Corner chisel for deep or through mortises?

[ear3]

I'm sketching out a project that might involve making through M&T joinery with wooden pegs.  I've done some basic M&T with regular chisels, but never a through mortise (at least not one on a piece of furniture), and I'm wondering if it's worth it to get a corner chisel for an application life this, where I will want absolutely clean and square corners on the backside of the mortise, since it won't be hidden?

Also, in terms of sizes, is the 1/4" basically good for most applications?

 

[MrGinCT]

Corner chisels can be tough to keep really sharp.  You should consider making up 90 degree corner blocks to use as chisel guides to make absolutely crisp corners.

 

[ear3]

Do you just mean some piece of scrap wood/metal set at the corner of the mortise to guide the blade and make sure it doesn't dig backwards past the scribe line?

Corner chisels can be tough to keep really sharp.  You should consider making up 90 degree corner blocks to use as chisel guides to make absolutely crisp corners.

 

[ear3]

Assuming I can keep them sharp, are they worth investing in for this sort of work?

 

[nclemmons]

I have a 3/8" corner chisel that I use from time to time for mortises and even cleaning glue out of mating faces during glue-ups.  But I cut most of them with just a couple of chisels, except for the majority that I use the Domino with!

For a through mortise, your biggest concern will be not blowing out the piece on the back side.  I think I'd start with a Forstner bit drilling out the pocket and a regular set of chisels, carefully marking from either side and then using your chisels or a razor knife to create a square set of alignment lines and working to that line carefully, alternating from each side.  That could be done with wood blocks that you glue together to give you a square pocket guide.  You could also try your MFS even as one approach.  But I have always found using the widest chisel I could into the corner gave me the best alignment rather than a corner chisel, particularly on through and 'show' mortises.

As an alternative to forester bits, I might even try the Domino along one edge to help with the material removal and then use a guide, corner chisel and regular chisel to clean things up.

I'd suggest a couple of practice runs on similar wood to get the technique down. 

 

[Kev]

Have you seen the ones in the little sleeve you whack with a hammer to clean corners? There's a few, Trend make one.

I'm assuming you're after traditional corner chisels ... I'd echo the same fear of effective sharpening !

Narex have a nice new (at least down here) 10mm corner chisel I "wouldn't hate having" [wink]

 

[ear3]

I have the hammer one for when I do hinges, but since I'm doing through mortises, so I need the real deal.

Have you seen the ones in the little sleeve you whack with a hammer to clean corners? There's a few, Trend make one.

I'm assuming you're after traditional corner chisels ... I'd echo the same fear of effective sharpening !

Narex have a nice new (at least down here) 10mm corner chisel I "wouldn't hate having" [wink]

 

[flair woodworks]

No, I would not use a corner chisel for that application. Other than hinges, I'm not sure where I would use one... And I usually use a flat chisel for hinges anyways even though I have a small corner chisel.

 

[HarveyWildes]

Corner chisels can be tough to keep really sharp.  You should consider making up 90 degree corner blocks to use as chisel guides to make absolutely crisp corners.

I agree.  I've got a Sorby corner chisel that I almost never use.  I might use it to clean up corners, but not to define them.  90 degree corner blocks are good, as long as you have the block well supported so that it doesn't move as you're chiseling.  Even with that technique, I'd do a rough mortise and then sneak up on the finished edges.  I've used sharp mortiser chisels as a hand tool before, with a mallet, but again you want to make sure that they are lined up perfectly.  Since I got my Domino, I've been tempted to try mortiser chisels with that, but I gave my mortiser and chisels to my son who is far more talented than I am.

 

[jtwood]

Assuming I can keep them sharp, are they worth investing in for this sort of work?

Corner chisels are great for cleaning dried glue out of corners, but are difficult to use in mortises.

I do a lot of Arts & Crafts furniture with through mortises.  If I am doing a couple of mortises, I have two short pieces of angle iron I have verified are 90° on the outside.  I clamp them to the board on the edge of the mortise along the side and across the end, to form an ell shape.  I use bench chisels of the appropriate size to square up the corners.  I guess you could use corner chisels there, but you wouldn't need more than a couple of small ones of different sizes.  I think it would be easier to use a flat chisel on the side and the end rather than trying to make sure both sides of a corner chisel are lined up properly.  If it is a through mortise, you are going to want to flip the board over and clean up from the other side, too.

