I bought a corner chisel + question about sharpening it

This one:

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I will be making through mortises in oak, or possibly some other hardwood. Some of the stock will be 1.5" thick. I was worried that squaring the corners of the routed mortises was going to be a debilitating chore, but I am encouraged by my first couple of tests with this chisel.

At its "just-from-the-package" sharpness, it makes a nice clean corner. Any imprecision will thus be attributable to my lack of skill rather than the tool. I intend to practice up some.

Next, it's not terribly difficult to plow through the oak. OK, I'm only gouging out a 1/4 x 1/4 corner in a 1/2" mortise, but it sure is easier with this purpose-built tool. My test runs have been on 3/4" scraps, so half the thickness I'll need, but it is very quick. My attempts with standard bevel-edge chisels were much more cumbersome. I think that the bevel on this chisel may be at a steeper angle, besides the corner configuration.

Now I need to learn how to keep it sharp. People recommended diamond hones, but I see at least 5 "colors" (grits). Any tips as to which one(s) I need?

Reply to
Greg Guarino
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It rather depends on what needs doing, wot? I use silicon carbide but the same ideas apply...

180/220/280 if I need to take out nicks, 400 & 600 to finish, rarely up to 1000. Don't forget the backs.

I would think silicon carbide on a block would work well for that, sharpen both edges evenly & simultaneously.

Reply to
dadiOH

I use the edge of an Arkansas stone to keep them honed.

Doing so religiously after every use, ten years have gone by with no real need to expend any extra "sharpening" effort.

Reply to
Swingman

Simple really. Just go down to the Town Hall and hone it on the corner stone. Glad I could help.

Reply to
Ed Pawlowski
[about sharpening a corner chisel]

Needs a special block or the geometry is wrong. If the corner chisel is 90 degrees and the edges are straight across, then the bevels on the inside are NOT at 90 degrees to each other.

For a 20 degree bevel at the edge, the corner chisel block would have to be

96.77 degrees

For other bevel, the formula is

cos(block_bevel) = sin(chisel_bevel) **2)

and you can't use the 'acos' function, because the branch is wrong...

Reply to
whit3rd

If the back faces make a 90-degree angle, then so will the ends of the inside bevels. I'm not sure how the "corner" can cut a perfect corner--I suspect that,without some deviation from what I have described,that it can't cut a perfect corner. In this case, I think if the corners of the tenons could were shaved just the slightest amount, that theywould have a perfect fit in a mortise cut with this tool. Or perhaps, one could finish with a regular chisel to create the "perfect corner" if desired. All of this just a guess--Bill.

Reply to
Bill

At my level of expertise it's unwise to be too certain about things, but I don't understand why you think that the cut won't match the shape of the chisel. Do you perhaps mean that the outside corner of the chisel must actually have some tiny radius to it?

Reply to
Greg Guarino

"dadiOH" wrote in news:mj7tc3$1k6$ snipped-for-privacy@dont-email.me:

Exactly - the corner chisel is just like any other chisel, so you'd use the same grits as you would for the same task on a regular chisel. Something pretty fine if you just need a light honeing, otherwise work up thru the grits. Diamond hones are good because you can get them in small sizes (with safe edges) that easily fit the bevel. As dadiOH says, you can glue silicon carbide sandpaper to popsicle sticks for the same result.

I think this is one of those tools where you don't want to touch the backs. Granted, the shape isn't as critical as something like a Forstner bit, but I think I'd just work the bevel, unless there was an obvious problem with the backs.

It would be a weird shaped block. I'd do both sides seperately.

John

Reply to
John McCoy

Either that, or there is a slice in the corner. Think about what the corner must look like if it is at the intersection of 2 bevels. It seems like to cut a real corner that the bevels would need to be separated.

Reply to
Bill

Just for fun, maybe use the tool on the edge of a thin board, fit a tri-square fit into the corner that was cut with the tool and let us know whether you can "see light".

Reply to
Bill

Could one square a corner with a single edge chisel? Of course, by doing one side at a time. Think of the corner chisel as two single chisels welded together.

Reply to
dadiOH

I suppose I could try that, but the corners I've made seem pretty crisp and square. Now, whether the cut is accurately aligned square with the piece is a matter of my eye acuity and hand dexterity, but the tool seems up to the task. Here's what I think the edge is shaped like, (schematically, of course, the angles are not correct) to the best of my ability to draw it:

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There are no curved surfaces in the drawing, all planes.

Reply to
Greg Guarino

It looks like a good tool and I have little doubt that it does a pretty good job. We just haven't got the answer to the question. I am sure that with a little help with a regular chisel, you can cut mortises with sharp corners if you want.

Reply to
Bill

Your question is misleading if it is not framed with context.

Are the edges cut by a properly ground corner chisel square/sharp enough for precision woodworking?

The answer is yes, even when you get down to wood fiber level:

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Anything more, and good deal less, than what is shown is not germane to the task the tool is used for.

Reply to
Swingman

It was not done on purpose. Your photo speaks for itself as to the "dilemma" I was contemplating. The "workaround" is evident in the photo.

Reply to
Bill

Figured you would say that, proving what I thought ... that you will see what your preconceived notions want to see.

The actual corner cut is the upper left, the same orientation as the chisel.

Reply to
Swingman

Don't get an attitude. I put quite a bit of thought into my replies. Based on the tool shown, my "preconcieved notions" had some merit. I did not figure that you would say what you did.

Reply to
Bill

FWIW, my 90-degree vee-gouges that are used for wood carving are not shaped like yours. Sharpening them is a frequently discussed topic.

Reply to
Bill

I'm still confused. What is it exactly that you guys are arguing about?

I have a chisel with a square corner. I'm struggling to imagine how that would not make a square corner in the wood. Is it that the chisel will push itself in a diagonal direction (toward the corner) due the the pressure of the wood on the wedge? Is it that the chisel might not be held vertically? (that one seems possible). Is it that the chisel (any chisel, I guess) may push the wood surface downward if it isn't sufficiently sharp, causing the edge (not the corner, specifically) to be rounded over a little?

I can only say that my test corners look pretty square so far. Getting that square corner precisely tangent to the arc seems like the bigger issue.

Reply to
Greg Guarino

So am I. It seems to be as to whether a 90 degree corner chisel will, in fact, cut a 90 degree corner...

If the sides of the mortise are precise a corner mortiser used to square hinge recess corners would index into the corner. One light tap and you would have a groove to sit the chisel into.

Reply to
Jerry Osage

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