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Heli-Coil tap size for 1/2-13

slow-poke

slow-poke

Ultra Member
I have only used Heli-Coils perhaps twice in my life.

I have a 1/2-13 stripped hole that needs to be repaired. I looked in my threaded widgets drawer and lo and behold I have some 1/2-13 heli-Coil inserts leftover from must be 20 years ago.

So my question is, do these use a regular tap (perhaps one size up like a 9/16-12 or some special oversized proprietary Heli-Coil tap?
 
E-Z Loc inserts use standard taps:

Inserts for Metals

www.mcmaster.com

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.
www.mcmaster.com www.mcmaster.com

Also available in oxide coated (12L14) if you don’t need SS. They sell installation tools, but you don’t need one.
 
yeah, HC made sure that only their taps can be used to cut the thread needed for their inserts
kinda like John Deere, Kubota, Mack, Apple...
 
Give me an hour or 3 and I'll check when I get home - that may be the one size that I have a heli-coil tap and inserts for (or its metric 12mm).
 
I just happened to use that exact same size to repair a stripped thread on my Bridgeport. Later on, I replaced the entire column support so it wasn't needed forever.

Here is the info I have on that.

The drill size required for a 1/2-13 Heli-Coil is 33/64ths.

The tap used is a special Heli-Coil tap, also known as an STI (Screw Thread Insert) tap. It is a 1/2-13 STI tap. It is not a standard 1/2-13 tap. Basically it cuts the same pitch as a 13tpi screw but it cuts it bigger to hold the insert required.

Some Key points to remember:

Heli-Coil taps are designed specifically to create the oversized threads needed to accept the Heli-Coil insert.

It is very important to use the Heli-Coil tap, and not a standard tap.

After drilling and tapping, the Heli-Coil is installed with needle nose pliers until it is fully engaged, and then the wire for the pliers is broken off so the regular 1/2-13 bolt can be threaded in.

When I first used Helicoils, I was very leery of them and assumed they would only carry part of the regular load. But that simply isn't true. The guys in our fastener lab showed me that once a bolt is installed, it traps the helicoil between the bolt and the original structure using larger diameter threads. The bigger diameter supports additional sheer loads such that the weakest link is still the original bolt. Amazing really! Just don't use them to replace grade 8 fasteners. They are not designed for that.
 
Thanks guys. It's fixed. I was able to tap deeper and get some good material. Some loctite for good measure and it seems solid as a rock. I wonder what I did with that tap?
 
In cases where i don't have the right thread inserts i'll make my own. For 1/2-13, drill/tap damaged threads for 5/8-18. Then take a 5/8-18 bolt and drill and tap the threaded end for 1/2-13 and part it off at the appropriate length or insert it using the bolt head and cut it flush with a zip disk. a dab of red loctite will keep it in place. An install tool can be a greased 1/2-13 bolt with a nut threaded on if you want to be fancy.
 
Susquatch said:
After drilling and tapping, the Heli-Coil is installed with needle nose pliers until it is fully engaged, and then the wire for the pliers is broken off so the regular 1/2-13 bolt can be threaded in.
Click to expand...
Why not just use the installation tools provided with the kits ? Makes life easy . :) Or just use a bolt and grind a tang on the end to drive the wire . ;)
 
mmcmdl said:
Why not just use the installation tools provided with the kits ? Makes life easy . :) Or just use a bolt and grind a tang on the end to drive the wire . ;)
Click to expand...

I don't recall any special tools in the kit. Kit might be different in Canada.
 
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