Re: Tapping Head setup

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1

Brian, thanks for the info. Yes, 10-28, and the spindle should be around 500. I had initially ran sheetcam using 1000 rpm, but some quick calculations show I couldn’t reach the IPM needed for retracting at that RPM. I manually changed that in the Gcode, neglecting the next hole that I had included.

I have two tapping heads. One is a Procunier 2E which is the cone drive type, That one is a bit longer and a lot heaver than the STM JSN7 head. The JSN7 looks
to be a knockoff of a Tapamatic, it uses a positive latching clutch arrangement vs a cone drive, so the 0.14” self feed has to be used in order for it to go into neutral.
On my little Taig short and light might work, the Procunier is just to big.

I am in the process of installing an index on the spindle now. All I have to do yet is to get the signal into my breakout box. I’m also in the process of setting up the spindle speed control to be controlled by Mach3.

My guess is that if I look at the post code, I can modify it for the “jerk back” at the end of the feed in.

Thanks for the bit about getting the Z up to speed before the tap contacts the work. I hadn’t considered that one.

Don


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Posted by: “Don Rogers” <Don@Campbell-gemstones.com>

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2

I think I’ve got it figured out some what. It looks like you need to calculate a value for “underfeed” so the tap is at the desired depth when the machine thinks it is at depth = underfeed.

Here are the rough measurements (taken with a 6" rule in bad light needing a third had to push and pull the tap holder while trying to read the rule on a black beveled edge.

At the neutral axial point, no pressure or pull on the tap, the top of the tap holder is 1/4" below the torque plate. You can compress, IE Z+ move the tap into the head 1/8" before it hard stops. You can pull the tap Z- by 0.14" before the cut feed is released. At Z- 1/2", the reverse is engaged. You can over feed the reverse to the point you are pulling the tap to Z- 11/16" before you reach the hard stop on that end.

This give you a lot of wiggle room on fine threads for feed and retract speeds. It makes getting an accurate depth of thread a bit more difficult.

I did a rough Excel to calculate the underfeed number. You start with the axil Travel, in my case 0.14". Depth of threads in inches, and TPI. It calculates the feed/ tap revolution, how many tap turns to take up the self feed, and then calculates the feed per turn needed which gives an underfeed %. which you enter in the tool table. The depth of the threads will change the underfeed. One could easily modify the post to do the calculations from the tool table and Operations inputs.

This handles the underfeed and axel travel, at least in theory. The retract still bothers me and looking at the post, I don’t think the step to engage the reverse clutch is needed, at least for my tap head.

I’m really open to correction on this.

Brian, I screwed up the tpi in my first example, 10-32 taps is was I was playing with and I have no idea why I plugged in 28 in the tool table.

Don

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Posted by: Don@Campbell-Gemstones.com

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3

Scratch my last note. It doesn’t look like I understood the post calculations and how axial travel works in it. Back to the drawing board.

Don

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Posted by: Don@Campbell-Gemstones.com

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4

Brian, yes, the Procunier is about bigger than the mill. It is a heavy hunk of metal. I would like one of the 1E size, but I picked this one up a few years back at a machinist garage sale for $50 and it included a full set of collets. Didn’t know what I was going to use it for at the time, but had to have it. I’ve put it to good use since but only in the drill press.

The STM is a Tapamatic style head. The one I have is for #0 up to 1/4" capacity, but #10 will be my largest tap for the work I’ll do with it. I also will be working aluminum for the most part. I think the mill will handle the torque OK, The biggest issue is belt slip, I’ve only stalled out the spindle once, and that was slinging a Fly cutter cutting a 3/16 deep cut and I jogging the cut vs running code and screwed up my feed. Even then, the motor was still cranking. .

The 0.14’ feed out is a value from the tapping head manual. “we guarantee this depth control within +/- 0.004” so they say.

We’ll see.

Thank again for the info and advise.

Don

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Posted by: Don@Campbell-Gemstones.com

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5
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6

Brian, I’ve always said there is a difference between being Precise, and being Accurate.

A friend of mine several years back won a big achievement award at IBM. Besides a big chunk of cash, there was a wrist watch that went with the award. I don’t remember the brand now but it was up there with the Rolex and above. Black face and A tick at 12, 3, 6, and 9, along with the claim of being accurate to within 2 seconds a year. His comment was that with no minute marks or a second hand how could you verify or debunk the accuracy claim.

