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#1
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Heli-Coil help!
Stripped out a carb stud on my LD340 and now Im trying to coil it. I tapped it out to the recommended thread size (3/8 coarse) and now I am threading the coil in. Well, the coil goes in about 3 threads and then the tang bends out and it wont thread anymore. I pulled it out with a pair of pliers with an unwinding motion and tap it again a little deeper this time. well this one goes in 4 threads and bends out again. I drill the blind hole through to the runner now and tap the whole F^ckin hole through, nice and easy. The third coil goes in 4 threads and bends out. What the Heck? So I am now using a coil that is only 4 threads deep, trimmed and it is not holding a torque (it is pulling out slightly) I think it'll hold, but this is Aerospace stuff? Im not flying anymore!!! Im going to buy a 3/8 to 5-16 stud and just use the threads I cut. So much for a $25.00 Heli coil kit...I was going to do them all!
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#2
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If you used a 3/8-16 tap you used the wrong tap. You need a special tap for use with the heli coil.
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#3
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Tap came with the kit!!!
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#4
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That's strange, I've put in lots of heli-coils at work and never had a problem, does the tap that came in the kit say Heli-coil and the correct size on it? Most of them are marked like that so they won't get mixed up with a regular tap, It sounds like the tap your using is not cutting a big enough thread even though it came in the kit, maybe it came with the wrong tap in it??? and the heil-coil is binding up.
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#5
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I think the tap is wrong. the kit is made by Perma-Coil and it is a 3/8 16 coarse tap. I think it should be a special 3/8 - 18 tap for a 5/16 - 18 thread insert right. Im pissed now because I already cut the threads in my intake 3/8 - 16. Oh well, I guess Ill just use a 3/8 stud now, of course Ill take the kit back, but not before I call the number on the kit and ask WTF!
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#6
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I think you have a handle on it now, the thread count is the same for ID and OD so it won't be SAE or USS on the OD.
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#7
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There is one more option that you could try. Go to the hardware store and buy a piece of threaded rod in 7/16" or even 1/2" diameter. Drill open the hole that you put the 3/8 tap into and use that as a plug and seal it good with Loctite. Then you can drill and tap the proper hole in the center of your home made plug or "homemade Heli-coil". It is a similiar concept as a heli coil, just thicker. I hate to see a good LD340 go to waste. It is worth a try.
It does sound like you had the wrong Heli-coil tap in the first place. |
#8
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There are a couple of other brands of thread repair kits that use standard taps. Keen-sert is one that comes to mind.
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#9
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Ok Im closing this post with some good news. I called Perm-Coil and the guy said there is no way that tap was supposed to be in that kit, it is not even the manufacturer they deal with. I wont reveal the place where I bought it, but its initials are PB...anyway, they exchanged it for a new kit with the correct tap STI, and 12 new inserts, and the Perma-Coil guy is sending me 4 solid inserts that go into a standard 1/2 -13 tapped hole for the trouble, even though it was not there problem. Thanks!
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