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Thread: Stripped out exhaust studs

  1. #1

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    Default Stripped out exhaust studs

    Does anyone know of a O-320 exhaust stud drill fixture for drilling out, or more importantly drilling for helicoil repair?

  2. #2
    rocket's Avatar
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    Default Re: Stripped out exhaust studs

    Bobby,

    is the stud stripped or the hole in the cylinder ? Good place for a photo.

    This is one of the places I like to ask how handy are you. Have you drilled a lot of holes in steel and Alumanum? Have you installed anhelocoil in somthing else before? If you have then fine, if not best to seek out someone who has, could save you a lot of money and time.

    There is a tool floating around. I've never used one, I just drill the hole but for the less experienced it's not a bad idea. Also I've made a tool to,do round moter studs back in the day with a thick plate of steel. Ha, I've been around long enough to say back in the day!

    some one will most surly chime in about that tool soon.

    Rocket

  3. #3
    Gilbert Pierce's Avatar
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    Default Re: Stripped out exhaust studs

    I made a fixture that bolts up to the good stud so yo can drill out the stripped one straight. Itís just a a straight piece of steel with two holes in it. Iíll locate it and take a picture of it. If you can use it Iíll send it to you. Back in the day when I was having to pull the exhaust every 100 hours, which was almost twice a year, wallowed out exhaust studs were a continuing problem. I havenít used it recently.
    Not sure it would be helpful if the stud is broken off in the cylinder.
    Last edited by Gilbert Pierce; 05-25-2020 at 08:24 PM.

  4. #4

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    Default Re: Stripped out exhaust studs

    Thanks for the reply, I have drilled out a lot of holes and done Helicon in other applications, but I am still not the best at it. My experience has been with heavy structure on the A-10s. When would repair a hole like this we typically used a guide and a reamer to prep the hole, mostly installing SS or Inconel bushings. This stud is stripe out of the hole in the cylinder and needs to be drilled and taped for a repair coil. I know a few people like yourself that can eyeball a hole and drill it straight, but i am not one of them, LOL . Thanks for the info.

  5. #5

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    Default Re: Stripped out exhaust studs

    Yes, would love to barrow that tool if you can find it. I think I need to barrow or fabricate a fixture and I am also think a piloted 21/64 reamer would be very helpful.

    Thanks you

  6. #6
    Gilbert Pierce's Avatar
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    Default Re: Stripped out exhaust studs

    Bobby, AS&S sells 0.003" and 0.006" oversize exhaust studs that sometimes fixes the problem.
    Attached is a picture of the drill fixture. One hole fits a normal size stud. The hole is for #Q drill bit for the 5/16" Heli-Coil drill bit. It's 1/2" thick so it should keep the drill parallel with hole after you get it centered up.

    The other picture is of the Heli-Coil tang breaker, Heli-Coil insertion tool, Q drill Bit, Heli-Coil tap, drill guide, and a Heli-Coil tool to champfer the hole before inserting the Heli-Coil. I don't remember if there is room there to use the inserting tool. In any event you can screw it in with a small pair of forceps.
    Tell me what you need and I will send it. You pay the shipping both ways.

    You will need the 5/16" heli-coil
    McMaster Carr or any automotive supply

    I had a customers Pacer recently with a heli-coiled exhaust stud that kept coming out. When I pulled the heli-coil I realized they had wallowed out the opening of the hole so only a few threads were holding the coil. A standard 5/16-18x.375" 6 thread Heli-Coil would not hold the stud in operation. I used a 5/16-18x.625 9 thread Heli-Coil and fixed the problem. I mention this as a watch-out when you are dealing with old cylinders that may have not been properly repaired.
    Attached Images Attached Images
    Last edited by Gilbert Pierce; 05-26-2020 at 01:44 PM.

  7. #7
    Glen Geller's Avatar
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    Default Re: Stripped out exhaust studs

    There are lots of videos on youtube showing how to install helicoils.
    Some are very basic (https://www.youtube.com/watch?v=bp31p8jSWaM) and some go into details of the presenter's life story.
    This one is a pretty good demonstration, starting about 2:25. https://www.youtube.com/watch?v=46bIm2xaLuc

    GG
    Last edited by Glen Geller; 05-26-2020 at 12:08 PM.
    Glen Geller
    1955 PA22-150 "One For Papa!"

  8. #8

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    Default Re: Stripped out exhaust studs

    Great info!! My plan now is that I am going to prep the hole with a .3281 X .3125, piloted reamer with a 5/8 length pilot and a follow on ream with a .3281 bottom reamer, both using Boelube. Then tape and install the helicoil. If the 5/8 pilot on the first ream won't hold it straight, I will fab a drill guide fixture like yours. What do you think? does that sound OK?

  9. #9

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    Default Re: Stripped out exhaust studs

    Thank you!!

  10. #10

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    Default Re: Stripped out exhaust studs

    What lock tight is recommended for Helicoils?

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