Clean edges on mortises

[Jon Ellwood]

I'm new to woodworking (24 months or so) and do it as a hobby. 

I was looking for some feedback on getting clean lines when cutting mortises. Using a chisel I have a tough time keeping the edges from getting a little bent or chipped. Pretty much everything I have viewed or read says you cut the mortise after the piece after it is all milled. I was wondering if the mortise was cut before it was planed down to final thickness if this could help alleviate the slightly damaged edges. Say if I leave a 1/16th of an inch to plane down after the mortise is cut? I only have hand planes for thickness and smoothing - no planer (yet).

Thanks!

[BonPacific]

When hand-chopping mortises, I find that good layout and scoring lines are the best aid to getting crisp edges. After scoring the edges of the mortise, i'll run my chisel around the whole perimeter, chopping a nice deep line around the edge, to keep the whole thing clean. Also, if you are cutting a lot of fractional imperial mortises (1/2", 3/4"), it can be helpful to use a metric set of chisels, which are a hair thinner than their imperial equivalents, which gives you a little wiggle room at the edges, reducing your chance of denting the sides.

Ultimately, the shoulders of your tenon are typically going to cover any irregularity or chipping at the mortise itself, so clean edges are only important for your own satisfaction. I understand the joy of "doing it right" but just make sure you aren't losing sight of the end product.

[OldSouthWoodCraft]

What edges are you referring to as being bent or chipped?

 

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[Al Capwn]

One of the mistakes I made was not using a knife/marking gauge to score the lines. That severs the fibers, which aids in removing chip/tear out. Next rookie mistake I was making was chiseling directly on that line. Big no no. What happens is there is nowhere for the wood to go, so it ends up damaging your lines (which will be your walls) as the chisel pushes backwards (because there is no path of least resistance). This happens in dovetails and mortises, principle is the same.

Are your chisels are sharp? Are you clearing out the bulk of the material inside of the mortise away from the edges?

[Jon Ellwood]

29 minutes ago, OldSouthWoodCraft said:

What edges are you referring to as being bent or chipped?

I'm referring to the edges of the shoulders. I tend to squish them when chopping or don't quite get a good marking line all the way around. Clearly the best answer is to keep working on skills to do them the right way. lol.

 

 

 

[Eric.]

Good advice from BP...the fact that it's moot on most mortises - unless they are through - kind of makes it a non-issue unless your mortises are so sloppy that it effects the fit of the tenon.

I wouldn't want to do any further milling post-joinery because that can throw off the fit, specifically the depth of the mortise and the mating tenon.  I do all of my joinery post-milling (and drum sander) so that the only material removed post-joinery is the microscopic amount that the smoothing plane or light sanding imposes.

[BonPacific]

3 minutes ago, Jon Ellwood said:

 

Wait, so you're talking about the tenon? Not the mortise? Let's make sure we're all on the same page here.

So you are working on the shoulders of the tenon? Are you really chopping on those? Because off the saw all you should need is a little paring with a chisel, but the same thing applies, score your lines deeply, so you have good registration for the paring cut or get a shoulder/rabbet plane.

[Eric.]

1 hour ago, BonPacific said:

score your lines deeply, so you have good registration for the paring cut or get a shoulder/rabbet plane.

Or just do them on the table saw in ten seconds and crack a beer.   M&T is one joint I'll never do by hand because you can't see the difference in a finished joint...it's not like dovetails where a hand sawn joint is visually different from a machine/jig made joint.  It just consumes time and adds no benefit to the end product IMO...unless you're a strictly hand tool only kind of guy, I'd consider using a different technique.

[BonPacific]

3 minutes ago, Eric. said:

Or just do them on the table saw in ten seconds and crack a beer.   M&T is one joint I'll never do by hand because you can't see the difference in a finished joint...it's not like dovetails where a hand sawn joint is visually different from a machine/jig made joint.  It just consumes time and adds no benefit to the end product IMO...unless you're a strictly hand tool only kind of guy, I'd consider using a different technique.

