• Please be sure to read the rules and adhere to them. Some banned members have complained that they are not spammers. But they spammed us. Some even tried to redirect our members to other forums. Duh. Be smart. Read the rules and adhere to them and we will all get along just fine. Cheers. :beer: Link to the rules: https://www.forumsforums.com/threads/forum-rules-info.2974/

Tap size for helicoil insert?

Does anyone know the tap size for a 7/16-20 helicoil insert? I bought a used kit on EBay and the tap in it is not the correct size.

I have the hole drilled out to 29/64, as called out in the directions.

I'm afraid it's not a normal thread size, and there for a special tap is required - at a cost i'm sure I won't like.
 

muleman

Gone But Not Forgotten
GOLD Site Supporter
I would think it was a 1/2-20 with that tap drill size. 27/64 is nominal for 1/2-13.
 
that's what I always thought too - it was basically the next thread size up...but the Helicoil website tells you every other detail BUT the thread size...

I know the tap part number is 7FPB, it's an STI tap, and the tap major dia is .5062
 

tommu56

Bronze Member
GOLD Site Supporter
the helicoil tap is the same pitch as the original thread the major diamater is bigger to give room for the coil to fit in

I prefer jergens inserts my self
you can replace the inset by drilling out the lock keys and spinning them out threading in a new tap the locks in
we used a lot of them in aluminum .
get_image.aspx

http://www.jergensinc.com/site/product_detail.aspx?group_no=3017


tom
 
Top