Using the Work Sharp to flatten chisel backs

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Forum topic by Purrmaster posted 10-30-2012 10:26 PM 3393 views 0 times favorited 14 replies Add to Favorites Watch
View Purrmaster's profile


915 posts in 2116 days

10-30-2012 10:26 PM

Hey there.

I got the Narex mortise chisels a day ago. The first thing to do is flatten the backs. Doing this with sandpaper on glass is a laborious and time consuming chore.

So I turned to my Work Sharp WS3000 to flatten the back of the chisel. I followed the suggested method in the manual and video. And what’s happening is that I am taking bites out of the back of the chisel. I am not getting a flat back. In fact it’s probably worse than the machining marks that the chisels came with.

I have tried using a light touch, a heavy touch, and everything in between. I’ve tried higher and lower grit discs.

I think the problem is that I can’t keep the chisel still and level. It chatters and jumps around on the glass wheel. The result is that I tend to be rounding the back of the chisel rather than flattening it.

I have tried both the left and the riight sides of the wheel for flattening. Though I believe using the left side is generally recommended.

Any ideas what I’m doing wrong? I know it’s not the tool’s fault.

14 replies so far

View David Craig's profile

David Craig

2137 posts in 3131 days

#1 posted 10-30-2012 10:35 PM

How flat is the sandpaper to the glass disc? If it is chattering, it makes me think that there might be a bump in the sandpaper somewhere. Sometimes, when you change the paper, residue from the previous disc can end up under the new one. I wipe the glass down with mineral spirits before adding a new sheet.

-- There is little that is simple when it comes to making a simple box.

View SASmith               's profile


1850 posts in 3010 days

#2 posted 10-30-2012 10:36 PM

What grit are you using to flatten the back?

-- Scott Smith, Southern Illinois

View Cosmicsniper's profile


2202 posts in 3181 days

#3 posted 10-30-2012 10:44 PM

How much of the chisel’s back are you trying to flatten?

-- jay,

View bondogaposis's profile


4755 posts in 2374 days

#4 posted 10-30-2012 11:43 PM

What grit sandpaper were you using? I’ve never needed to resort to power tools to flatten a chisel back, even cheapo Stanley Fat Max chisels.

-- Bondo Gaposis

View Robert Brown's profile

Robert Brown

151 posts in 2714 days

#5 posted 10-31-2012 12:11 AM

I have a bunch of chisels (old, new and abused), including a Narex set. I had same problem as you so I tried different methods. The one below works for me.

First I try I flattening the backs on the WS3000 with power off. Just doing it manually. If an 1/8 inch from edge gets flat, I am happy and stop there.

Some chisels would take too long to do manually. These, I would lightly hold back of chisel in position on WS3000 before I turn the power on. I can do this down to 3/8 inch wide chisel. For some reason I can not do a 1/4 this way. I have to do it manually, which ain’t too bad; being small and all.

I start with coarse to semi-coarse sandpaper and work my way up to fine. I use that rubber stick a lot to clean up the sandpaper.

Also I use the right side of the disk with the sandpaper going away from the edge. And away from me BTW. :)

It took me a little practice. The bigger the chisel, the easier it was. So maybe start with your biggest chisel.

Hope this helps or you find something else that does.

View paratrooper34's profile


915 posts in 2974 days

#6 posted 10-31-2012 12:39 AM

The problem with using a WS 3000 for the backs of mortice chisels are that the chisels are fat and that makes them somewhat top heavy when trying to flatten the backs. I found this out when flattening the backs of my mortice chisels and saw right off that they do not get the same treatment as regular bench chisels. Because they are so fat, any little movement from side to side at the top of the chisel, which may seem minute or not even felt, equals a big movement of the chisel at the area being abraded. Thus, they round over very quickly. Once I figured that out, I made sure to keep that area absolutely flat on the wheel. I do it by using a light touch.

I suggest doing the thinner ones, 3/16 and 1/8, strictly by hand as it only takes a second or two to really mess those ones up. I also suggest using finer grits on the WS 3000 until you develop some muscle memory to keep the backs flat on the wheel. With the finer paper, you don’t take off so much metal during your “learning” phase.

