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R8 Question

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  • #16
    so how about a thrust bearing on the drawbar? anybody s done it?


    • #17
      Originally posted by dian
      so how about a thrust bearing on the drawbar? anybody s done it?
      I believe lubing the head+thrust washers was also recommended to improve torque transmitted to the collet. Im not so sure id want to go all the way to thrust bearing, Its a lot of force, And you do want enough friction to prevent vibration from loosening it.
      Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


      • #18
        if you slip an endmill in an R8 collet, you probably have one of the following issues:

        1. cheap collet that isn't hard enough and tool is slipping and deforming the collet.
        2. drawbar isn't tight enough.
        3. cut is too aggressive.
        4. wrong sized collet for the tool. I have seen people use drills that are too small for an R8's grip range far too many times.

        I have stalled the 3HP motor on my geared head industrial hobbies RF45 clone, pushed cuts so hard that the entire head tilted about its pivot on the Z axis (a 2.25" holesaw in 1.5"x.083" wall 4130 DOM on a solid 5/8" saw arbor does crazy things), but have never had an endmill slip out of a regular R8 collet.

        I stripped the stock drawbar, though. I hacked the stripped threads off and TIG welding a 7/16" grade 8 bolt in its place, which has worked fantastic for about 5 years now...

        my collet insertion/removal procedure includes 3-4 full force whacks with my palm on the end of the combination wrench on the drawbar. Rapid, forceful blows generate an impulse load in the assembly that gets the amount of tensile loading on the drawbar you need to keep everything tight enough to stay in place.

        With practice, you get a feel for how much angular displacement each strike on the wrench causes and it becomes very easy to repeatably apply a consistent torque.


        • #19
          Here's a good site dealing with collet usage.

          Location: Saskatoon, Saskatchewan, Canada