helicoil tap

[mielke]

For some reason i'm having trouble on tapping for helicoil inserts. I have a 1/2-13 insert and putting it into 304SS as far as i can see online I need to drill a 0.53" hole and use a 1/2-13 STI tap. (first of all am I correct so far?)

I ruined a tap already, it appears the hole is a little too small.

 

[mrainey]

Interesting that my Heli-Coil manual recommends a 0.531 drill for steel, but specifies the minor diameter after tapping as 0.5166/0.5273

Is it possible that you have a form tap? The minor before tapping would be 0.557 for a theoretical 75% thread.


Software For Metalworking

http://closetolerancesoftware.com

 

[mielke]

It's a straght fluted tap and I'm thinking were having problems evacuating the chips causing it to break. Trying a spiral flute next

 

[bob8907]

304 can be gummy. Raise coolant concentration to 10% or use dedicated fluid, and peck tap if you are going more than 1.5xD. Lube can be a MAJOR issue. If you are doing a blind hole with straight flute, good luck. I think most problems there can be solved with a good designed tap and better lube.