Well, this is the Hand Tool Village :). I agree with you when I'm building a piece of furniture, not enough difference to matter. But I do enjoy hand cutting a M&T in that pure hobby time, when I'm doing it for the joy of feeling the saw and chisel after a stressful day of work.

[Eric.]

1 hour ago, BonPacific said:

Well, this is the Hand Tool Village

Yeah...oops...missed that.  And chiseling a mortise clean and square is certainly an important skill to have in your pocket, because you'll inevitably need it at some point.  But for tenons...man it's hard for me to justify the time commitment to cut those by hand.  I find a smoothing plane much more relaxing than a saw...but that's me.

[Jon Ellwood]

When hand-chopping mortises, I find that good layout and scoring lines are the best aid to getting crisp edges. After scoring the edges of the mortise, i'll run my chisel around the whole perimeter, chopping a nice deep line around the edge, to keep the whole thing clean. Also, if you are cutting a lot of fractional imperial mortises (1/2", 3/4"), it can be helpful to use a metric set of chisels, which are a hair thinner than their imperial equivalents, which gives you a little wiggle room at the edges, reducing your chance of denting the sides.

Ultimately, the shoulders of your tenon are typically going to cover any irregularity or chipping at the mortise itself, so clean edges are only important for your own satisfaction. I understand the joy of "doing it right" but just make sure you aren't losing sight of the end product.

 

That's great advice. It is for sure all about doing right even no one will probably ever see it.

 

 

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[Jon Ellwood]

Wait, so you're talking about the tenon? Not the mortise? Let's make sure we're all on the same page here.

So you are working on the shoulders of the tenon? Are you really chopping on those? Because off the saw all you should need is a little paring with a chisel, but the same thing applies, score your lines deeply, so you have good registration for the paring cut or get a shoulder/rabbet plane.

 

No I meant the edges of the mortise. Like the rim. I used the term "shoulder" incorrectly. The little chips and dents are usually completely hidden. But I know they are there.

 

 

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[Eric.]

1 hour ago, Jon Ellwood said:

No I meant the edges of the mortise. Like the rim. I used the term "shoulder" incorrectly. The little chips and dents are usually completely hidden. But I know they are there.

The anal woodworker is a good woodworker, and there's definitely a place for chronic OCD...but you gotta pick your battles.  If the corners of a mortise that will be completely hidden are a little bruised, that's not really something worth spending your OCD capital on, IMO.  Crisp shoulders on the tenon and a dead flat mating area around the mortise are way more important.

Your line of thinking is generally appropriate, though.  Better than the alternative.

[Jfitz]

I'm with Eric on this one....that's not a battle even worth thinking about.  That'll be totally hidden.  If you really want to get your knickers in a bunch, make a test mortise in a scrap board, and then rip it open on the table saw to expose the inside of the mortise for inspection.  Probably not something that would look overly pretty - it's there, sure, but it's a functional mortise and will not be seen.

 

 

[Tom King]

The sharpness of the chisel matters for this.  It's almost impossible to do with a chisel that just came from the store.  First strike needs to be just to highlight the line.  Second comes back to undercut the first strike just to take out a small chip the width of the chisel.  Second strike on the line can be harder than the first, but never hard enough for the bevel to force the back of the chisel too hard against the beginning of the edge of the mortise to distort it.  Beyond that, the edge of the mortise is just the guide.

Don't use the edge of the mortise as the first strike until you get some more experience to get a feel for how hard you can strike.  Taking some out of the center of the mortise first makes it easier to keep the edges pretty.  If it's a race, you might start on the edge, but by asking this question, you're not ready for the races yet.

[Jon Ellwood]

Thanks to everyone for taking the time to reply. All good information! For a hobby that has quickly turned to an obsession/addiction I think the most exciting part the vast amount of knowledge and skills left to learn. And having a community such as his to share the journey with is just a very very cool thing. Thanks all.

 

 

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