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Thread: linkert thread /helicoil

  1. linkert thread /helicoil

    i've got a good linkert going now but when i went to put on the breather i found one of the threads was stripped. i want to stay with the proper thread so i ordered a pack of 12/24 helicoils. i have repaired a number of threads by drilling and taping to the next size and putting in a coil. the 12/24 helicoil measures .280 on the outside and has 28 tpi. i have a lot of taps and some good reference material, but nothing comes close to the correct size for this coil. the helicoil pack says use a #1 drill but gives no refrence as to what tap to use. does helicoil have a special tap for this size? could it be metric? i'm a cheap ass so i hate to purchase the whole 12/24 kit to fix one hole, but i may have to. maybe some of you guys have the kit and can tell me what the correct tap should be. i don't mind purchasing the tap, but don't need the drill bits and installation tool. thanks!

  2. #2
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    Re: linkert thread /helicoil

    If your heli-coils have 28 TPI you have the wrong ones. There is a reason they are called 12/24. Ant if I recall a 1/4 24 tap will work for those. But that is a special tap so since you are a cheap ass you may be out of luck!
    Robbie

  3. #3
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    Re: linkert thread /helicoil

    I buy a lot of 'special taps' from Travers Tools on-line. Another good one is 'MSC-Direct'.
    52 HydraGlide
    59 Pan/Knuck Chopper
    77 Stroker Shovel FLH
    94 Evo Secret Components

  4. Re: linkert thread /helicoil

    the helicoils are 28 tpi on the outside, not the inside, as the 12/24 bolt goes right in. the outside threads and inside threads on helicoils are not necessarily the same tpi. the pack says use a #1 drill, i finaly ran across a chart that says use a #1 drill for a 1/4 40 tap, still doesn't seem right for this as my 28 tpi gage matched up pretty well with the outside of the coil.

  5. #5

    Re: linkert thread /helicoil

    Eye side with Robbie on this one. If they're Helicoils and they're 24 threads-per-inch on the inside, they're 24 t.p.i. on the outside. It's not magic, it's coil of "square wire" coiled on a 45-degree angle. If wire one-twenty-fourth of an inch across were laid in a coil a mile across, it would still be 24 t.p.i. inside and outside.
    That's the reason for the special taps required to renew the threads, they're all oversized on the outside to spec. of the thread you're trying to renew, but the same thread gauge on the inside. Sometimes you get lucky, like common quarter twenty four being suitable for renewing a 12/24 thread.
    You only have to own a couple of the "kits," including the thread tool with the slot on the end to turn the inserts in with in a couple ranges of size , if yor cheap. You need the common, but specified ,drill size to do the over-bore. But almost each tap is a specially-sized "bastard thread."
    Sarge, Gerry Lyons, Fla.
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  6. #6
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    Re: linkert thread /helicoil

    We used to repair those treads in copper and bronze in the following way: Buy bronze or brass bolt of about 1 1/4 to 1 1/2 the size of the original bolt. They have standard thread for standard taps. Drill hole of inner size of bolt thread in the housing, tap same thread as bolt. Screw bolt in, and saw off the protruding rest, make nice flat. Punch a centerpoint, drill the right hole for the original screw, tap original standard thread, and it`s fixed. can`t be done cheaper. Allways watch out the inner size of bolt thread is bigger than the outer size of carb bolt. Need a scetch?
    Apocalyps 21.

  7. #7
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    Re: linkert thread /helicoil

    Forgot something: Don`t forget to fasten that piece with some good locktite and some small centerpunches along the rim. Or: first tap the thread in the new bolt before mounting it in the housing. Make a slit in it then for your screwdriver. Easy as the cat`s violin. Shine on...
    Last edited by Gerard; 10-03-2009 at 08:05 AM.
    Apocalyps 21.

  8. Re: linkert thread /helicoil

    i 'm an idiot! of coarse the inside tpi has to be the same as the outside. i am going to look through my tap asortment and see if i have a 1/4 24 tap in. i bought a lot of stuff from the estate of a neighbor who died years ago. there was a lot of obsolete taps ect. with them

  9. Re: linkert thread /helicoil

    YEE HAW! SUCESS AT LAST. i dug around through various taps and found a 7mm 1.0 tap. it measured .280 on the outside so i drilled and tapped a peice of scrap alumunim i had... perfect fit. drilled out the carb hole with a #1 bit, tapped 7 mm, and put in the helicoil. i suspect the 1.0 metric pitch must figure out to about 24 tpi. it sure feels good to solve a tough problem once in a while.

  10. #10
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    Re: linkert thread /helicoil

    Yeah, it's the smallest of issues that stop us in our tracks sometimes....
    But............... 7mm is slightly larger than 1/4", if I recall. One inch is 25mm, that much I know.
    52 HydraGlide
    59 Pan/Knuck Chopper
    77 Stroker Shovel FLH
    94 Evo Secret Components

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