"Paul K. Dickman" wrote:

"Pete C." wrote in message
. com...

"Paul K. Dickman" wrote:

The elections are over and it is time to get back to some on topic
discussions.

I am looking to put together a purpose built soldering machine and I want
to
pick your brains.

I have a 6"x8" piece of 16g polished brass sheet and I need to soft
solder
an 8" brass piano hinge to the polished side. The hinge needs to be
moderately well located along one edge, but the tolerances are loose. For
reasons of finish and subsequent machining, spot welding or riveting are
not
feasible.

The polished side of the brass has a thin coat of lacquer and a sheet of
protective vinyl on it. I need to protect the polish and the lacquer in
the
non soldered areas, so heat needs to be very localized and handling kept
to
a minimum. It is for a production run of 100 pieces.

For prototyping I tinned the hinge with an iron. Then I would remove the
vinyl from the sheet in the soldering area. Using the rest of the vinyl
as a
mask I would sand off the lacquer and flux the area and removed the rest
of
the vinyl. The sheet was clamped between a couple heat shields and then
tinned. The two pieces got clipped together with spring clips, heat
shielded
and sweated together with a torch.

This worked fine for onesey twosey, but would suck for a hundred pieces.

My plan is this:

I use a strip heater like this,

http://www.mcmaster.com/#die-strip-heaters/=k3s9ef

attached to a hunk of copper buss bar as an 8" long soldering iron.

The pieces will be tinned and clipped into a jig. I have a scrap of
architectural bronze extrusion that I think will work well for this. It
has
enough thermal mass to warm up and not chill the work, but it has enough
flanges and surface area to release some of the heat and let the joint
solidify in a reasonable time.

The hot 8" iron will be clamped down on the hinge side with a couple of
toggle clamps, allowed to heat the pieces up till it sweats and released.
The pieces remain clipped in the jig til the solder hardens. (can be sped
up
with water mist) The next set gets clipped in and the process repeated.

If I am lucky, I would love to eliminate tinning the sheet as well

I have about $400 parts and labor budgeted in for this machine. After
that,
it's all piecework. My profit depends on being frugal and productive so I
don't want to spend a lot of time fiddling around.

If anyone has any ideas or insight or a better way, I would appreciate
hearing about it.

Paul K. Dickman

Have you considered adhesives? No heat required and with the right
adhesive it will be at least as strong as soldering.

I have used some adhesives on metal to metal that impressed the hell out me,
but this would be a bad application. In the end the sheet gets slit up into
eight 1"wide x 6" long fingers that flip up and rest on the hinge just past
a 90 deg swing. That would put 5 1/2" of leverage on a 1/2" wide glue joint.
I think that is asking for a peel failure.

Paul K. Dickman

3M and Locktite have app engineers that could likely confirm or deny
that issue with a phone call or two.