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Author Topic: Mortise depth for a timber frame bed  (Read 538 times)

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Offline carlor

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Mortise depth for a timber frame bed
« on: June 21, 2017, 12:16:25 pm »
Hi there,

I'm new to timber framing and I'm building a timber frame style bed. I'm planning on using draw bore pegs to pull the joints together but what I haven't been able to find is a "formula" for mortise depth other than to make them 1/4 inch deeper than the tenon. I realize that since it's just a bed, it won't have to deal with the same stresses a barn would, but I'd like to build it in the "traditional" way.

Is there a formula? My first joints will be roughly a 5" x 4 1/2" cross beam going into a 5 1/2" x 5 1/2" leg (all in Douglas Fir). Based on what I've found, the tenons should be about 1/4 the width of the beam so I'm making them 1 1/4" wide but I'm not sure how long to make them. Apparently you need enough "relish" on the other side of the peg hole to make sure you don't blow out the tenon. My current design has the tenon at 4" but I don't know if that's not long enough or just overkill.

So, my questions are:
- based on the sizes, what depth of mortise/length of tenon would you suggest
- Are there any guidelines for where to place the peg?
- How big a peg would I use in this instance?
- How much of an offset should I use for the peg holes to pull the joints together?

Any help would be greatly appreciated by this complete newbie  ;D

Thanks,

Carlo.

Offline Jim_Rogers

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Re: Mortise depth for a timber frame bed
« Reply #1 on: June 21, 2017, 02:12:12 pm »
4 1/2" rail should be 1 1/8 inch tenon, but in your case you could just do a 1" tenon with a 1/2 peg.
Or if you want to do a 1 1/2" tenon with a 3/4" peg.

Place the peg 1 1/2" off the shoulder of the rail. If you're doing housings in the bed post then 1 1/2" off the housing.
Draw bore would be no more then 1/8", a 1/16 should work as well.

You could make the side rails tenon long and do a through mortise on the corner post.

Jim Rogers

Search for timber frame bed here there should be some pictures of what other's have made.
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Offline WV Sawmiller

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Re: Mortise depth for a timber frame bed
« Reply #2 on: June 21, 2017, 03:10:12 pm »
Carlor,

   Not an answer to your question but I bought the Lumberjack Tenon cutter and it came with a nice little book of plans including a bed design. Since the size I bought was 1-1/2" peg (I never knew that was the term for the dowel looking piece before reading Jim's post) so the rest of the logs sizes are based on using that size tenons.
Howard Green
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Offline ljohnsaw

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Re: Mortise depth for a timber frame bed
« Reply #3 on: June 21, 2017, 03:58:12 pm »
I would think about doing a through tennon and then have a wedge to lock it in place.  Then you would be able to knock down the frame when you want to move it (plus it would be easier to fit through the bedroom doorway!).
John Sawicky

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Offline Don P

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Re: Mortise depth for a timber frame bed
« Reply #4 on: June 21, 2017, 06:54:43 pm »
I like that idea. Makes it easier to tighten back up after seismic events.

Offline carlor

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Re: Mortise depth for a timber frame bed
« Reply #5 on: June 22, 2017, 11:56:46 am »
Thanks for the reply, Jim. This really helps a lot. I was considering the through mortises but opted to keep the tenons hidden. I couldn't change now anyways, as I already bought the wood and didn't account for the extra it would take. I've attached a diagram of the bed design to give you a better idea of what I'm working on. (should have done that in my original post).

 

4 1/2" rail should be 1 1/8 inch tenon, but in your case you could just do a 1" tenon with a 1/2 peg.
Or if you want to do a 1 1/2" tenon with a 3/4" peg.

Place the peg 1 1/2" off the shoulder of the rail. If you're doing housings in the bed post then 1 1/2" off the housing.
Draw bore would be no more then 1/8", a 1/16 should work as well.

You could make the side rails tenon long and do a through mortise on the corner post.

Jim Rogers

Search for timber frame bed here there should be some pictures of what other's have made.

Offline carlor

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Re: Mortise depth for a timber frame bed
« Reply #6 on: June 22, 2017, 11:59:23 am »
Hi John,

I'm building the bed in my garage at home but will assemble it at the cottage. If I ever need to take it apart, I'll knock / drill out the pegs but once it's there, it'll most likely stay :)

Thanks,

Carlo.

I would think about doing a through tennon and then have a wedge to lock it in place.  Then you would be able to knock down the frame when you want to move it (plus it would be easier to fit through the bedroom doorway!).