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  1. #1
    Registered
    Join Date
    Oct 2008
    Posts
    1839

    Power Tapping

    Tapped some holes yesterday with the extension compression tapper. It worked ok. Figuring out the dwel time made the first hole a little rogugh, but didn't detroy the part. Seems like a shorter dwell than the actual reversal time, and set the tap to go just deep enough to compelte the thead is the way to go. Could be tricky with blind holes. Fortunately I was tapping through holes.

    I started by adjusting the little voltage output pot (I doubt its PWM) as close as I could at 500 RPM. My optical tach read from 499.X to 501.X in low gear. I fgured that was as close as I could get. I started with 1.7 seconds dwell, and it jammed up a little on reverse. Cut it to 1 second dwell and every hole after came out perfect. I used the conversational tapping in PathPilot. Its nice that it calculates a lot of things for you automaticall. Can somebody tell me where to turn off the flood coolant in conversational please? I use tap magic for tapping. A drop or two in each hole is wonderful. I get thousands of holes in aluminum out of a tap in one of my tapping heads on one of the drill presses before a clutch starts to slip. I do wear out taps in 4140HT, but I can still get a lot of holes depending on tap sze and engagement percentage.

    Now I admit I was being conservative for aluminum, but it was a lot slower to tap five parts on the mill with the TC tap holder than it is to tap them on the drill press with a tapping head. I'm not counting the time to zero the stock, setup a work stop, or change the speed range of the mill. I figure on those things as a one time cost in time for a batch of parts. Just removing he part from the vide, installing the next part and tapping it. That's really no surprise though. My drill presses that have tapping heads installed are set at 750RPM and they double speed reversing out.

    So, how aggressively do you guys tap with a TC holder in the mill? Can you get it to approach the time of a tapping head on a drill press? Obviously it will vary depending on the tap size and the percentage of engagement. I typically use 50-55% thread form in most steels and 75% thread form in aluminum. My most common size tapped holes are 10-32, 1/4-20, and lately 5/16-18.

    Last thing. Do any of you tap in high gear? The time to swap the belt pulley is not that long, but if doing multiple parts it would be nice to include tapping as part of the job, rather than have to setup to unload and reload every part to tap it afterwards, or have to swap the belt twice on every part. Obviously you can save on some of that with nested parts. Just tap them all as the last operation if the remaining stock is strong enough to support that.
    Bob La Londe
    http://www.YumaBassMan.com

  2. #2
    Gold Member
    Join Date
    Feb 2006
    Posts
    7056

    Re: Power Tapping

    Bob,

    Does your machine have a braking resistor? If not, consider adding one - it will GREATLY reduce the require dwell time, as you'll be able to make the spindle stop VERY quickly. That will, in turn, allow you to run higher RPM when tapping. With an ideally setup T/C head and g-code, the T/C head should be just about as fast as the reversing tapping head.

    Regards,
    Ray L.

  3. #3
    Registered
    Join Date
    Nov 2007
    Posts
    1642

    Re: Power Tapping

    Typical output of my cam software based on my settings. With t/c unit just remember if you use speed sliders in PP return those to 100% "I know that gets people now and then" and feed is based on spindle speed.
    Most examples I see people tap s1000 I'm slow so I use s500 and appropriate feed for thread pitch

    (Hole machining 0.25-20 Tap)
    N14480 T54 G43 H54 M6
    (0.25-20 Tap)
    N14490 S500 M3
    N14500 G0 X0. Y0.
    N14510 Z0.2
    N14520 M49
    N14530 S500 M3
    N14540 G4 P0.4
    N14550 G1 Z-0.75 F25.
    N14560 M4
    N14570 G4 P0.3
    N14580 Z0.2
    N14590 M3
    N14600 G4 P0.6
    N14610 G30 Z0.2 M5
    N14620 M48

  4. #4
    Registered
    Join Date
    Nov 2013
    Posts
    345

    Re: Power Tapping

    I've struggled with tapping in my 770 since I bought it 5 years ago.
    It's been pretty-much hit-or-miss for me.
    As I described in my other post, I've gone back & forth between long-hand and G84 formats, neither has been that great without an encoder on the Z axis.
    I've been tapping in low gear, 800 RPM for larger taps (1/4" up to 5/16"), and 1000 RPM for smaller taps (below 1/4"). Dwell time = P0.8
    I can get it to work, but I get nervous every time I have to tap.
    On high-dollar parts, I just hand tap and use the spindle as a guide. I don't have much faith in Tormach tapping routines. (unfortunately)
    It would be nice if one of the eggheads at Tormach would make a chart of recommended feeds/speeds for tapping in both Steel and Aluminum. ( I can wish, can't I)

  5. #5
    Junior Member
    Join Date
    Jun 2014
    Posts
    1369

    Re: Power Tapping

    I guiess I am really slow here??

    safe height .5
    320 rpm
    #6 to 5mm 10 ipm
    dwell .5
    no blind holes machine tapped
    use machine taps only, found this out the hard way!
    use oil, and plenty of it.

    I worked with 300 series stainless for over 40 years, mabe a bit gunshy?? The solvent type Rapid Tap worked wonders with it.
    mike sr

  6. #6
    Registered
    Join Date
    Oct 2008
    Posts
    1839

    Re: Power Tapping

    Quote Originally Posted by popspipes View Post
    I guiess I am really slow here??

    safe height .5
    320 rpm
    #6 to 5mm 10 ipm
    dwell .5
    no blind holes machine tapped
    use machine taps only, found this out the hard way!
    use oil, and plenty of it.