If you are going to do a lot of mortises in the future, I would suggest investing in a mortising machine.  The square chisel with the drill through the center takes care of most of, if not all of, squaring the corners.  If you keep them sharp, this is the easiest way to do a lot of mortises with great results.  The machine takes care of drilling out the center section of the mortise and squaring everything at the same time.  Usually all you need to do is use a flat bench chisel to clean up the inside of the mortise.

Steve

 

[WarnerConstCo.]

Just get a pig sticker.

 

[bdiemer]

No, I would not use a corner chisel for that application. Other than hinges, I'm not sure where I would use one... And I usually use a flat chisel for hinges anyways even though I have a small corner chisel.

I agree with Chris. Corner chisels are not generally used for mortises. A good sharp mortise chisel is hefty and will give you a nice square cut. Best advise I can give is practice on scrape. I prefer the methods that work slowly to the end knife lines. On thru mortises make sure you cut equal amounts from both sides of the wood. There has been talk of Narvex products. I have used their mortise chisels several times and find they work very well.

 

[ear3]

Thanks for the advice.

 

[ear3]

So I went ahead and got the Narex corner chisel:

View attachment 1

Arrived this morning, and as I was looking it over, I noticed that the edge is not square -- you see how it's deeper at the corner than along the edge.  The effect is that when you try to set up the cut, it rocks inward towards the bevel side.  But maybe this is a normal design for corner chisels, and might have some advantage I'm not aware of when starting cuts?

View attachment 2

Anyway, I tested it out.  After two whacks with the mallet in white oak, this is what the edge looks like (did not hone the blade myself -- but it felt sharp out of the box):

View attachment 3

View attachment 4

So I'm going to return it, and am just kind of put off from ever buying a Narex chisel again, even though I'm basically happy with my Narex bench chisels.  Going to look at LN as an alternative for corner chisels.   

 

[jtwood]

The corner chisel should be used to clean up the corners of a mortise that has already been drilled out or routed out, where rounded corners are left.  Or, to clean up the corners of a mortise created by mortise chisels.  It is not designed to gouge out the corners like a mortise chisel is used, from scratch.  If you used it to gouge out the corners, I'm not surprised that there was that kind of damage to the chisel.

If the chisel is sharp enough, it can be used like a gouge, being pushed by hand.  Very light taps with a mallet can assist, but it is really just designed to clean up the mortise, not create it.

Steve

 

[ear3]

Most of the mortise had already drilled out on my drill press.  I was just squaring up the corners.

The corner chisel should be used to clean up the corners of a mortise that has already been drilled out or routed out, where rounded corners are left.  Or, to clean up the corners of a mortise created by mortise chisels.  It is not designed to gouge out the corners like a mortise chisel is used, from scratch.  If you used it to gouge out the corners, I'm not surprised that there was that kind of damage to the chisel.

If the chisel is sharp enough, it can be used like a gouge, being pushed by hand.  Very light taps with a mallet can assist, but it is really just designed to clean up the mortise, not create it.

Steve

 

[Michael Kellough]

The general procedure for squaring mortises (at least for me) is to reserve the corner chisel for just the visible part of a mortise that surrounds hardware. That's why the spring loaded versions are perfectly fine.

Farther down in the mortise it doesn't matter if the corners are square as long as there is no wood in the way of the tenon passing through. I overcut the corners slightly with the mortise chisel and aim to just keep the four cheeks of the mortise straight and square as the tenon. Another option is to chamfer the corners of the tenon (to avoid clearance issues) if it's a blind tenon.

 

[ear3]

Thanks for the tip.  I got the corner chisel because I'm trying to going to make a through mortise and tenon.  But maybe I'll try that trick of scoring the visible part of the mortise on both sides with the spring loaded version (which I have), and then use the corner chisel (or something else if after I return the Narex I don 't get another one) to clean out the corner further down the mortise.

BTW, was at TFWW again today -- not really by design, but had a client meeting less than a 10 minute drive distant, so I couldn't resist.  Walked out with one of their Ray Illes mortise chisels  [wink]

The general procedure for squaring mortises (at least for me) is to reserve the corner chisel for just the visible part of a mortise that surrounds hardware. That's why the spring loaded versions are perfectly fine.

Farther down in the mortise it doesn't matter if the corners are square as long as there is no wood in the way of the tenon passing through. I overcut the corners slightly with the mortise chisel and aim to just keep the four cheeks of the mortise straight and square as the tenon. Another option is to chamfer the corners of the tenon (to avoid clearance issues) if it's a blind tenon.