3/8-24 Helicoil bolt

[kccadcam]

I'm going to modify a 1/2-20 SHCS to 3/8-24 Helicoil Thread to hold a part down.
(tapped hole without the insert installed)
I can find specs on the tapped hole all day,,
Where would I find the actual Male thread specs?
Just subtract a few thou off the pitch dia. and call it good?

 

[gcode]

I'm going to modify a 1/2-20 SHCS to 3/8-24 Helicoil Thread to hold a part down.
(tapped hole without the insert installed)
I can find specs on the tapped hole all day,,
Where would I find the actual Male thread specs?
Just subtract a few thou off the pitch dia. and call it good?

 

If you can find a full  Helicoil catalog, in will include Helicoil tap dimensions
Once you know the major and minor you can turn some trial threads and tweak them  till you
find the fit you are looking for

[kccadcam]

If you can find a full  Helicoil catalog, in will include Helicoil tap dimensions
Once you know the major and minor you can turn some trial threads and tweak them  till you
find the fit you are looking for

I can find how long the tap is...
I've been looking thru Tap catalogs, Helicoil catalogs, every catalog I can think of....
Still no go...

[kccadcam]

Even ChatGPT can't find it......
Been arguing with it for awhile now.....

[kccadcam]

Finally ChatGPT figured it out:

I apologize for any confusion earlier. Here are the actual tap dimensions for a 3/8-24 STI (Screw Thread Insert) tap:

Tap diameter at the outer edge: 0.367 inches
Tap diameter at the base: 0.342 inches
Tap drill size: 25/64 inch (0.3906 inches)
Tap chamfer length: 1-1.5 threads
Tap thread length: 0.625-0.75 inches (depending on tap length)
Tap square size: 0.3125 inch (5/16 inch)
Overall tap length: approximately 2.5-3 inches
It's important to note that these dimensions are based on standard industry specifications and may vary slightly depending on the manufacturer or supplier of the tap.



What is the Pitch diameter and pitch diameter tolerance?



The pitch diameter and pitch diameter tolerance for a 3/8-24 STI (Screw Thread Insert) tap are as follows:

Pitch diameter: 0.3376 inches
Pitch diameter tolerance: +/- 0.0003 inches
The pitch diameter is the diameter at which the width of the thread and the depth of the groove are the same, and it's a critical dimension for ensuring proper fit between the Helicoil insert and the threaded hole. The pitch diameter tolerance indicates the acceptable range of variation in the pitch diameter of the tap, which is typically specified to ensure that the tapped hole meets the required thread specifications.

It's important to note that these dimensions and tolerances are based on standard industry specifications and may vary slightly depending on the manufacturer or supplier of the tap.

[Incogneeto]

It is usually on the package.

Did you get off your ass walk down to the floor and look at the helicoil package??

Or did you just click a lot?

[kccadcam]

It is usually on the package.

Did you get off your ass walk down to the floor and look at the helicoil package??

Or did you just click a lot?

Not the insert, I need the tap specs.....
I'm making a bolt.

[Incogneeto]

Not the insert, I need the tap specs.....
I'm making a bolt.

It's Friday!! I Bolted an hour ago.

It's a 3/8-24.

Did you check the Machinist's Handbook?

[Incogneeto]

Shadow graph the pitch dia/effective dia of the tap and do what you said - reduce a couple of thou

Uhh He prolly doesn't have an optical Comparator in his Orofice.

https://www.machiningdoctor.com/threadinfo/?tid=39

I was being a smartass no offense meant.

But you should have a machinist handbook just cause.

will give you all dimensions and Tolerances. for nearly all threads.

Good Luck.

[Jim at Gentex]

Also I have found recently that the engineering customer support at Heli-Coil is very good.

We recently had a cracking issue with tapping a 4-40 STI hole in a small plastic part, and they were very helpful in getting it resolved.

You may get your answer with a single phone call. 

[Rstewart]

I've said for years that someone should sell fixturing bolts that would fit into a Helicoil tapped hole that didn't have the insert installed

[gcode]

I've said for years that someone should sell fixturing bolts that would fit into a Helicoil tapped hole that didn't have the insert installed

I suspect licensing and royalty issues would make it too costly to be worth the trouble

[crazy^millman]

I have just always made my own at different shops. The information was readily available from the Helicoil Website. I have just kept digital copies of these things going back 20+ years. I did this on a part 20+ years ago and had to get Parker Haffin to allow us to do so. I told them I couldn't figure out a different way to make the parts. They did a 6 week review and finally approved it. I have had the same discussion with at least 10 other companies over the years and everyone of them fights it. They worry it will fatigue the threads to use them for machining operations. I always laid out a min torque spec when doing this depending of the size of the bolt and the material. Once they all realized that was already considered before doing it they bought into allowing the process. Funny most times the degreed engineers did even realize that there's a specification for the correct amount of torque to be used on a Helicoil insert. We use 25-40% of that for the machining operations and we are well below the threshold of elongation for that size of insert in that material.   

[kccadcam]

Found a great reference, time to go into the STI Bolt business...
https://www.judgetool.com/products/thread-plug-gages-sti-helicoil-inch-duplicate/