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17th July 2013, 07:39 PM #1
Width of paper/stone (accidental back bevel)
I'm in the process of giving all of my pitted and rusty old chisels a really good lapping with sandpaper on glass. The paper is wider than the length of the blades and I'm finding that on a new sheet of paper or using a longer chisel on paper worn down by a shorter one that the tip can sometimes bog down on the less worn bit of paper towards the end of a push stroke. So far, at the end of the 120 grit stage (progressing at 40-60-80), only one chisel has developed a small but deep back bevel at the tip, but I'll grind that off later.
While I'm not having any real trouble so far, would it be better to cut my paper a little thinner than the length of the blades so the tip fully crosses over the far edge? Or is it not going to be that much of a problem as I progress to the higher grits as long as I concentrate on not putting pressure on the tips and working from longest chisel to shortest?
Edit: Oh yeah, I'm rotating the glass/paper a few times during its use to try and keep it levelish.Every time you make a typo, the errorists win.
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18th July 2013, 02:34 AM #2GOLD MEMBER
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Interesting puzzle. The tools must be in very poor condition (rust pits?) to need such coarse grits. I don't recall starting with anything rougher than 400 or so.
I'm an advocate for pull strokes only. I color the bevels with a black felt marker so that I can see exactly where the metal is coming off. That has also taught me to compensate for applying too much pressure on the right side (bevel down). Otherwise, all my chisels would be skews by now.
Next, I do only enough at each grit stage to see the chisel face cleaned off. Little 10X magnifier shows me that I'm often willing to stop just before I really should.
My current set up is a piece of stone countertop long enough and just wide enough for 3 x 1/2 sheets of sandpaper. Masking tape just at one end seems OK for my style. Angle diagram card to keep me consistent.
My spokeshave blades are 28 degrees and about 55mm wide. Those and anything smaller seem to come up just fine.
Any of this help at all?
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18th July 2013, 03:18 AM #3
Yeh, they're pretty knackered. Most of them are my dads's old ones (45+ years at least). Trojan, Micky and Stanleys and they certainly haven't been looked after, although I have seen much worse.
I got them functional a while ago and I know I could do just the end inch or two but I figure that while I'm out of action in the shed and have the time I might as well give them all a really good clean up.
I've been using half sheets lightly sprayed with contact adhesive on a slightly larger piece of glass mounted on MDF so that I can use the paper from the front and back with baby oil as the lubricant (coz it's cheap for such a big job). It's seemed to have worked ok so far.
When I'm lapping at such low grits I use push/pull with a little pressure across the whole back of the blade and make sure I'm keeping it level with the teeniest tiniest amount of upwards pressure on the handle. Instead of a marker, when I'm finishing up on a grit I give about 7/8 of the chisel one or two very light horizontal strokes across well worn paper so that when I have removed those lines with the next grit I know that I'm ready to move up again after a few more passes for good measure.
This one chisel I've made a back bevel on is an anomaly from all the times I've used this method before. I must have stuffed something up early on with bad pressure and/or digging the tip in...maybe from a too deep a push stroke and gone into the bevel leading into the shaft. But it, and a Lie Nielson vid on sharpening, got me thinking about the width of the paper as a factor.Every time you make a typo, the errorists win.
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18th July 2013, 06:57 AM #4GOLD MEMBER
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Well, if you make the back bevel the same as the front bevel with a total included angle of 20 degrees = you have just created your own carver's stop chisel.
Hindsight tells me that I fumbled around quite a bit with the whole sharpening scenario. Eventually, I found ways and means to get a consistent & satisfactory result. Regular, European-style carving tools are straightforward. I now have 9 crooked knives and they are a major challenge. Four of them are listed as Haida-style carving knife blades in the Lee Valley Catalog.
All I have of my Dad's tools is a single 1/4" (6mm) chisel. Long story.
I have a few of my Grandfather's tools: pair of dividers and a folding ruler come to mind as I use them with carving. He was a boat builder, no idea where all the rest of his things went.
Good luck with the old things.
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