Flattening Plane Bottoms and Advice on Functionality

(Take me to the short version)

This is a popular topic on forums. For a plane, and let’s assume we’re talking about stanley planes because the decent versions are practically impossible to improve on functionally, there aren’t very many things that need to be right. But before we move on, if you want to check these basic things every time you have a plane that seemingly doesn’t work as well as others:

• Check to make sure the iron is sharp. If needed, resharpen and see if you can shave hair off of your arm with the iron both bevel up and bevel down. Sharpness and lack of a false edge or burr fragment will do this.
• Confirm that you have cutting clearance with the iron. If needed, hone with a medium stone and a guide at 33 degrees or so until a burr is raised and then go over the same angle or a degree or two steeper with the finest media you have thoroughly without lifting (this is a dead common issue on planes and irons I’ve examined – it’s sneaky because the iron may still look good)
• Check that all screws on a plane are tight and that the handle and the knob cannot physically be separated from the casting. You can have a very sneaky issue with planes where the front screw on a rear handle (if there is one) holds the handle tight (to the eye) against the casting, but in use, the handle lifts/vibrates with lack of firmness. this is a torturous thing to not notice, but relatively common as handles continue to shrink with age (fast at first, but they never really stop) and everything looks good but the thread on the metal stem does not allow complete tightening. A mechanical fix is needed for the rod and boss in the handle to apply very firm downward pressure

Those are probably the three that are most common that aren’t related to flatness. Everyone mentions the first, but the other two are not as visually obvious and can drive you crazy. After all, with the third bullet point, you turn the screw, it’s tight and won’t go any further, but you can’t see that it’s just fully seated in the casting and the boss at the top of the handle isn’t actually applying pressure. I like to fix this one with small washers – you can reduce thread length by shortening the bolt, but do it a thread or two at a time and not “i’ll just grind a while” and find out that the thread quality in the casting isn’t so great and is only tight at the bottom – which you can suddenly not reach.

OK, but What About Flatness

Raffo – note the tangent, it’s avoidable for some, seemingly not for me.

For everyone else, the items above are related to flatness, because flatness isn’t immediately easy to see. Clearance issues are easy to feel with experience, so are flatness issues. The little handle trick is harder to see and easier to just test by fixing rather than some other way.

Flatness of the variety of several thousandths at the toe and heel, where both are low and a feeler would go under the middle is not easy to measure, but it’s a real pain. If the error goes the opposite direction and there’s no twist, you will never notice it – as in, if you put two thin feelers under the toe and heel and the mouth still touched a flat surface, no problem.

Even if you can measure things, there’s mental trap here with this whole slightly hollow in the length idea, and I’ve gotten a lot of flack for actually measuring what matters and reporting. Why? You can push the plane down only moderately hard and push all of the “bad” flex out – if the heel and toe touch only on a machinists reference surface, it’s probably not more than 10 pounds to get the center of the plane to touch. You will not be doing this in use, though, and when you plane, the toe and heel won’t always be on the work. You’ll never plane a fine flat surface with a plane like this perhaps other than once for show if you can win a bet doing it.

However, this seems to be common. I can’t say “90% of planes will be ____”, but I can say that of lower wear planes, especially later, I have seen a lot of planes with the low toe and heel, but the amount low is small. I think this is an artifact of stanley’s manufacturing. I’m not a machinist, so I’ll leave it to them to say why, but I did finally see a machinist this week mention that if the last passes aren’t fine, low toe and heel will remain. Too bad the bias wasn’t the other way around, we’d never notice it.

So, What does this Mean for You?

I have addressed flattening planes functionally in videos and maybe on here before. I rely on a 1.5 thousandth feeler and a starrett straight edge. I haven’t got a great idea of how you would be able to check things reasonably well with a lesser straight edge because a 3 thousandth error over 2 feet is below the spec of a lot of steel straight edges. Starrett’s spec is something bonkers – like 2 ten thousandths per foot.

Doing this by hand is different than with a surface grinder, though. You only need to do what counts. If I refer to plane probably needing 2 or 5 thousandths or whatever it is removed, I am not measuring in the last tiny fraction of the toe and heel. I just don’t care whether or not the last bit where there can be a big fall off is addressed. It’s possible that a beat up toe or heel could be multiples of the error.

