I had an old tool and die man tell me he always used powdered lime to protect a part from heat while welding. I tried it, and was completely amazed! I covered a bolt body with it,inside and out,and welded on a new bolt handle. I could touch the bolt body in back of the bolt root, which was covered with lime, right after welding, it was actually cool to the touch. Is this a trick used often and I just never heard of it?

I've heard of it being mixed with oil as a quench for springs, but not as a heat stop.

Did you make a paste with water?

Years ago when I was forging and doing blacksmithing, I used lime for annealing at times. I would get the part above critical temperature and plung it into a welding rod can full of lime and leave it over night. The lime held the heat quite well and allowed the part to cool very slowly, thus giving me a dead-soft condition for that metal.

The heat transfer coefficient of lime that allowed it to remain at it current temperature for extended times will also allow a cool part to resisit becoming hot.

I also think it was in one of the earlier Gunsmithing Kinks, plus I have read about it in an old gunsmithing text-likely either Dunlap's or Howe's.

As Marc stated this has been used for years in anealing. The heat insulating characteristics should work equally well for preventing heat tranfer.
-Don

I used it dry, and as the lime had been outside before I used it, quite chilly. I bet put in the freezer before use would be an excellant idea. I'm sold on it now.

TSJ-

I'm confused as to how you got the lime to stay on the bolt- did you sort of bury it leaving the area you welded exposed?

thanks.

You're making it too complicated. My heat sink is a big bucket of water sitting next to the welding bench. Make a pass and quench it, make a pass and quench it, make a pass and quench it. With practice it is fast, the color never spreads beyond the root, and, you can still shape and finish it easily with a file.

It was an old Mann. action, where the bolt handle was part of the safety lug. I just burried it in lime, inside and out. When I got done, a file still wouldnt touch the surface of the lug and 1/4" away the bolt handle filed up nicely.

Thanks, TSJ. I figured while I had you, I'd get as complete an explanation as I could for reference later.

appreciated.