[TheForge] A different needle question

[Bruce .]

The problem with polishing is that it is mainly the eye that needs
tempering.  There just isn't much surface area, and I don't want to get my
face close enough to see what's there.  I may come back to this idea, but I
might have stumbled upon a better one.

Bruce
NJ


On Tue, Oct 22, 2013 at 3:54 PM, David E. Smucker
<davesmucker at hotmail.com>wrote:

> Best way to color temper something of this nature is to place a steel
> plate on your stove (gas works best) and then place the items to be temper
> on the plate.  This lets you seen the color without looking at the flame
> and lets you stop the temper action by dumping the contents of the plate in
> to a pan of water.  Not sure why you are having issues polishing the
> needle, just use a buffing wheel.  The use of the plate to heat treat gives
> you control over the rate of heating (slows it down).  Have used this to
> temper small parts, it is an old machine shop practice.
>
> Dave Smucker
> Brasstown, NC
>
> -----Original Message-----
> From: theforge-bounces at mailman.qth.net [mailto:
> theforge-bounces at mailman.qth.net] On Behalf Of Bruce .
> Sent: Monday, October 21, 2013 6:24 PM
> To: Blacksmithing List Sponsored by ABANA
> Subject: [TheForge] A different needle question
>
> ​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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