I have never install a heli coil before as a thread fix. I have looked at the necessary kit that includes tap, installation key, and thread inserts. However the inserts are only half as deep as the hole I would like to install them in.
Q. can I insert one thread unit, screw it to the bottom and then install as second unit on top?
Q. how do you get rid of that threaded end that the key fits into. Break it off somehow?

You dont need to use two of the helicoils. One should be enough. What are you needing to fix a hole in? Intake or something like that?

So to answer your first question. No, there is no need to insert more then one unit. The pigtail at the very bottom of the threaded helicoil is suppose to go all the way to the bottom

Second question. All you do just unscrew the plastic installation tool. Leaving the coil inside. its just for grabbing that pigtail at the bottom of the threaded helicoil to run it all the way down. Then you unscrew it leaving the helicoil inside.

A hole that has been repaired with a helicoil has stronger threads then the actual threads that were in the hole originally.

You can't install at thread insert on top of the other because the thread lead might not on would not line up with the first insert installed.

By rule one and a half of the dia of the bolt in depth is all the strength that you will achive. In other words if you have a 1/2" dia bolt, that would be 3/8" of an inch in length to achive the maximun strenght of the bolt.

The tang that is used by the install tool is broken off by pushing down or tapped on the handel of the install tool with the palm of your hand.

Mike

Just make sure you drill the hole straight(square) to the horizontal surface.

Helicoil inserts are available in different lengths, from "1 x Diameter" to "3 x Diameter"

By rule one and a half of the dia of the bolt in depth is all the strength that you will achive. In other words if you have a 1/2" dia bolt, that would be 3/8" of an inch in length to achive the maximun strenght of the bolt.



Mike


1/2" x 1.5 = 3/4"

LK

Thanks for the replies.
I am repairing a chrome trim piece on my son's drum kit. A fancy chrome bolt holds a leg onto the bass drum. The bolt is 5\16 thick.
I think you're right, one insert will hold enough. However, the bolt has to be screwed in and out a bit every time the drum kit is moved to a gig as the leg will either be removed or turned aside each time the drum is moved.
One final Q---- should I use Locktite on the heli coil insert before screwing it into my newly tapped hole? I have red and blue locktite handy.

No need for the locktite - just try to get the helicoil out once its in there!! besides, some would seep through the coild and gum up the new thread area.....

You can't install at thread insert on top of the other because the thread lead might not on would not line up with the first insert installed.

Not true.

The helicoils always line up cause they are going into the same threads cut by the special oversize tap. Have installed more than one insert many times. It might be overkill, but its better to be safe than sorry.

1/2" x 1.5 = 3/4"

LK
I stand corrected, typo

Not true.

The helicoils always line up cause they are going into the same threads cut by the special oversize tap. Have installed more than one insert many times. It might be overkill, but its better to be safe than sorry.

Sorry for the misleading information that I provided, It would appear that I should just read the post and not reply.

To close this thread, I just installed the heli coil. It went in real nice and boy, are those new threads real nice and strong. Perfect repair.
I only needed one insert as it was just the right length.
Thanks to all replies, and yes all replies are welcome. Just a bunch of guys BSing in a shop.

Heli-coils are Not put to the bottom of the hole, it is installed "1" thread deeper than the lowest part of the top for the hole, so that the tail won't pull up out of alignment.

If you bend (use a punch to start it)and fold the top of heli-coil, then use a screwdrive to unthread the Heli-coil, if you need to remove it.

The one and a half depth is "Only" for plate steel (with out a heli-coil). Nothing else.

I have been a Investment Mold maker since '74, and I install 100's and 100's of Heli-coils a year!

Pat

Heli-coils are Not put to the bottom of the hole, it is installed "1" thread deeper than the lowest part of the top for the hole, so that the tail won't pull up out of alignment.

If you bend (use a punch to start it)and fold the top of heli-coil, then use a screwdrive to unthread the Heli-coil, if you need to remove it.

The one and a half depth is "Only" for plate steel (with out a heli-coil). Nothing else.

I have been a Investment Mold maker since '74, and I install 100's and 100's of Heli-coils a year!

Pat
{Quote}
By rule one and a half of the dia of the bolt in depth is all the strength that you will achive. In other words if you have a 1/2" dia bolt, that would be 3/4" of an inch in length to achive the maximun strenght of the bolt.

