On Thu, 20 Jan 2005 14:02:17 GMT, "Tom Gardner"
wrote:

I have a situation that I need help with. I have a big bunch (3k) of
brushes that need better tuft retention for a special application. The
brushes are 7" long x 3-1/2" wide and have 50 holes/tufts in them. Each
hole is 1/2" deep x 9/32" dia. and each tuft is 3 flat wires bent 180 deg,
and stapled into the hole with a 18 ga., 1/4" crown x 1/2" leg staple. I am
thinking of injecting glue of some kind into the hole with the wire. These
brushes are already made. If I can inject glue or epoxy into the holes, the
material will have to be able to withstand the brushing action and not
crumble or pop out. I wonder if carpenter's glue would work. I'm looking
for leads for some type of powered dispenser too. My budget needs to be
under a buck apiece including labor.

Apparently, the action of the brush in this application is way different
than normal. They use the brushes in a linear motion that is parallel to
the staples. They use the sides of the flat wire to break spoo up rather
than the face of the flat wire to "sweep" like a normal use. This action
has a tendency to rock the staples out even though the tuft retention is
over 40 pounds pull-out strength. (Where's that Unabtaniun when I need it!)

You need low viscosity, particularly if not using vacuum. Scotchcast
#3 Electrical Resin is very low viscosity (1600 cps at 23C), is
designed to wet fine wires and has quite a long pot life (several
hours) at room temp. Deposit a drop at the base of each tuft by
means suggested by others, then put the workpieces in a 200F oven for
about 8 hours. It will get even thinner under heat (25 cps at 200F,
about like 5W motor oil), will wick down into the hole around the
wires and then will cure hard but not brittle.

One worry might be that any glue might wick up the wires as well as
down. Won't know that until you try, I guess.