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BT3 HELI-COIL Horror

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  • BT3 HELI-COIL Horror

    After experiencing the blade height stripped thread failure, I went thru the lengthy (& stressful) procedure of installing a heli-coil. I
    thought
    I had everything aligned in the drill press to drill & tap for the coil. Alas, when I installed the threaded shaft it did not "quite" line up with the hole in the bottom bracket. Off about 1/2 of the hole. I considered hogging out the bracket hole, but realized this would only misalign the shaft & motor assembly and jam up.
    Is my best solution to buy a NEW motor assembly?

    P.S Thanks to JohnG for his detailed description of the rebuild process.

  • #2
    The drill must not of stayed centered in the hole and cut out one side. The only thing I could think to do to salvage the motor would be to dig the helicoil out and make a new solid insert to fit in its place, install the insert, then drill and thread the new insert the proper thread. Id make the new insert out of a piece of fine thread bolt the appropriate size for the new hole.
    i much prefer to use a threaded insert which is a threaded solid piece of steel vrs a spring shaped insert like the helicoil. Threaded inserts use a standard size drill/tap vrs the weird sizes for a helicoil.

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    • #3
      Thanks capncarl. My hindsight gets better every year.
      What I ended up doing was leave the motor assembly in the saw, drilling out the coil (which was ugly), then re-drilling and tapping for a new coil. Probably not enough thread left to hold the coil for long but seems to work for now. When that fails, I'll try the threaded insert route.
      Thanks again for your input.

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      • #4
        Originally posted by Phil View Post
        What I ended up doing was leave the motor assembly in the saw, drilling out the coil (which was ugly), then re-drilling and tapping for a new coil. Probably not enough thread left to hold the coil for long but seems to work for now. When that fails, I'll try the threaded insert route.
        Your experience is fairly common for Heli-coils, one reason they are not considered a "permanent" repair. A solid insert like a Time-Sert works much better and is a permanent repair. Unfortunately the cost is higher.

        Watch for people parting out BT3's, you may be able to get a good used one for a reasonable price. Just make sure you get the right one, there were some variations in the part.

        --------------------------------------------------
        Electrical Engineer by day, Woodworker by night

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        • #5
          Yeah, I guess "permanent" always depends on how much stress is on it, and other factors like oxidation. I completely agree on his recommendation for Time-Sert kits. Just something to have around the shop if you work on metal stuff all the time, from motorcycles to tools to Jeeps. Something is going to break where it can help.

          That said, I've had Heli-coils stay in place "forever" in light-duty applications.

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