[TheForge] Forge temps

Sat Apr 4 02:34:56 EDT 2009

Good run down on thermocouples...thank you Bruce..pf

Bruce Freeman wrote:
> First, go to this website:
> http://www.omega.com/toc_asp/frameset.html?book=Temperature&file=tc_colorcodes
> Look in the "Maximum T" column and select a thermocouple wire with the
> lowest suitable  maximum temperature.  I suggest K, for example. (Read
> the column "Comments Environment" for details that concern you.  For
> example, in a gas forge with the flame blowing out all the holes, the
> environment inside is "reducing" and a thermocouple that can't
> tolerate a reducing environment won't last long.  If the flame is
> completely inside the forge, then the environment is oxidizing.  If
> the thermocouple is only placed in the forge for short periods, this
> won't matter.  The thicker the wire , the less this matters, so favor
> the smaller-numbered gauges.
> 
> Now consider either bare wire or ceramic insulation for the thermocouple:
> http://www.omega.com/pptst/BARE_SH_DH_OV_ELEMENTS.html
> For example, sh-1-14-K-12 will run you about $20 for a 1-foot length.
> 
> You will need a millivolt meter.  This one from  HF is great, and
> despite the price on this webpage, has been selling for $3 at HF
> stores recently:
> http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90899
> 
> IF you can connect the thermocouple directly to the MV meter, then
> you're almost home free.  If not, then you need extension wire.   For
> precise measurements, you need extension wire of exactly the same
> composition as the thermocouple (so you don't make new thermocouples
> at the junctions).  This is only about $0.62 per foot, but they want
> you to buy 100 ft.  The gauge of this wire doesn't matter at all.
> 
> SO, you might just keep the junctions at room temperature or close to
> it, and just use copper wire as your extension wire.  This will
> introduce errors, but these should be small if all extraneous
> junctions are at room temperature.
> 
> Finally, you'll need a mV vs temperature chart for your type of thermocouple.
> http://www.omega.com/thermocouples.html , or for the type K, measuring
> in deg. F:
> http://www.omega.com/temperature/Z/pdf/z218-220.pdf
> 
> What this chart tells you is that at about 2000 F, the thermocouple
> will give you about 45 mV - easy to measure on the mV meter.
> You take your measurement, then come back to this chart to read the
> temperature.  Skip the "1" to "10" across the top, and just read mV in
> the "0" column, which will give you deg.. F within 10 degrees.
> 
> 
> On Fri, Apr 3, 2009 at 7:38 PM, Bob Willman <blcksmth at wcnet.org> wrote:
>>        One could use Tempil sticks. They are accurate and reasionably
>> priced.
>>
>>
>> Bob Willman
>> Bowling Green, Ohio
>> The Eagle's Anvil
>> WB8NQW
>>
>> -----Original Message-----
>> From: theforge-bounces at mailman.qth.net
>> [mailto:theforge-bounces at mailman.qth.net] On Behalf Of Mark Novak
>> Sent: Friday, April 03, 2009 6:12 PM
>> To: theforge at mailman.qth.net
>> Subject: [TheForge] Forge temps
>>
>> How do y'all measure and control the temperature of your respective forges,
>> for accurate annealing? I don't have a pyrometer that goes over 1000ºF, but
>> I got ahold of some S-7 I'm going to use for center punches and which needs
>> to be annealed at 1500-1550ºF for 20-25 minutes (for a hand tool of this
>> size). I have no idea how hot my crappy atmospheric propane forge burns, let
>> alone how to maintain a somewhat consistent temp.
>>
>> Help!
>> Mark Novak
>> Fireworkspdx.com
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