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| Hand plane technique question http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10102&t=13653 |
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| Author: | WaddyThomson [ Sat Sep 15, 2007 11:17 am ] |
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I joined my German Spruce that I got from BobC at the last Swap Meet, today. The one I am going to replace my Sitka top with. I have a pretty good surface on the top face, and was beginning to work it down to about 2.5mm with a plane, working the back side. I noticed that I am getting thinner toward the center of my stroke than at the ends. I am trying to get a good start, with the front edge of the plane nice and flat on the top before starting the stroke. My shavings are roughly .0015 to .0020", so I'm not taking big bites. They are not full width, but my blade is very slightly curved so the corners don't dig. I don't get it. Anyone have any thoughts as to what a "novice hand tool woodworker' does that might cause that? Or, do I need to jus work from the center out until I get the edges down and get a fairly consistent surface, the finish out with a scraper? |
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| Author: | WaddyThomson [ Sat Sep 15, 2007 2:32 pm ] |
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That's what I was trying to do. Strokes seemed smooth. Maybe the boards were thinner in the middle to start with. I just kinda didn't expect that. I'll just work from the middle out, till I even things up. This stuff planes nicely, vs that set of Sitka I was working before. Still has grain direction, but you can barely feel it. |
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| Author: | Chas Freeborn [ Sat Sep 15, 2007 2:56 pm ] |
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Does the surface you're holding the top on (benchtop, workboard, etc.) have a hump in it where the center of your top falls? If so it's telegraphing up through your top and you're planing it flat. Another possibility is that your plane sole is not flat; in your case it would be convex from toe to heel, hence a "hobby horse" cut. -C |
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| Author: | WaddyThomson [ Sat Sep 15, 2007 3:10 pm ] |
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Plane's flat. I did the lapping myself. However, I didn't think about the work surface not being perfectly flat. That's something I should check. Also make sure it isn't flexing at all under the pressure. Thanks. |
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| Author: | Martin Turner [ Sat Sep 15, 2007 7:40 pm ] |
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Waddy, Are you running a caliper over the back as you plane it? If the problem is variation in original thickness the caliper reading should show same. If the back is warping slightly that could explain the bigger bites at periphery of the back. If I dont pay attention I instinctively seem to lean on the wrong end of the plane near the peripheries and take more off. I try and have more weight on the front of the plane when starting the cut and move the weight to the back of the plane as I get to the other end of the board. Cheers Martin |
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| Author: | WaddyThomson [ Sat Sep 15, 2007 11:42 pm ] |
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[QUOTE=kiwigeo]Waddy, Are you running a caliper over the back as you plane it? If the problem is variation in original thickness the caliper reading should show same. If the back is warping slightly that could explain the bigger bites at periphery of the back. If I dont pay attention I instinctively seem to lean on the wrong end of the plane near the peripheries and take more off. I try and have more weight on the front of the plane when starting the cut and move the weight to the back of the plane as I get to the other end of the board. Cheers Martin[/QUOTE] I didn't take a caliper reading before I started, except at the edges to see what the general thickness was. I figured it was probably fairly even since it had been run through a thickness sander before I got it. That's on me. I now need to make it right. Thanks Martin. |
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| Author: | KiwiCraig [ Sat Sep 15, 2007 11:53 pm ] |
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I'm with Chas. on this one. When planing thin material it's of importance to have a perfectly flat surface .A hump in the middle of your bench will give you a hollow on your piece. I cover my flat planing area with a thick glass sheet. I cover that with poster board. |
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| Author: | WaddyThomson [ Sun Sep 16, 2007 12:28 am ] |
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It is a very good point. I have a fairly good size piece of granite counter-top. Maybe I should be using that for my planing surface. |
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| Author: | KiwiCraig [ Sun Sep 16, 2007 11:16 am ] |
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Sounds good Waddy, providing the granite is big enough (and flat enough ) Glass is the most reliably flat surface . Get a really thick piece ! Wooden bench tops , ply or whatever move around a whole lot . I use a strip of wood about two foot long and 3 or 4 inches wide ,cam clamped to the end of the glass topped bench , as a stop. For soundboards etc., that wooden strip is only about 2 m.m. thick so as to not interfere with your plane strokes. Craig Lawrence |
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