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PM935TV Head Position

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HighWall

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#1
I've had my PM935 Variable speed mill for a few years and never changed the front to back adjustment of the head. It came about 1/2" forward from flush with the colums. Is there a benefit to having it further out from the column or is it a matter of expediency? It seems it would be less stiff when racked out, but I can see it would be desirable for certain setups. Does it hold zero during fore and aft adjustment? I suppose these questions could be answered with a dial indicator and some time spent, but I thought I'd check what accepted practice might be. Where do you keep yours adjusted to?
 

wrmiller

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#2
I position the head such that when the table is centered under the head in Y, the table is centered on the knee. This allows me to reach beyond the back of the table and beyond the front. Which I've not had to do yet, but it's there if I need it.

If for some reason I need to extend or retract the head I would automatically do a tram. I don't know if it's needed, but I'd want to make sure.

Disclaimer: I don't do real heavy milling on my machine so my setup works fine for me. If I needed to do some real heavy cuts and wanted maximum rigidity, I'd probably move the head as close to the column as possible for the job.
 

Bob Korves

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#3
I normally position my ram so it is as far back as possible with the spindle center still able to reach the far side of the table at the same time. On my mill (a Millrite, smaller than a Bridgeport) that position is very close to the ram retracted as far as possible. When needed, pull out the ram as far as is needed to reach what you need to reach. My Millrite could easily reach the center of a 40" round part if needed, possibly 48". Yes, it will be less rigid, but at least you can cut it. Sometimes it also pays to swing the turret to reach something, even something that is not in the vise or on the table, even a part mounted to a fixture on the floor for maximum part height. Always try to think outside the box and enjoy the exceptional capabilities the designers built into the machine. For many users, the head never gets nodded or tilted, the ram never gets moved, the turret either, and all they can see is the spindle and the vise. Which sounds more like a drill press... The long table is only used to move the centered vise. You can have a part mounted on the side of the table or directly to the table. Take off the blinders and see all the many possibilities.

Move and lube the ram and turret every so often or they will be frozen tight when you need them!
 
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Rickwjenn

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#4
Good post. Any advice on how to square the head to the X and Y axis? I am a newbie and have the CNC part down but am in the basics on the mill setup/truing.....
 
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