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PM 727M Stuck in High

Livnpaintball

Steel
Registered Member
#1
IMG_1214.JPG Well I must say I'm disappointed with this initial introduction to my new machine. I set it up, leveled it, did the run in and that was a mistake. After the run in I drained and refilled the gear box. While draining there was a Hugh amount of metal in the fluid. Added some new fluid and tried to run it again. To my surprise it was stuck in High Range. After talking to Matt I finally took it apart today to find a fair amount of metal shaving, High-Low keyway (86) was dinged up and the sealed bearings on the bottom of the gear box are shot. For anyone who buys one of these I fully recommend you to open up the gear box and clean it out.
 

cut2cut

Active Member
Active Member
#3
I got my PM-940 in January. I knew I'd be removing the gearbox for a DIY pulley and belt setup due to the assumption the gearbox would be noisy. Sure enough, it was noisy as hell, some people don't mind, but I do, a lot. I also took the opportunity to replace the spindle bearings with AC bearings so I could increase the spindle speed without worry the bearings would fail. Upon pulling apart the spindle there was a large amount of "scale" from the casting process in the spindle carrier (the bearing seats are pressed into ), both loose and about to come off so I did my best to remove it with a wire wheel that happened to be the right OD and with an extension I was able to run it through the entire spindle carrier. If I had not found and fixed this, I'm sure the bearings would have failed very quickly due to the scale getting into the bearings, if they had not already.

Long story short, if you go to my new "mod" thread, and determine if your 727 head and bearings are similarly sized as the 940, you can use my method to get rid of the gearbox and gain some RPM in the process. [edit: changing the bearings isn't required, but if you want to increase the maximum RPM to greater than 3200, it is required...]. Once all is said and done, its whisper quiet now, but I cannot say it will hold up over the long term and the part that made me nervous the most was replacing the bearings and it requires a press, and I even had to sand down one of the bearing seats to ensure it would go together, too little and it won't, too much and there will be slop and runout.
So far so good though...

http://www.hobby-machinist.com/threads/my-pm-940-cnc-modifications.57976/#post-476921

Jake
 
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cut2cut

Active Member
Active Member
#5
Thxs c2c, hoping the spindle bearings are ok but now I have to check those to
I noticed that some people have had to replace a seal that rides near the top of the spindle in the gearbox because they noticed oil dripping down the spindle carrier cavity out through the lower spindle "cap". This leaking oil would surely move the "scale"down further and into the lower bearing. This was another benefit to removing the gearbox, no need to worry about that seal and oil changes... etc. and if there was a lot of metal shavings running around, it likely kills the seal in the process...

[edit of my precious post above --> changing the bearings isn't required, but if you want to increase the maximum RPM to greater than 3200, it is required...].

Jake
 
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Greebles

Active Member
Active Member
#6
I have trouble changing between High and Low on my PM-727M. Takes some force and "wiggling" of the spindle to get it to switch over. Wondering if I will need to pull the head apart also. Not looking forward to that.

-Denzil