Casting Pot Temp. Setting vs Thermometer

[alamogunr]

I've been having difficulty getting good boolits at lower temperatures. I use a thermometer mostly to clean WW so I don't melt a bunch of zinc WW. I never really paid a lot of attention to the Pro-Melt. I decided to heat up a full pot and check the temperature at various settings.

I have 2 thermometers. One I bought many years ago from Bill Ferguson, the other when GAR was liquidating inventory. Both are Tel-Tru. According to their website, the one I got from Bill, is a laboratory model. The one from GAR is an industrial model. These are the results:

Pot Setting #1 (Lab) #2(Ind)

650º 580º 560º

700º 610º 600º

750º 700º 680º

800º 780º 760º

I might add that at the 650º pot setting, there was sludge around the edge of the pot. It probably extended 1/2" below the surface.

I plan to use the Lab grade thermometer for my settings. Either would probably and if I can rig up a bracket to hold the Industrial thermometer in the pot, I don't think for my purposes that a max difference of approx 3.5%(Lab vs Ind). The Industrial model has threads under the dial, probably for mounting in a tank wall.

I know someone will suggest a PID as the only solution, but I don't really want to fool with one right now. Maybe someday.

Can anyone see a serious fallacy with my plan?

BTW Does anyone know how to keep columns aligned?

[Calamity Jake]

Looks like you need to use the 750° setting on the pro melt to have 680-700° alloy temp. anything less
isn't hot enough, use the thermometer of choice as I can't see 10-20° in melt temp making a difference.

[Mike W1]

Looks like you need to use the 750° setting on the pro melt to have 680-700° alloy temp. anything less
isn't hot enough, use the thermometer of choice as I can't see 10-20° in melt temp making a difference.

Got to go with what you have but I have to pass on a short while ago I was casting with 2 Lyman moulds and one wouldn't fill out. Was at 635° with my PID. Kicked it up to 645° and both moulds filled out nicely. 10° can make a difference.

I calibrated my Tel-Tru with boiling water and it came closer to agreeing with my PID probably within ± 10°.

[bangerjim]

I do not even worry about what temp the lead is at. I know when it casts good boolits and when it does not......and what to do to correct the problems......all WITHOUT a thermometer or controller.

I can tell from the way the sprue cuts if the lead/mold is at the right temp and if the boolits that fall out will be keepers or not.

Works for me.......for a loooooooooooooooong time!

If you just MUST know the temp, develop a coorelation between the known setting and the most accurate thermometer and then just forget the cal marks on the knob.......just like many folks do that buy those cheeeeeep toaster ovens to bake PC boolits in.


I sell PID-based controllers in my company, know the technology and applications inside and out......and I still do not use one! This is not rocket science.....it is just melting lead. Good boolits comes from experience, not from a digital readout.

bangerjim

[alamogunr]

I didn't think about using boiling water. Not sure how accurate that would be since the thermometer dial reads 200º to 1000º.

I do have some "pure" soft lead. Should be good enough to determine when it melts and then solidifies. It could be that both my thermometers are "off".

I just discovered(I'm not too observant) that the industrial model can be adjusted. A tiny set screw secures the dial. Just turn the dial to make the reading agree with whatever I'm using as standard. At least both thermometers will agree.