Pm727 quill accuracy

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Driveslayer45

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So, got my new mill all setup, pm727v. During my setup checks I discovered that there is a variance of a few thousands between the quill wheel, the dro and a dial indicator I setup. It doesn't always seem to be consistent, I have to down feed several hundred thousands with significant inconsistency, almost like the downfeed is slipping. But then it gets better. Better is defined if I move the handwheel .010 the dro will read .0085'ish. the dial indicator is fairly close to the dro with maybe a .005-.0075 variance. And it varies a little as I turn the handwheel so I cannot simply account for the variance.

I cannot see anything to do about this so I am open to suggestions.

Thanks
 
In many cases the difference like that is it may have a metric screw and the error is in the conversion to the handwheel imperial dial.

I don't have that same mill but a different PM mill. I don't think I've ever even read off the quill handwheel dial before. Since I have a DRO for the quill, I have no reason to look up at the quill handwheel dial.
 
What attracted my attention is it seemed to have alot of movement before the sro would start picking it up So I put a dial indicator under the quill. I tried tightening the dro as I saw movement in the body, but that didn't help.

PM States they use true inch screws not metric, maybe that's just on the x and y. I've not checked the x and y accuracy yet, I'll do that today
 
I use the Quill DRO as a guide. if I need accuracy, I measure what I have and adjust accordingly.
 
I wonder if you have a spring return like the RF30. If it's not tight and helping keep the head up I get play from the head floating between the play of the quill, if that makes sense. I never look at the dial since I put a DRO on it. I also have to be careful to keep some drag of the quill lock to keep things from not dropping against the play. There is no way to take the play out of the quill feed so several folks have come up with putting air springs on them to be more consistent than the coiled return spring.

My cheapo igaging DRO on the XYZ is really good at getting back to zero in all axis. But it almost always "drops" the first .001".
 
I think that the quill feed is not included in the true inch claim by QMT. And I also see on mine that the graduations on the handwheel would be incorrect for it to be true inch pitch. on mine also the quill dro was pretty close to a dial indicator.
 
There is a thumb s few on the left hand of the head, looks like it is the the center of a cool spring, is that what you are referring to c-bag? If so what is it actually for?

I will do some tests of the dro against a dial indicator and disregard the handwheel dial.
 
Driveslayer45 said:
There is a thumb s few on the left hand of the head, looks like it is the the center of a cool spring, is that what you are referring to c-bag? If so what is it actually for?

I will do some tests of the dro against a dial indicator and disregard the handwheel dial.
Click to expand...
... Thumb screw....
 
Sounds just like the Rf30. If I remember right it's tied to the opposite end of worm drive for the quill. It helps the head return to the up position and also takes the play out of the mechanism by keeping spring pressure on it. Drill presses have it too. Mine was completely loosened when I got it. Mine was made in '88 and well worn so who knows if it was loosened on purpose or never adjusted. Maybe your manual will have something about it?
 
So that thumb screw tightens a notched cover that does allow you to tighten the quill return spring. After tightening the spring it seems to work better but the dro and quill is off. But, after the first .040", the dro seems to stay on track compared to a dial indicator. The quill dial, is off by about .0008 per .010..
 
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