How would I cut this mortise?

[Jeff Ranck]

I'm a long time lurker, but not a very frequent poster. I'm definitely an intermediate power tool worker and a newby at most hand tool operations. I've read most things I can read on the forum about MT joints and I have a question for a bed I'm designing.

It is a recessed panel bed with posts/beams rail/stile (what do you call those parts on a bed anyway?) of 4.5x2.5. The rule of 1/3 (or 1/2 I guess if I'm a power tool user) says the tenon should be somewhere between 7/8 and 1 1/4 thick. So call it 1" to make the numbers easy (gives a 3/4" shoulder). If I use the length = 5x thickness, I run out of board space, so maybe I use 3 3/4 for the length. Leaves 3/4" from the bottom of the mortise to the outside edge.

Since the boards are long (76" for the stile/stretchers, 57" for the posts), I'm thinking more of hand work than machine work.

Question: how would you cut that mortise (1" wide by 3 3/4" deep)? It's pretty big and deep.
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[lowell holmes]

The real experts should weigh in on this.

I would mark the mortise on the post using a marking knife. A box cutter works fine for this.

I would use a 1" auger bit in a brace and drill holes inside the limits of the mortice. The holes should be the depth of the mortise.

Then, I would clean the mortice up with a sharp chisel. I have timber framing chisels that will work to that depth.

The other option would be to rip the posts in half, cut half of the mortise in the ripped face of each piece, and then glue the halves back together.

[Jim Matthews]

Brace and bit with a guide standing behind it to keep the drilling straight. It's a trivial exercise that can be difficult to perform.

A nice wide chisel afterwards to clean up the sides. If you clamp a square to your bench, you can guide by eye.

Phil Lowe uses a small six inch ruler inserted into the mortise to check the side walls for parallel.

[Terry Beadle]

I am "assuming" that the corner depicted is a head on a bed frame. Assuming this, the tennon doesn't need to be so deep. Especially if you pin it on the back side or thru pins ala Green n Green. An inch and a half would be more than enough. You may also want to consider making the tennon in two parts instead of one big one to help with the wood expansion with in the joint.

To make the mortise, I'd use and end mill on my drill press to remove the majority of the waste. If I wanted to go neander, I'd use a good mortising chisel about 1/2 inch wide. Using the brace and drill as described by Mr. Holmes is a good option and very quick. I'd probably make a jig to keep the drill bit at 90 and I'd probably use a 3/4 or 7/8ths inch bit instead of the full 1 inch so that I could jig cut the sides.

[Pam Niedermayer]

You can always go the two-tenon route. But if you go with one, the 1/3 rule is there to keep the tenon from blowing out the sides; so there's nothing wrong with going smaller than 1/3.

Pam

[lowell holmes]

Thinking more about it, I would define the mortise witha gage and marking knife. I would at that time, carefully, chop a mortise using my LN 1" bench chisel about 1" deep, maintaining the edges of the mortise. Then I would use the brace and bit to excavate the remaining wood and clean up the sides with one of my big chisels.

[Matt Radtke]

Any reason the tenon couldn't be through? Obviously, it might not look right for the style you want. That said, it seems to me it would be much easier to cut two mortises roughly 2" deep (from each side) that happen to meet in the middle.

[Frank Drew]

Jeff,

In order to protect the end grain at the top of the mortises and the ends of the stiles themselves, leave your stiles (the vertical posts) longer than their finished length by maybe 1/2"-1" until after glue up; this is good practice for any mortise and tenon assembly. Also to protect the mortise top end grain, have more shoulder at the top of the tenon (1/2"-3/4", maybe) than the bottom (where as little as 1/8" would be fine); you could do a mitered haunch at the top of the tenon to accomplish the same purpose.

[For both aesthetic and structural reasons, you might consider altering your design slightly so that when finished the stiles project a bit above the top rails. Just a thought...]

I think your proposed tenon length, or just a bit shorter, would be fine; in general I like long tenons because they're stronger than shorter ones -- more mechanical strength and more gluing surface. It's more work to cut deeper mortises, though. And be sure to make the mortises a little bit deeper than the tenon length, in order to give any excess glue a place to collect.

Drill and chop, or chop all the way, either will be good practice and fun (but work).

[Russell Sansom]

1) I have always called the uprights on a bed "posts."
I would make the tenon shorter. You need enough wood to keep from blowing out the tip of the tenon when the drawbore pin pushes against it. Glue on a tenon this size is possibly more to keep it from wiggling in the mortise than supplying glue surface. The strength of the joint comes from pulling the shoulders tightly against the post.
A through mortise is a challenge because the "far side" mortise has to be cut precisely and to avoid being unsightly and it has to meet the mortise coming from the other side with good precision. A wedged through tenon is a wonderful joint that I don't see as often on the forums as I see in my own work. But for a bed post I would stick to a good old drawbore.

2) There are plenty of tutorials for hand-cut mortises here on the SMC.

[Jeff Ranck]

Thanks for all the suggestions. I have read all the tutorials I could and even did a test run in some glued up softwood to see how I could manage with my existing tools - bench chisels and a drill (electric - not brace and bit). The result was a bit rougher than I wanted. There are a lot of these in the headboard/footboard and tuning could be a real bear if I'm not accurate to start with.

I did consider a through tenon, but it wouldn't match the design. There is a crown piece that goes on top of this portion, so I couldn't leave the posts projecting up after glue up (although I probably will until I finish chopping the mortises).

Maybe I'll make it a bit shorter (I'm going to pin them anyway) so I don't have to go quite so deep. (Of course, I can envision two pins at a 45 degree angle in the corner for aesthetic reasons, which puts me back to a longer tenon.)

I like Lowell's suggestions about carefully using a bench chisel to define the mortise first and then using a drill to remove waste below. I'll try a couple of those in the test wood to see how that works.

Jeff.

[John Coloccia]

To get a clean mortise using the drill and chisel method, especially if this is the first time, take a block of wood and clamp it to the edge of the mortise as a guide. Then your chisel can ride the guide block and you'll get a nice, straight and clean mortise.

[Chris Fournier]

I wouldn't attempt to make this mortise by any means because it is unnecessarily deep at 3 3/4". The cross grain glueing over 3 3/4" would likely be a liability! The 1" width is fine but there would be no advatage to going deeper than 1 1/2" in my opinion.

[Pam Niedermayer]

I wouldn't attempt to make this mortise by any means because it is unnecessarily deep at 3 3/4". The cross grain glueing over 3 3/4" would likely be a liability! The 1" width is fine but there would be no advatage to going deeper than 1 1/2" in my opinion.

1-1/2" is cope and stick territory, and we all know how easily kitchen cabinets fall apart. And it leaves at most 1/2" for pegging, not good.

Pam

[Adam Cherubini]

I've done a few of these including 2 beds. I cut these like a timber framing would, drilling holes and cleaning away the waste with wide chisels. I think it's helpful to have 2" and even 2-1/2" chisels for work like this.

For a bed, I like to make really stiff connections. I use bend bolts and feel these do a great job. I use the bed bolts only in tension (not shear) using the tenon for shear. In that case, you don't need such a deep tenon. Alternatively, I have drawbored joints like these (or workbenches). Don't need a super long tenon for that either.

Adam

[george wilson]

That tenon is so close to the edge,it could break out of the edge. I suggest moving the tenon to the bottom of its member,to add thickness to that thin top edge. The tenon will still be as large,but the top could be at least 1/2" thicker,if the drawing is to scale.