PM935 Z axis Power Feed photos?

[Alan H.]

I am considering adding a power feed on the Z axis of my PM935TV milling machine.

I would ike to see some photos of your PM935 Z power feed installation along with the limit switches.

Any advice and insights you could offer would also be appreciated.

Thanks in advance for the help.

 

[wrmiller]

I have a PF on my Z-axis (sorry, no install pics nor limit switches) and the only problem I had was having to turn/move back a shoulder on the provided shaft.

But mine is the older non-lever type of PF. You may not have that problem.

 

[johnnyc14]

I ordered a z axis power feed from Matt for my older Taiwanese 10 X 50 mill and its the same model that fits the PM935.



This drive sleeve is a light press fit and is keyed to the shaft. I tapped it off with a plastic hammer.





Then the lock nut for the micrometer dial threads off.





The micrometer dial hub is threaded on, I removed it with a strap wrench. Those threads are where the new extension shaft threads on.






Three screws hold the bearing plate on. Yours will most likely be socket head. My original bearing plate was broken so I used regular hex head screws wh3n I rebuilt the mill a couple of years ago. The z axis bevel gear shaft can be pulled out now if you choose to do so. It's a good time to add new grease to the bevel gear.





The new extension shaft threads on and must have a roll pin installed to keep it from threading off when the crank is turned CCW.



There are 2 floats for a wrench machined on it. Tighten it firmly asmit will now hold the bearing into the bearing new bearing plate.



After the extension shaft was tight i drilled a 3/16" hole through both shafts and installed a roll pin. The roll pins are not supplied in the kit.









The 2 extra holes in the new bearing plate are used to mount the motor housing. I had a little interference between the housing and the knee casting on my mill. I used a disc grinder to remove a little of the knee casting for clearance.



The new drive hub is threaded onto the shaft instead of keyed so it must also be pinned as the last step after the proper drive gear backlash is established.



After the motor housing is installed the hardest part is establishing the correct backlash between the drive gears.



I hope this helps. If you would like pictures and a description of that process I can add them later.

John

 

[Alan H.]

Thanks John for the wealth of photos and all the detail!

Did you use the limit switch set up?

 

[johnnyc14]

No problem Alan. I did use the limit switch hardware that came with the kit.

The track was pretty flimsy so I made up 2 spacers to fit between the rails of the track to prevent it from being crushed by the fasteners. I mounted the track and limit stops to the body of the mill. I had to make up some more spacers so it would be perpendicular to the knee travel.



I mounted the switch to the knee using the supplied L bracket and spacer. All the mounting screw holes are M6.

 

[johnnyc14]

This is the procedure I used to establish the correct backlash between the drive gears.
There are 2 sizes of shims in the kits, the smaller OD ones are for the drive gear backlash adjustment and there is quite a selection of thicknesses in the kit. The larger OD ones are for spacing the micrometer dial and again there are a few different thicknesses.



The brass bevel gear is keyed to the new extension shaft but to adjust the backlash you must leave the key out. I started with .060" of shim stack. When I hand threaded the drive hub onto the shaft I could feel the shaft binding as the 2 gears were forced together with no backlash. I kept adding shims and re-testing until I could feel backlash when the drive hub was hand tightened. Then I engaged the knee locks and firmly tightened the drive hub to be sure there was still backlash. I then started reducing the thickness of the shim pack in .005" increments until the backlash disappeared. At that point I added .005" back to the shim pack and achieved the minimum amount of backlash with no binding between the 2 gears.





My final shim pack thickness was .105" and I noted that on the kits manual for future reference.



Then I installed the key onto the shaft and finished the assembly with the drive hub firmly tightened to the shaft again. The shim for the micrometer dial is the one that allows minimum clearance between the dial and the motor housing with no rubbing between them.









Now the drive hub has to be pinned to the shaft. I drilled the 3/16" hole through 1 side of the gear in the mill to get it started straight then installed the hub back onto the shaft and finished drilling through the shaft and the other side of the gear with a hand drill.



The kit comes with a spring designed to keep the manual crank handle dis-engaged from the drive hub so it doesn't whip around when power feeding. I had to modify my home built drive handle hub to include a pocket for the spring. I made the pocket deep enough so the handle hub is pushed firmly away from the drive hub. I basically copied the dimension of the pocket in the kit drive hub.





My home made handle hub has a square 1/2" drive hole machined in the end of it where I used to use a drill to power the knee up and down. I made up a square washer to fit this hole. The new extension shaft has a M6 hole in the end so I found a screw that would bottom in the threaded hole and hold the handle hub onto the shaft but still allow it to rotate on the shaft. A liberal amount of grease was used between the handle hub and the shaft.













The whole job went pretty well. The only thing that didn't come in the kit was the 2 roll pins. The only fussy part is getting the backlash correct. I probably spent an hour messing around with that but now that I have done it once I cold probably do it aging in 10 minutes. The instructions in the kit are pretty much useless. It seems like a very high quality kit and looks to be made by the same company that makes the "Align" brand X axis power feed that came with my mill which is over 30 years old.



John

 

[Alan H.]

Okay John, you have given us the "Full Monty"!

Thanks for taking the effort to put all these photos, explanations, and instructions up. They'll help me and others, I am sure.

 

[johnnyc14]

I thought I would record it while it's still fresh in my kind. Enjoy your new mill.

 

[Alan H.]

. . . . . . . . . . It seems like a very high quality kit and looks to be made by the same company that makes the "Align" brand X axis power feed that came with my mill which is over 30 years old. . . . .
John

John, Just for clarity - The PM Power Feeds are made by ALSGS and they are made in China. The Align Power Feeds are currently made in Taiwan. As one might expect the Aligns are significantly more costly than ALSGS.

I have been studying Power Feeds in the past couple of weeks and it has been interesting to dig into the Asian suppliers and try to sort through all the rebranding, copied designs, and try to find some clarity! I discovered that Servo (the American mfg) is now offering an Asian model with their name on it. I guess it's go Asian or go broke these days.

From what I've seen, I am betting the ALSGS is one of the largest manufacturers around. There seem to be a huge number of rebranded ALSGS units out there. I imagine that the more experienced sellers know how to get the better units from them. From another business/market, I understand that managing Asian (particularly Chinese) suppliers is challenging to say the least.

Here are their websites:

ALSGS
Align

 

[johnnyc14]

That's good information, thanks Alan. Something else I learned from Matt is that there are a couple of different designs based SAE or metric threads on the feed screw shafts. Some have 3/4" 16 tpi threads and others are 19mm X 1.5mm thread. Mine has SAE threads and that was the only style Matt had in stock. I think all the machines Matt sells are that way.