Sharpening Help

[Edward Clarke]

I'm new to sharpening hand tools and I've run into trouble on my very first attempt. I have an old second hand set of mifer "chrome vanadium" chisels that I am practicing on. It looks like the prior owner tried to flatten the back of the chisels with a stone or something that was not flat...

I've spent several hours (!) trying to get the back of the 25mm chisel flat and I'm at the point where taking a bench grinder to remove the last 1/8 inch of the chisel is looking quite attractive. I'm using Norton water stones and a DMT Dia-Flat to flatten the stones. At this time I have not been able to get the back flat enough to continue on to the 1000/4000 stone that's next in the series.

What cuts faster than a Norton 220 grit waterstone? I need to get the back flat before I can actually start to sharpen anything. Will those DMT dia-sharp stones do the trick? At least the coarsest one? I think there's a store that carries them near here.:mad:

[Curt Putnam]

I'd probably just use sandpaper. Start with 80 grit and work up to about 150 or 220. Mount on granite if you have it, if glass then use it, if not then MDF. Nothing wrong with buying a coarse stone except for the cost. I'd want to be sure your technique was correct before spending a lot of money.

[David Paulsen]

I only use old used chisels. (berg chisels as I'm from Denmark) So I usually always have to use a lot of time in flattening the back. But it has gotten heaps easier as I now use dmt stones instead of water stones, and I don't have to worry (that much) about flatness, as the diamonds are truly flat. It's defeating work having to both flatten a chisel back, and a water stone at the same time.
It can still take quite a while though. And if it the iron is really bad, I have used sandpaper on granite, glass or mdf. The sandpaper seems a lot quicker and can get you closer to where you want to be. If you still got a millimeter or so left from the edge... Grind it off and go back to living a carefree life. Perfectly unperfect, as this rare earth is. It's summer, finally in Denmark now.

[David Paulsen]

Ahh, Curt beat me to it...

[Andrae Covington]

..."chrome vanadium" chisels ... I've spent several hours (!) trying to get the back of the 25mm chisel flat ... Will those DMT dia-sharp stones do the trick?

This is exactly how I stripped many of the diamonds out of my extra-coarse DMT stone, trying to flatten the backs of a set of Narex chisels, which are chrome manganese.:( These chrome-whatever steels seem to be very tough and durable, which is great for holding an edge, but require more time and effort in sharpening. I was, at the time, a doe-eyed member of the flat earth society, so I was really trying to flatten the back of the chisel. Eventually I settled for about 1/16" or whatever I could get right at the edge. Curt's sandpaper on granite suggestion is worth considering for this task.


...I'm at the point where taking a bench grinder to remove the last 1/8 inch of the chisel is looking quite attractive...

This sounds like the chisel is "bellied"... the toe, near the edge, is rounded up from the rest of the back? That is the worst. Personally I wouldn't completely rule out the option of grinding back, if the rest of the back of the chisel is pretty flat.

[jamie shard]

+1 on sandpaper. It really is the least maddening way.

[Steve Friedman]

Agree 100% with Curt's advice. Just be careful because it's easy to dub the edge of a blade on sandpaper. I like 3M Gold PSA sandpaper because it has very thin backing and a very thin layer of adhesive. The less "give" in the paper, the less likely you are to dub the edges.

Andrae's caution about a bellied back is important. Use a straightedge to see if the back is convex at all. Removing a belly by hand is extremely difficult because there is lots of steel to remove and you are essentially trying to balance the chisel on a hump. Therefore, if there is belly, you have (IMHO) two choices, as Andrae suggested. One is to avoid having any of the belly touch the abrasive and just flatten a very thin strip along the edge. The back won't be flat, but you'll be able to sharpen the chisel. The other is to use a grinder (or some other powered abrasive) to grind away the belly. It's virtually impossible to do this and get a flat back, so you actually want to end up with a little concave area where the belly was. From there, you should be able to flatten by hand, leaving the concave section untouched. If you use the chisel enough (as in long enough to wear it away), the concave area will disappear.

