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Normally, I flatten my planes with adhesive sandpaper stuck to a sheet of glass. This has worked for my planes up to a #5. Now I have a #7 joiner that is taking forever to flatten. There is a low spot right around the throat and if I use the plane in my shooting board, the edge it creates is concave. I can't joint backs and tops with it.

The problem with sanding the bottom is that you don't sand away low spots. You have to sand away all of the rest of the plane sole and bring it down to the low spot. I'm making less and less progress and my arm and shoulders are aching.

What do you all do to flatten the sole of a #7 joiner? I've considered sending it out to a machine shop to be milled but I don't know any machinists or even how to find one in my area. I recall reading somewhere that the flatten their large planes on a large belt sander. Has anyone here tried that?

I have flattened planes on a belt sander. Make sure that the platen is flat on the belt sander. The blade assembly needs to be installed but retracted. You need to be aware of how hot things get. Heat may cause some distortion. (And, don't run dust collection which might pull sparks where you don't want them.) You can tell by the scratch pattern when you've hit all the spots. The belt sander gets the plane close to flat. Now, you can finish up on the sandpaper and glass. If you sand in a different direction or in circles, the scratch pattern will show when you're done.

Mike,

I can do it for you. Send me a message (or give me a call!) and we can talk it through.

There are lots of ways to do it- sanding, milling, grinding. I prefer hand scraping as the final surface. It can be done to right around .0002 or so (depending on the accuracy of your surface plate), it looks beautiful when fresh, and the wear is obvious as it gets worn in (not that there should be much on a wood plane).

Is it a little over the top? Maybe- I had flattened a beam to act as a straight edge years ago and used it occasionally to join tops (with PSA sandpaper) when the grain wouldn't cooperate with planing. I did it as best I could against my truest surface at the time and it still took a while to get the joint perfect when in use. A few months ago I scraped in a proper cast iron straight edge and the difference is very apparent. A few swipes and done, over and over.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

Burton,

I'm not familiar with hand scaping cast iron. What tool(s) and procedure do you use? (I have a machinist's 24"x18"x3" thk granite surface plate that is certified for less than .0005" across the whole surface.)

Ed

Ed,

The simplest tool looks kind of like a chisel but is sharpened with a slight negative rake and the end is slightly rounded. You use that to "push" the metal out of the way in very small increments. The marking is done with a non-drying pigment spread very thin on a surface plate and the work is spotted by rubbing it lightly over the ink. You scrape the high spots.

In essence it is very simple. single flat surfaces are the easiest. It takes some elbow grease doing it manually but once in practice it isn't that bad for small-ish surfaces. They do make powered scrapers which help A LOT in getting close.

Its proper application is in aligning machine tool bearing ways. The finished surface is a collection of high spots which acts as a flat surface. For bearing ways the depressions hold much more oil than 2 ground surfaces could and aids greatly in keeping them lubricated.

_________________
Burton
http://www.legeytinstruments.com
Brookline, MA.

Actually it's not necessay to flatten the entire sole of the Plane. It's much quicker to remove the areas that need it. If you apply the same concepts as that used for the sole of a Japanese wooden plane it works perfectly well on metal Planes. The one to avoid is the hollow just ahead of the blade, that's the one that really affects the function of the Plane.

Here's how metal scraping works.

https://www.youtube.com/watch?v=LkdkouWiDFs

Kevin Looker

_________________
I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

Thanks, Burton and Kevin. I know very little about metal working (or wood working for that matter) and your help is appreciated.

Burton,

I have used my granite surface plate with sandpaper to joint wooden plates and it works well. It sounds like you have done the same. I did not fully understand if you were saying you have had problems doing so. Or were you just saying you were having occasional problems using a plane due to some wood's grain lines?

Ed