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Thread: BT30 or R8/TTS?

  1. #13
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    Default Re: BT30 or R8/TTS?

    Quote Originally Posted by keen View Post
    Hi Ray. Your comment "The Tormach PDB CANNOT be used with BT30, for several reasons."

    I imagine that is because a pull stud PDB needs more travel to operate, and maybe a bit less force, so a redesign is needed. Please add any info you have on this eg more comp air consumption, design of cylinder, etc.

    Cliff
    Correct. The Tormach PDB, and Belleville stack, allows only about 0.05-0.075" of travel - barely enough to release a TTS toolholder. Pullstuds typically require something like 1/4" travel to release the pullstud, and that much travel requires a looooooong stack of Bellevilles - typically on the order of 100-150 of them. They need to be constrained, to prevent "whipping" when the spindle is spinning, so they are typically mounted inside the spindle, which means a MUCH larger thru-bore, and an internal step just above the gripper to retain the bottom end of the stack. The gripper requires a machined recess to house it, center it, and close it. So, unless the spindle is specifically designed to be used with a gripper, pull-studs, Belleville stack and a PDB, you won't be able to do it, without MAJOR re-machining of the spindle itself. I'd be surprised if the Tormach BT30 spindle has any of those features, since it appears to me it is intended to be used with a simple manual drawbar.

    BTW - Using an ATC with BT30 would also normally require spindle indexing, to align the toolholder to the drive dogs. However, with a 1.5HP spindle, the drive dogs are not, technically, required. With proper drawbar tension, the taper alone is enough to prevent the toolholder from slipping on the taper.

    Regards,
    Ray L.



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    Default Re: BT30 or R8/TTS?

    Quote Originally Posted by SCzEngrgGroup View Post
    I'd be surprised if the Tormach BT30 spindle has any of those features, since it appears to me it is intended to be used with a simple manual drawbar.
    I believe the MX machines are getting a different BT30 spindle provisioned for a PDB and ATC.



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    Default Re: BT30 or R8/TTS?

    Thanks Ray - Good information. Current BT30 spindles and PDB will not suit.

    Yes I wondered if dogs and spindle indexing is really needed - this must be a tempting cost saving option...

    Do you have any thoughts on comp air with that much more travel, will a comp air source upgrade be also needed?

    Cliff



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    Default Re: BT30 or R8/TTS?

    Quote Originally Posted by keen View Post
    Thanks Ray - Good information. Current BT30 spindles and PDB will not suit.

    Yes I wondered if dogs and spindle indexing is really needed - this must be a tempting cost saving option...

    Do you have any thoughts on comp air with that much more travel, will a comp air source upgrade be also needed?

    Cliff
    With BT30 any compressor will do, and any combination of large and/or multi-state air cylinder, or mechanical linkage, or hydraulic intensifier can easily generate the force and travel required. TTS is the difficult one, since it requires MUCH higher drawbar tension for decent retention. Commercial VMCs typically use 40 or 50 taper spindles, which require as much as 3-4000 pounds of drawbar tension. They nearly all use hydraulic intensifiers.

    Regards,
    Ray L.



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    Default Re: BT30 or R8/TTS?

    Hi Folks

    Here is part 2.

    Cheers Cliff






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BT30 or R8/TTS?