PM25- Roller Bearings for End Plates of Lead screw?

[alfaspider]

Has anyone added roller bearings to the end plates for the lead screw of the PM25, or similar mills?

Recently added a DIY table motor drive to the left side and removed one end plate. The end plates have oil ports, which I assume are sufficient for hand cranking the table. With added speed/movement from a motor drive there might be excess wear on the lead screw, so wondering if any one has added ball bearings to reduce friction?

Don't anticipate going CNC anytime soon but would like to see if anyone bored out the end plates and what type of bearings might work best for limited home/hobby use. Thanks,

 

[BaronJ]

Hi Alfaspider,

When I made my mill table drive I simply replaced the handwheel on the left side, leaving the end plate and bearings intact.
I replaced the handwheel with a plastic gear and drove that from a car screen wiper motor.

 

[alfaspider]

Thanks,

But I was asking if you added a roller bearing where the lead screw goes through the end plate of the mill table. Also if anyone added roller ball bearings to the other side of the table for the hand crank.

My DIY motor drive is pretty much the same thing with an aluminum plates and a wiper motor driving some plastic gears.

On the PM25 there is a white removable endplate and an oil port for lubrication. I think a roller ball bearing needs to surround the lead screw to reduce additional friction from the motor drive that is added.

 

[BaronJ]

Hi Alfaspider,

No ! My mill already has ball and thrust bearings in the end plates, on both ends.

 

[alfaspider]

OK- thanks-

The PM25 sold here by Precision Mathews does not have bearings or even bushings at either side of the table. It does have oil ports near the hand crank. This mill is sold in other countries, so perhaps different importers set different production requirements?

Can not tell what brand or model you have, but the gear drive looks similar to one I put together using a wiper motor.

CNC conversions usually add roller bearings and a more precise lead screw, but I am just concerned about increased friction and wear of the un-bushed lead screw with using a motor drive. thanks again

 

[BaronJ]

Hi Alfaspider,

Sorry ! My mill is an Optimum BF20LB. Each end of the table has a ball race and a thrust bearing. The backlash is taken out by adjusting the nut that holds the handwheel on. I modified the plastic gear with a brass bush that simply replaced the handwheel. The gear is driven by one of a pair of gears that is in turn driven by the gear mounted on the wiper motor shaft.

These pictures show the gear and the brass bush that I made to replace the handwheel.

 

[T Bredehoft]

I put ball bearings on each end. I noticed, before I put the motor in it cut the effort by 1/3 to turn the crank.

 

[BaronJ]

Hi Guys,

Certainly adding ball races and thrust races to the table leadscrew will improve the feel and can be used to reduce backlash. Actually it surprised me a little that the mill in question only had plain sleeves and no thrust bearings. I would have at least expected those.

 

[alfaspider]

Thanks--
Noticed the chip tray was green and not blue..., but not sure if this mill is sold outside the US as a different make, model and /options...

I did pretty much the same thing for the table drive, only used 3 gears: one on the table lead screw, one on the wiper motor arbor, and an idler gear that is used as a clutch.

What is the setup for your directional change lever? Noticed the arrows in your first photo. How does it engage and dis-engage the drive? Can you add a couple of closeup photos?

I made plywood templates for the end of the PM25 table, and positioned some plastic gears on arbors for the motor and table, then a swing arm lever to move the idler gear.

(was working with a friend on similar project so shot short video clips to send back an forth to explain my trial and error progression.

This has worked fairly well, but I may redesign the gear box, add some bushings on the motor arbor and the ildler lever, and then roller bearings on the end of the lead screw.

Thing is it seems to work for now.

 

[dcsleep]

My PM-25MV has bearings on the right side but not on the left. There's a bearing on each side of the end flange. Tightening the handwheel nut links the table to the leadscrew and loads the bearings to eliminate any play in the table movement (beside the leadscrew backlash adjustment). This makes the right handwheel the "driving" end of the table. The left handwheel simply turns the leadscrew so it appears the designers felt a simple hole with lubrication was sufficient. All of this is shown in the component diagram in the manual.

I've considered adding a bearing on the left side as well but not sure it's needed so I haven't done it. Interested in what others think.