Steve

[David Paulsen]

And if all else fails you can do it the modern way... use the steel ruler trick, and create a "back bevel". I have not personally had to do this yet, and I hope the day never comes where I am defeated to succumb to such clever tricks. I like the wrestle.

[Jessica Pierce-LaRose]

On wider tools where flattening becomes a bear, I've had success using a grinder (a small grindstone chucked in an electric drill is great for this) to hollow out part of the back - particularly to combat a bellied back by making a slightly concave portion (like a poor-man's version of a japanese chisel) to get make consistent flattening easier, and partly to remove material quicker to speed up the flattening process. I tend to go back and forth between the grinder and lapping on a coarse abrasive sheet. Lap a bit, figure out where the high spots are, grind them a bit, and go back to lapping - back and forth until you get there. Stay away from the edge and the sides while grinding. When done, you may end up with a few heavier scratches, but keeping them farther back from the cutting edge and they aren't a real issue. The tools I've done this on, the grinding marks are light enough they become honed away with repeated sharpenings. This method was suggested by Garret Hack in one of his books.

I've mentioned this here a couple of times before:

http://www.sawmillcreek.org/showthread.php?188224-When-to-Replace-Plane-Iron&p=1945429#post1945429

http://www.sawmillcreek.org/showthread.php?169415-Getting-a-handle-on-sharpening-stones&p=1743439#post1743439
(there's a link in that post to a Google Books page which may let you preview the page in question)

[Winton Applegate]

Yah back flattening can be a death march. Especially with the modern wear resistant alloys. Whew !
It might be worth a glance at how the Japanese deal with the problem. They produce a hollow along the whole back of the chisel and leave just a thin boarder to flatten.
http://www.google.com/search?q=japanese+chisel+hollow+back&safe=off&client=safari&rls=en&tbm=isch&tbo=u&source=univ&sa=X&ei=RPaWUcTqIofJyQGfwIHwBw&ved=0CDsQsAQ&biw=1289&bih=621
The diamond plates are nice to have but I put some serious wear on mine trying to flatten the older Lie-Nielsen plane blade backs. The LN blades of the last few years are sooo much better ! Thank you LN.
I don't seem to have stripped the diamond grit off the plates luckily but not near as aggressive as when new.

The 80 grit paper on a flat surface is good advice. The purple or blue abrasive is really sharp and longer wearing than say the gray/black wet or dry paper.

What is better cutting than a Norton 220 ?
I was going to say just about anything that comes to mind including toilet paper and downy bird feathers.
I must have got a lemon Norton 220. Mine is super soft in that it wears away very rapidly and just turns to like little gritty ball bearings. Doesn't do do do as far as abrading blade backs.
My Shapton 120 though is just right. A really well made stone. I am not saying it is going to be better for back flattening than the 80 grit paper though.
I use the 120 primarily for changing the primary bevel on my blades. I can here the power grinder crowd shifting around in their chairs. You are right. Just grind it.
Finally I may have missed it but I am thinking the ruler trick and chisels don't mix. Did you mean when sharpening plane blades only ?

[Winton Applegate]

Oops,
Sorry Joshua. We were typing and thinking alike at the same time.

[Jim Koepke]

Finally I may have missed it but I am thinking the ruler trick and chisels don't mix.

My thought also.

jtk

[David Paulsen]

Ofcourse you are right, the ruler trick would not be neat for a chisel. Must get some sleep.

[Noah Wagener]

what areas are being touched by the stone? When i first started restoring blades i would start out on a extra course dmt dia sharp stone. when it looked like the back was being touched by the stone across the full width i'd move on to 1000 grit water stone. the middle of the backs of the blade would polish quickly but the sides were not touched leaving the scratches from the diamond stone. i thought i must have been rocking the blade somehow on the diamond stone and made the back convex. I d go back to diamond stone and concentrate on just pressuring the center of the back.
In my naivety it never dawned on me to check the stone. Turns out the stone was dished. Not from use but came that way as i had the above problem of removing more metal from the sides of the backs of blades. You could rock a straight edge on a hump on the non abrasive side of the plate. They gave me a new one at Woodcraft and the guy checked it with a straight edge and assured me it was flat. I did not want to ask to check myself in case he might have felt insulted. Sure enough this thing was same shape. But as you have the dia flat maybe it is not an issue. I find it interesting that they label it dia "flat" as if this is the prominent feature that is not availible on previous models. The error is compounded when you are putting a hump on chipbreakers and trying to match them with humped backs of blades. Not a pleasant way to enter into woodworking. I just assumed it was flat.

