Large mortises?

[Bryan Hunt]

When cutting a large mortise - say 3/4" to 1" wide, do you use a brace and bit to hog out the bulk of the material or pure chisel? When using a brace and bit, is there much concern for the chisel twisting when going back to clean out the remaining waste? Any other words of wisdom?

[Rob Luter]

I use a drill press and a forstener bit. Heresy for a Neanderthal perhaps, but more accurate than if I used a brace and bit.

[Brian Holcombe]

If they’re also long then I would much rather just chop them out.

[steven c newman]

Usually just chisel them out....

[Normand Leblanc]

Yep, just chisel them.

[Jim Koepke]

Mine have been done both ways. Overlap the drill bit a little and then you won't have as much twisting of the chisel since you will be paring away the Vs left between the bored holes.

Roy Underhill does this on an episode called "Big Ash Mallet":

http://www.pbs.org/video/big-ash-mallet-jn5sfd/

He first chops a shallow mortice as a guide for the bit placement.

jtk

[William Fretwell]

The really big ones (2"x6") I drill out first, then pare to the line. Can also drill a hole top & bottom, thread the bow saw and cut lines.

[Stanley Covington]

Drilling before chisel work makes cutting a mortise quicker, but usually less precise, especially if you use a brace.

[Warren Mickley]

One technique we sometimes use for a wider mortise is to make two narrow mortises, like 1/4 or 5/16, one on each edge, and then chop out the material in between. Depending on your skill with a mortise chisel, this could be faster or more precise.

[James Pallas]

One technique we sometimes use for a wider mortise is to make two narrow mortises, like 1/4 or 5/16, one on each edge, and then chop out the material in between. Depending on your skill with a mortise chisel, this could be faster or more precise.
Good advice here. It's no fun beating a 1 inch mortise 5 inches long into a hickory bed post. Two 5/16 ones and a little clear out is much easier. I leave those big chisels to the timber framers.
Jim

[Daniel O'Connell]

Good advice here. It's no fun beating a 1 inch mortise 5 inches long into a hickory bed post. Two 5/16 ones and a little clear out is much easier. I leave those big chisels to the timber framers.
Jim

Kinda wonder at that point if just doing a dual mortise and tenon joint might not be a better call than a single one. Wish I was experienced enough to know off the top of my head ;)

[Stanley Covington]

Kinda wonder at that point if just doing a dual mortise and tenon joint might not be a better call than a single one. Wish I was experienced enough to know off the top of my head ;)

Good point. Twin tenons make a much stronger joint in some ways than a single tenon. More glue area (not usually an issue in big tenons) and especially much more resistance to torsion (twisting). If the tenon is acting in tension (withdrawl forces) and secured with a pin, then effective cross-sectional area of twin tenons may be seen as less than a single tenon of the same cross sectional area in some conditions. It depends on the size of both members being joined and the forces involved.

Cutting twin tenons precisely in large timbers takes superior skills in layout, saw-work, and chisel-work than for cutting a single tenon. Not something for the amateur to attempt in an actual timber frame without practice.

[Jerry Olexa]

I usually get the bulk out by drilling and the rest with a chisel...

[Mike Holbrook]

Loose Tenon? Make a mortise in both pieces and make a tenon to fit the two holes? The tenon can be glued to one or both pieces. Biscuits, dowels, dominoes are all loose tenons. You can make more or less loose tenons depending on the pieces being joined. Drawboring would be a variation of a loose tenon as well. A tenon or peg with the grain running the full length of the tenon is a stronger tenon and relatively easy to make.

[Daniel O'Connell]

Cutting twin tenons precisely in large timbers takes superior skills in layout, saw-work, and chisel-work than for cutting a single tenon. Not something for the amateur to attempt in an actual timber frame without practice.


At this point in the hobby I am having trouble enough getting single mortises chopped consistently. Acquiring a couple good mortise chisels has helped

[Kurtis Johnson]

Well, I've seen bit brace recommended more than once. Gotta come from some handed-down tradition. I imagine old timers had it down pretty fair.

[Stanley Covington]

Well, I've seen bit brace recommended more than once. Gotta come from some handed-down tradition. I imagine old timers had it down pretty fair.

It is indeed traditional. But unless you have lots of experience with brace & bit, I suggest you practice on scrap first to see how close to the edge, and how straight you can drill.

[steven c newman]

Or..buy one of these...
373284
For those really big jobs...can even be tilted for an angled mortise....

[Ryan Lee]

When I took a timber framing course, we scored the line with a knife, then hogged out the material with a drill, then cleaned it up to the scored line. If you leave about a 32nd of an inch you can get a nice clean line slicing down with the edge of the chisel in the score line.

[Frank Necaise]

I use a drill press with a forstner bit, then break out the chisels. Just finished making 12 for my Roubo workbench.

[Bryan Hunt]

Thanks everyone for the advice. I went with defining the mortise with the chisel, hog out the bulk of the waste on the drill press, and finish with the chisel. It worked great.

[Prashun Patel]

I found different techniques useful in different situations.

Another way you can try if you are amenable to a hybrid approach:

Define the walls of the mortise down about 1/4". Then use a top-mounted bearing pattern bit on a router to cut to depth. This gives quick and clean sides and a bottom that does not require paring.

This also works well on pieces too large to take to the drill press.

My mind wants me to become quick and facile with chopping. But my elbows and shoulder don't think so on anything north of 3/8".