Lastly, I wouldn’t get too hung up on getting the entire back surface of a mortice chisel flat and polished. As long as the business end is sharp, it will do its job. You won’t use a mortice chisel like a bench chisel (i.e. for paring and such), so you really don’t need to spend the time to polish the backs.

Good Luck!

-- Mike

View Purrmaster's profile


915 posts in 2116 days

#7 posted 10-31-2012 01:02 AM

I should have said that I have been able to flatten the backs of my larger bench chisels with the Work Sharp. Because those stay in place. The mortise chisels won’t. And you are correct: The slightest wobbling of the chisels results in a lot of metal being removed. I’m trying to get a Work Sharp induced gouge out with glass and sandpaper on one of them.

I’ve used 120, 220, and 400 grits so far. I’ve jumped between grits to see if any is more cooperative than the other. I checked for bubbles. There aren’t any. I’m using a combination of Klingspor discs and Work Sharp (Norton, actually) discs.

I’m trying to flatten as much of the chisel back as I can. I read you need to do that with mortise chisels instead of the 1 inch or so for bench chisels. Though I don’t entirely understand why as I doubt I’ll need to sink a chisel inches deep into a piece of wood

View MonteCristo's profile


2099 posts in 2211 days

#8 posted 10-31-2012 04:17 AM

I don’t think a Work Sharp or similar is the way to go. Too easy to screw it up. Some things are just better done by hand.

-- Dwight - "Free legal advice available - contact Dewey, Cheetam & Howe""

View Purrmaster's profile


915 posts in 2116 days

#9 posted 10-31-2012 07:33 AM

I suspect you’re right. I’ve basically abandoned the Work Sharp for this. How much of the chisel back needs to be flat? The chisels are several inches long.

View David Craig's profile

David Craig

2137 posts in 3131 days

#10 posted 10-31-2012 08:10 AM

Flattening is most crucial where the wedge of the blade and the back meet. If you are flat for about an inch from the edge down, you should be fine. The length of the blade is more for leverage than anything.

-- There is little that is simple when it comes to making a simple box.

View Howie's profile


2656 posts in 2946 days

#11 posted 10-31-2012 01:29 PM

I agree with David Craig (and others). I only flatten about an inch to inch and a half max on any of my chisels including the mortising. I use a WS3000.

-- Life is good.

View JesseTutt's profile


854 posts in 2133 days

#12 posted 10-31-2012 02:09 PM

I don’t have any problems flattening the backs of my bench chisels with the Work Sharp 3000 (hereinafter “WS”). I have sharpened 1/2” to 1 1/4”. The package deal I got gave (sold me) enough glass disks so that I can have each grit on a separate side, so the only time to remove paper is when it is worn out.

Process I use:
1. Place the desired grit disk on the WS facing up.
2. With the WS running, lower the “back” of the chisel (closest to the handle) onto the spinning disk, with the sharp edge pointing in the direction of rotation. That is, a particular particle of grit moves from the handle side of the back to the sharp cutting edge. The other direction would have the sharp edge trying to cut the sandpaper.
3. Use a single finger to put moderate pressure on the center of the portion of the chisel on the disk.
4. Slowly slide the chisel back and forth (sideways).

-- Jesse, Saint Louis, Missouri

View Purrmaster's profile


915 posts in 2116 days

#13 posted 11-01-2012 12:43 AM

The bench chisels, at least the larger ones, seem to handle the Work Sharp okay. The mortise chisels not so much.

On the thinner mortise chisels I’m even having trouble keeping things steady with sandpaper on glass.

JesseTutt: Your technique is basically what I’ve been doing, except I haven’t moved the chisel back and forth.

View thebigvise's profile


191 posts in 2923 days

#14 posted 11-01-2012 12:52 AM

I’m with MonteCristo. I feel that lapping 3/4” of the back and honing the bevel by hand (with a jig) is the way to go. I have had good luck with Norton waterstones: 1000, 4000, and 8000.

-- Paul, Clinton, NC

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