It's really the same sort of thing as a box joint jig except the space between the key and the blade is wider. You can find any number of box joint jig plans and modify them to suit.
Build one, not that tough. I use a sled, not a miter gauge but both will work. And for a torsion box, you will not to have slip fit joints. Cut the gap a bit thicker, just press the pieces until they are flush. When building furniture, I get real close then go to a plane or scraper to get a joint with no gap. You will not have to get that fine.
(01-03-2019, 09:01 PM)DaveR1 Wrote: It's really the same sort of thing as a box joint jig except the space between the key and the blade is wider. You can find any number of box joint jig plans and modify them to suit.
Thank you very much for the tip.
Soon I will start building the jig let you know the updates.
Jack, I have built a number of torsion boxes, and i don't know if cutting laps will save any time. I normally just staple the tops of the cross pieces together. While I didn't realize it at first, the strength of the torsion box comes from keeping the top and the bottom the same distance apart - that is why you see some industrial torsion boxes made with cardboard as the spacers. I don't think the stiffness of the web itself adds any rigidity. On on the ones I have made, while the core had a ton of sag in it when stapled together, the torsion box was a rigid as a pool table once glued up.
01-05-2019, 09:39 AM (This post was last modified: 01-05-2019, 09:39 AM by handi.)
I have built many, many torsion boxes.
I just use the miter gauge with a Dado blade set up.
A small stop on the rip fence is all the measuring needed.
Set the fence, cut all of the parts of a length on both ends at that setting, then move the fence and repeat.
The “egg crate” inside the box will not be seen so minorvariations do not matter.
What IS important is that the slots are all in the same place across the ribs.
It is also not critical that the halflap cuts fit snug.
I built a 4'x 8' torsion box out of mdf 7 years ago. I glued and pinned the slats together, no half laps. It has been sitting on 2 saw horses in the garage since then and is as flat as the day I made it.
Mals
Mals
You can educate the ignorant - You can't fix stupid.
(01-05-2019, 09:39 AM)handi Wrote: I have built many, many torsion boxes.
I just use the miter gauge with a Dado blade set up.
A small stop on the rip fence is all the measuring needed.
Set the fence, cut all of the parts of a length on both ends at that setting, then move the fence and repeat.
The “egg crate” inside the box will not be seen so minorvariations do not matter.
What IS important is that the slots are all in the same place across the ribs.
It is also not critical that the halflap cuts fit snug.
So have I. That is because it is amazing how strong they are. Here are a few T-box shelves that I built for the shop about 12 years ago,:
These shelves are about 16" x 42". They weigh at most three pounds apiece. They never sag. I weigh 195 lb and stood on top of them when suspended at each end. There was no bend that I could detect. They are in service today.
Rip to width. Plane to thickness. Cut to length. Join.
(01-08-2019, 08:28 PM)Edwin Hackleman Wrote: So have I. That is because it is amazing how strong they are. Here are a few T-box shelves that I built for the shop about 12 years ago,:
These shelves are about 16" x 42". They weigh at most three pounds apiece. They never sag. I weigh 195 lb and stood on top of them when suspended at each end. There was no bend that I could detect. They are in service today.
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