CNC conversion bearings for PM mills?

S

sc0ch

H-M Supporter - Diamond Member
H-M Lifetime Diamond Member
Joined
Feb 13, 2020
Messages
21
I have a PM833 that's underway to CNC control...

Sourcing bearings has been a pain!!!

Who knows a good source for CNC bearings?

I'm stuck with a [15 x 32 x 9 mm] form factor because all parts were cut to that [inner x outter x depth]. Purchases so far:

6002 15x32x9 bearings from Grainger were expensive and, upon test, cannot handle axial loads. Maybe another source for 6002 bearings are better for axial loads?

"7002 15x32x9" axial bearings from Boca Bearings had no markings and no tapered race insofar as I could discern. In short, evidently they were NOT 7002 bearings. Sent them back before any axial load test....oops

7002 15x32x9 axial bearings from Ebay were complete garbage. Yes, they showed a tapered race, but they were gritty. No smooth rolling there. $9 bearings are, unsurprisingly, potentially garbage.

Any help appreciated.
 
Last edited:
What was your plan for constraining axial loads before you started? Is the bearing your only means of doing so?

Doubling angular contact bearings is how axial loads are usually handled. I think there is a 7002 size analogue in double-row, but who wants to pay for that.

Just scratching my head and thinking about your run of the mill Chinese ball screw supports, and coming up with more than one way to manage thrust than relying on the radial support bearings.. What are all the other kids doing?
 
A 6008 is a deep groove radial ball bearing. It can handle about half of it’s load rating as an axial loaded bearing, but is meant primarily for radial loads. A 7002 is an angular contact bearing, but not even close to the same size as a 6008, did you mean 6002? The last two digits are the bore size, so an 08 is a 40mm bore, but an 02 is a 15mm bore. Neither one has a tapered contact surface, the ACB is a ball bearing with a contact angle at usually something like 15 or 25 degrees for spindle bearings, it is not easy to see just looking at the bearing.

How did you do your axial test for your bearings?

You mentioned the bearings were not marked asymmetrical, are you talking about being marked for the high spot of runout? If so, unless they are marked P5 or better, you wouldn’t see that.
 
  • Like
Reactions: B2
Ischgl99 said:
A 6008 is a deep groove radial ball bearing. It can handle about half of it’s load rating as an axial loaded bearing, but is meant primarily for radial loads. A 7002 is an angular contact bearing, but not even close to the same size as a 6008, did you mean 6002? The last two digits are the bore size, so an 08 is a 40mm bore, but an 02 is a 15mm bore. Neither one has a tapered contact surface, the ACB is a ball bearing with a contact angle at usually something like 15 or 25 degrees for spindle bearings, it is not easy to see just looking at the bearing.

How did you do your axial test for your bearings?

You mentioned the bearings were not marked asymmetrical, are you talking about being marked for the high spot of runout? If so, unless they are marked P5 or better, you wouldn’t see that.
Click to expand...

Yes, they were 6002, I corrected the original post and removed assymmetrical. What I meant by assymmetrical is tapered, but that's certainly unclear!

Tested the Grainger 6002 bearings with my finger! They were smooth in radial load, but caught in axial load (perhaps catching on the metal dust shield).

Just tried another outfit, will let you know what happens.
Would love to know what the other kids are doing. This is a build that resembles ArizonaVideo's CNC conversion for the PM25-MV, but upscaled for the PM833. I bought the PM833 conversion kit from Heavy Metal CNC, but only two parts and the screws proved useful.... Before his death he updated the kit, presumbably so more is usable, but I have the older version.
 
There is some clearance in the bearings, so if they are cocked a little as you do your testing, it can appear as if they are not running smoothly. Rotating them with your finger is not going to tell anything unless they are severely damaged. All bearings of the same number should perform similarly, ie all 6002 bearings will have about the same load ratings (assuming quality manufacturers, all bets are off for the no name brands coming out of China). A deep groove ball bearing like the 6002 can handle about half it’s catalog rating in the axial direction, but it is not the ideal bearing to use for something like that. It’s usually used because they are cheap and work well enough. Angular contact bearings are designed to have good performance in a combined radial and axial loading, but they require the proper amount of preload and might not work with the design you are constrained by. Is this for the z axis leadscrew?

You can get quality bearings at BDI www.bdiexpress.com, looks like the 6002 is only about $20-22 from quality brands. You’ll be spending a lot more than that for ACBs so maybe stick with what’s in there.
 
  • Like
Reactions: B2
Alright, some bearings came in from an ebay outfit and they seem great! Or at least smooth and supposedly matched:

www.ebay.com

7002CYDUP4 Nachi Angular Contact 15mm x 32mm x 9mm Abec-7 Japan Ball Bearing | eBay

Find many great new & used options and get the best deals for 7002CYDUP4 Nachi Angular Contact 15mm x 32mm x 9mm Abec-7 Japan Ball Bearing at the best online prices at eBay! Free shipping for many products!
www.ebay.com

Good to know these, and potentially the www.bdiexpress.com option, are available.
 
Last edited:
Let us know how the install goes. I want to replace mine to try to mitigate the hot spindle when used in high gear.
 
I am also converting my pm833tv to CNC with my own design. Japanese made NSK-TAC series super precision angular contact bearings is what I purchased. This series was specifically designed for supporting ballscrews.

The Nachi-TAB series were also specifically designed for ballscrew supports. I know the standard 7002 will work just fine but I would have chosen the 15TAB04 instead. If you are wanting a specific bearing you can contact Nachi/NSK/SKF/NTN/FAG directly and ask them who your local distributor is. That distributor can usually get what you need in a timely manner, at least the ones near me can.

Eric
 
You must log in or register to reply here.
Back
Top