PM835S spindle run-out

[Batmanacw]

A couple of suggestions.Try cleaning the spindle taper with a very fine scotch brite pad. Then measure run out directly on the spindle taper at multiple locations. If you see excessive run out note if it is happening in a narrow strip or in a more generalize manner. Mark the high spot with a sharpie then run the machine for a minute and repeat the measurements. Did the high spot move or remain in the same place?

If it moved then you may have a bad bearing.

I measured every 0.050" along the taper. What became apparent is what showed in the video above. There is a bulge in the taper. I don't know how but it's there. It wasn't apparent before my last project.

I won't replace the spindle without new bearings. I need to find a shop that can regrind the original as a spare.

I received the machine in October of 2020.

 

[B2]

@Batmanacw

A thought. I do not know your mill, but looking at the PM site manual shows: Figure 4-7 Spindle nose-piece lock screw.

Have you removed this screw and checked it and associated parts for wear or damage? It is hard for me to believe that you bent your spindle before sheering this lock screw off, or at least part way off. If it is damaged it could be jamming your spindle off center a little. There should be some sort of safety mechanism that would yield before bending precision parts. This may not be it, but maybe there is some part elsewhere. By the way, in my PM940M-VS-CNC manual from a few years ago these parts (set screws) are not even shown/mentioned in the exploded drawings.

I accidentally took a big bite with my 2" fly cutter when the head vertical dropped down about 0.1" and stalled the motor! ... and a lock screw like this was sheered part way in two. It was jammed in the hole and who knows how much run out I had at that point. Later it finished off the break and then the spindle turned freely by hand and removing a cutting tool was impossible. The PM guys helped me figure it out. I had to take the assembly apart and even then it was hard to get to.... so as to get it out. It turned out to be one of two set screws in the same hole. One is used as a lock for the spindle nose and the one on the outside of it is used to lock the first one in place. The deeper one was sheered into parts and they were sort of smeared all over the place.

Good Luck.

Dave L.

 

[Batmanacw]

@Batmanacw

A thought. I do not know your mill, but looking at the PM site manual shows: Figure 4-7 Spindle nose-piece lock screw.

Have you removed this screw and checked it and associated parts for wear or damage? It is hard for me to believe that you bent your spindle before sheering this lock screw off, or at least part way off. If it is damaged it could be jamming your spindle off center a little. There should be some sort of safety mechanism that would yield before bending precision parts. This may not be it, but maybe there is some part elsewhere. By the way, in my PM940M-VS-CNC manual from a few years ago these parts (set screws) are not even shown/mentioned in the exploded drawings.

I accidentally took a big bite with my 2" fly cutter when the head vertical dropped down about 0.1" and stalled the motor! ... and a lock screw like this was sheered part way in two. It was jammed in the hole and who knows how much run out I had at that point. Later it finished off the break and then the spindle turned freely by hand and removing a cutting tool was impossible. The PM guys helped me figure it out. I had to take the assembly apart and even then it was hard to get to.... so as to get it out. It turned out to be one of two set screws in the same hole. One is used as a lock for the spindle nose and the one on the outside of it is used to lock the first one in place. The deeper one was sheered into parts and they were sort of smeared all over the place.

Good Luck.

I think I was using too high torque on my drawbar and it belled out the nose a tiny bit and revealed a flaw in the taper. The taper runs out less than 0.0001" except the 0.0002" hollow hump about 1/4 the circumference.

The Spindle with shipping and new bearings is around $500. That's not too hurtful. I'll order it when I've got the spare cash.