Centroid Community CNC Support Forum

The tilt worm drive re-installed. Also the quill feed shaft going in.

Quill clock spring installed. I had purchased a pin spanner wrench to remove a nut elsewhere, it was a perfect fit for the clock spring which made pre-loading the spring while starting the screws EASY BUTTON easy.

Know when to sub out a job I say. The Clearpath servos are quite a bit larger diameter than the original SEM's so they won't just bolt on to the original servo mounting plates. I called on Front Panel Express CNC for this job.

This mounting plate bolts onto the cast iron bracket on Z with thin head countersunk socket head cap screws. The Clearpath servo bolts down over the top, overlapping the screws, bolting in place from underneath in the slotted holes.



The spacer to clear the Clearpath servo C face brim.

While you have that head apart, you might want to look at:
viewtopic.php?f=64&t=1944&p=13245

tblough wrote: ↑Thu Feb 13, 2025 5:25 pm While you have that head apart, you might want to look at:
viewtopic.php?f=64&t=1944&p=13245

Thanks for link. I'm going to use the encoder shaft on the back of the spindle motor for this. As your thread details there are some issues with mounting it to the spindle pulley hub assembly, it moves up/down. Is rather inaccessible after. But I also found quite a bit of nasty debris and oil in there when I disassembled the head.

The Marathon Black Max 5hp spindle motor however comes with an encoder shaft at the rear specifically for mounting an encoder. It's completely external of the head and 100% accessible. The only issue would be the double reduction low speed range of the head. But I was talking with a guy on another forum and he mentioned you can configure for dual inputs so one at the 1 to 1 spindle motor to spindle high speed range and a 2nd for the reduced spindle speed in the low speed range. I have not fully looked into this but that seems the way to go. If I'm switching into low speed range switching to the 2nd input isn't a big deal.

With the encoder on motor, you will not be able to do peck tapping. You need the encoder on the spindle to give exactly one index pulse per spindle rev in order to be able to retap the same hole.

tblough wrote: ↑Fri Feb 14, 2025 4:43 pm With the encoder on motor, you will not be able to do peck tapping. You need the encoder on the spindle to give exactly one index pulse per spindle rev in order to be able to retap the same hole.

The motor and spindle turn at the same RPM. 500rpm on the motor = 500rpm on the spindle. It's a 1 to 1 ratio.

Coolidge62 wrote: ↑Sat Feb 15, 2025 4:34 am

tblough wrote: ↑Fri Feb 14, 2025 4:43 pm With the encoder on motor, you will not be able to do peck tapping. You need the encoder on the spindle to give exactly one index pulse per spindle rev in order to be able to retap the same hole.

The motor and spindle turn at the same RPM. 500rpm on the motor = 500rpm on the spindle. It's a 1 to 1 ratio.

That might be ok if there is no lash in the drivetrain to the spindle.

Better solution is the encoder directly connected to the spindle.

Uwe

Those Black Max motors are induction machines and while they may be available with encoders and designed for variable speed operation with VFDs, they are still going to be quite limited in terms of torque. The torque available at stall (0rpm) will be similar to the torque at rated speed (1800rpm at 60Hz) ie ~20Nm or 15lb-ft, which won't be much use for tapping. For that you will likely need the low ratio, at which point the motor encoder isn't 1:1....

From where I'm sitting, you either fit a spindle encoder now while you can or you take the pragmatic approach and forget about rigid tapping. A tension/compression head is a perfectly good alternative solution, although admittedly it doesn't come with the same bragging rights. You can make up for those by mastering thread milling, which doesn't require any form of encoder.

https://dpbrowntech.com/products/Marathon/BlackMax.php

I love Centroids rigid tapping, super fast, reliable and ok with dirt cheap ER collets. No expensive compression stuff....
Depth of the threads is always equal depth, what more could you dream of?
Well worth putting the encoder right on the spindle.



Uwe