> Are all type-K (or same type) thermocouples interchangeable? If I 
> found
> one sleeved and ready for kiln application, and type K, can it be
> accurately substituted for the K tc that came with my digital meter?

Essentially yes.


> ... can I extend the leads, either by
> soldering or lugs?

and

> However, I'm lead to believe by some of
> what I've read that the tc wire has to be carried throughout.

Yes, that's almost always the best solution - and it's cheap and 
readily available - see longer version below.

Applied common sense will allow you to work this out in any given 
case.
EVERY inter-metallic junction is a thermocouple.
If you extend it with wire of the appropriate identical type in each 
leg then they are zero-potential thermocouples and will not add extra 
potentials. If you join to eg copper in each leg you will have 
different couples in each leg and a potential difference will be 
caused. If the joins are at a point of intermediate temperature and/or 
uncontroled temperature them you will have a random addition to your 
signal. If you temperature controlled the junction point or if you 
measured the junction temperature you could account for the extra 
potential but in about 99.99% of cases it's easier just to use the 
"right" wire. It's readily available and quite cheap.



        Russell


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