Hand Tools

Re: Questions on sole flattening

Jack Dover
Let me skip (1) for now. Also, we're talking about flatness only, right? No other issues like twisted sole, non-squareness, etc.

2. Related, if a novice planer is using an unacceptably unflat plane what would they experience that would tell them they need to flatten it?

The primary indication would be inability to set it it for a fine shaving (for a certain definition of "fine"). The iron will protrude as indicated by a sliver test, an eye, etc, still it won't shave at all. A user will give more iron, then some more, then suddenly it will engage and produce a thicker shaving. Depending on how non-flat a sole is, it might still be useable, or it might require too much force to push it.

3. If an experineced planer is using an unacceptably unflat plane what would they experience that would tell them they need to flatten it?

I think that pretty much the above. Any other potential issues can be mitigated with a particular planing technique.

4. How do you flatten a plane on sandpaper glued to something flat without overcutting the leading or trailing edges?

Given that we don't need machinist level of flatness tolerance, there's maybe a couple of things to keep an eye on.

It seems that the common consensus that lapping surface should be sufficiently long so that a plane doesn't go over the edge. Which is kinda makes sense: parts that don't touch abrasive aren't abraded, so there's a risk to lap a concavity.

The second one is the more pressure applied to a particular area the more material is abraded (to a point, I guess). So either don't apply any downward pressure at all, or flip the plane end-to-end frequently, like, every minute or so. Being mindful about pressure all the time is also a good idea.

And as we do it with every operation where a setup doesn't guarantee an outcome - check often. Cross-hatch with a sharpie, a good steel ruler and some inexpensive feeler gauges will give you a good idea where you're going with the process. Check out David's W. recent video, he constantly monitors progress while flattening a plane that's notorious for being a pain to lap.

Just in case you're wondering where this comes from: a few months back I've mailed a Stanley #4 clone to my friend. It was a nice specimen: no rust whatsoever, just some dust, very nice price. The plane was functional, I just sharpened and it produced quite a decent shaving. Didn't measure the actual thickness, but I would be totally satisfied with it when I was just starting. Bet you would be happy with it too. Shavings didn't float in the air though and attempts at setting it finer was like described. Wasn't the first time I have observed this btw. So long story short, this guy is into machining, so he has surface plates and knows the relevant parts way better than me. For a number of reasons he has scraped the sole and we observed a very noticeable change in performance. Like, it was performing at least as good as my other planes and I would dare to say even better than some, on par with premium planes. After toying for a bit he has polished out frosting from the sole, again, carefully. Apparently lapping tends to remove more material closer edges, but it seems it doesn't matter up to a certain point.

Now let me read other responses.

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