Thread: Hand Plane fettlers should read this

Is it possible that what you are seeing is not the result of the body of the plane flexing but merely you putting selective pressure on one part or another resulting in an uneven lapping?
Cheers,
Jim

Michael, according to Newton, you would be twisting the plane body a bit, but the millimicron amount would be most unlikely to be measureble by the comparatively crude method of a try-plate & dye. My first guess is that your 'twisted grip' is applying a little more pressure to one side, and amplifying dye deposition in the highlighted areas. The differences you are highlighting must be in the thousandths to sub-thousandths range, & I suspect this would settle as you proceed & approaach closer to a flat sole. So hopefully, your previously scraped soles will all be pretty true, but I suggest it is precisely the reason that lapping on abrasives almost never gives a truly flat sole, because you constanly rock the body ever so slightly when lapping, & this is exacerbated by a higher grip........

Well, tht's my take, anyways, and besides, even if those soles of yours aren't flat to molecular-distance tolerances, they sure feel good enough for anything I would want to throw at 'em!

Cheers,

Jim beat me to it!

Originally Posted by jimbur

Is it possible that what you are seeing is not the result of the body of the plane flexing but merely you putting selective pressure on one part or another resulting in an uneven lapping?
Cheers,
Jim

I am not lapping. What you are seeing there is different spotting by twisting the body of the plane when I put it down on a granite surface plate.

Originally Posted by IanW

Michael, according to Newton, you would be twisting the plane body a bit, but the millimicron amount would be most unlikely to be measureble by the comparatively crude method of a try-plate & dye. My first guess is that your 'twisted grip' is applying a little more pressure to one side, and amplifying dye deposition in the highlighted areas. The differences you are highlighting must be in the thousandths to sub-thousandths range, & I suspect this would settle as you proceed & approaach closer to a flat sole. So hopefully, your previously scraped soles will all be pretty true, but I suggest it is precisely the reason that lapping on abrasives almost never gives a truly flat sole, because you constanly rock the body ever so slightly when lapping, & this is exacerbated by a higher grip........

Well, tht's my take, anyways, and besides, even if those soles of yours aren't flat to molecular-distance tolerances, they sure feel good enough for anything I would want to throw at 'em!

Cheers,

You're missing the point Ian, I am not making a comment about how I spot before scraping, nor am I worried that my scraped planes are not flat. What I am showing is that I can twist the sole and I use my surface plate to demonstrate the point. This shows up as the two spottings in pic 2 and 3. What I am doing is supporting Paul Sellers statement with visual evidence. I am not saying that this is the total reason why lapping sucks, I agree with what you say about rocking. All I am trying to do by this post is show the photos that support that the plane sole can be twisted vis a vis' Paul Sellers point.
Edit. In photo 1, which is a true spotting there is spotting on both sides of the heel and toe. In pic 2 and 3 there is spotting on both sides of the toe and heel respectively, while the other end has only one side spotted. It is only possible to do this by holding a twist in the sole..

To say it another way, the relaxed spotting pic 1, you could pick four points, toe left and right and heel left and right. It is not possible to make only three of those spots touch the dye and not the fourth as in pic 2 and 3 without twisting the plane. I am not saying it is a great twist (and it does not stay btw) the spotting returns to normal when relaxed) nor I think is Paul. But if it happens a bit, it will add to the uneven wear when lapping which will then make rocking even easier...

You might also conclude that if it is pretty easy with hand pressure to twist the body of a metal plan a few thou, then ordinary or hard use could have it moving around like a trampoline - at a very low scale.

My question then would be ... is it all that important to worry about the flatness of the sole to such an extent (other than as an exercise)?

It might also explain the performance expected from infill planes - I'm guessing they have a larger heft and rigidity.

And what about the woodies?

Cheers,
Paul

Originally Posted by pmcgee

You might also conclude that if it is pretty easy with hand pressure to twist the body of a metal plan a few thou, then ordinary or hard use could have it moving around like a trampoline - at a very low scale.

