PM727 Issues

Thanks mak91, I actually changed the spindle bearings a few weeks ago. I do have the top bearings that the gear drive runs on. That did seem to be a different process entirely. I pulled the top 2 snap rings and had no way to pull them. How did you get those out?
Thanks,
Sean
 
mak91 said:
A public service announcement for pm727 owners. Two things you might want to check to prevent future failures. First is the wiring in your control box. Make sure the crimps are good and tight by giving a slight tug on the wire. I had loose crimps which caused heat buildup to the point the insulation melted off the wires and shorted out which eventually fried my motor. The second thing to check are the spindle bearings. Mine were bone dry with no lube which caused bearing failure.
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Yeah....I had a small fire in my terminal box up on motor from loose wires. I found two wires crimped differently on either end so it was wired backwards(spindle direction) a bit of a mess. I'm gonna say it's A PSA to all PM owners to at least up the electrical boxes and take a gander.
 

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GunsOfNavarone said:
Thanks mak91, I actually changed the spindle bearings a few weeks ago. I do have the top bearings that the gear drive runs on. That did seem to be a different process entirely. I pulled the top 2 snap rings and had no way to pull them. How did you get those out?
Thanks,
Sean
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I removed the top plate of the gear box and pressed the 6007 bearings out from the bottom side.
 
GunsOfNavarone said:
Ah gotcha. Did the top spindle gear drive come out as well?
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Yes it did. There are two plugs in the top of the gear box. If you pull those plugs and you are real careful I think you can pull the top plate without pulling all the gears out with the top plate. I wasn't that lucky. I think the trick may be to have a second set of hands and have them push down on the gear shafts (that are exposed by removing the plugs) as you lift the top plate off. If you end up pulling all the gears out you need to watch for the little moon shape brass shims that ride in the gear slot and connects to the shift lever. The shims will drop out of where they belong and will need to be put back in place when assembling.
 
Just repacked my spindle bearings on my year old 727V. Tricky part (aside from finding the mystery screw behind the screw) was to get the preload right, enough to keep the spindle runout down, but still spin without heating. No easy way to do it except to install, check, run, recheck, curse, uninstall, adjust and repeat. I started down the road of looking into the drive gears, but the motor is stuck, really stuck and I didn't feel like dealing with it at this time. Perhaps the the next bearing repack.
 
Starr, I feel you. 4 times in/out for me. The proper pre load is a bit concerning. I found over tightening and slightly loosening worked "best" BUT adding the position of the nut locking washer complicated it greatly. I never found a position that allowed me to lock it where I felt best about it, it was always slightly too tight or too loose. I figured that the next regressing interval, things will be fully seated/worn in and might possibly be easier. I feel no play and my laser temperature reader found null increasein temp after 10 mins of running, whereas the previous attempt it went way up.temp
it's like the Little Red Riding Hood scenario, not too loose, not too tight. Not too packed, not too under-packed.....but just right.
 
I am shopping for a manual mill to offset my cnc mill workload. Pre-machining is a better term to use. I have the 727v as one of my choices. Now I am unsure if that is the best choice. I have enough recurring issues with my cnc that I want the manual to be available for production if the need arises. Has there been any real feedback seen on the new 728vt. Have been comparing the 25mv the 727v and the 728vt. Not crazy about belt drives but I like the speed choices they provide. One of the biggest selling features on the 728 is the better ways and gibs. Scraped ways are always better for oil retention. Was just trying to stay under $4k with the DRO.
 
I have a PM-727V that gets used for hobby purposes and have no real complaints. The PM-728VT costs 50% more and is probably nicer in most ways.

The 727V will have much better performance at lower RPMs due to the gear drive, maybe 4x the torque at 200 rpm. This will make things like drilling big holes, using slitting saws, or tapping threads in steel or cast iron much easier.

For milling aluminum with carbide tooling, the 4000 RPM and tighter spindle of the 728VT will be your friend.
 
jaek said:
I have a PM-727V that gets used for hobby purposes and have no real complaints. The PM-728VT costs 50% more and is probably nicer in most ways.

The 727V will have much better performance at lower RPMs due to the gear drive, maybe 4x the torque at 200 rpm. This will make things like drilling big holes, using slitting saws, or tapping threads in steel or cast iron much easier.

For milling aluminum with carbide tooling, the 4000 RPM and tighter spindle of the 728VT will be your friend.
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The bulk of my work is grade 6061 aluminum so the variable speeds are essential. I love the 728vt but the price is indeed up there. By the time I add the DRO, stand and power feed that jumps up to mid $4000's. Trying to stay under $4000. Have a cnc vertical mill, a floor drill press and a mini mill with the belt conversion on it but am ready to upgrade to a better manual and remove the mini mill from my shop.
 
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