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IndustryArena Forum > MetalWorking Machines > Tormach Personal CNC Mill > Newbie - Why are my tools pulling out?
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  1. #1
    Join Date
    Dec 2003
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    673

    Newbie - Why are my tools pulling out?

    Brand new machine and TTS holders
    3/8" 4 flute cutter
    .075 Radial DOC
    .200 Axial DOC
    Cutting Iron (Brake Rotor)
    Holder is clean
    Tried various speeds and feeds, currently 2ipm and 1000rpm

    Doesn't sound bad, but holder is walking out of the spindle. I'd think this wasn't much of a cut?

  2. #2
    Join Date
    Feb 2006
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    7063
    If the holder is pulling out of the collet, then you're not tightening the drawbar enough. The outside taper of the collet should be very lightly coated with anti-sieze. The collet bore, and the TTS shank should be completely clean and dry. Drawbar should be tightened to 15-25 ft-lbs.

    Regards,
    Ray L.

  3. #3
    Join Date
    Sep 2012
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    0
    Sounds like u could have a loose pull stud or a draw bar issue ...I had this happen recently on my Hass VF2SS and it was due to a air pressure air regulator problem ..Start with checking the pull stud then go to draw bar and air pressure...
    By the look of your speeds and feeds im assuming your using a HSS roughing endmill ...And cutting Cast Iron correct ?

    Hope this helps..

  4. #4
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    Sep 2012
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    If its a manual mill then disregard some of my comments..

  5. #5
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    673
    Quote Originally Posted by HimyKabibble View Post
    If the holder is pulling out of the collet, then you're not tightening the drawbar enough. The outside taper of the collet should be very lightly coated with anti-sieze. The collet bore, and the TTS shank should be completely clean and dry. Drawbar should be tightened to 15-25 ft-lbs.

    Regards,
    Ray L.
    I followed the instructions when I set up the PDB, and then I tightened it some more after pull out, but still not liking it. I've taken much heavier cuts on my old mill drill that I did my own cnc conversion on without any issues like that. Hmm.

  6. #6
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    Feb 2006
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    If you're using the Tormach PDB, then you need to put more pre-load on the Belleville springs.

    Regards,
    Ray L.

  7. #7
    Join Date
    Mar 2009
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    1863
    I had the same problem when my machine was new, but after I cleaned all the TTS shanks with acetone, and properly tightened the PDB, no more problems.

    The manual says to tighten the drawbar until it holds the TTS holder, then go 2 full turns after that. I went 2 1/2 turns.

    Order an extra set of belleville washers NOW. The belleville washers WILL fail, and they never fail at a time that you can pick up the phone and order more. They will fail a half hour after Tormach closes on Friday night, so now you're stuck till Monday, plus however long it takes UPS to get them to you.
    You can buy GOOD PARTS or you can buy CHEAP PARTS, but you can't buy GOOD CHEAP PARTS.

  8. #8
    Join Date
    Dec 2003
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    673
    Quote Originally Posted by Steve Seebold View Post
    I had the same problem when my machine was new, but after I cleaned all the TTS shanks with acetone, and properly tightened the PDB, no more problems.

    The manual says to tighten the drawbar until it holds the TTS holder, then go 2 full turns after that. I went 2 1/2 turns.

    Order an extra set of belleville washers NOW. The belleville washers WILL fail, and they never fail at a time that you can pick up the phone and order more. They will fail a half hour after Tormach closes on Friday night, so now you're stuck till Monday, plus however long it takes UPS to get them to you.
    lol. Probably good advice. I didn't use acetone, but gotta do something. I did go an extra 1/2 turn already... Pretty disconcerting though. Will do lighter cuts for now I guess.

  9. #9
    Join Date
    Jun 2007
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    3738
    Correctly designed, with the correct size washers, and combination, they will exceed 2M cycles.
    If washers break, then the stack design is wrong for the application.
    I use 3 3/4 turns for about 1000lb tension, and this is not a Tormach.

