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Tom, for what it's worth - I found a picture on-line of the factory replacement thermocouple for the newer digital control versions of this furnace. I'm thinking it would fit the older models as well. I'm just using it for a visual reference though.
TC746X1A.jpg (Size: 20.93 KB / Downloads: 104)
I also found of copy of the "OPERATION AND REPAIR MANUAL AND PARTS LIST
SERIES 1256 & 1257"
BTFB1300-1400Manual.pdf (Size: 254.56 KB / Downloads: 1)
in which it states the following about replacing the thermocouple:
Quote:19. Examine the thermocouple, and, if it is good,
reinsert it into the chamber. It should extend
about 1-1/2" into the chamber. Make sure
porcelain insulator is in place for the thermocouple
to pass through on the steel
back plate. Replace clamp and screw.
(Excessive scaling, pitting, or cracks are
some indications that the thermocouple
may need to be replaced.)
So I guess now I just have to decide on which length thermocouple I need from McMaster. 12, 18, or 24 inch. If I get one long enough to reach the PID terminal block, I shouldn't need additional thermocouple wire - should I? 
Willie
Very nice Willie 
What are you plans for the furnace ? a wee bit of color case hardening maybe 
Rob
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That would be nice Rob, but I don't think I would ever have the time to learn how to do a proper job of it. I'm just wanting to do basic hardening, tempering and annealing of small parts. Trying to do it with my oxy/acetylene torch and box of crayons (Tempilstiks) leaves a lot to be desired. I have enough problems just seeing in general - much less seeing and recognizing the temperature of steel by color (colour). 
I just ordered a cheap PID temperature controller. As Dave H. (the other one) pointed out, controllers with multiple set points for ramp/soak times and the like are much more expensive. Another issue for me is trying to hold a part at a steady/even temperature with a torch for any length of time is difficult. Not to mention down right costly with the price of acetylene these days! 
The gent that I bought the furnace from was using it for annealing brass .22LR cases that he swedged into jackets for making his own .22 centerfire bullets. (WAY too much work IMHO.) But he is moving to a distant State and didn't want to lug it with him I guess. Worked out well for me though. 
Willie
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Willie
That is a piece of magic - very nice piece of kit
DaveH
a child of the 60's and 50's and a bit of the 40's 
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Highpower (12-05-2015)
Willie - for annealing, I just heat the part until a fridge magnet that I have stuck to it becomes molten and runs off. At that point I stick it in a drum of ash and leave it to cool slowly over night.
Hunting American dentists since 2015.
RobWilson
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Hawkeye (12-05-2015)
(12-05-2015, 07:41 AM)Highpower Wrote: That would be nice Rob, but I don't think I would ever have the time to learn how to do a proper job of it. I'm just wanting to do basic hardening, tempering and annealing of small parts. Trying to do it with my oxy/acetylene torch and box of crayons (Tempilstiks) leaves a lot to be desired. I have enough problems just seeing in general - much less seeing and recognizing the temperature of steel by color (colour).
I just ordered a cheap PID temperature controller. As Dave H. (the other one) pointed out, controllers with multiple set points for ramp/soak times and the like are much more expensive. Another issue for me is trying to hold a part at a steady/even temperature with a torch for any length of time is difficult. Not to mention down right costly with the price of acetylene these days!
The gent that I bought the furnace from was using it for annealing brass .22LR cases that he swedged into jackets for making his own .22 centerfire bullets. (WAY too much work IMHO.) But he is moving to a distant State and didn't want to lug it with him I guess. Worked out well for me though.
Hi Willie
LOL I stopped using crayons when those laser temp guns came out much more user friendly , and they come with a lazy american setting , Adding a multi set point controller is taking your furnace to another level , having that feature is a must for some modern alloys . watching with interest.
Rob
PS you probably know this but others may not , stick a few bits of charcoal in the furnace with your part , it uses up the oxygen in the furnace chamber as it burns and so cutting down on the scale/oxide on parts ,its not a perfect solution but it is an improvement. Keep the door shut as much as possible .
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EdK (12-05-2015)
(12-05-2015, 01:42 AM)Highpower Wrote: So I guess now I just have to decide on which length thermocouple I need from McMaster. 12, 18, or 24 inch. If I get one long enough to reach the PID terminal block, I shouldn't need additional thermocouple wire - should I?
Willie,
The MC thermocouples are of similar design except they use a bunch of the ceramic spacers along the full length of the wires. You would only need to use enough of them to reach through the wall of the furnace. And no, if you can place the PID close enough to connect it directly to the thermocouple wires, you would not need any extension wire. That's a good thing because any connections act as additional junctions that affect the reading. The type of wire needs to match the different types of thermocouples, to reduce that effect.
Tom
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Willie,
Ed
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(12-05-2015, 08:54 AM)Mayhem Wrote: Willie - for annealing, I just heat the part until a fridge magnet that I have stuck to it becomes molten and runs off.
Yeah, that's what I have been doing with my crayons.
Willie
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f350ca (12-05-2015)
(12-05-2015, 09:47 AM)TomG Wrote: (12-05-2015, 01:42 AM)Highpower Wrote: So I guess now I just have to decide on which length thermocouple I need from McMaster. 12, 18, or 24 inch. If I get one long enough to reach the PID terminal block, I shouldn't need additional thermocouple wire - should I?
Willie,
And no, if you can place the PID close enough to connect it directly to the thermocouple wires, you would not need any extension wire.
Tom
My thought (for now) is to gut the original controller and gauge from the (vented) lower enclosure and install the new parts in their place. Then just route the new thermocouple down the back of the case like the original.
That's where they are in the newer digital versions, no?
![[Image: cq5dam.thumbnail.450.450.png]](http://www.thermoscientific.com/content/dam/tfs/LPG/LED/LED%20Product%20Images/Heating%20Equipment/Furnaces/F30149~p.eps/jcr:content/renditions/cq5dam.thumbnail.450.450.png)
I guess it will depend on how big the new SSR and heat sink are (I have no idea...) as to whether or not it will all fit inside, and not be subject to overheating. Another wait and see....
Willie
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