In the latest issue of Fine Woodworking Mark Schofield mentions that you solved the problem of joining the wire “trusses” to the arches on his “High Tension Table” by using threaded inserts. Could you please elaborate on how this was accomplished.
Thanks
Phil
Replies
Phil,
I started writing up how to make the wires but it is taking a fair amount of time. I should be able to finish and post it in a few days.
John
Phil,
Basically I made a tapped hole in the table leg and a small threaded brass fitting that the cable passed through.
The tapped hole was drilled at 90 degrees to the surface of the leg using a 5/16" drill bit. For tapping you need as much depth as possible, so drill carefully and stop about 3/16" short of breaking through the back side of the leg. After the hole was drilled, I reinforced the wood fibers with a thin epoxy. Once the epoxy had fully hardened, I tapped the hole for a 3/8-16 thread.
To tap the full depth of the hole you need to use two taps, first a regular tap which has a tapered point for getting the threads started, followed by what is called a bottoming tap which has a blunt end. Bottoming taps can be purchased from a machinists supply house, but a serviceable one can be made from a standard tap by grinding away the tapered tip. After using the two taps, I recoated the threaded hole with epoxy, let it fully harden and then ran the taps through again to clean up the threads.
The inserts for attaching the wire were made from 3/8-16 threaded rod purchased at a local hardware store. I'm a machinist so I cut and drilled the inserts using a metal lathe, but they would be easy to make using hand tools.
To make the inserts without a lathe, you need to be able to hold the threaded brass rod in a vise without damaging the threads. Being you will have a 3/8-16 tap, the easiest thing to do is make a hardwood block that will fit in the vise jaws and then tap it through and cut a saw kerf into one side of the tapped hole. Now, to hold the rod, you only need to thread it through the block and then clamp down on the block with the vise, the saw kerf will allow the block to grip the rod.
The easiest way to make the inserts is to work on them while they are part of the longer rod and then cut them off of the rod as the last step. Start by flattening the end of the rod with a file, center punch it and then drill about 3/4 of an inch into the rod with a small diameter drill that will allow you to easily pass through stainless steel picture hanging wire. Now, using a hacksaw, cut a shallow screwdriver slot in the end of the rod. The last step would be to saw the insert off of the rod, the piece would probably be around 3/8" long, and then clean up the newly sawn end with a file, using a triangular needle file to clean up the threads.
The stainless steel cable is passed through the hole in the brass insert and the end of the wire is capped off by a short length of tubing made from a small diameter electrical wiring butt connector, I think I used connectors meant for telephone wiring that I purchased at Radio Shack. If the connector has a plastic sleeve on it, pull the sleeve off and throw it away. The tubing was crimped with a wiring tool and then reinforced by soldering the cap into place with silver bearing solder. Fluxing the end of the cable before you crimp the tube in place will insure that the solder flows into the joint properly.
The inserts should thread easily into the tapped holes if you spring the arches in a little bit so that there is no tension on the cable while you install it. Since the cable is coming out of the insert in the middle of the slot, you can't use a full sized screwdriver to turn the insert, but I found that a small narrow tipped screwdriver inserted in the slot to one side of the cable was sufficient to turn the insert into the hole.
Hope this helps, if anything isn't clear, let me know.
John White
Edited 6/12/2006 5:06 pm ET by JohnWW
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