Pins in tubing: surface finishing

Jul 10, 2007 5 Replies
P

Awl--



OK... Pretty much have the direction of my assembly strategy, much thanks for the earlier discussion.



So now I bang in my pin, which of course cannot be flush with 1" diameter--or any diameter--tubing.



How do I finish the pinned surface?



  1. radius the pin first, and align the radiused end so that matches the tubing radius? Then polish?
  2. set the pin as is in the assembly, slightly protruding, and grind to match the tube surface? Hopefully without hitting the tube too much, as I plan on finishing the tube by spinning it in a lathe with Scotchbrite.

I lean toward (1), but also don't have a lot of confidence in the alignment process, as there is not with which to align. I dread (2), cuz I don't see how to do this without unduly touching the tubing, and then having a finish mismatch there to clean up.



Appreciate as much detail as possible, or alternative suggestions.


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J

Friction weld the two parts together.

John

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P

Yeah, keep in mind the mixture of materials: F'sure, SS; then with alum, and/or bronze guts.

Here's what ahm thinkin, mebbe too complicated:

Bang in sed pin, with about 1/8 protrusion. Put assembly in fadal, along X in grooved vise jaw (with pin sticking out in Y), and run a bitty concave cutter in X, to put radius on pin, to match radius of tube. Remove assembly, bang in pin flush w/ tube, w/ radiused set/punch ditty.

then, spin/Scotchbrite assembly.

Goodgawd.... But I don't really see another way, at least not right now w/ what I got.

And if I don't have to fuss too much at each step, mebbe will turn out pretty efficient.

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D

A few ideas:

Drill a slight countersink on each side of the tube. This would remove any burr and create a slight recess to peen the pin into location.

Use decorative button headed pin(s) like the ones that keep nameplates on machines. I never found the fluted ones I was looking for, but this is the general idea:

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A roll pin that is slightly too short.

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P

Really an excellent idea, that I toyed with earlier, but am just now realizing that it would indeed solve a lot of problems finishing-wise AND lend an interesting cosmetic/aesthetic touch. I'm hoping that the ones I would like use (brass/copper) would withstand the shear, which I could also hedge w/ some epoxy.

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