I’m fairly new to wookworking. Is there some simple test to determine if a plane iron is acceptably sharp. I realize it may depend on the use, the wood etc. and that the true test is how it performs for you. But without putting the plane back together can a simple test be performed. I am suspicious of the hair on the arm test. Last night I flattened the back of a plane iron methodically using a flat granite slab and wet/dry grits from 220 up to 2500. I got a good mirror finish and then turned it over and ground a 30 degree bevel with 220 wet/dry. Without going any further than 220 I could shave the hair off my arm. But I am quite sure that this blade is not going to be considered sharp by very many wookworkers. Is there some other test or is 220 all you really need? I then went from 220 directly to 2500 for a micro bevel without using intermediate grits and it seemed to be somewhat sharper.
A related question. With a 30 degree bevel and a slight micro bevel I probably had a 32 or 33 degree bevel. What is an appropriate general purpose bevel? This was a #5 Jack Plane I think. What about a 9 inch smoother and a stanlely block plane?
Frank
Edited 1/21/2005 3:07 pm ET by Frank
Replies
There are tons of posts, articles, and books on this issue if you care to look. But if you take it to 2500 grit sandpaper on both sides it will be definitely be sharp "enough."
shaves your hair it will certainly shave wood
Wicked Decent Woodworks
Rochester NH
" If the women dont find you handsome, they should at least find you handy........yessa!"
I learnt sharpening (and hand planing) just a few years back and it changed my woodworking. One thing I have come to realize since is that "repeatability" is important. It is useful to use techniques for sharpening, and a level of sharpening, that are efficient from a time point of view. Else, sharpening is such a big deal that one is tempted to push a not-so-sharp edge, just to delay having to sharpen.
I think you've discovered just how important it is to flatten the back. Both surfaces on the iron must meet, and both must be sharpened, just like a double-beveled knife blade. Taking the microbevel through all the grits should result in a blade that's sharper still. The rep at the Lie-Nielsen booth at woodworking shows can take a hair off his arm without TOUCHING THE SKIN..! Is that necessary? Well, it seems to reduce tearout when smoothing, otherwise, I really don't think so. It's a cool endeavor, though, huh? Just how sharp IS sharp anyway?
Charlie
Hmm..
I spent a few hours today with blades and Nortons water stones. Put nice "sharp" edges on several plane blades and chisels.
An hour later I got a 1/2" long splinter in the side of my thumb. I found a razor knife blade and tried to cut it out as it was getting buried each time my thumb moved. Razor barley scrathed my skin. I then grabbed a fresh chisel and it cut the thick skin like butter and I got the spinter out. That's sharp!
To answer your question you have to strike a balance between degree of bevel and type of wood and your own habits to determine this. I used to put beautiful egdes on my mortising chisels-about 30ยบ as I recall. I would roll this back with ease after slamming it in some oak with a heavy mallet. Not good. Of course I could shave with it but it was not the right kind of sharp.
I've since been investing in Japanese chisels and these seem to fit my methods and materials. I can get a great sharp edge that lasts. And that is the key.
If your using sand paper get as fine as you can for the final grit. I used to go, depending on starting condition of the blade-180-220-320-600-1200-1500. Wet and dry. The finer grits are available from auto body supply stores. When I found 1500 I found a new level of sharp.
HTH
Notrix
I would be wary of any test because a test is not necessary. If the edge is sharpened properly then you can not see any light reflecting off of it. Look at a edge after your first grit of sharpening and see how the light reflects off of the cutting edge. What you are aiming for is a point and not a blunt edge. Smoothers, Jacks and block planes will all generally have the same bevels and micro bevels. Bevel down planes are all the same only there length and width make them different. I sharpen mine at a 25* angle on the grinder add about a 2* bevel to that and about a 2* micro bevel to that. That is what Lie-Nielsen recommends to do. I sharpen to 8000 grit on Norton waterstones. I don't know what a related grit in sandpaper is but I think that I read somewhere that 2000 equals 8000 grit waterstones. Good luck and if you want to really know how to sharpen then buy Rob Cosmans Sharpening techniques at Lie-Nielsen. Peter
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