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This is a martin with aluminium top , the bridge keeps coming off , I think i used epoxy last time , what do you suggest ?

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Rivets!   Well maybe not a rivet but, seriously, given the materials involved, this looks like a prime candidate for 4-40 machine screws.  Yeah, desperate measures but it's an oddball top, sooooo....

I'd install two, each about 1/4" behind the pins, between the E & A and the B & E string pins. First countersink the screw heads (I think they're about 3/16" dia) so the heads will sit about 1/8" below the surface of the bridge but still leave plenty of 'meat' under them. 

Once the bridge is where it needs to be, use the center of the 3/16" countersink and drill straight-through the bridge and aluminum with about a .110" drill for the threaded shafts.

You could epoxy again now, then install the machine screws, washers and nuts. Clean the squeeze-out and let it sit overnight.  Re-tighten the nuts and make a pair of rosewood (or ebony) plugs to match the bridge, so they'll sit proud of the countersink depth.  Glue in place and let them dry.

File, sand & touch-up the plugs to match the bridge ...and that bridge shouldn't be going anywhere.  Check the tightness of the nuts after a few hours of playing and re-tighten as needed.  

Mike , that sounds good , I didnt like the idea of screws coz i had a picture of pearloid plugs , but ebony plugs is a good way to go . PS your drawing is wonderful to an old guy like me .

I tried yesterday to post this but had problems signing in. All good now so;

I've built a couple of instruments where wood and aluminium are glued together with epoxy. Just before applying glue to the aluminium I scour the area of the metal to be glued with a stainless steel brush.

The idea is to get rid of, or at least pierce, the surface layer of aluminium oxide. If you don't do this you are glueing to the layer of oxide and not to the metal itself.

My process was, mix the glue, abrade the area with the stainless steel brush, then apply the glue to the metal with as little delay as possible. After that you can take as much time as the glue itself will allow. Incidentally I didn't use expensive glue. I used the cheap pound shop five minute epoxy for most of the processes. If a job was going to take longer than a couple of minutes I used the more expensive epoxy.

Thanks Ron , I gave it a course sanding and used a hi strength epoxy 12hr type its all clamped up now with a caul inside , there is no bridge plate at all and I will add screws later.

I would just like to reinforce Ron's emphasis on gluing ASAP after sanding or otherwise scarifying the aluminum.

The speed at which aluminum will  oxidise  is unbelievable. Over the years I have hand lapped on PSA on a surface plate well over 1000 aluminum box section sanding beams, and it still amazes me that if I interrupt the lapping  process for between thirty and sixty  seconds, when I pick up the beam and recommence sanding I can instantly tell by the feel of the aluminum  that a film of oxide has formed. It feels slicker, and takes a few strokes before the abrasive starts to bite again.

If I were using epoxy to glue  ebony to aluminum, I would scarify the gluing area of aluminum with a graver just before gluing, (as well as coarse-sanding)  and I would also "tooth" the gluing area of the ebony.

ok thanks Murray.

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