On Mon, 28 Dec 2015 14:07:50 -0000 (UTC), unk wrote:

On Mon, 28 Dec 2015 04:55:53 -0800, Larry Jaques wrote:

On Mon, 28 Dec 2015 12:23:39 -0000 (UTC), unk wrote:

I'm repairing an crank handle for a nice old tripod. The handle is made
of some sort of black plastic, and the bit made to repair (reinforce
across the break) it is steel. The steel bit sits inside the u-shaped
channel of the plastic. I expect there is a bit of draft so the epoxy
I'm planing on using to embed the steel bit has to stick good to that
plastic.

Recommendations?

That's a high-energy repair, with rotational as well as axial loads.

I'd probably drill, tap, and screw the piece together with 4 small
screws, perhaps with some 3m 5200 adhesive (or ShoeGoo) to initially
stick it together.


This one's broken right where the end of the u-channel meets the spinner-
knob mount. It's across the narrowest part of the 45 degree join.
Here's a pic of the handle:

https://www.manfrottospares.com/en/i...route=product/
product&product_id=9294

The knob mounts into a 15/64" hole that leaves about 1/2" vacant on the
back side. I cut a bit of drill that size and silver soldered it into a
bit of 3/16" by file-to-fit that is bent at 45 - disappears right into
the u-channel and as long as it stays there it will be stronger than the
original.

I was wondering if prepping it with an agressive solvent like carb
cleaner would help; also though of keying the sides of the channel so the
epoxy block would not just be reliant on surface adhesion.

Whether the epoxy sticks will depend on the type of plastic and how
much plasticizer it has in it. In any case, that's a marginal joint.

If that bent piece is long enough, you could wrap the joined area in
fiberglass, soaking it with epoxy as you wrap, until it's as ugly as
you can tolerate it. g Overwrap that with Saran wrap and then sand
it off when you're done. That will make it a little neater.

--
Ed Huntress