[R-390] How are your knobs ?

[Robert Moses]

A word on acetone: it polymerizes and leaves an organic residue. If you
want a clean surface wash off the acetone with distilled water and then
bake off the water film after shaking out the drops that you are able
to. (Baking would be at about 240 F (120 - 140 C ) for a day or 2. I am
assuming that you are talking about the 2 larger metal tuning knobs.)
Before baking non metal parts test to be sure that they will not be
damaged.

On 05/16/2014 08:16 AM, Charles Steinmetz wrote:
> Dave wrote:
>
>> Where do we get this 'metal glue'?
>
> The OP said he used some version of cyanoacrylate ("super glue"). 
> There are many versions -- every hobby store and machine supply has
> lots of them.  Choose by (i) substrates (get one for metal to metal
> bonding), (ii) the gap (that you will have between bushing and knob),
> and (iii) working time.  Most manufacturers publish detailed brochures
> aimed at getting you to the right choice, and they also have help
> lines you can call and someone will tell you what to get.  You may
> need to apply an accelerator before the adhesive.
>
> Barry wrote:
>
>> think they're referring to a product similar to JB Weld
>
> JB Weld is epoxy.  Very good epoxy, as is West System epoxy.  Either
> of these would be a fine choice (I'm more familiar with epoxies than
> cyanoacrylates, so I'd probably gravitate to one of these if I didn't
> have help choosing a cyanoacrylate.  If the clearance is tight, you
> may want to thin the mixed epoxy with a little acetone to make sure it
> wets the whole bond surface (but don't go crazy with the thinning).
>
> For either adhesive, you want the parts scrupulously clean.  I'd
> probably drop the knob and bushing into a can and cover them with
> acetone, let them sit a day or two, scrub the contact surfaces well
> with a stiff brush (a brand new .45 caliber bore brush should be great
> for the knob), then change the acetone and let them sit another day. 
> NB: acetone may remove the knob finish.
>
> Epoxy would benefit from some "tooth" on the bonding surfaces (40 grit
> sandpaper -- to do the bore, put a split into the end of a dowel and
> insert a strip of sandpaper).  I don't think cyanoacrylates need that
> much tooth, but do what the manufacturer suggests.
>
> Best regards,
>
> Charles
>
>
>
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