Hand Tools

Re: Questions on sole flattening

Steve D, CT
This should be a non-controversial thread... :b

I think context matters in evaluating flatness. I don't bother flattening my #5 scrubs as long as they work. For a smoother taking very fine shavings I would try to get as flat as possible. Peak performance in any plane would be at perfect flatness and would decline from peak as flatness varies from perfect. How far off perfectly flat would determine the maximum level of performance. If a 1/32 cut is being taken then a lapped sole is overkill.

The bench planes I worry about are smoothing and jointing planes. A jointer used for flattening isn't as critical because there are other planes following its use but for edge jointing I would want flat.

For question 2, a novice would flatten their plane about 5 minutes after Googling "handplane."

I find that the benefit of a very flat plane comes when taking a very light cut, which most closely cuts the board to match the plane sole. The round sole 101s and compass planes will try to make surfaces matching their contours. If a sole is twisted, arched or bellied the plane will be happiest creating the opposite shape on the work.

Also, when the plane doesn't match the work the cut will be interrupted by the mismatch. Again, for rough work it doesn't matter so much.

I sharpened up an ebay plane and started testing it. I put the whole plane on a board face and turned the adjuster until I could feel the blade start to cut. Because of the balance of the plane that means the plane is resting on the area behind the blade.

When I went to start a cut and registered front end of the plane on the end of the work the cut was much heavier. Backing off the cut would cause the shaving to stop as the back end of the plane was used to register the cut.

That's a pretty extreme example but this plane was obviously used a ton. The ends of the corrugations show heavy wear from abrasive bits exiting the grooves and you can see the typical angle of push that the user had. Smaller differences in performance would be seen with less severe sole deviations but there is a diminishing return from increasing the flatness.

In your example of removing material from the midsection while protecting the ends, I would arrange my abrasive to only contact the middle until the sole is almost flat. That could be using 8" of paper on a 15" plane or turning the body of the plane so the ends overhang the sandpaper. Checking often is key so an ugly gouge is avoided.

To keep from making a flattening session a rounding session I first do a single pass on the last paper on my sandpaper stone to see the wear pattern. Depending on the amount of material coming off I would choose the initial paper. For really coarse work I have found cutting sanding belts and gluing to a substrate works well. IMO, using a finer grit for more stroke will not give the same result as a coarser one for fewer. I also will use the whole sandpaper, overhanging the edges through the session. As sandpaper loses grit it changes thickness so only using the middle of the paper creates an abrasive bowl shape that transfers to the plane.

I also press the plane down in the center, avoiding the sides so I don't unconsciously bias one side.

If you use a new LN or LV plane, that would demonstrate the capability of a high flatness plane. The cuts are very consistent end to end on a board. Wonky planes are more variable and fussy. Thats not to say vintage planes are fussy but can explain why a vintage plane doesn't keep up with its stablemates.

There are methods I see online that make me cringe. For that reason I shy away from "restored" planes although my plane buying days should be long past.

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