Chinese Router Spindle Bearings

[wizzardworks]

Heeeeeeellllllp!!, Well after 760 hours the spindle bearings on my J-cut 6090B failed. Upon dissassembly I found there had apparently never been any lubricant in them. This is the 1.5Kw 2 bearing spindle motor. The bearings are angular contact ball bearings The designation number is 7002CTA and I need a soure to buy a few. The cheapest price each I have found is $134.60 and one source priced them at $444.00 each The ID is 15mm the OD is 32mm and the thickness is 9mm. They are angular contact ball bearings with a phenolic separator ring. The maximul listed RPM is 48,000 however I only operate at 10,000RPM and am looking for a dimensionally interchangable angular contact bearing. I only cut MDF.
A new spindle motor is $242 delivered so the $269.20 for two bearings seems excessive. I contacted the bearing manufacturer in China and they no longer produce this bearing. They are also made by NSK and Timkin among others for $344 apiece.
The bearings are easily changed if I can only find some of them. Any help would really be appreciated.
On a semingly unrelated item, my linear bearings did not have grease in them either and no fittings were installed for the zerks. I screwed some 6mm straight grease fittings in, however the grease gun won't fit due to the proximity to the guiderail. I can't screw in 45 degree fittings and plan to add a piece of flatbar (!/4 X 3/4) with 1" long 4-40 screws on top of the grease hole with 45 degree fittings installed. The plunger type grease gun used for chain saw nose sprockets works to some extent.

wizzardworks

[brumby]

Hi,
I have fitted similar 7002 bearings are fairly common in the automotive industry used in idler bearings and spigot bearings. They cost about $10. Maybe worth checking specs

You could always order the same ones for China for $3ea plus Shipping Buy 7002C angular contact ball bearing, 15X32X9mm angular contact bearing, 7002 bearing, 15X32X9mm 7002C 7002AC single-row angular contact bearing wholesale and retail at Aliexpress.com

Cheers

[TDA]

Take your pick

Unrated
7002B Bearing Angular Contact 15x32x9 Ball Bearings

ABEC 7
7002CYP4 Nachi Angular Contact Bearing 15x32x9 Abec-7 Japan Ball Bearings

Full Ceramic
7002 Angular Contact Full Ceramic Bearing 15x32x9 Ball Bearings

[wizzardworks]

Originally Posted by brumby Hi, I have fitted similar 7002 bearings are fairly common in the automotive industry used in idler bearings and spigot bearings. They cost about $10. Maybe worth checking specs You could always order the same ones for China for $3ea plus Shipping Buy 7002C angular contact ball bearing, 15X32X9mm angular contact bearing, 7002 bearing, 15X32X9mm 7002C 7002AC single-row angular contact bearing wholesale and retail at Aliexpress.com Cheers

Brumby, Thanks. I used your search suggestion on e-bay and ordered two at $9 each with free shipping from Anaheim Ca, vendors name irvineman. The 15x32x9 also found a lot of a bearing number 6006z zz deep groove ball bearing. I got a few of those as well. They were $13.46 for 10 bearings with free shipping. I am a little concerned about the angular contact bearings. Theese need to be mounted in pairs, prefferably back to back. My spindle is a 2 bearing variety with the collet end bearing having both races located. The top end bearing has the inner race restrained and the outer race floating as the expansion (for heat) bearing. This prevents the upper bearing from countering axial loads in one direction and the bottom (collet) bearing only designed for axial loads in one direction. I will put it back as designed and if there are future problems I can try the deep groove Nachi brand bearings. It may be that changing bearings at 500 operating hours would be a good idea. The bottom bearing retainer can also be fitted with a grease fitting, however the failure was due to brinelling of the outer race which grease may not prevent. The failure had warning signs of a shorter spindle wind down time when shutting off the motor about 15 hours before failure.
wizzardworks

[sburck]

I was wondering if one of these Chinese spindles could be modified to have a runout of less than two microns, rather than the 5 microns (listed on keling as the runout for all their high speed spindles). Would replacing the bearings with higher precision units do this? Would the arbor and housing need to be modified??? I am toying with the idea of making a small mill for micro machining, not necessarily micron sized stuff but pretty close if possible.

[wizzardworks]

Sburck, I am useing deep froove ball bearings which are Nachi brand bought from seller irvineman on e-bay. I tried replacing with angular contact bearings and had another bearing failure. To use angular contact bearings they must be in a pair back to back because they only take thrust in one direction. On my spindle they are at oppoends with the bottom bearing able to float for heat expansion and therefore unablt to take thrust loads. There are spindles available with three bearings providing the two back to back for thrust as an upgrade for metal cutting. Useing higher precision bearings would not be a good ghoice. The higher speed bearings actually have more clearance than low speed bearings. This is because as the bearings operate they get warmer and expand taking up the clearance. Clearances from C3 thru C5 are available. Bearings made of silicon nitride often called ceramic bearings are also available for use at much higher RPM and you might inquire about deep groove versions of them, however they may be $60 each.
The bearings are not the only source of runout. Runout can be described as a deviation from center axis of the shaft. This would result in the tool bit operating in a slightly eccentric motion and removing stock at it's own diameter plus the eccentricity.
Accuracy of the collet bore centering in the spindle shaft and the accuracy of the concentricity of the collets themselves also are sources of runout along with bearing clearance. If you determine the runout of the cutter you would then define the diameter of the tool bit to the larger size for the offset of the tool path in your G-code. The code would then make the part on size. Most procrams like EMC-2 and Mach3 require a backlash calibration of the router or milling machine to compensate for lost motion when changing direction on an axis. Some microsteps (stepper motor) or encoder pulses (servo motor) are ignored when the spindle reverses direction to compensate for the lost motion of the backlash.
I have a J-cut 6090-B CNC router which is sold as an engraving machine and appears to be amazingly accurate and has kept that accuracy for over 1400 operating hour so far. This machine would be a good start for what I understand you want to do.An incrase in accuracy by defining the actual stock removed by the cutter and backlash calibration in the electronics should allow fabrication of very accurate parts.
You might also research suppliers of micro machined parts and see what model of machine tool they are useing and check out the machine tool to see what type of guideways and feed screws they are built with. If they are useing magnetic levitation and the rail is a linear motor that would be tough to duplicate at home, but if they are applying the same hardware we use then the accuracy will come from the electronics.
wizzardworks