Kind of like that with the tapping head as you point out. No way to tell for sure, but it is precise

Don

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Posted by: Don@Campbell-Gemstones.com

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7

Hi…

I have seen this has turned into a large Post…


I use Sheetcam for my Plasma Cutter, but I have Never used Sheetcam to Program a mill…, I also have a CNC Machining Center, and I use another software to generate the G Code for the mill…


This is the Code for a Tapping Cycle I use:


T4 M6
G0 G90 X1.0827 Y-4.0827 S255 M3
G43 Z1. H4 M8
G0 X1.0827 Y-4.0827
G84 G98 X1.0827 Y-4.0827 Z-1. Q0.0625 R0.1 F15.9
X5.2165 R0.1
Y-1.0315 R0.1
X1.0827 R0.1
G80




This cycle is for 4 Holes 3/8"-16, at 255 RPM, and a feed rate of 15.9 IPM. It just basically “synchorinizes” the RPM to the Feed Rate to match the pitch of the thread 3/8"-16.


There is no Dwell Time, and no other paramaters, just goes in, and then, it reverses spindle rotation, and goes out.


For this cycle to work, I MUST use a Floating Tap Holder. If I dared to use a Rigid (NOT Floating) Tapping, the Tap would certainly break, or cause quite some trouble. Maritool.com has some different Floating Tap Holders…, I realize these holder are big, but maybe this can guide you in the right direction…


I hope this helps…





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Posted by: zrtorres@hotmail.com

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8

Les,

My STM head which I think is a knock off of the Tapamatic head requires the dwell. I figure that dwell of 5 index pluses would cover the required dwell but It would be nice if that were a variable to allow for different self feed length and for the TPI you are tapping. If the dwell were to long, it shouldn’t mater,

The % underfeed with an index on the spindle, allowing the G95 moves isn’t need in my opinion. My tapping head at least 1/8" of compression or tension on the tap before jamming or going into neutral. I think the % underfeed just adds some confusion to the movement for an indexed spindle.

For my head, I would like to be able to set the actual depth less the self feed, for example a 0.500" depth would require the feed to stop a 0.360" feed with a dwell of X revolutions of the spindle before starting the retract. As the STM is not a friction feed like my Procunier head, it is a positive latch, so the jerk to engage the reverse clutch isn’t needed.

Looking at my Procunier 2E, at rest, the tap spindle is fully engaged with the drive clutch. There is no compression spring, so an overfeed at the start would be a problem. Pulling on the tap, there is only about 0.020" of pull on the tap prior to going into neutral. Full reverse is engaged at 1/8" pull on the tap. This is considerably different than the STM head and would require a quite different motion control. I’m not sure what the bottom dwell would need to be on this head, if any. I also think that the condition of the clutch cones will have a big influence on the need or lack of need for over / under feed on the travel.

Don


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Posted by: “Don Rogers” <Don@Campbell-gemstones.com>

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9

Les, I looked at the Tapmatic doc, it works different than either my STM or Procunier does. There is no self feed for this version of the Tapmatic, It feeds to full depth of the thread. The STM needs to stop feeding and dwell long enough for the 0.14” of additional self feed to take place, the retract.

Based on what I see, there needs to be three options for tapping heads, and probably more.

The Gcode now generated does match the info in the Tapmatic link. It shows Brian’s type Tapmatic that reverses at feed speed.

The retract speed is handled in the tools setup OK, It gives me my 2X retract speed when I enter the 200%.

Thinking about it more, I believe two tool table additions would solve the difference issues.

  1. ad a variable Dwell at bottom. Dwell= TPI*Axial Travel rounded up to the next whole number of index pluses. IE 32 TPI * 0.14” = 4.48, rounded to 5 so you would dwell for 5 indexs before feed out starts.
  2. If Axil is 0, the use existing post.

Just designing on the back of a napkin here. I”ll play with the post and see what I can come up with.

Don

BTW, I realized after I posted the concern about stalling a stepper that Mach3 will limit the moves to prevent that.

Don



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Posted by: “Don Rogers” <Don@Campbell-gemstones.com>

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