  10. #10
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    Feb 2006
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    Quote Originally Posted by Spinnetti View Post
    Brand new machine and TTS holders
    3/8" 4 flute cutter
    .075 Radial DOC
    .200 Axial DOC
    Cutting Iron (Brake Rotor)
    Holder is clean
    Tried various speeds and feeds, currently 2ipm and 1000rpm

    Doesn't sound bad, but holder is walking out of the spindle. I'd think this wasn't much of a cut?
    BTW - Your RPM is at least 2X what it should be, or your feedrate is 1/2 what it should be, assuming HSS tooling. If carbide, it's even worse. For cast iron, you should be running 30-50 SFPM, and your chipload should be on the order of 0.002"/tooth for HSS. For carbide, double or triple the SFPM.

    Regards,
    Ray L.

  11. #11
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    Jun 2006
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    3063
    Quote Originally Posted by djkms View Post
    If its a manual mill then disregard some of my comments..
    It's probably a Tormach mill.....

  12. #12
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    Jun 2006
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    3063
    Quote Originally Posted by Spinnetti View Post
    Brand new machine and TTS holders
    3/8" 4 flute cutter
    .075 Radial DOC
    .200 Axial DOC
    Cutting Iron (Brake Rotor)
    Holder is clean
    Tried various speeds and feeds, currently 2ipm and 1000rpm

    Doesn't sound bad, but holder is walking out of the spindle. I'd think this wasn't much of a cut?
    There is a Tormach tech support document on toolholder/collet slippage here:

    Product Documents | Tormach LLC | We provide personal small CNC machines, CNC tooling, and many more CNC items - ER Collets and Tool Holders

    which basically says the same thing that Ray did.

    I've had the same problem until following those gudelines.

    BTW, are you using Tormach TTS holders or another brand?

    Mike

  13. #13
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    Dec 2003
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    673
    Quote Originally Posted by MichaelHenry View Post
    There is a Tormach tech support document on toolholder/collet slippage here:

    Product Documents | Tormach LLC | We provide personal small CNC machines, CNC tooling, and many more CNC items - ER Collets and Tool Holders

    which basically says the same thing that Ray did.

    I've had the same problem until following those gudelines.

    BTW, are you using Tormach TTS holders or another brand?

    Mike
    Thanks, I did read that, and followed those guidelines. Its a brand new Tormach PCNC1100, and holders.

  14. #14
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    Dec 2003
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    Quote Originally Posted by HimyKabibble View Post
    BTW - Your RPM is at least 2X what it should be, or your feedrate is 1/2 what it should be, assuming HSS tooling. If carbide, it's even worse. For cast iron, you should be running 30-50 SFPM, and your chipload should be on the order of 0.002"/tooth for HSS. For carbide, double or triple the SFPM.

    Regards,
    Ray L.
    Thanks Ray, that's what I was looking for. I'm always chicken to crank up the feed. Seems like different software gives me different stuff. Is there a chart somewhere that gives starting SFM for various materials and best cutter type for that material? Seems like a bit of voodoo.

    Cheers.

  15. #15
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    Apr 2009
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    14

    pullout

    I have also had problems when using End mills, with the TTS holder pulling out of the R8 collet on heavy cuts (770CNC, Carbide 3/8" endmill, 1018 steel) even after I followed the tech note about cleaning/greasing the drawbar etc. I found that if I used my auto Torque wrench and tighened the drawbar to >20 ft-lbs, the pull out stopped. Unfortunately, I then bought a PDB and if I set the preload to anywhere near 20 ft-lbs, the tool would not release when the PDB was operated (@105 psi air). So for heavy cuts I have been tightening manually which defeats the purpose of the PDB but gets the job done. Recently I watched a video on You-Tube (look for "TTS Runout - R8 Collet") about honing the R8 collet to get a better grip on the holder and reduce runout which might help reduce pullout when using less drawbar torque but haven't had a chance to see what the results are.

    Bruce

  16. #16
    Join Date
    Jul 2007
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    131
    Quote Originally Posted by bruce34rr View Post
    I have also had problems when using End mills, with the TTS holder pulling out of the R8 collet on heavy cuts (770CNC, Carbide 3/8" endmill, 1018 steel) even after I followed the tech note about cleaning/greasing the drawbar etc. I found that if I used my auto Torque wrench and tighened the drawbar to >20 ft-lbs, the pull out stopped. Unfortunately, I then bought a PDB and if I set the preload to anywhere near 20 ft-lbs, the tool would not release when the PDB was operated (@105 psi air). So for heavy cuts I have been tightening manually which defeats the purpose of the PDB but gets the job done. Recently I watched a video on You-Tube (look for "TTS Runout - R8 Collet") about honing the R8 collet to get a better grip on the holder and reduce runout which might help reduce pullout when using less drawbar torque but haven't had a chance to see what the results are.

