Re. Odd tap size

[slinMI]

Sonny2 was asking about an odd tap size of I/2 inch by 14 TPI. I think what you have is a Heli-coil tap for a 7/16" 14 thread repair insert. For every size of thread there is a drill and tap set that is used to tap an oversized threaded hole into which the thread repair insurt is placed. The taps are larger than the nominal original bolt dia. to allow room for the insurt, but must have the same TPI pitch as the original bolt/hole. I could be wrong , of course. My data book shows tap deill sizes for 1/2" x 12,13,20,24,and27 TPI and 7/16'x 14,20,24,and27 TPI

 

[Anonymous-0]

I agree with you on that.There is a sorta rare thread on a Harley[oilpump studs and such] that is 1/4-24,but a 10-24 heli-coil tap works as well.Nowhere in the MSC catalog is a 1/4-24 listed.The thread pitch does not change for heli-coils but the hole size is the only difference.So now all he needs is the right size drill bit the heli-coils themselves and the installation tool to repair 7/16-14 stripped threads.Bag it ,mark it ,put in in the thread repair drawer not the glass case.

 

[Bud in FLA]

Check the straight pipe size chart - 1/2-14 is a straight pipe thread.
INCH TAP DRILL SIZES

 

[Anonymous-0]

But 1/2 inch pipe thread is a whole lot bigger in diameter than 1/2".

Gerald J.