How to contaminate wheel wts..

[Frosty]

Set up my thermocouple/thermometer, newly acquired from Harbor Freight, yesterday with a batch of wheel wts. To protect the wire thermocouple, I cut eight inches from the closed end of a scrap arrow that I assumed to be aluminum, stood it open end up in the melt and put the wire in the tube. Used a visegrip lightly clamped on the tube at right angles and lying on top rear of the RCBS pot to keep it from floating. Cast for about an hour with good results and the TC working as advertised until I ran the temp. to 850*F. Then I got obvious contamination and poor bullet fill-out. When I examined the the arrow shaft, I discovered the bottom two inches had melted. I now believe yhe arrow was made of zink or an alloy of it. Aluminum melts at 660*C. Had to discard the whole twenty pounds of metal. Broke my heart.

Any comments about arrow metalurgy from you learned fellows?

Incidentally, the thermocouple wire was blackened but its function was unimpaired.

Regards to you all,

GL

[pdgraham]

Set up my thermocouple/thermometer, newly acquired from Harbor Freight, yesterday with a batch of wheel wts. To protect the wire thermocouple, I cut eight inches from the closed end of a scrap arrow that I assumed to be aluminum, stood it open end up in the melt and put the wire in the tube. Used a visegrip lightly clamped on the tube at right angles and lying on top rear of the RCBS pot to keep it from floating. Cast for about an hour with good results and the TC working as advertised until I ran the temp. to 850*F. Then I got obvious contamination and poor bullet fill-out. When I examined the the arrow shaft, I discovered the bottom two inches had melted. I now believe yhe arrow was made of zink or an alloy of it. Aluminum melts at 660*C. Had to discard the whole twenty pounds of metal. Broke my heart.

Any comments about arrow metalurgy from you learned fellows?

Incidentally, the thermocouple wire was blackened but its function was unimpaired.

Regards to you all,

GL


850 is pretty toasty... and Zinc melts at 787 F...

I'm wondering if you could have skimmed the zinc off??? :confused:

[Frosty]

The zink? formed a red-hot layer on top the melt. I decided recovery was impractical. Never certain of complete success.

GL

[44man]

There is no zinc in arrows, only aluminum. There are several different alloys used. Yes, it will melt in a lead pot. An aluminum pan full of lead used when smelting can lose the whole bottom. It doesn't have to be at the full melting temperature to slump apart.