[TheForge] A different needle question

[Paul N]

Thanks Bruce,
 
I just looked up the flash points of vegetable oils; they are about 600*F.

I'm not making any needles at the moment but this sounds like a great method for gauging temperature of small objects. Another bit of info to squirrel away for the future. I hope I can remember it ! 
 
**Paul
 

________________________________
From: Bruce . <freemab222 at gmail.com>
To: mspencer at tallships.ca; Blacksmithing List Sponsored by ABANA <theforge at mailman.qth.net> 
Sent: Tuesday, October 22, 2013 5:56 PM
Subject: Re: [TheForge] A different needle question


Okay, here's an update.  It happens there's only two degrees of separation
between me and Tom Latane', so here's an interpretation of a vague memory
(Marshall's) of Tom's approach to tempering a spring (influenced heavily by
information on hardening and tempering needles from an article in an early
edition of the London Encyclopedia (late 19th century, I think -- from
Google Books):

Heat to red and do all the bending work needed at this temperature.
Heat to red.  Allow to cool in air (to normalize).
Heat to red and immediately quench in veg. oil (to harden).
Heat oily needle over flame till oil bursts into flame and immediately
quench in veg. oil.

Seems to work.  Too soon to be 100% certain, but I've got about a
half-dozen needles reshaped, hardened and tempered by this procedure.  They
seem hard, and I haven't had anything break on me yet.

Bruce
NJ


On Tue, Oct 22, 2013 at 6:49 PM, Bruce . <freemab222 at gmail.com> wrote:

> Umm, yes.  A bit of organic matter falls in and my apparatus (and me)
> disappear with only a small mushroom cloud left behind.
> Turns out lye has about the right melting point too, and I don't plan to
> use that either!
>
> Bruce
> NJ
>
>
> On Tue, Oct 22, 2013 at 2:57 PM, Mike Spencer <mspencer at tallships.ca>wrote:
>
>>
>> Bruce wrote:
>>
>> > 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.)
>>
>> Molten sodium nitrate (MP 306C  582.8F) or potassium nitrate (MP 334C
>> 633.2F) or a mixture of them.
>>
>> I recall reading a long time ago that some person or company used a
>> molten KNO3/NaNO3 mixture to create an ornamental blue patina [1] on fancy
>> dress spurs. [2] Temp seems about right for what you're doing.
>>
>> With your background, I don't suppose I need to mention the potential
>> risk of dropping random organic material into molten nitrates. :-)
>>
>>
>> - Mike
>>
>>
>> [1] Not to be confused with "hot bluing" in a water solution of
>>    potassium nitrate and sodium hydroxide.
>>
>> [2] Does anyone here wear spurs with formal wear?  1st Cav officers at
>>    the innaugural ball? Senior RCMP officers at a coronation? Or
>>    maybe just drugstore cowboys with hand-made $1000 boots?  Or kinky
>>    people who...um, not going there.
>>
>>
>> --
>> Michael Spencer                  Nova Scotia, Canada      .~.
>>                                                            /V\
>> mspencer at tallships.ca                                    /( )\
>> http://home.tallships.ca/mspencer/                        ^^-^^
>> ______________________________________________________________
>> TheForge mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/theforge
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:TheForge at mailman.qth.net
>>
>> TheForge mail list group photo site is
>> http://www.shutterfly.com/
>> Login: blacksmithblacksmith at hotmail.com
>> Password: anvil
>>
>> This list hosted by: http://www.qsl.net/
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
>
______________________________________________________________
TheForge mailing list
Home: http://mailman.qth.net/mailman/listinfo/theforge
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:TheForge at mailman.qth.net

TheForge mail list group photo site is
http://www.shutterfly.com/
Login: blacksmithblacksmith at hotmail.com
Password: anvil

This list hosted by: http://www.qsl.net/
Please help support this email list: http://www.qsl.net/donate.html