Coming to the end of a long day, I have finally produced a prototype tube expander. There are a number of them on the market today for the instrument repair business, but this design is a bit different (simpler for one thing). I got the idea from a local man who repairs instruments. He’s a former oboe maker, oddly enough, and even has a set of pipes that he’s working on. He hasn’t tried this design yet, but thought that it might work. It does.
Here are the pictures:
This is a full shot. The left end goes in the tube, the right helps hold the rod while the cross bar is being turned.
This is what it looks like assembled. The piece with the parallel slot does the expanding. You’ll be able to see the tapers that make it expand in the next shot.
There are six items on an 8-32 threaded rod. From left to right:
- 8-32 Nut
- Threaded piece of steel with 60 degree taper on one side.
- 8-32 nut that has had the hex removed (so that it fits in the next piece)
- Steel tube (3/32" thick? - I just eye-balled it, cut down from the same stock as the tapers). 60 degree inward tapers on each end.
- Same as #2 above, but not threaded - cut to just slip over rod.
- Piece of steel that I had laying around with a threaded hole cut in it. This actually tightens the whole assemble. I did have a nut which I tightened with a socket slipped over the rod and a vise-grip, but it wasn’t elegant enough
I can insert spacers between #5 and #6 to change the placement in the tube. This can be tightened in place or can be slightly tightened and then forceably removed from the tube.
I hope that others will find this useful.
Erik