This apparently creates controversy, because I’m not the only person talking about these things. I’m measuring with a starrett and only checked feelers. My smaller straight edge has some mile and has been cleaned up a couple of times, but I have another that’s mostly unused to check it against. This is what a toolmaker would have. To get a 24″ starrett for someone who doesn’t care about this stuff is a bit of a push as it’s over $100 at this point. That’s a trivial expense to me, but I wouldn’t spend $100 for sandpaper for a $1000 project. We all have our priorities.

With all of this in mind, you have to decide what camp you’re in, because there are two that are definitely false camps: 1) the machinist who says nobody can make a plane flat by hand. This is a false statement, and perhaps a victim of society’s inability to properly use terms that mean probably vs. definitely. 2) that you can just lap every plane flat with a defective polished tombstone. maybe you can do it with many, but you can’t do it with all.

So, my camp is simple. I will always do this by hand. it’s extremely uncommon for it to take longer than 1 1/2 hours, and sometimes it’s 10 minutes. Neither of those is longer than waiting to get a plane back, and the cost (close to zero, just the cost of sandpaper and maybe some wear on a file) is less than what it would cost to ship a plane one way. Your camp may be sending the plane off to be machined even if you could do it by hand – because you want to. Or because you don’t know at all and you don’t want to. Either of those is fine.

But try to avoid becoming someone who lowers the discussion level by repeating something you’re told and declaring that it’s universally true. I have been told more than once that a plane that I flatten won’t be flat. There are never any questions about what I’m observing to declare a plane flat, because someone who has concluded that is engaging in mental laziness – the conclusion occurs before the discussion.

I will admit when someone says they just started woodworking and they’re lapping all of their planes, I squint a little bit, too. It’s probably better to wait a little bit so you know what to expect performance wise.

And what’s that? that if you have a known flat surface, you have a plane that will plane that surface and make a continuous shaving from end to end without clipping ends off, and when you switch planes around, each will continue the efforts of the prior without any time spent planing the wood to the shape of the plane sole.

Why this is controversial – and it seems to be – is beyond me. If you’re going to do a significant volume of work and you have to take four shavings depth across a large panel for every panel after a try plane just to get a smoother or jack-set-as-smoother shaving to be continuous, only to find that the surface is convex……well, that’s not realistic. It’s just one more small way to figure out who says they do most of their work by hand, but doesn’t.

Back to What this Means for You

Here’s my advice – don’t assume you’ll do a perfect job flattening your first plane if you want to do that. And if you do, take it slow and have a good reference straight edge. I’ll stay out of going all the way back through what counts in this case, but keep in mind even small errors (like dirt on a bench top under a glass lap) will throw you off. Check often, do no more than you have to.

If you want to get a plane ground because you just don’t want to do any of this, by all means, go for it. Just don’t believe it’s the only option. If there is a menu of solutions and they all work, then pick one and don’t worry about it – worry about how to learn to use the plane so well you would trust it in all work and use it for pleasure.

Premium Planes will Guarantee Success?

No, but they will increase your odds of having to do nothing.

I’ve only had about four LV planes, and I didn’t keep any of them long enough to get to knowing how accurate they were.

I have had ten Lie Nielsen planes – half new and half not. Two out of 10 were hollow just under 2 thousandths. They would not create a flat or slightly sprung joint. The first, I was afraid to fix ( a LN 8 bought new ) and the second ( an LN 62 that I bought testing the unicorn ) I just fixed. Same error in height, but shorter plane and more consequence to it. I would plane a surface flat to the starrett and the 62 couldn’t touch the center of it if it had any length at all. No bueno.

I’m not encouraging you to modify premium planes. At this point, I have no qualms. I knew I wouldn’t keep that plane, but I also knew that even in an anonymous ebay listing I could explain what I did to improve it clearly enough that it would sell easily. It did. On a straight auction, it brought far more than new price.

I sold the 8 much earlier disclosing why I was selling it. it also had no problem selling as stock. Maybe someone didn’t believe that it would matter. By the amount of use on the used LN’s I’ve bought, it probably wouldn’t. I couldn’t match plane a cabinet side joint with the plane and not have the ends separated, though, and that should be doable without ever having to check the joint in the first place.

lastly, I have from time to time gotten a stanley plane that’s so worn or beaten that I won’t flatten it. It’s bad enough that I don’t think I would bother sending it to be ground, either. Who wants a stanley plane with .03″ (not .003″) of material removed. I don’t. That’s the nature of buying older planes. Most days, you get a big mac. Some days, you’re eating fine chocolate right out of the box, and some days, you’re eating with the dung beetles.