    Bruce
    That would be my video and since then I have installed a PDB.
    For any who are interested, this is my experience.

    Using a Cleveland 1/2", 3 flute, powdered metal aluminum rougher in a set screw holder for contouring 6061:

    Pre PDB:
    RPM 3200, feed 55, radial .17 (30%), depth .35 = MMR 3.27, .9 HP

    Post PDB:
    RPM 3200, feed 40, radial .17 (30%), depth .3 = MMR 2.04, .56 HP

    So the PDB caused a pretty good hit to the MMR. I have preloaded my bellevilles to the limit of the holder just releasing. I also experience pull out at any level of chatter. Pre PDB I could get away with a little.

    I'm thinking about trying these:

    McMaster-Carr

    The're dimensionally the same. They have a working load of 1890 lbs and a flat load of 2698 lbs. This seems to be correct for a R-8 drawbar tension. (Based on a Google search but nothing official)
    They come in high carbon steel and 17-7 PH stainless at double the price.

    Any opinions of which material would be better?

    Has anyone who has purchased Tormach replacement bellivelles...what was the cost?

    Thanks,
    Barry
    Tormach PCNC1100, Mach 3 R3.043.037, MastercamX5 level 3.

  17. #17
    Join Date
    Feb 2006
    Posts
    7063
    FWIW - Several years ago, I decided to build an air-actuated PDB for use with TTS. I did a fair amount of testing, and determined that 2500# drawbar tension/ 25 ft-lbs drawbar torque was required to get maximum TTS retention. At the time, even Tormach did not have a spec for drawbar tension (I talked to one of their engineers), and expressed interest in hearing my results once I completed the testing. I believe they eventually ended up at about the same numbers I did. So, anything less than that, and pull-out is a possibility. With Belleville springs, force vs. displacement is HIGHLY non-linear, especially once you exceed the rated compression, and I concluded I'd need on the order of 4000 pounds to adequately release a Belleville stack that provided 2500# tension when the PDB was disengaged (or, a really tall Belleville stack, which was not an option). So, a Belleville stack that provides a flat load of 2698# I would expect to be considerably less than optimal.

    I solved my problem by building a PDB that uses a 400 oz-in stepper motor and 50:1 planetary gearbox to directly tighten/loosen the drawbar. This gives me a consistent 25 ft-lbs tightening torque (and ~2500# drawbar tension), and up to 75 ft-lbs loosening torque. In about 5 months use, I have NEVER had a TTS holder pull out on my 3HP knee mill. As an added bonus, I can just as easily swap R8 tools in and out with the PDB, by just loosening 10 turns instead of the 1.5 turns I use for TTS, all under software control.

    Regards,
    Ray L.

  18. #18
    Join Date
    Dec 2003
    Posts
    673
    Lots of great info here. Thanks for the "conversation".. I've got a lot to learn, and am soaking it all up. Would it be possible to add one or two more pairs to the belleville stack?

    BTW, I may get the ones from Mcmaster - but not in stainless (not as good for springs).

  19. #19
    Join Date
    Jan 2012
    Posts
    789
    Quote Originally Posted by Spinnetti View Post
    Thanks Ray, that's what I was looking for. I'm always chicken to crank up the feed. Seems like different software gives me different stuff. Is there a chart somewhere that gives starting SFM for various materials and best cutter type for that material? Seems like a bit of voodoo.

    Cheers.
    I highly recommend G-Wizard. It has saved me more than it's cost in broken bits. It got me through to voodoo phase to where I can have a good guess myself on proper feeds.

  20. #20
    Join Date
    Nov 2010
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    360
    Quote Originally Posted by Spinnetti View Post
    Thanks Ray, that's what I was looking for. I'm always chicken to crank up the feed. Seems like different software gives me different stuff. Is there a chart somewhere that gives starting SFM for various materials and best cutter type for that material? Seems like a bit of voodoo.

    Cheers.
    GWizard says 800RPM, 5-6IPM for your cut.

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