I wasn't refering to the heli-coil on the one and a half depth, just the bolt.
I work in a mold shop as well and have installed 100's of heli-coils for what it's worth

{Quote}
By rule one and a half of the dia of the bolt in depth is all the strength that you will achive. In other words if you have a 1/2" dia bolt, that would be 3/4" of an inch in length to achive the maximun strenght of the bolt.

I wasn't refering to the heli-coil on the one and a half depth, just the bolt.
I work in a mold shop as well and have installed 100's of heli-coils for what it's worth


I guess I wasn't very clear. I was referring to what "Chris R" was saying to run the heli-coils to the bottom of the hole. If you run it to the bottom and something is wrong with it or you can't get the tail off right, it's then a bitch to get back out, and then your bolt could be to short. And the middle i said something about your 1.5/dia.

The maximun strength of a bolt is measure by pulling it till it brakes, the maximun bolt holding is measured by it's thread holding before stripping of the bolt threads, (1.5 x dia.) not the material it's screwed into. "specifications torque" (headbolt, oil pan, crank pulley, etc) is the maximun safe strength, of a particular bolt dia/thread into a particular material (plate steel, cast steel, cast iron, plate aluminum, cast aluminum, plastic, lead, wood, brass, etc).

You wouldn't want the same length/torque headbolt in a cast iron block as a cast aluminum block. Longer threads will help to get closer to get the same squish strength.

A wet bolt torque will holded tighter then a dry bolt torqued to the same number of torque.

I didn't mean to upset you or anyone, but I didn't go along with what was said, about something I do every day for 30+ years!

Pat

I guess I wasn't very clear. I was referring to what "Chris R" was saying to run the heli-coils to the bottom of the hole. If you run it to the bottom and something is wrong with it or you can't get the tail off right, it's then a bitch to get back out, and then your bolt could be to short. And the middle i said something about your 1.5/dia.

The maximun strength of a bolt is measure by pulling it till it brakes, the maximun bolt holding is measured by it's thread holding before stripping of the bolt threads, (1.5 x dia.) not the material it's screwed into. "specifications torque" (headbolt, oil pan, crank pulley, etc) is the maximun safe strength, of a particular bolt dia/thread into a particular material (plate steel, cast steel, cast iron, plate aluminum, cast aluminum, plastic, lead, wood, brass, etc).

You wouldn't want the same length/torque headbolt in a cast iron block as a cast aluminum block. Longer threads will help to get closer to get the same squish strength.

A wet bolt torque will holded tighter then a dry bolt torqued to the same number of torque.

I didn't mean to upset you or anyone, but I didn't go along with what was said, about something I do every day for 30+ years!

Pat

I guess I figured the tab that the installation tool is to go all the way down to the bottom of the hole so you can run the bolt all the way down. I didnt think of the consiquences if something wasnt right and you needed to get it out.

You do a lot more of them then I do. What do you do with the tail if its not supposed to be run all the way down? I havent done this to many times.

If there is one invention on the planet I wish I could have came up with. The Helicoil is one of on the top of my list.

The "tail" is to be broken off after the insert is installed. The bolt can then go all the way through the insert. It isn't for removal. Wont really matter if it's left on at the bottom of the hole as long as the bolt doesn't bottom out on it.

When you get it to the depth you want, then you ("I") use a pin punch and tap it with a hammer. ( don't hit hard just firm to crack the tail off, if it bends only, just bend it back and if it doesn't fall off, tap it again. (Don't hit it in the center of the hole, but towards the base of the tail)
If you tap a hole (even if you use a bottoming tap) you still don't get threads to the bottom of the hole, and that means the bottm of the thread gets smaller till no threads, and if you run the heli-coil to the bottom, the thread hole gets smaller also and the bolt will not fit and it will ruin the bolt threads and the heli-coil.
You can heli-coil anything you can tap, just don't let the heli-coil stick out of either side of a plate.
I myself don't use the inserter that you get with the kits or the hand crank inserter, we make ours out of bolts, easier to use.
I have blocks of lead and plastic that I use all the time on building my R/C airplanes, with heli-coil in them. When you have soft material that you need to bolt and unbolt, you install a heli-coil so that the threads don't pull out and last almost for ever.

Pat