My question then would be ... is it all that important to worry about the flatness of the sole to such an extent (other than as an exercise)?

It might also explain the performance expected from infill planes - I'm guessing they have a larger heft and rigidity.

And what about the woodies?

Cheers,
Paul

I haven't quantified the level of twist but it is most certainly pretty small (a rebate plane like a #10 1/2 is even more flexible) and I think the flex is likely mostly to occur through the shoulders at the line of the mouth. I think it is small enough to be meaningless when planing and anyhow you, er well I, don't have a death grip on the plane when planing. But with lapping it is cumulative. I don't know about woodies and infills. I didn't want to associate the act of planing with anything I'm talking about in this post however.

Originally Posted by mic-d

I am not lapping. What you are seeing there is different spotting by twisting the body of the plane when I put it down on a granite surface plate.

thanks for the clarification Mic.

Since we rarely go don to thousandths when working wood, just how significant is this perceived problem? How much time did Malouf, Krenov or Nakashima put into getting their planes perfectly flat? I'm no metal machinist and hardly a woodworker, just a part-time rust collector but I am interested in just how flat does flat have to be?

Cheerio,
Virg.

PS Paul Sellers then puts what to me is almost a mild splay on the edges of his plane. How does this effect flatness?

Originally Posted by Virgil

Since we rarely go don to thousandths when working wood, just how significant is this perceived problem? How much time did Malouf, Krenov or Nakashima put into getting their planes perfectly flat? I'm no metal machinist and hardly a woodworker, just a part-time rust collector but I am interested in just how flat does flat have to be?

Cheerio,
Virg.

PS Paul Sellers then puts what to me is almost a mild splay on the edges of his plane. How does this effect flatness?

Hi Virg, this may sound short, but I don't want this thread to become a discussion about plane flatness, it's been done to death on here before and I've said a fair bit about what I think if you want to do a search. This thread is about answering the question, 'can you twist a plane as Paul Sellers says in that video?' that's it. 'Cause, can't stop others telling you what they think

That small bevel Paul puts on the perimeter of his plane does nothing to upset the 'flatness' It would still bear on the majority of the rest of the sole...

If people were really really interested in quantifiable differences in the deflection//twist of the different types of planes in use (ie wood/infill/stanley etc.) I could be convinced to test it with the laser interferometer (it's good to 0.00001mm or 0.0004 thou). I doubt the usefulness of such tests but it might be interesting and or surprising to have the data.

Originally Posted by Brobdingnagian

If people were really really interested in quantifiable differences in the deflection//twist of the different types of planes in use (ie wood/infill/stanley etc.) I could be convinced to test it with the laser interferometer (it's good to 0.00001mm or 0.0004 thou). I doubt the usefulness of such tests but it might be interesting and or surprising to have the data.

Well I will express an interest! I'd like to see how much hand pressure can twist a plane body, and if it is an amount measureable by less sophisticated means . I know Michael says it can, according to the dye distribution method, but I have my private doubts that it is really measuring twist in the body, and not reflecting the way pressure is applied. If your gear has that sort of sensitivity, and you can rig up a suitable test bed, it ought to be able to put the matter beyond doubt. Be nice if your setup can measure the trorque applied as well as the deflection of the plane body.......

cheers,

Originally Posted by IanW

Well I will express an interest! I'd like to see how much hand pressure can twist a plane body, and if it is an amount measureable by less sophisticated means . I know Michael says it can, according to the dye distribution method, but I have my private doubts that it is really measuring twist in the body, and not reflecting the way pressure is applied. If your gear has that sort of sensitivity, and you can rig up a suitable test bed, it ought to be able to put the matter beyond doubt. Be nice if your setup can measure the trorque applied as well as the deflection of the plane body.......

cheers,

You bloody skeptic!!
I'd be interested in seeing results from the laser interferometer too.

me too lol