Fab Lab Skill Builder: How to Use and Program an Auto-Reversing Tapping Head

We have recently started offering a new auto-reversing tapping head, made exclusively for us by Procunier in Lakeland, Florida.  You’ll find Procunier tapping heads used in machine shops around the world – they’re a bit pricier than some of the other tapping head options we sell, but also really excel when using very small taps or when there is a need to tap a lot of holes at once (high duty cycles).  In this latest Fab Lab Skill Builder Video, Mike shows us the basics for how to setup and program this type of tapping head.

Auto-Reversing Tapping Heads work with a gear/clutch mechanism that reverses the rotation of the tap without the need to program a reverse spindle command to out-feed the drill. In the case of the Procunier, this mechanism operates on a 2:1 reverse ratio; that is, the out-feed needs to be 2x the in-feed. There are a few different ways to program an auto-reversing tapping head. Towards the end of the video, Mike demonstrated the M871 code, which is one of a set of pre-programmed M-codes for the Procunier Tapping head that we’ve included in the latest release of the  PCNC control software (downloads available here).  These codes make the Procunier a snap to use.  Just enter the appropriate tap pitch in the DRO underneath the M-code (M871, M872, M873, or M874) that you want to program.  The M-code will automatically calculate the appropriate in-feed and out-feed based for the programmed spindle speed.

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Here’s a short example program to show M871 in some context:

(Tap: 1/4-20)
N10 G90 G80 G40 G54 G20 G17 G50 G94 G64 (Safety block)
N20 M3 S1000 (Spindle on CW)
N30 G0 X2 Y2 Z.1 (Rapid to Above 1st Hole)
N40 M871 P.6 (Begin Tapping 1st Hole)
N60 G0 X3 Y2 (Rapid to Above 2nd Hole)
N70 M871 P.6 (Begin Tapping 2nd Hole)
N50 M30 (Program End)

We’ve got a couple more programming examples in the following tech document, both for the Procunier and also the Tension Compression tapping heads that we offer:

Download  CNC Tapping Guidelines here.



Andrew Grevstad

With over ten years of professional experience in advanced manufacturing systems, digital design tools, and applied software, Andy Grevstad has worked in product development and technical support for Tormach since 2008. Grevstad has received engineering degrees from Michigan Technological University and the University of Wisconsin-Madison. He is a regular contributor to Digital Machinist magazine and also blogs weekly about CNC milling and related topics on the Tormach blog, Milling Around.

Andrew Grevstad

One thought on “Fab Lab Skill Builder: How to Use and Program an Auto-Reversing Tapping Head

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    10/03/2012 at 3:01 pm

    I have been using a TTS modified Procunier 1E tapping head for many years on my Tormach series I 1100. The Procunier has proved to be extremely reliable, as I have tapped 10s of thousands of blind holes on my Tormach with the Procunier. I am glad to see Tormach has partnered with Procunier to offer essentially the same tapping head as the the proven Procunier1E. BTW one of the really useful option I have for my Procunier is a set of Pro-Quik quick change tap collets that making changing tap sizes a literal snap. http://www.rockford-ettco.com/Portals/44/Pro-QuikTap.pdf

    Don Clement

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