Hand Tools

Subject:
Re: Questions on sole flattening

Robert Hazelwood
#4: By keeping consistent pressure as you lap. If you alternate pressure during your stroke, which is natural, it will tend create additional convexity, especially if it was convex to begin with.

I try to concentrate pressure on the center of the plane, or around the mouth. I don't hold the knob when lapping, but put my front hand over the frog area. Rear hand on tote but careful not to apply downward pressure, only forward. And for the most part I only do strokes in one direction, going forward. Lift and repeat, etc. Going back and forth rapidly like a lot of people do makes it difficult avoid shifting the weight between the front and back ends.

You can also check with a straightedge as you work. If you start to notice convexity, you can spot-remove material in the center (with small sanding block, file, scraper, etc.). Same for twist. It's kind of like flattening a board with a plane - you can't just scrub it blindly and expect to make it perfectly flat. You have to pay attention to what's going on, figure out where the high spots are and attack those, and avoid the low spots, etc.

You have to use fresh paper in a coarse enough grit or you will never get anywhere, lose composure, and start scrubbing wildly. I would not lap for more than 5 minutes without changing the paper; it probably cuts an order of magnitude faster during the first minute of use than the fifth. Changing the paper and cleaning the lap is a pain, but very worth it. This might be the most important tip I can give- the difference in a 1 hour job vs. a 10 hour job. And I figure the quicker it goes, the less likely to mess up the geometry.

Ideally the lap is much longer than your plane. Something like David Weaver's 4' glass shelf lap let's you take long controlled strokes without having to alter pressure, and will remove a lot of material with fresh paper. If your lap is shorter than you will have to check your work more often, and consider doing spot removal. My surface plate is 18" long and works well for a #4, and I've done a 5-1/2c on it. I also do a 22" wooden try plane on it, but it would not be sufficient for lapping a #7 or 8. You could only use it to locate twist and high spots, then flip the plane over and spot remove. Lap a little at the end to even the surface finish.

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