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Posted: 7/21/2008 4:35:13 PM EDT
I stripped out the aluminum thermo housing on my truck. I plan to install a heli coil. The hole is about an inch deep. It takes a 6mmx20mm bolt. Do I install 2 heli coils since they are only about 3/8" long or just one?
Link Posted: 7/21/2008 4:36:49 PM EDT
Yep, put in two
Link Posted: 7/21/2008 4:39:43 PM EDT
[Last Edit: 7/21/2008 4:43:47 PM EDT by JAMES77257]

Originally Posted By stoner63a:
Yep, put in two



Only one. The threads will not line up if you use two. If that happens, you will be in trouble.

ETA: They also have a little prong at the bottom used to install them.
Link Posted: 7/21/2008 4:40:04 PM EDT
Have fun with that, HeliCoils are a pain in the butt. Big time. Just remember take your time.
Link Posted: 7/21/2008 4:41:49 PM EDT
One will do.
Link Posted: 7/21/2008 4:44:21 PM EDT
Do a Time-Sert
Time sert
Link Posted: 7/21/2008 4:48:44 PM EDT
[Last Edit: 7/21/2008 4:54:51 PM EDT by ultramagbrion]

Originally Posted By speedfreak955:
Do a Time-Sert
Time sert


The kit for one job would be expensive but they totally eclipse the helicoils in any use.




Only one. The threads will not line up if you use two. If that happens, you will be in trouble.

ETA: They also have a little prong at the bottom used to install them.


Nope....Stacking them will work fine because the are aligned in the thread created by the helicoils tap...........just make sure you remove all of the tang/tab/prong .
The two coils dont have to butt up against each other to work right.



Have you got room to enlarge the hole in the housing and just go to a bigger sized bolt? Say an 8mm or 5/16 ?

Id go that route with an allen head bolt
Link Posted: 7/21/2008 4:51:05 PM EDT
I install heli coils all the time. They are usually smaller and not the kind you use in your car but i still use them. They are very easy to use. Just dont over drill your hole and you will be fine.
Link Posted: 7/21/2008 4:58:58 PM EDT

Originally Posted By ultramagbrion:

Originally Posted By speedfreak955:
Do a Time-Sert
Time sert


The kit for one job would be expensive but they totally eclipse the helicoils in any use.




Only one. The threads will not line up if you use two. If that happens, you will be in trouble.

ETA: They also have a little prong at the bottom used to install them.


Nope....Stacking them will work fine because the are aligned in the thread created by the helicoils tap...........just make sure you remove all of the tang/tab/prong .
The two coils dont have to butt up against each other to work right.



Have you got room to enlarge the hole in the housing and just go to a bigger sized bolt? Say an 8mm or 5/16 ?

Id go that route with an allen head bolt



If you remove the prong, how can you use the tool to install it?
Link Posted: 7/21/2008 4:59:25 PM EDT

Originally Posted By stoner63a:
Yep, put in two


+1
Link Posted: 7/21/2008 4:59:58 PM EDT
When I rebuild aluminum engines, I drill and Heli-coil all bolt holes.
Link Posted: 7/21/2008 5:00:45 PM EDT

Originally Posted By JAMES77257:
Only one. The threads will not line up if you use two. If that happens, you will be in trouble....


No, the pitch of the helicoils is the same as that of the fastners that go in them. That won't be a problem.
Link Posted: 7/21/2008 5:10:28 PM EDT
If you have the room, use two. Be sure to drill the hole deep enough to allow for tapping deep enough for both inserts remembering that you are using a tapered tap rather than a bottoming tap. Install the first heli-coil deep enough to allow the second one to go in at least one thread deeper than flush. Break off the first tab and be sure to get it out of the hole then install the second insert until it reaches the first one. Break off the tab make sure it is out of the hole and you're good to go. I've done a million of these with no problems.

I've on occasion not been able to get the depth I wanted and gone so far as to trim off a couple of coils on the second insert.
Link Posted: 7/21/2008 5:15:53 PM EDT

Originally Posted By JAMES77257:

If you remove the prong, how can you use the tool to install it?



Well , I ment after its installed.................but Ive put a bunch of them in by hand and also with a bolt with a nut run up the threads enough to screw the coil on.
Link Posted: 7/21/2008 5:18:35 PM EDT
Link Posted: 7/21/2008 7:04:53 PM EDT
not to confuse the issue but the original hole goes partially thru the bottom of the housing. if you can imagin a hole drilled almost all the way thru a part with a rounded bottom. What I see from the bottom appears oval shaped because its on the side of the rounded portion. Should I drill all the way thru clean and install the 2 inserts? I thought about drilling thru and putting a washer and nut on the bottom to hold it tight and screw the threads but being that it comes thru not exactly on the bottom, the washers and nut wouldnt sit flat on the surface.

how can I put in 2 inserts? The barb/tang/tab from the second one will be 1/2 down in the hole unless I screw it in upside down with the barb on the top and just clip it off when the insert is flush. I may be able to use the bolt to screw it in a little further. How much holding power does it really take to hold a billet thermostat housing on? the 2 other bolt appear good to go. I will use some anti sieze for sure.
Link Posted: 7/21/2008 7:08:38 PM EDT
[Last Edit: 7/21/2008 7:09:13 PM EDT by Thatdude333]
From engineering school, I know that having the first 6 bolt threads engaged hold like 99% of the load, anything after 6 threads is negligilbe, so I'd go with 1 if it has 6 thread revolutions or more.
Link Posted: 7/21/2008 7:12:25 PM EDT
A single insert is MORE than enough. In like materials, for example steel in iron, the first 3 threads take 90% of the load. In a steel bolt/aluminum block, the load is spread out over more threads. In a 6mm bolt, that is a pitch of 1mm. There should be 10-12 threads on the insert. Since the insert is stainless steel, the increased diameter more than compensates for the reduced number of threads.
Link Posted: 7/21/2008 8:11:38 PM EDT
[Last Edit: 7/21/2008 8:27:07 PM EDT by Sheldon]
I recently stripped out the tensioner bolt in my aluminum blocked Honda. I got the Heli Coil kit and from what I read you can install more than one in the same hole. The small tab the installation tool engages during installation will snap off when the Heli Coil bottoms out out against the bottom of the hole, or against any previously inserted Heli Coil. Google 'Heli Coil installation' and you'll get a TON of info. Practicing on a scap piece of aluminum would be nice too....I burned thru most of my coils for practice.
Link Posted: 7/21/2008 8:14:29 PM EDT
One coil. I've used them a couple of times. They worked great.
Link Posted: 7/21/2008 8:17:32 PM EDT
Heli-Coils are easy. There is NO reason to use two; a bolt only needs engaged thread length to be about the same as the bolt diameter. 8mm or so of threads is plenty adequate for a 6mm bolt.
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