    I worked with 300 series stainless for over 40 years, mabe a bit gunshy?? The solvent type Rapid Tap worked wonders with it.
    I use Rapid Tap sometimes, but my goto is Tap Magic all metals formula.
    Bob La Londe
    http://www.YumaBassMan.com

  7. #7
    Registered
    Join Date
    Nov 2007
    Posts
    1642

    Re: Power Tapping

    Quote Originally Posted by popspipes View Post
    I guiess I am really slow here??


    320 rpm
    #6 to 5mm 10 ipm
    dwell .5
    .

    I use the formula 1 / pitch x rpms for feed setting Imperial
    or pitch x rpm / 25.4 metric taps


    and vary hole size for the material as per chart and use lots of lube. and thread mill anything above 1/4" size

  8. #8

    Re: Power Tapping

    I tap at 750rpm typically, 1 sec dwell at the bottom, up/retract feed at 10% slower than down, feeding to clear the part by .200" to be sure I don't pull the last couple threads when rapiding to Z clear. 6mm x 1.0, 10-24, 1/4-20 and 5/16-18. Depths up to .75. I run two brake resistors, haven't seen a real change is stopping speed.
    RAD. Yes those are my initials. Idea, design, build, use. It never ends.
    PCNC1100 Series II, w/S3 upgrade, PDB, ATC & 4th's, PCNC1100 Series II, 4th

  9. #9
    Gold Member
    Join Date
    Feb 2006
    Posts
    7056

    Re: Power Tapping

    Quote Originally Posted by R.DesJardin View Post
    I tap at 750rpm typically, 1 sec dwell at the bottom, up/retract feed at 10% slower than down, feeding to clear the part by .200" to be sure I don't pull the last couple threads when rapiding to Z clear. 6mm x 1.0, 10-24, 1/4-20 and 5/16-18. Depths up to .75. I run two brake resistors, haven't seen a real change is stopping speed.
    You won't get a change in speed by simply adding a braking resistor - the VFD also needs to be programmed to USE it. With NO braking resistor, stopping from even 1000 RPM can take several seconds. With a braking resistor, properly configured, it should stop from 1000 RPM in a small fraction of a second. My Novakon will stop from 6000 RPM in under a second. At tapping speeds, it will stop and reverse almost instantly. The Tormach should do the same.

    Regards,
    Ray L.

  10. #10

    Re: Power Tapping

    Quote Originally Posted by SCzEngrgGroup View Post
    You won't get a change in speed by simply adding a braking resistor - the VFD also needs to be programmed to USE it. With NO braking resistor, stopping from even 1000 RPM can take several seconds. With a braking resistor, properly configured, it should stop from 1000 RPM in a small fraction of a second. My Novakon will stop from 6000 RPM in under a second. At tapping speeds, it will stop and reverse almost instantly. The Tormach should do the same.

    Regards,
    Ray L.
    It's programmed. And of course yours is better.............
    RAD. Yes those are my initials. Idea, design, build, use. It never ends.
    PCNC1100 Series II, w/S3 upgrade, PDB, ATC & 4th's, PCNC1100 Series II, 4th

  11. #11
    Registered
    Join Date
    Aug 2013
    Posts
    986
    Quote Originally Posted by Bob La Londe View Post
    Tapped some holes yesterday with the extension compression tapper. It worked ok. Figuring out the dwel time made the first hole a little rogugh, but didn't detroy the part. Seems like a shorter dwell than the actual reversal time, and set the tap to go just deep enough to compelte the thead is the way to go. Could be tricky with blind holes. Fortunately I was tapping through holes.

    I started by adjusting the little voltage output pot (I doubt its PWM) as close as I could at 500 RPM. My optical tach read from 499.X to 501.X in low gear. I fgured that was as close as I could get. I started with 1.7 seconds dwell, and it jammed up a little on reverse. Cut it to 1 second dwell and every hole after came out perfect. I used the conversational tapping in PathPilot. Its nice that it calculates a lot of things for you automaticall. Can somebody tell me where to turn off the flood coolant in conversational please? I use tap magic for tapping. A drop or two in each hole is wonderful. I get thousands of holes in aluminum out of a tap in one of my tapping heads on one of the drill presses before a clutch starts to slip. I do wear out taps in 4140HT, but I can still get a lot of holes depending on tap sze and engagement percentage.

    Now I admit I was being conservative for aluminum, but it was a lot slower to tap five parts on the mill with the TC tap holder than it is to tap them on the drill press with a tapping head. I'm not counting the time to zero the stock, setup a work stop, or change the speed range of the mill. I figure on those things as a one time cost in time for a batch of parts. Just removing he part from the vide, installing the next part and tapping it. That's really no surprise though. My drill presses that have tapping heads installed are set at 750RPM and they double speed reversing out.

    So, how aggressively do you guys tap with a TC holder in the mill? Can you get it to approach the time of a tapping head on a drill press? Obviously it will vary depending on the tap size and the percentage of engagement. I typically use 50-55% thread form in most steels and 75% thread form in aluminum. My most common size tapped holes are 10-32, 1/4-20, and lately 5/16-18.

    Last thing. Do any of you tap in high gear? The time to swap the belt pulley is not that long, but if doing multiple parts it would be nice to include tapping as part of the job, rather than have to setup to unload and reload every part to tap it afterwards, or have to swap the belt twice on every part. Obviously you can save on some of that with nested parts. Just tap them all as the last operation if the remaining stock is strong enough to support that.
    I started out wit a tc but went to thread milling 5 years ago and haven’t looked back. It seems perfect for the Tormach

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