[TheForge] A different needle question

[Paul N]

How about getting one of those cheap H-F non contact thermometers 
Then heat up something more massive to the desired temp and place the needles on there for 15 minutes or so?


**paul

Sent from my little tiny screen and keyboard. Any autocorrect errors are solely for your entertainment.

> On Oct 21, 2013, at 5:24 PM, "Bruce ." <freemab222 at gmail.com> wrote:
> 
> ​I am altering the eye shape of a few commercial needles.  They're too
> brittle to work without normalizing, but onc​
> ​e normalized, they bend just fine.
> 
> Now I need them hard again.  Well, dunking in water while at a red heat
> works for that -- but leaves them more brittle than ever.
> 
> A tempering operation (to purple or blue, probably) is quite easy on a
> chisel, but even SEEING the colors on a needle is a challenge.  For one
> thing, there's no good surface to polish.
> 
> I've tried a couple methods, all without success -- my toaster over doesn't
> get hot enough, like, maybe 450 F, despite what the dial says.   (520 F =
> purple, 540 F = blue, 590 F = peacock, according to one reference.)  I
> tried heating an iron griddle to these temperatures and leaving the needle
> on it for about 5 minutes -- no luck.
> 
> I considered using a salt or solder bath, but find no appropriate salt and
> that I'd need 80/20 to 85/15 lead/tin solder -- which is not readily
> available -- to get a liquid bath of the right temperature.
> 
> I'm considering a sand bath or a furnace, using a thermocouple to monitor
> temperature, but as you can see, this is getting increasingly complicated
> for what should be a rather simple task.
> 
> Hence, I'm soliciting suggestions how to temper a needle.  Any notions?
> 
> Bruce
> NJ
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