I bought a corner chisel + question about sharpening it

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This one:
(Amazon.com product link shortened)
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?
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Greg Guarino wrote:

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.
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On Saturday, May 16, 2015 at 10:06:16 AM UTC-7, dadiOH wrote:

[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...
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whit3rd wrote:

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.

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On 5/17/2015 12:47 AM, Bill wrote:

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?
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Greg Guarino wrote:

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.

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Bill wrote:

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".

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On 5/17/2015 9:43 PM, Bill wrote:

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:
https://www.flickr.com/photos/gdguarino/17811797242/in/photostream/
There are no curved surfaces in the drawing, all planes.
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Greg Guarino wrote:

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.

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On 5/18/2015 7:11 AM, Bill wrote:

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:
https://picasaweb.google.com/111355467778981859077/EWoodShopJigsFixturesMethods?noredirect=1#6150316313543515938
Anything more, and good deal less, than what is shown is not germane to the task the tool is used for.
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Swingman wrote:

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.

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On 5/18/2015 7:50 PM, Bill wrote:

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.
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Swingman wrote:

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.

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Swingman wrote:

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

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On 5/18/2015 8:50 PM, Bill wrote:

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.
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wrote:

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.
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Jerry Osage wrote in

Me too :-)
I think it started with the assertion that you can't use a square block (or any other shape block) with abrasive on it to sharpen both bevels at once. Which is pretty much a true statement, in my opinion.
It then wandered off, because, I think, Bill was envisioning a V-gouge (which has the bevels on the outside, if I'm not mistaken, and thus won't cut straight down like a corner chisel).
John
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On 5/19/2015 12:56 PM, "Jerry Osage" wrote:

I don't think that would work in this case. Those "hinge" mortisers square up to two perpendicular edges. In my case, at least the first cut involves a straight edge and a semicircle. (imagine the oval plowed out by a 1/2" bit in a router that moves laterally).
But I do plan to "start" the grooves - or at least the one at the end - with a straight 1/2" chisel.
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Greg Guarino wrote:

We weren't arguing. At least I wasn't. Have you tried sharpening yet? I might carve a pop-sickle stick or similar (preferable something stronger), to help with that bevel near the corner. Be careful not to round over any edges when you are sharpening. You can't be too careful on that--take your time. Be careful not to round over the bevels. Pay careful attention to what you are doing--that you are not rounding over the edge, and you'll have good results. Put the tool in a vise, or similar so it doesn't move! Careful strokes and all will be well. Try to "feel" the angle of the bevel (you can!) No rounding! ; )
Bill
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On 5/19/2015 8:41 AM, Greg Guarino wrote:

No argument, simply stated a fact regarding the performance of a common woodworking tool, with proof to back it up, based on an observation that prior discussion had degraded into nothing more than guesses/ill informed conjecture by those who have not used the tool.
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