What happened?

[tulsabrewdaddy]

Used a step bit to get the hole to 7/8". Then I used the keg tool to give the lip, but the lip cracked. This is just the lid so it's not that big of a deal but I'm trying to figure out the cause so it doesn't happen to the walls of the pots. I will say the lid and bit where both very hot at a couple of points thought the drilling. I was using veg oil as a buffer but I forgot to add it (the first time) until I saw smoke. Even with the oil it smoked a couple of different times. Any ideas or advice is appreciated.

 

[day_trippr]

The simplest possible answer is the metal got so hot it became brittle.

A sharp bit, turned very slowly, kept well lubricated, and stopping to let the work cool as you go along, could make a big difference in the outcome.

There's a good chance you no longer have a sharp bit. If that pot is worth the effort it's probably worth the price of a new bit before you attempt to drill again...

Cheers!

 

[flynfrog]

work hardened with a step bit. Made it worse trying to cold form it.

I wouldn't use a step bit in stainless a good cobalt bit high drill pressure low rpm

 

[tulsabrewdaddy]

Thanks for the advice. Ditched the step bit and got much better results.

 

[l3asturd]

I use a step bit with cutting oil. Then I ream out the hole to get it nice and smooth. This is a fairly important step. You can also use the same cutting oil to lubricate the dimple tool while dimpling.

I've done several full couplers and half couplers in my kettles without any cracking. I don't have a picture of the inside but I'll try and take a few today.