On 12/28/2015 11:15 AM, wrote:
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.
Mechanically rough up the surface of the plastic to give it some
"tooth", then glue with a good repair epoxy.(I have no brand
preference, but I have some "west system" stuff left over from
aircraft work that I would likely use in a case like that - if it were
me.

My go to epoxy is Huntsman 10, previously Araldite by Ciba Geigy
http://tinyurl.com/nlnldt3
That's the small tube, I generally buy it in the 9 oz size, but Amazon
is out, you can probably find it elsewhere. I has a long shelf life even
after opened. I've used it after 10 years. It's grey when mixed.
http://www.amazon.com/Huntsman-Fastw...ct_top?ie=UTF8
I did a repair similar to yours on a on my radial arm saw crank handle
more than 15 years ago, it's still holding strong. That handle is all
aluminum, but I used Fastweld 10 for years on plastic parts in the
consumer electronics repair business. Where ever possible we used 0.25"
or 0.35" steel rod to pin parts before epoxy.
Mikek