer hard metal of a western blade, but with only the placed soft metal to absorb shock, i.e. without the laminated soft metal on the side of the blade away from the hammer blows.

[David Weaver]

I think you're taking chances if you do it, but you might learn something.

There is a forge weld between the wrought iron on a japanese plane and the hardened steel (hagane). That may be of significance in terms of how much protection there is. There is definitely significance that when you bend the wrought iron above a spot in a japanese tool, each time you strike the same spot, it is working the exact same spot on the hagane. The jigane bends because you've deformed it and the hagane has no choice but to move with it because it is bonded. If you strike a loose piece of soft metal that's not welded to the hardened metal, you might not achieve anything other than denting the soft metal.



That said, even if you place a soft metal on top, it has to be better than subjecting the hardened metal to direct hammer strikes.

Even though tapping out is a common procedure in japanese plane irons, from what I've seen, that doesn't seem to suggest that there aren't serious failures (cracks) even when the technique appears to be applied correctly. Those cracks are to be followed with a lot of grinding to remove the damaged thickness.

You can just pitch the iron if that happens and get another one.

[george wilson]

Unless the Western blade is WELDED to softer metal,and the hard steel is fairly thin,you will break the hard steel anyway. The welded aspect is VERY important. Do this at your own risk,but I guarantee you'll break any DECENTLY hard piece of steel if you hit it hard enough to bend it.

[Chris Vandiver]

Wait, the Japanese woodworking list postings I referred to lead to my idea of tapping on a piece of soft metal (lead or tin) placed on top of the hard metal of the western blade, not tapping directly on the hard metal itself. The purpose of the soft metal being to take the place of the soft metal laminated to the very hard metal of a Japanese blade.

As we all know, users of Japanese tools tap on the soft metal part of the laminate routinely in order to remove a little bit of the hollow from the back of the blade. What was surprising in the list postings I referred to above (but can't find just now), it appears that some users of Japanese tools place soft metal over the *hard* metal side of their blades and tap on said soft metal to *intentionally create more hollow*, i.e. to intentionally create more low area on the backs of their blades. In that case, the hard metal is protected from hammer both by the soft metal placed between them, AND by the soft metal laminated to its other (non-hammer) side.

The question is whether this will work with the somewhat softer hard metal of a western blade, but with only the placed soft metal to absorb shock, i.e. without the laminated soft metal on the side of the blade away from the hammer blows.

I have worked with Japanese blades for quite a long time and I've worked side by side with many a Japanese carpenter and I have never seen or heard of the technique you try to describe. But I guess if you have seen it on the Internet, it must be true.:) Still, in answer to your original question, it is possible to tap out a western laminated iron by tapping on the soft iron back of the blade(bevel). You can in effect, re-shape the blade. It is something that you have to be very careful doing and you run the risk of chipping, cracking or even breaking the blade. Definitely a skillful endeavor.

[Aaron Rappaport]

I have worked with Japanese blades for quite a long time and I've worked side by side with many a Japanese carpenter and I have never seen or heard of the technique you try to describe. But I guess if you have seen it on the Internet, it must be true.:)

Well, I don't THINK my leg got pulled. The technique was described on the now-moribund Japanese Woodworking List, by someone who (who I can't remember) who seemed credible, presumably because they'd made many previous credible posts. I wish I could locate the post!

It was described as highly non-standard and non-routine, but successfully executed.

[bridger berdel]

I have tapped out an old western blade with a very thick wrought iron body and a pretty massive inlaid edge. a really nice blade, actually. most of the shaping done woth the cold forge was to the wrought part, but the hard part moved a little. it's been a couple of years now and not a lot of use but some and the blade is holding up well.

Bridger

[bridger berdel]

tonight I flattened a blade that had a pretty convex back. first I hit it quick on the hard arkansas stone to show up the high spots. then I used an air die grinder fitted with a small sanding disk to hog out the high spot. just a quick wipe, and stay away from the edge. then back to the stone, rinse and repeat until the shiny flat from the HA stone is getting close to the width of the blade. then go to a coarse stone and achieve a consistent scratch pattern removing all of the sanding disk marks. progress through the grits with stones till done.

this is very fast and if you don't get wild with the disk it's pretty predictable and safe.

Bridger

[Aaron Rappaport]

That is GREAT to hear! What abrasive, grit #, rpm, and disk diameter were you using?

[george wilson]

By Western type blade,I meant solid tool steel blades. The laminated old fashioned ones are a different story. Should have read more carefully.

[bridger berdel]

the die grinder says 20000 rpm. 2" disk, looks like 80 or 100 grit.


That is GREAT to hear! What abrasive, grit #, rpm, and disk diameter were you using?