Ditto what Shawnette said.
The welding shop near me let me mix different sizes and just weigh them all together.
For example, I tell them I need 10 of 3/32 and 5 of 1/16 and they just weight them and charge me per pound. And I don't even have to buy full pound either. I think last time I paid about $13 or so per pound... They were 308L.
TIG rods come in 36 inches in length so you could either make 4 -9inch ones or 3 -12 inch mandrels or whatever size you would want.
Hope this helps...
