Flattening chisel backs...I'm going to go crazy!

[Shawn Swafford]

Does anyone have a good method for flattening chisel backs? I have tried coarse waterstones and 220 grit wet dry paper on a cast iron top. I can get it pretty close but there is always some light under my straight edge. I'm only trying to get the last 1 1/2" flat. Any suggestions??

[Mark Singer]

I would not go coarser than 1000 grit. Just hold it flat and go back and forth with med pressure. Also a circular motion is often good. After 1000 at least go to 4000. Then hone the bevel.

[Michael Campbell]

Does anyone have a good method for flattening chisel backs? I have tried coarse waterstones and 220 grit wet dry paper on a cast iron top. I can get it pretty close but there is always some light under my straight edge. I'm only trying to get the last 1 1/2" flat. Any suggestions??

Well... at the risk of sounding like a heretic, I don't do it. Call it a character flaw, but like a plane iron I put on a teensy "back bevel". The rest of the backs are straight /enough/ for indexing, and only the tip 1/256" of it is actually used for cutting.

So, what I do is scary-sharp the back, but I have it raised on a round toothpick, so only that last cutting-edge section actually touches the abrasive.

The downside of this is that I need to do it whenever I put a new hollow grind on it, whereas if you flatten the "whole" back, you only do it once. But, it only takes less than a minute, so I consider that an ok tradeoff.

Your mileage may vary of course, but this works for me.

[Jerry Crawford]

I'm with Mr. Campbell. Why go to all the trouble to flatten more than an inch or so. I do have chisels that I've flattened for 4 or 5 inches but they were flea market pickups I was rehabbing and to get a good edge I had to take soem of the pits out of the back. For an inexpensive but absolutly flat surface I've had good luck using a piece of window or plate glass under some wet/dry emry paper.

[Dennis McDonaugh]

I am lazy. If its going to take more than...oh three minutes to flatten the back of a chisel, I take it over to the belt sander and give it a few seconds to take off the high spots. Then I use 220 and 320 sand paper before using water stones.

[Bob Smalser]

http://pic3.picturetrail.com/VOL12/1104763/3302197/40506079.jpg

I don't put any secondary bevels on the back of chisels...with the belt sander, there is no need to. Complicates things.

[Joel Moskowitz]

All you need to do is flatten the cutting edge - an 1/8" or so is plenty. Incidently Western style chisels were intentially make with very slightly hollow backs so it is easy to flatten the cutting edge but really annoying to try to flatten the entire back. Also so far every time anyone has showed me a chisel or plane blade with a totally "flat" back I discover it is actually convex at the cutting edge. (on waterstones the build-up of slurry makes this happen)

[Shawn Swafford]

Thanks for all the replies. I now have them as flat as they need to be :) .

Shawn

[Alan Turner]

I hate to disagree with such experienced knuckledraggers, but . . .

My view is that even a tiny micro bevel on the back of a chisel or a block plane blade is bad since that lack of flatness makes the chisel want to move forward, towards the bevel side, in a chopping or paring type of action. But, only 1" or less needs to be perfectly flat. I start with 100 grit SC paper on granite till flat, and then am able to move up the grits to an 8000 waterstone pretty quickly, although it sometimes takes awhile on the 100 grit depending upon condition.

[Dennis McDonaugh]

I agree with you Alan, but only if the microbevel is narrow. When you flatten only an inch or so near the tip, you have, in effect a very wide microbevel. I think you can get the same effect by placing something very thin under the blade while flattening the back. Only an area within an inch or so of the tip comes in contact with the abrasive. It has minimal affect on paring operations in my experience.

[Steve Wargo]

Flat is flat, and square is square. In order to achieve a uniform edge the back of the chisel needs to be prefectly flat along the cutting edge. With a micro bevel it will cause the chisel to creep. I know it sounds dumb, but are you sure your straight edge is true? I built an entire piece using a guilt edge square that was off, and couldn't figure out my all of my joints were gapped slightly. Stick with it, the backs should be flat.

[Michael Perata]

I am lazy. If its going to take more than...oh three minutes to flatten the back of a chisel, I take it over to the belt sander and give it a few seconds to take off the high spots. Then I use 220 and 320 sand paper before using water stones.

I was with Dennis on using a belt sander to flatten chisel/plane backs.

But - now I have a Wood Artistry Lap-Sharp and I can take a chisel back from manufacturing marks to 1 micron in about 10 minutes. (I once did the entire back of a Stanley 16-911 2" chisel in 15 minutes!)

[Rick Hoppe]

I agree with Joel. I don’t think he’s talking about actually putting a back-bevel on the chisel.

I don't polish the whole back OR make a back-bevel. Once I’ve flattened the back with a coarse stone, I’ll switch to my 5000 stone. Holding the chisel perpendicular to the length of the stone, I’ll put about the first ¼ inch of the chisel’s back on the edge of the stone. Putting firm thumb pressure on the edge, I’ll move the chisel side to side. After about 10 or 20 strokes, I’ll slowly move more of the blade onto the stone for about 15 more strokes. I’ll do the same with my 8000 grit stone.

Looking at the back of the blade what you see is a shiny edge that gradually feathers off toward the handle.

[Joel Moskowitz]

Rick - exactly right - a back bevel on a chisel would compromise performance.