Reply with QuoteNVM...I decided to order NSK C0 double shielded for both. I'll will post how they work out.
X2 Spindle Bearings
OK I have my spindle apart and know what size bearing to but what is the best brand. I'm looking at NSK, SKF and FAG.
As far as sizing goes here is what i'm looking at.
Top: 6206 = 30mm X 62mm X 16mm
Bottom 6007 = 35mm X 62mm X 14mm
Should I go with double shielded non-contact or non contact seal?
Also, Should I go C0 or C3 clearance?
The reason I'm replacing the existing bearings is to hopefully reduce noise and heat.
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Last edited by wam; 01-14-2010 at 05:33 PM.
NVM...I decided to order NSK C0 double shielded for both. I'll will post how they work out.
Hi Wam;Originally Posted by wam
I've just joined the forum, and yours is the first post I've read & responded to - Do either of us get a prize or something?
I have an X2 also, and just wanted to ask why you selected those bearings. I did the belt drive conversion before CNC'ing the X2 and wonder about the original bearings when running 4300 RPM for hours - So far so good, but I will look forward to your report on the new NSK bearings.
Have you done the belt drive conversion to eliminate all the gear whine?
Best Regards,
Ken
The new NSK bearings came and I installed them today. Notes, I did not measure run out or sound with the OEM bearings so this is not exact science. The run out with the NSK bearings is .0005 measured with a 1/8" collet chuck and a 1/8" carbide bit. Run out was measured on the bit. The sound is slightly quieter but I have an issue with my pulley setup that I need to make a new pulley for the spindle. Heat after 15 minutes of no load was lukewarm. The bearings have a limit rating of 11K with grease according to NSK. I will never run them that fast as I just bought a Wolfgang spindle for carving wax. Overall Im glad I went through the trouble of changing them out.
Last edited by wam; 01-22-2010 at 09:11 AM.
Will you post the part numbers on the bearings.
Thanks.
I purchased them from Applied. The part numbers are somewhat standardized across the industry.
Top: 6206ZZ $18.08
Bottom: 6007ZZ $24.98
These are single row deep groove double non contact shielded bearings. You can also go with various shielding and sealing options but these had the highest RPM range.
http://www.nskamericas.com/cps/rde/x...20Bearings.pdf
Last edited by wam; 01-22-2010 at 09:15 AM.
Sorry if I appear dim but why the single row deep groove instead of a taper roller?
I sort of understand the radial force in milling suits the SRDG type but surely clamping the spindle reduces the load capacity? I'm thinking maybe a SRDG to the lower (where the radial milling forces are greater) with a taper roller at the top to better take a preload................or am I over thinking this? I just see the potential for the SRDG to 'float' vertically?
Tapered bearings are only useful if you have two of them. The "correct" setup would be a pair of angular contact bearings, either one at each end of the spindle, or a pair at one end, and a radial bearing at the other. Deep groove bearings will likely not work particularly well at high speed, once adequately pre-loaded. They will certainly be very sensitive to preload.
Regards,
Ray L.
Cheers for that Ray - thats what I thought, the AC's would require a correct length spacer so preload clamping could be exact? so I guess somewhat more involved......and expensive!
Not necessarily. If you put both AC bearings at one end of the spindle, you can use a pair that will be properly pre-loaded when simply clamped together with no spacers. Without a surface grinder, you'll have a hard time doing any better than that. I've had good luck even with the inexpensive AC bearings from vxb.com. I use their AC bearings, costing $14 for the pair, to support the ballscrew on my Bridgeport quill drives, and get essentially zero float on the screw, and very smooth operation. On these small mills, there is so much flex in the basic machine, the tiny amount of lash you *might* get from inexpensive AC bearings is completely lost in the noise.
Regards,
Ray L.
Sorry but I don't think that you are dim.... I went to the 4 hour online school for bearing engineering. I wanted to minimize noise and from what I have read the roller bearings increase noise. I could have used AC bearings but another thread suggested that there was no real benefit in this application. So that took me back to the single row deep groove bearings.
The advantage of AC bearings is higher axial load capability. Deep groove bearings have more axial capability than standard ball bearings, but still not much. Tapered rolllers are best in terms of combined axial and radial loads, but also highest in friction and noise. Virtually all serious (i.e. - non-hobby) milling machine spindles use AC bearings, at least until you get into the very high speed ones.
Regards,
Ray L.
Just to keep my head straight.......Radial load is perpendicular to the bore of the bearing and axial is parallel to the bore?
Just for grins I turned a new motor pulley this morning and ran the spindle at what should have been about 5200 for half an hour. The spindle reached a temperature of 130 in 20 minutes then leveled out.
Axial load = drilling
Radial load = milling
Joe
Whatever bearings you use, if you have only one at each end of the spindle, you have to preload both bearings, one against the other. You will not be able to make a spacer accurately enough to properly apply the prelaod. Most cheap mill spindles have preload adjustment by a threaded nut, which is very difficult to set correctly, consequently overheating is primarily due to too much preload, not because the bearing quality is not good enough.
Also the maximum bearing rpm quoted by the manufacturer for single bearings is with minimum or zero preload. If you apply preload, as you should, then the maximum rpm is reduced as is the life.
If you want to move up market then you need a matched pair of AC bearings on the bottom end, which gives you an accurate pre-set preload, and a floating bearing on the top end, which avoids any temperature effects on the expensively purchased preload. But then you probably have to modify or build a new spindle in order to fit them.
Phil
Hi,
Matched AC bearings pairs cost more than the mill itself, and cannot be installed anyway...
I have moved to tapered roller bearing on my X2, little bit more noisy but it's not relevant since cutting sound is way larger.
Preload is set by nut, far away from optimum and very difficult to set. For this I use a power meter on th supply. This gives me the exact position where it start to draw too much power.
On the X2, you also need to make sure that upper bearing is somewhat loose on the spindle, or you won't be able to set preload easily (once over-tighten, you should release the spindle entirely and re-do the preload).
