Form thread cast iron?

[lucky7]

Had a suggestion to form thread roughly 50 1/2” 13tpi hole in cast iron. I have limited experience form threading aluminum and none with other materials. Would be using a mag drill. Worth looking into, or just continue regular non spiral cutting taps?

Thanks for info.

Lucky7

 

[Mtndew]

Typically you don't form thread cast iron.

 

[MrWhoopee]

Cast iron is too brittle, it will not cold-flow. Best outcome will be a very rough 1/2 in hole, worst will be cracked or broken part.

 

[rklopp]

What happens if you form tap ductile iron? I've never tried. I realize form tapping gray iron would go badly.

 

[lucky7]

Thanks for responses.

L7

 

[Limy Sami]

Had a suggestion to form thread roughly 50 1/2” 13tpi hole in cast iron. I have limited experience form threading aluminum and none with other materials. Would be using a mag drill. Worth looking into, or just continue regular non spiral cutting taps?

Thanks for info.

Lucky7

I'd be looking at taps specially for CI ............IME&O they make quite a difference.

Like these Machine Taps for Cast Iron and Abrasive Metals (there are others but I knew where to find these )

 

[DDoug]

Apply a single drop of Molly-dee to the forming tap, and it will run like going thru hot butter.....

 

[Limy Sami]

Hot butter won't form threads.

 

[DDoug]

Hot butter won't form threads.

Hence my suggestion to use Molly-Dee.....
https://www.practicalmachinist.com/...let-me-count-ways-223073/?highlight=molly+dee

 

[EmGo]

Hot butter won't form threads.

Picky, picky, picky ...

btw, where is Pat Paulsen now that we need him ?

(Okay sorry, but it was too funny. Cutting not forming taps for cast iron, I agree.)