PM 940 PDF Question

[hotrats]

My 940 leaks oil around the spindle, and the gear selector knobs. So much so, that I keep a container to catch. I've not seen a tutorial, or guide to change out the seals for this model - is there a guide, or maybe videos detailing at least some of the procedure?
Another angle - has anyone modified their 940M to a variable speed from gear head? If so, I guess same question - any information on the procedure?
Thanks in advance for any info!!

 

[B2]

Hi, I too have the a 940M-CNC-VS. It is a geared head and has a VFD to get variable speed. Yes, it drips oil, but not as bad as yours. I think my leaks are mostly around the gear knobs. It is not so bad that I want to tear it down.

When I was starting out there were a couple of folks on this site who were converting their machines from geared heads to belt driven. I will have to think a bit to recall who was doing this. I do know that who ever it was took the head off and more or less completely rebuilt it and installed higher quality bearings. It think there was a CNC conversion or purchase involved. It several was years ago. maybe 2018 or even 17. Not recent.

Not for sure, but this may have been @phazertwo

 

[B2]

Look at this thread, especially some of the middle postings.

I’m FINALLY getting around to making a upgrade thread on my PM-940-CNC-VS, but

Another PM940-CNC-VS Thread...

Congrats! Nice update and pix! You should be very proud and you are a fine american taking such good care of your family and property. That tree is one amazing job. Bet you notice "big sky" for the next few weeks! The shed looks great. What all is going in it? Fusion360 is great and I...

www.hobby-machinist.com

 

[hotrats]

Look at this thread, especially some of the middle postings.

Another PM940-CNC-VS Thread...

Congrats! Nice update and pix! You should be very proud and you are a fine american taking such good care of your family and property. That tree is one amazing job. Bet you notice "big sky" for the next few weeks! The shed looks great. What all is going in it? Fusion360 is great and I...

www.hobby-machinist.com

Thanks for the links, I'll read up. I didn't even know if a vari speed conversion was feasible. I've not seen many references to changing out the seals in a 940, but seem to remember one saying that after changing his seals out, if it happend again, he'd just let it drip.

 

[B2]

My 940M leaks too. But not so bad that I'm going to tear into it. I just put a paper towel under the drip when I am not using it. I think the drip continues for awhile after shutdown, then may stop at some point.... maybe the leak is only while it is running, but there is oil still running down slowly. I sometimes use my machine to cut out patterns in wood. This is when I really do not like the leak as it stains the wood.

Lots of folks have added VFDs to there mills to get variable speed. The CNC version of the PM940 had it built in. It works fine.

I think the real reason some folks have changed the the drive is to get a quieter belt machine and to get the RPM up. But to do this one probably needs to put in better bearings. I have never tried to speed mine up to the max that the VFD frequency could put out as I was concerned about what this might do to the spindle bearings. The max spindle speed on mine (recommended) is 3200 rpm. At one point I thought maybe I could do engraving, but for this you need very high spindle speeds. Anyway, the machine is not accurate enough anyway. Too much backlash which would break the small tooling needed for engraving.

 

[hotrats]

d top coverMy 940M leaks too. But not so bad that I'm going to tear into it. I just put a paper towel under the drip when I am not using it. I think the drip continues for awhile after shutdown, then may stop at some point.... maybe the leak is only while it is running, but there is oil still running down slowly. I sometimes use my machine to cut out patterns in wood. This is when I really do not like the leak as it stains the wood.

Lots of folks have added VFDs to there mills to get variable speed. The CNC version of the PM940 had it built in. It works fine.

I think the real reason some folks have changed the the drive is to get a quieter belt machine and to get the RPM up. But to do this one probably needs to put in better bearings. I have never tried to speed mine up to the max that the VFD frequency could put out as I was concerned about what this might do to the spindle bearings. The max spindle speed on mine (recommended) is 3200 rpm. At one point I thought maybe I could do engraving, but for this you need very high spindle speeds. Anyway, the machine is not accurate enough anyway. Too much backlash which would break the small tooling needed for engraving.

Since returning from Asia, I've been doing a few things in my 'shop'. I did replace the speed control shafts "O" rings, and replace the screws that held the covers, as they were made of 'butter' steel, very soft. Now, i can tell the major oil leak is from around the spindle.
I'm thinking now that I'll go ahead and pull the motor, top cover, and have a look inside...

 

[B2]

Hey @hotrats ,

Did you pull the top off and look around at the bearings etc? Pictures?

I kind of remember @phazertwo or @cut2cut or @TomS, who have written about their 940M's may have taken the head apart. One of them may have even made drawings while converting to a belt driven system.... I think. It has been a while. Try this string https://www.hobby-machinist.com/attachments/img_0997-jpg.257212/

 

[hotrats]

Hey @hotrats ,

Did you pull the top off and look around at the bearings etc? Pictures?

I kind of remember @phazertwo or @cut2cut or @TomS, who have written about their 940M's may have taken the head apart. One of them may have even made drawings while converting to a belt driven system.... I think. It has been a while. Try this string https://www.hobby-machinist.com/attachments/img_0997-jpg.257212/

Actually, I did. Replaced the transmission speed control shaft's "O" rings 1st. While that stopped the leaking there, still leaking around the quill. I have it disassembled now, waiting on bearings. Have some photos, will post up later.

 

[verbotenwhisky]

I have the 940V-PDF so not a leakage issue as I do not have a gearbox. The issue I had with the head on mine was bearings, they were all labeled as NSK bearings but they didn't take much abuse (not really a great term but what I could think of) I changed all the bearings to Timken and the issue went away. I mention this only to say the seals are likely just as suspect, I would consider changing them out.

 

[hotrats]

Since we got back from asia, and I got caught up a bit, had a couple 'projects' I wanted to do. Which ended up with dealing with the oil leak from the mill head, as it's rather aggravating. Also ended up modifyng my bandsaw motor mount as original project has a bit of steel to cut.
Disassembly wasn't as complicated as I imagined. Their was some wear on the spindle bearings, not bad. One sealed bearing was bad. New bearings & seals are ordered.
Prolly a good thing to check out the insides anyhows as considerable sludge/sand in some areas. Troubling also was the drip oiler for the fine feed/power down feed didn't drip on any gears, just the bottom of the case.
1st photo shows a little excess oil in what should be a dry area.
The oil seals were very hard, brittle, and loose on shaft.
It will be nice to have a drip free mill!
As these things go, My Tacome developed a serious vibration. A bad universal is the culprit. The driveline has 3 u-joints, and a carrier bearing. I have nothing to press bearing off/on, so after calling around one shop told me a machine shop would be able to and gave me their number. Nice guys. "way' out in the country, at the end of a almost 1/2 mile drive way. shop and house on the banks of a river. Drive way pic included.