Sharpening - dealing with the wire edge.

[John C Cox]

Hey guys.

I would appreciate some tips for dealing with the wire edge when sharpening.

I got a set of Aldi chisels.... So far so good - except they take a hideous and persistent wire edge when sharpening. That's aggravating - because the wire edge can peel off on the work - leaving a chipped chisel or a dull spot....

Thanks

[Pete Taran]

Sounds like so far not so good. A wire edge when sharpening at coarse grits is normal, but should disappear when moving to finer grits. If you have edge failure while using your chisel, one of two things is happening. Either your sharpening angle is too small (like 20 degrees and using that chisel for mortising) or the steel is of dubious quality, or possibly both. I've been watching for the Aldi chisels at our local store, but they have never come in stock. Not that I need new chisels by any means, but just to check out the quality and test the hardness. They have not appeared here in NeOH. Sounds like they would make good chisels for beating in a tool box, but not cabinetry work.

[Jim Koepke]

It is often said once the back of a blade is flattened it will never need to be worked on again. Well, that is wrong. The back needs to be worked to get rid of the wire edge or the burr as some call it. There are many ways this is done. For me, it is done on the next stone. Some folks do not worry about it until the finishing or polishing stone. To me it seems better to get it off at each step.

My routine if the edge is rather worn is to start with a 1000 or 2000 grit stone then the wire edge is removed on a 4000 stone by pulling the back of of the blade on the stone. If the wire persists, then the bevel is pulled on the stone. This is repeated as needed alternating from back to bevel.

After the finishing stone, 8000 in my case, any burr or wire edge is worked on the 8000 stone or on a strop.

A few blades will hang on to the wire. In that case a few test cuts on a piece of scrap will usually take care of it.

This is pretty much the same if instead of water stones you are using oilstones.

My blades are made up of an eclectic accumulation from many makers. All the different steels do not act the same. A few of my blades seem like they could be stropped for an hour and there would still be those little pieces of metal trailing behind. It looks like small pieces of foil stuck to the edge.

jtk

[John C Cox]

Honestly - these Aldi chisels are performing better than my brand new Pfeil chisel - which cost 4.5x more for 1 chisel than the entire set of Aldi chisels. I am not happy with the Pfeil so far - as the edge keeps rolling on spruce!

[Rob Luter]

I work the back as Jim suggests above. As a final step I drag the edge through the end grain of a soft pine board. It strips any wire edge off. It's a tip I picked up in an issue of Fine Woodworking.

[Patrick Chase]

Sounds like so far not so good. A wire edge when sharpening at coarse grits is normal, but should disappear when moving to finer grits. If you have edge failure while using your chisel, one of two things is happening. Either your sharpening angle is too small (like 20 degrees and using that chisel for mortising) or the steel is of dubious quality, or possibly both. I've been watching for the Aldi chisels at our local store, but they have never come in stock. Not that I need new chisels by any means, but just to check out the quality and test the hardness. They have not appeared here in NeOH. Sounds like they would make good chisels for beating in a tool box, but not cabinetry work.

Another possibility is that he didn't spend enough time on his polisher (i.e. at the fine grits).

To the OP: Can you see or feel the wire edge in the sharpened chisel, or are you inferring its presence from the subsequent chipping?

If the former then you need to spend more time working the chisel on fine stones. If the latter then look to Pete's suggestions.

[Prashun Patel]

If you are getting a prominent wire edge at the higher grits (5000-8000) I am jealous. It's hard to see and feel at those grits. Achieving it means you are properly honing to the edge. Removing should almost always be easy by swiping the back on the highest grit once or twice, then inspecting the front and possibly going once on that side.

[John C Cox]

Sharpening setup:

worksharp electric unit. I am sharpening at 25-27 degrees of thereabouts... It is typically a bit higher angle than the original factory bevel grinds on my chisels.

Nearly everything I am doing is "paring".. Basically zero mortising. I haven't hit a chisel with a hammer or mallet in a couple years.

The wire develops visibly at the lower grits (220 and 400) when grinding out chips.
As I move up the grits - I can still see the wire edge, though it gets progressively finer.
When I rub the edge across my thumbnail after the micromesh grit - I can see the "edge" appearing to shift over.... This is the wire...

