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Posted to rec.crafts.metalworking
Paul Stivers
 
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Default Bonding a steel pin to copper sleeve.

For the game of steel tip darts, I have some hammerhead moving points
that thread into the dart barrel.
http://www.edarts.net/st_darts/hhpoints.shtml The moving points are
supposed to prevent bounce outs if the point hits a wire on the
board. I don't want the points to move though.

The point is basically a hardened steel pin, and the clip is a copper
(I think) sleeve. The clip has an appearance like tarnished copper,
and looks like fresh copper if I scratch it. The round cylinder back
of the clip has 4 slots cut in it to make 4 leaf springs (sort of)
which apply friction to the point as it moves in and out on impact
and removal from the board.

I degreased the parts with spray carburetor cleaner, then acetone
soak, then isopropyl (rubbing) alcohol soak, then blow dry. I then
glued with Loctite 271 thread locker red. It didn't hold very well.
One point came loose after a half hour of throwing the darts. The
others have held, but if I take the point and place it tip down on a
piece of Plexiglass and tap the sleeve with a hammer, it comes lose.

The technical report on Loctite 271
http://tds.loctite.com/tds5/docs/271-EN.PDF says only ¼ strength when
bonding to brass versus steel. I figured similar on copper but
figured I'd give it a try as other dart players have used 271
successfully for this purpose. If I had it to do over again I would
have taken emery cloth to the steel points to remove the black
coating and get down to bare steel. On the ones I knocked loose, it
looks like the failure was along the glue/copper surface though.

So, I'm looking for something that will do a better job of bonding
the steel point to the copper sleeve. It has to withstand thousands
of cycles of repeated impact during normal dart play.

For prep, and to remove the Loctite 271, I'm going to wire wheel and
coarse sand paper the points to bare steel at the bonding surface,
and scratch up the inside of the copper sleeves with a needle file.

I'm tempted to try soldering them. I don't want to add much weight
and certainly don't want to add un-uniform amounts of weight across
the three assemblies. I have some fine solder wire with flux in it
that might do the job well. I could apply the solder at the slots in
the sleeves and hope a thin layer wicks in around the pin. Not sure
whether to use a solder iron or propane torch. I'll try the solder
iron first. I'm afraid I'll warp or even evaporate the sleeve with
the torch.

Another possibility is the clear Loctite that you see in most
hardware stores.

Thoughts on these approaches? Other ideas?

Thanks,
Paul S.