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4th December 2023, 02:51 PM #1Senior Member
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Big Round Mortice and Tenon Joinery for Knockdown Bunk Bed
I'm building a bunk bed for the kids.
bunk_bed_v2-rendered-75.jpeg
The posts are 75 x 75 Celery Top Pine. It's designed to be assembled/disassembled into 2 separate beds (top and bottom). This is just for easy transportation, and getting it in/out of rooms.
I don't want to use any hardware, going for solid joinery instead.
Whaddaya reckon? Anyone think my solution below is a bad idea?
So here's my solution. This is just a test joint using construction timber of similar size.
IMG_2716 Large.jpeg IMG_2715 Large.jpeg
The plan is for the posts on the top bunk to have mortices, and bottom bunk posts get tenons. Tenons are 20mm into a 22mm mortice, and they won't be glued up. The CTP is really dense and heavy. Old salvaged stuff. Personally, I reckon it'll be absolutely fine to just sit on top without any fasteners. Especially if I get a nice push fit like I did in the test.
I could do wedged pegs later if it seems flimsy. But I'd rather keep the simple aesthetic.
Here's how I did it, for those interested.
- The mortice was cut with a router and template using a 3/8" spiral up cut bit.
- For the tenon, I marked out the shoulders with a gauge, cut most of the waste away at the bandsaw, then 1/4" flush trim bit with a template to get crisp tenon, cut slightly above the shoulder line. Then cut the shoulders in with chisel and router plane.
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4th December 2023 02:51 PM # ADSGoogle Adsense Advertisement
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4th December 2023, 07:39 PM #2
It looks alright to me. I like that you could make top caps for the tenons so you can set 'em up as two singles without too much hassle.
I suspect it'd be a good idea to make allowances now for some sort of fastener, even it's just an ugly old screw. I don't know about your kids, but I remember lying in the lower bunk and "ceiling walking" on the top bunk to annoy my younger sister. I never actually popped the top bunk off the legs, but dang I came close a few times...
ie. better safe now than sorry later.
- Andy Mc
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4th December 2023, 08:17 PM #3Senior Member
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Two really good ideas right there. The integrated ladder and the railing on the top bed could look potentially odd when beds are setup as 2 singles. But the flexibility is good.
I reckon you're right about securing them together. It'd look good to do a through pin in brass that finishes flush to the face. I've got some ~5mm brass rod somewhere, which would do nicely. The fit would have to be perfect, or it could look silly. And drilling the hole would need to be dead nuts accurate and square. I'd probably do with the good old mirror trick, drilling from the outside-in on both side for clean holes.
Good one!
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5th December 2023, 09:30 AM #4GOLD MEMBER
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Lot of time spent mucking about with cut tenons. Would be quicker to bore both pieces and cut up a broom stick to make the tenons. Can be glued into the bottom leg if you want but not really necessary and becomes a problem when the beds are to be used as singles. Receiving end of the tenons need to be domed to help with alignment when the beds are being stacked. When beds are single, remove the broom stick (if it hasn't been glued) and fit the end caps of your choosing.
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5th December 2023, 06:12 PM #5Senior Member
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Another good idea!
Can do that on drill press or lathe (parts are too big), So it's a plunge router and template (25mm max depth), or a forstner in battery drill. That's possible... but I reckon it'd be difficult to get straight holes that are also very snug fit for alignment.
Then again, I managed it fine when boring 19mm dog holes in my workbench, so... I suppose I could also turn some dowel to be just the right fit. This option has definitely got me thinking... Thanks Rusty!
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6th December 2023, 01:22 PM #6GOLD MEMBER
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There is no advantage sinking the dowel further into the timber than necessary. Keep the boring shallow and any deviation from exactly plumb would have minimal consequence.
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6th December 2023, 03:40 PM #7Senior Member
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Just thinking if I want to secure the joint with brass pins to stop any accidents, then 38mm (1 1/2 inch) round tenon glued into the bottom post is probably the go.
Once they're all fitted, then dry fit and clamp it up for alignment before drilling for brass pins.
I think you're right mate. This would be faster and simpler. Therefore likely to be better and more accurate, as there are fewer opportunities to stuff it up.
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6th December 2023, 05:55 PM #8
I wouldn't pin them. Cut your round M&T as per test pieces. Add a dowel a decent length into each for safety. Can be a bit of steel pipe or similar. Bore for the dowels by making a guide on the lathe that locates using the M&T. Make some caps as per Skews suggestion for use as singles. Even if the top bunk gets lifted via sibling annoyance it won't fall because of the Safety-Dowels (Safety-Dowel is a copyright of NCArcer Inc. )
Those were the droids I was looking for.
https://autoblastgates.com.au
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6th December 2023, 09:10 PM #9
WARNING WARNING
just a heads up keep them as single beds, there is nothing more exciting after a nice nice in bed with the bride than a 5 year old screaming from top bunk at 11.30PM
Daddy Daddy Iam going to be sick you leap out fly into their room just in time for her to throw up all over you.
I speak from practical experience and that was 35 years ago.
suffice to say they had single beds the next night.I would love to grow my own food, but I can not find bacon seeds
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