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Post by sainty on Jun 15, 2008 8:34:05 GMT
Posted by jay on Today at 1:58am
oh were it that simple. Key to the convex problem is to note that the heel follows in the cut (let's stick to planing edges, it gets worse with faces) and the cutting iron follows the mouth. Cutting depth is not constant, but follows an arc whose aspect is defined by the angle described by mouth and heel. I'd try to explain more fully, but frankly it makes my head go pop; that's a job for someone with a maths GCSE. I suspect segments (line and circle) are significant.
The upshot is that planing your straight piece of timber would result in a minutely convex piece with the right hand side slightly shallower then the left.
I think even for my theory based solution, it's probably a step too far. The difference in the projection of the blade due to the tipping of the sole of the plane during the stroke is so small as to be negligible. I've just tried to draw it and its too difficult to represent on a diagram. On a No6 plane, the blade to heel dimension is about 300mm and the blade projection is about 0.01mm on a fine shaving. I would be surprised if the reduction of the planing depth reduced significantly enough to change that depth from 0.01mm As to what you do with a convex piece of timber i think we are all saying the same thing - you do whatever you can to make it a concave piece of timber and start from there. ;D rgds Sainty |
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Post by Scrit on Jun 15, 2008 19:16:55 GMT
So what we need are planes with dovetail slide, like a felder surfacer, behind the mouth so the rear sole moves down with the blade. Stanley did make a #72 chamfer plane which coul be made to work that way.......... Scrit |
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Post by tusses on Jun 15, 2008 22:20:56 GMT
what you need is the blade to be like a potato peeler. The shaving will go through the blade and back down under the heel giving the perfect size shim to keep the plane bed parallel to the cut line regardless of cutting depth  in theory obviously ! |
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mikeb
New Member
Posts: 14
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Post by mikeb on Jun 16, 2008 7:18:09 GMT
Scrit - do you mean this one...??  cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=180249786579&ssPageName=STRK:MEWA:IT&ih=008Personally, I've often thought that this is the only real way to make a plane work properly; although obviously the traditional style body is easier to manufacture. If, as has already been posted earlier, one end of a bench plane is effectively "floating", why does everyone keep banging on about the importance of a dead flat sole?? Surely, if the plane is only slightly out of flat (not twisted obviously!) it should not make much difference... Mike |
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Post by mrgrimsdale on Jun 16, 2008 7:57:26 GMT
snip If, as has already been posted earlier, one end of a bench plane is effectively "floating", why does everyone keep banging on about the importance of a dead flat sole?? Surely, if the plane is only slightly out of flat (not twisted obviously!) it should not make much difference... Mike Just another popular woodworking myth. You need to have the lip in front of the blade firmly down on to the wood surface, which means concave is not good, but otherwise things are less critical IMHO cheers Jacob |
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in theory obviously ! 
