Hi All,,
I'm looking for a source of sliding fit brass tubing, the OD of the smaller tube must be 20mm, OD of outer tubing I think should be about
21.6mm or thereabouts. Lengths min of 300mm long.Anyone got any ideas? I've looked about a bit on the web and saw smaller stuff. The inner tube is standard 20mm brass, but its the outside one seems to be impossible to get!
Thanks in advance
Fran
Maryland Metric and Parker steel are the biggest dealers of metric stuff in the US.
Small Parts Inc, in FL has telescoping brass tubeing. I don't know if they go this big, but they might. See
Get a slightly large tube and draw it over a mandrel (piece of 20mm stock) through an annealed fender washer. Or experiment with a softer die, put something inside the smaller tube, and draw the larger tube over that (grease it up first).
Chris
(this email address no longer works)
Damn. When you find some of the larger size, would you PLEASE tell me where you found it! I think we have harmonic tubing convergence here. :^)
Jim (ISO brass brake sleeve tubing...20 mm bore)
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Okay guys,
Buy the B-TTRB-15H from Small parts - 15/16" OD tubing .029" wall
Buy 36692820 Thomson Industries Metric Linear Shafting Diameter: 20 mm Length: 18 Material: Steel $23.56 from MSC Or sacrifice a bit in quality and get regular drill rod.
Drill and tap both the ends of the bar for say a 3/8" stud (drill rod will be easier, but the shafting should only be case-hard)
Anneal the last inch of the tubing in a propane torch flame (dull red in dark room)
Pop it in a collet with only 1" sticking out. Use the edge of a toolholder to spin the ID a bit below 20 mm.
Turn a half-inch piece of heavy wall 20mm OD tubing from bar stock.
Braze that in the end of the tube.
Find or fabricate a big fender washer. Anneal it (outside - zinc fumes) Dish it slightly by punching with something shallowly tapered - big bearing ball, trashed dead center, anything handy.
Grease up the mandrel with lard or crisco. Put it in the tube. Grease up the tube with same. Stick it into the fender washer.
Pull or push the tube and mandrel through the washer. You need to do it steadily all in one go, so anything mechanism that has to be cycled is unsuitable. Pulling via a piece of threaded rod with a nut runing on it should work tolerably for a single use provided you key it somehow to prevent the work from rotating. I use a hand-cranked shop-built drawbench based on roller chain.
Flip it around, put it through a 20mm diameter bushing, and pull the mandrel back out again.
The wall thickness will be a little bit more than you may want - I'd suggest living with it, though you might bring it down by reapeated drawing or very carefully machining while it is still on the mandrel.
If you want a steady supply, talk to one of the tube mills such as K&S/Special Shapes co, or talk to the S.E. Shires Trombone Company -
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