Since having published the details of where to obtain it in small quantity (directly off their web store), I’ve seen a number of folks over on CNCZone pick up a tube. One fellow (gd.marsh on CNCZone) is now testing the spindle on his Chinese mill to 8000 rpm–cool beans!

After seeing all this, I finally place my own order for a tube of the magic grease. I’ll be using it on my IH mill belt drive project, when I finally get to it.

You want Kluber Isoflex NBU 15. It ain’t cheap–about $30 with shipping for a 50G tube–so what makes its so magical? This diagram will serve to illustrate:

Bearing Speed Factor vs Spindle RPM

Bearing Speed Factor for 7207 AC Bearings Showing Grease vs Oil Lubrication Regimes

Those “dN” numbers are called “bearing speed factors.” They basically tell us how well the lubrication is working on the bearing, and hence how many rpm it can turn. That diagram shows the normal regime for grease versus a need to go to an oil mist system. Most recent VMC’s are using oil mist, BTW. Anyway, the magic of Kluber Isoflex NBU 15 is that it has a BSF of 850,000 dN rather than the normal 400,000 dN found with most greases.

That 7207 is the bearing size my IH mill takes for its spindle. With ordinary grease, the absolute redline would be 8K rpm and realistically I should probably hold it to 6,000 to 6,500 or so. It’s no wonder this is the speed range for Bridgeport mills and the like too. However, with the magic Kluber grease, much higher speeds become practical. 8,000 or even 10000 is doable. Since dynamically balanced tooling is recommended at 10,000 or up, I doubt I’ll be running there, but 8,000 rpm would be sweet. A whole raft of the earlier CNC mills, like the Tree Journeyman series, as well as more recent VMC’s took 8,000 rpm as their target speed and its a good one for aluminum work.

My IH mill will only do 1600 rpm with the current gearbox. If I could run it at 8,000 rpm I could literally be feeding my programs 5x faster in many cases. Sheesh, I may need to look at tuning up my servos so I can get my positioning up from its current 120 IPM.

 

 

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