# PM727 Issues



## mak91 (Nov 22, 2019)

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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## markba633csi (Nov 22, 2019)

Oh yucko, you should definitely let Matt at PM know about that (if you haven't already)
Mark


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## mak91 (Nov 22, 2019)

The electrical issues happened a year or so ago, PM replaced the motor no problem. They said there was no wire harness for the machine even though each individual wire is clear marked. I got some wire/crimps from the hardware store and made my own. The bearings are a recent problem and it was recommended from them that I buy better bearings. I am not sure if they consider their own bearings crap or not but honestly I think a little grease would have gone a long way to preventing this. You are on your own to figure out how to disassemble and replace this stuff. Luckily I have the tools and a 20 ton press to do this with.


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## MikeWi (Nov 22, 2019)

I forwarded this to Matt.


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## qualitymachinetools (Nov 22, 2019)

I am not quite sure who this is, only found customer one in Ringgold, GA, and that machine is about 2 months shy of 3 years old. Is it converted to CNC and running constantly or faster than stock?  Thats the only time Ive seen anything like that, just asking because of the comment about we recommended buying better bearings leads me to believe it was converted and / or sped up, that would be why it was recommended to get different bearings.  Not how its sounding like you got the machine last week with dry bearings and we told you to go buy bearings.  If that is the case, let me know who you talked to here and they are going to have a problem.  
     It definitely does not hurt to check bearings and is good to do when new, but I have never seen one that was dry like that when new or recently put in to service. If anything they over-grease them from the factory and I am on them about not using too much grease.     I would check them about 1 time per year though, or every 500 hours or so of use as a general rule.


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## mak91 (Nov 22, 2019)

You are correct, my machine is almost 3 years old and not cnc'd. I am a hobbyist and don't use this machine that often. NSK bearing were recommended as an upgrade when I asked if the bearings were covered under warranty.


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## Driveslayer45 (Dec 5, 2019)

As a fairly new 727v owner i though the oil in the headblock served to oil the gears and the spindle bearings.. if that is not correct are the instructions for the spindle bearings in the manual?


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## higgite (Dec 5, 2019)

Driveslayer45 said:


> As a fairly new 727v owner i though the oil in the headblock served to oil the gears and the spindle bearings.. if that is not correct are the instructions for the spindle bearings in the manual?


It sounds like you didn't get a manual with your machine. Here you go... https://www.precisionmatthews.com/wp-content/uploads/2017/06/PM-727M-V-4-16-2018-v4-Web.pdf

Tom


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## GunsOfNavarone (Dec 8, 2019)

@mak91 I need to replace the spindle bearings/seals. Where did you source yours, and advice changing them?


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## mak91 (Jan 8, 2020)

GunsOfNavarone said:


> @mak91 I need to replace the spindle bearings/seals. Where did you source yours, and advice changing them?


Which bearings are you going to replace ? If its part number 36 and 50 in the manual bearing numbers 30205 and 30207 there is no seal to worry about. I got them locally from an industrial bearing / hardware store. If you have to change the 6007 bearings part number 6 in the manual things will get interesting. You will have to remove the top cover of the gear box to change them. There are seals related to the 6007 bearing but mine looked good so I didn't change them. Even though the 6007 bearings are inside the gear box they are NOT bathed in oil. PM originally told me they were, they are NOT, they are above the oil and grease packed.

The only tricky thing to taking the spindle out is there is a screw hidden behind a setscrew on the left side of the head. You must remove the set screw and use a flat head screwdriver to loosen up the screw some so the spindle can drop completely out. If you have to replace the 6007 bearings the motor and top plate must come off. There is a plate sitting on top of the 6007 bearings that screws onto the top plate that also must come off. Here are the official instructions that PM emailed me. They leave a lot to be desired but will get you going in the right direction. Also the bearings are available from multiple places just google the bearing numbers like 6007 or 30205 and you'll get lots of hits, go with a name brand and a known seller.

Hello Friend

it is need open that top casting.

1.,open electric box.and Remove side connecting screw with          top casting.

2..remove motor.

3.please checking this picture.remove two plug.

4.remove spindle Snap ring and remove this top casting.

5.replace bearing

6.Restore them

if there are any question,please let us know.thanks

best regards

Mr.Chen yuan


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## GunsOfNavarone (Jan 8, 2020)

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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## GunsOfNavarone (Jan 8, 2020)

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.


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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## mak91 (Jan 10, 2020)

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



I removed the top plate of the gear box and pressed the 6007 bearings out from the bottom side.


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## GunsOfNavarone (Jan 10, 2020)

mak91 said:


> I removed the top plate of the gear box and pressed the 6007 bearings out from the bottom side.


Ah gotcha. Did the top spindle gear drive come out as well?


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## mak91 (Jan 11, 2020)

GunsOfNavarone said:


> Ah gotcha. Did the top spindle gear drive come out as well?



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.


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## starr256 (Jan 12, 2020)

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.


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## GunsOfNavarone (Jan 12, 2020)

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.


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## mrproduxn (Jun 3, 2020)

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.


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## jaek (Jun 3, 2020)

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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## mrproduxn (Jun 3, 2020)

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.


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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## jaek (Jun 3, 2020)

727V has variable speeds too, it just doesn't go as high (3000 rpm vs. 4000 rpm).


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## mrproduxn (Jun 7, 2020)

I did buy a pm 728v-t yesterday with DRO, x axis feed, a good keyless chuck, the stand and 2 of the 4" "precision" vises.


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## jaek (Jun 7, 2020)

Congrats! When does it arrive?


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## mrproduxn (Jun 8, 2020)

jaek said:


> Congrats! When does it arrive?


They have 50 base machines ready to ship now. Around June 25th for mine. Backordered because of the DRO. The feed motor also backordered until early August.


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## mrproduxn (Jul 2, 2020)

New toy arrived today.


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## Cad cam man (Apr 13, 2021)

GunsOfNavarone said:


> 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.


Do any of you guys have a picture of the control board or can you see your control board mine is filled with black plastic for security purposes? I just got my mill 3 weeks ago and the terminal blocks where these wires are look a bit different


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## GunsOfNavarone (Apr 13, 2021)

I’m don’t have any clue what the newer units are like. I believe mine is 2016, but my capacitors and this terminal block is built onto the side of the motor. Your’s seems like a better setup. This is the block and wires that were burned to a crisp. Terminal block was almost entire melted and screw post were just rattling around in the blocks hollowed out body.
For whatever it’s worth...here’s mine prior to the repairs.


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## 7milesup (Apr 13, 2021)

Cad cam man said:


> Do any of you guys have a picture of the control board or can you see your control board mine is filled with black plastic for security purposes? I just got my mill 3 weeks ago and the terminal blocks where these wires are look a bit different


The black "plastic" that you are referring to is called "potting".  It is actually an epoxy that is poured into/onto the circuit board.  It can serve two purposes...  1.)  In a higher vibration environment it reduces the chances of components coming loose or breaking off.  2.)  Some mfg's do it to force you to buy a new board vs repair should something go wrong.


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