Hand Tools Archive

A novel method for flattening plane bottoms..

David Weaver
..on larger planes that aren't practical to lap, or on mild steel planes that are very resistant to abrasive lapping.

I apologize if some folks don't like an imgur link, it's just easily (practical) for me to sequence pictures in it and provide comments about what i'm doing. outside of what's described in this (I don't get ad revenue or any incentive for using this site, by the way - not directing traffic to it - I don't know if it's possible for people to get anything from the site, but like youtube, I don't care - I don't do ads).

At any rate, in the middle of my plane building blitz, I built two infills after building 3 before, and got to buying older infills. I like the norris a13 pattern, as well as spiers. I've since sold several of the infills that I bought as patterns, but I paid the moon for this plane because they're not common and when it showed up, it was very worn and very out of flat. Fine for heavy panel work, but not good at getting to a try planed surface and doing finish work or making a very flat surface for subsequent smoothing quickly.

It was so far out of flat that I sat it aside. At lunch, I decided to fix it today. I've used this method many times, and just didn't address this sooner out of laziness.

Some planes are too out of flat to lap into flatness with the appropriate low effort that I prefer, and when I was making my last two infills, I realized that in order to move to the last tiny bit of impractical perfection that you need to go to to match an LN plane, I needed to figure out how to match them or better them in flatness. I suspect most planes are flatter than their 1 1/2 thousandth spec by a wide margin. I have a 1.2 thousandth feeler and that is my goal - within reason - as shown at the end of this progression- the very heel was very high and never did get filed in this progression to any significant amount and once it was within about 2 thousandths, I stopped. The rest of the sole passes the 1.2 thousandth test straight off of the file.


The beauty of this process is it requires no machine tools. Just marking fluid, a lap (that must be very flat as it's the reference), a good straight edge (I have two starretts that I bought new), a feeler, a file ($8 black max imported simonds is my preference - they're flexible and cut faster than anything else short of a vixen) and some 80 grit paper for the lap.

Lapping something like this would be huge labor, the result would be less accurate, at a higher cost (it would spoil a lot of the psa paper), and for a mild steel infill, generally not possible - especially at the level of accuracy.

Filing took half an hour, and I didn't sweat. This is a feel thing, much like dimensioning wood. Learning to feel what's fast cutting for the file and what's not, and avoiding problems by not doing anything that isn't necessary.

The edge at the end is literally 80 grit sandpaper to initially prepare the file and a turkish oilstone (the ones written about in holtzapffel but almost never found). prep time after the 80 grit sandpaper was pretty much the same as a single sharpening session, so future refinement can occur in use.....

.....or I can legitimately sell this plane to someone who will use it without knowing they'll never enjoy using it.

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