Sigma makes a 240 grit stone which i imagine is real fast. I just got their 1000 grit stone from Veritas and it cuts much faster than the brand new extra coarse diamond stone i got in the above exchange. Loose silicon carbide may work faster and you dont have to worry about adhesive. i imagine based on the situation you described you would go through lots of paper which would entail scraping glue each time. In my experience that wet dry paper that gets recommended loses effectiveness after about five strokes. I think i've read someone even suggesting silica sand for rapid grinding. They use it in sandblasting so it must have some abrading properties. Too bad there are no public ashtrays anymore or you could try it for free.

Some people above mentioned that Japanese woodworkers tap a hollow in their blades. Maybe you could tap it flat? In Handplanes for Woodworkers by Scott Wynn he explains how to tap blades hollow with pictures.

bon chance

[Jim Matthews]

Have a look at Paul Seller's sharpening method. It works for me.

If the back has a hollow, you v
can get progressively long flat runs, and still have a chisel that will register at two points.

The longer the flat, the closer those two points will be.

If the chisel has a convex arc, it could be a struggle to get ONE flat as opposed to several facets. I would not expend my shop time in that effort, when a fresh set of the Narex chisels are readily available for short money.

I use silicon carbide sandpaper (wet-dry) stuck to a sink cut out of granite. I use 3m spray 77 to hold the sheets down.

[Charlie Stanford]

Sandpaper, as others have said. I cut it and lay it atop an oilstone so that I don't impart a greater or lesser degree of flatness than the chisel will see when backed off on a day-to-day basis. This is most important. You will be incredibly frustrated if you flatten to a higher degree than your stones and then start to hone them daily and realize the stones themselves are having their say about the backs, which of course is inevitable over time.

Here's how flat the backs need to be, it's simple and often vastly over-complicated and overwrought to what end I am not sure: when backed off on your finishing stone the burr is flipped back to the beveled side. If the burr doesn't flip immediately, in one or two swipes, then the back is not as flat as the stone upon which it is being worked. Unless you are working on an obviously out of flat stone, being able to move the burr back to the front is all you need to worry about. If you work on stones that need comparatively constant maintenance to maintain a workable level of flatness then you have another layer of slight complication you will have to address. It's not a deal killer, but it has to be considered.

P.S. I call the beveled side the 'front' and the flat side the 'back' if this wasn't already clear.

[Edward Clarke]

I would not expend my shop time in that effort, when a fresh set of the Narex chisels are readily available for short money.

Actually, this whole chisel set is being used to learn how to sharpen without screwing up my good sets of chisels. I have a set of the Blue Spruce paring chisels and another of the bench chisels. They're expensive, beautiful and I had to wait nearly a year to get the bench set. As in learning to drive, use an old VW Rabbit rather than a new Porsche 911.

After looking at the original 25mm chisel with a magnifier, I can only conclude that someone used it to pry with and bent up the end. I've ground it back to the flat area and am going to reshape the end completely. Yes, the chisel is now an eighth inch shorter, but it IS flat. I'll add a 25 degree bevel with the grinder and then continue on to the next grit on the back.

I would have had to remove a lot of steel to save that little bit of length.

[Jim Matthews]

Sorry, I skipped over the reference to practicing in your original post.

I wonder if you're right about the prying: if the chisel was inserted with the flat facing up,
and it was rocked downward - the bending moment would be in the middle.

Since I can't really abrade more than a few ten thousandths (what ever the grit size of the abrading material might be)
on a flat substrate, you might have an impossible task at hand.

Did you hold a straight edge to the chisel back?
If you can see light, or worse yet, get a feeler gauge under the low spots it may be a job for machine tooling.

You won't need any of that with the Blue spruce stuff.
It's dead flat, on the back.