On 23/10/16 19:04, robobass wrote:
I make an unusual product (www.basscapos.com) which must be polished to jewelry standards, but includes a 5/16-24 threaded brass stud which is soldered to a brass bar. Torch soldering naturally produces firescale, which is hard to remove from the threads. There is a very effective product to combat this called Cupronil. You first preheat the work to maybe 600°f and then spray it on. It leaves a coating which protects the part. Works wonderfully. Problem is, I am going through it like mad. I have tried a bunch of different pump spray bottles, but none give me a nice focused spray pattern so that I don't waste the bulk of it. It wouldn't be such a problem if I could buy it in my country (Germany), but I can't. I suppose I should invest in an airbrush. I have a compressor, but I like the simplicity of a spray bottle, and the airbrush would still involve some experimentation to get it right. Can anyone think of an application where a precise pump spray bottle is used and easily available? Cupronil seems to be similar in viscosity to water, but it is enough different that a bottle which gives a perfect spray pattern with water isn't very good with Cupronil.

Thanks!
Can you shield the thread in someway to prevent the buildup of the
firescale such as a graphite cap or some other material. I silver solder
some parts from time to time and the part is supported and rotated on a
graphite post and doesn't seem to suffer at all so far from the heat,
IIRC the silver solder melts around 630C. For me the parts are then
tossed into the dilute sulphuric acid pickle to clean up the flux and
then finished machined and cleaned up with a mill saw file and
Scotchbrite so not to jewelery standards.

I looked up the cupronil and that clashed with cuprinol in the UK but
telling google I meant cupronil turned up Rio Grande in the US, I wonder
if gas fluxer fluid might have similar properties. If you don't know a
gas fluxer then basically the fuel gas IIRC on a OA rig is bubbled
through a flux solution, containing methyl borate?, and so a continuous
low level flux is applied to the area being brazed for better results
than rods dipped in flux. Not common in the UK but still in use by some
of the high end bike builders such as Brompton and very near me Curtis
cycles, the guys work is an art form
http://www.curtisbikes.co.uk/curtis-bikes/ .