If I use the chisel at this point - it will roll the wire edge visibly...

Throughout the sharpening process - I give the back a go on my Extra-fine Diamond stone to ensure the burr doesn't roll over the back.

I am giving it a sideways run through soft wood (spruce or pine) and can see some of it come off... Not always all of it.

I typically then strop the bevel and touch up the back on my diamond stone... And repeat this as I work to keep it cutting well..

[Rob Luter]

Do you know the type of steel the chisels are made from? Years ago I had a coffin smoother with a homebrew iron I got at an antique store. It was over 1/4" thick. I took it to a toolmaker at work to have him grind a fresh primary bevel on it and flatten the back. He set it up on a die grinder and established a mirror flat back and perfect 30* bevel. No matter what, he could never seem to get rid of a feathery wire edge. I did some research on the steel and it turned out the chemistry wasn't very good for edge tools. It would harden OK, but the grain structure was too large as I recall. I would have to constantly hone it to get it to cut and always had to add a steeper microbevel to get rid of the wire edge.

[Kurt Cady]

I want to bet that you are using 200 and 400 grits way too often and getting a large thin feathery wire edge like you would get when re-shaping the bevel. I can visibly picture in my mind what you are seeing, something similar to what I saw with Narex chisels and a Worksharp (similar steel I believe) when I first started.

Here's an idea. Only use anything less than 1000 to reshape the bevel at 25deg. Then completely remove the wire edge with a high polish on the back. Next, sharpen at 1000 and up at 27 degrees. Do not move to the next grit until you can feel a wire edge with your fingers - it is very small, but can be felt. Hard for me to see without magnification. this will make your wire edge much smaller. Also, I don't know what grit your extra fine diamond is, but I doubt it is anywhere close to 8000 or the green compound - and I wouldn't use it to remove the wire and polish the back. It is also possible the chips you see are actually scratches on the back from the fine diamond stone.

I personally go many many many sharpenings until I go back to less than 1000.

Also, once you finish, you should essentially polish the back on a very high grit stone until the wire comes off completely. This is where the ruler trick comes in handy for plane blades - not chisels.

[John C Cox]

Re: crystal structure...

I was wondering about that...
Large crystal grain size can be caused by lack of normalizing or poor heat treatment even with "modern" alloys that are otherwise well behaved for this.

[Patrick Chase]

If you are getting a prominent wire edge at the higher grits (5000-8000) I am jealous. It's hard to see and feel at those grits. Achieving it means you are properly honing to the edge. Removing should almost always be easy by swiping the back on the highest grit once or twice, then inspecting the front and possibly going once on that side.

It's actually quite easy to get a prominent wire edge at the higher grits: Just don't work them enough to remove the one from the lower grits. Beginners do that all the time, and I suspect it may be happening here.

[Patrick Chase]

Do you know the type of steel the chisels are made from? Years ago I had a coffin smoother with a homebrew iron I got at an antique store. It was over 1/4" thick. I took it to a toolmaker at work to have him grind a fresh primary bevel on it and flatten the back. He set it up on a die grinder and established a mirror flat back and perfect 30* bevel. No matter what, he could never seem to get rid of a feathery wire edge. I did some research on the steel and it turned out the chemistry wasn't very good for edge tools. It would harden OK, but the grain structure was too large as I recall. I would have to constantly hone it to get it to cut and always had to add a steeper microbevel to get rid of the wire edge.

Oh, so you're saying your plane iron was made of A2? :-)

Sorry, I couldn't resist. Terms like "large ... grain structure" are of course relative.

IIRC Aldi advertises their steel as Cr-V, which can refer to an extremely wide range of alloys. Some of them take very refined edges, others are veritable chip-fests.

[Patrick Chase]

To the OP: I would lay off the extra-fine diamond plate. That's very coarse relative to any polishing stone, and may actually be drawing a burr. Just focus on using your polishing stones and untreated leather for now.

[lowell holmes]

Take a piece of wood and glue some rough raw hide to it. Then after sharpening your chisels, strop the edge on the rawhide.

I learned this from Paul Sellers at Homestead Heritage in Waco Texas 15 years ago. Try it, it works.