Rigid tap Problems

[A+ Machining]

I have a 2001 3020VMC with rigid tapping. I bought this machine used and I have been having problems rigid tapping.
I have been using the RPM.2 in the set up line. I have been tapping at 500 rpms or less.
I put the G84.2 in the line before the tapping block
G84.1 with the Sxxx.2 in the tapping line.
I can tap anywhere from 3 -12 holes no problem and then the tap breaks just after it enters the part.
If I put a tention compression holder in I can tap 100's of holes no problem.
Any suggestions?

Thanks
A+

[DSL PWR]

Pull the sheet metal off and check your belt tensions. (I don't know if the encoder is on the spindle or has it's own belt)

[IN2GLAMISGIRL]

If you are tapping 3/8 and up try tapping in low range (don't use .2 after your S word. It does sound like it could also be a dirty optical encoder. It is mounted on top of the spindle motor under the top cover. Fadal switched to a totally enclosed unit several years ago. If you can see the encoder disc it is the early style subject to oil contamination, clean it with alcohol on both sides.

[Skillet]

Why do you use G84.2? My machine needs G84.1 and no decimal after the Speed statement. Do you run your holes as one canned cycle or each one individually? That can make a difference, if you don't cancel the cycle in between each hole, with G80. Here is a sample.
N160T3M6
N165G0X1.7135Y3.5651S480M3M8E1
N170Z1.0H3
N175Z0.25
N180G84.1X1.7135Y3.5651R00.25Z-0.8375S480F30.0
N185X3.2548Y4.3032
N190X4.9047Y3.5
N195X6.0987Y4.3249
N200X7.6184Y3.3915
N205X8.8124Y4.3467
N210G80

[Neal]

Has your rigid tapping system been calibrated lately? There are parameters that adjust the tracking of the r/tap.

Neal