[rusmannx]

In fact DC brushed motors have been used extensively in motion control and CNC since its inception and in fact a DC motor has maximum torque at zero rpm, and in the case of servo or high end spindles, the torque remains fairly flat over the rated rpm range.
Al.

Thanks. I've been told the AC Spindle has a flatter torque curve than DC.

Also, as a 3phase spindle advertised to go as low as 4kRPM, a 3:1 reduction could give me a nice range of 1400RPM to 8kRPM. I think I'm going to try it, since I already have it.

[Al_The_Man]

Thanks. I've been told the AC Spindle has a flatter torque curve than DC.

.

Google 'Torque curve for induction motor'
Al.

[carlowens]

Thanks. I've been told the AC Spindle has a flatter torque curve than DC.

Also, as a 3phase spindle advertised to go as low as 4kRPM, a 3:1 reduction could give me a nice range of 1400RPM to 8kRPM. I think I'm going to try it, since I already have it.

so back to your thread rusmannx, sounds like a good plan but are your spindle bearings able to handle 8000rpm?

[rusmannx]

so back to your thread rusmannx, sounds like a good plan but are your spindle bearings able to handle 8000rpm?

I bought new bearings but haven't swapped them in yet. They are ABEC7 or something, but if they fail I'll go to the expensive ones (ABEC1?).

The Kluber grease calculation says I can go to 16kRPM for this bearing size, but of course I won't.

[websrvr]

I bought new bearings but haven't swapped them in yet. They are ABEC7 or something, but if they fail I'll go to the expensive ones (ABEC1?).

The Kluber grease calculation says I can go to 16kRPM for this bearing size, but of course I won't.

ABEC rated bearings are usually referenced in the skateboard industry, P rated in spindles and motors, C in ballscrews and other motion components.

• ABEC 1 Approximately equal to ISO P0 (lowest precision reduces RPM, suitable for electric appliance motors where axial and radial precision is not required) (lowest cost)
• ABEC 3 Approximately equal to ISO P6 (highest RPM / acceptable precision, suitable for 24K router spindles)
• ABEC 5 Approximately equal to ISO P5 (high RPM / suitable precession, for high speed 18K router spindles)
• ABEC 7 Approximately equal to ISO P4 <--- you have (good compromise for precision and RPM, suitable for up to 12K mill spindles)
• ABEC 9 Approximately equal to ISO P2 (low RPM / best precision, suitable for 6K high precision mill spindles) (highest cost)

China ABEC7 are more likely to be ABEC5 and grease plays an important role in bearing life and sustained RPM.

At work we have a 40K RPM programmable micro drill, every 6 months I get the nasty task of greasing the bearings (it runs all day drilling PCB's), the grease is tan in color and tacky like peanut butter, I put some angular contact bearings in a sherline spindle head and used this grease, after 2 years I decided to repack the bearings, when I removed the pulley to extract the shaft, it looked like I just finished greasing it, now I just check it on occasion to be sure the grease hasn't dried up or hardened.

Don't laugh, yes, I still use it for small engraving tasks since it has an ER20 collet shaft in it and the 1/2in shank spiral point 0.006in engraving bits fit it.

[gcofieldd]

I bought new bearings but haven't swapped them in yet. They are ABEC7 or something, but if they fail I'll go to the expensive ones (ABEC1?).

The Kluber grease calculation says I can go to 16kRPM for this bearing size, but of course I won't.

It sounds like you have replaced the bearings in your spindle, but have you checked the bearings in the head of your mill? These larger bearings are the limiting factor for your spindle speed. Let me know if you find any sealed bearings that large that go above 8,000 RPM. The fastest I have found are 7,500 RPM.

Also, automation direct is selling the BLDC spindle motors again, which may be a good solution for you.

CNC Milling Spindle | Automation Technology Inc

[rusmannx]

It sounds like you have replaced the bearings in your spindle, but have you checked the bearings in the head of your mill? These larger bearings are the limiting factor for your spindle speed. Let me know if you find any sealed bearings that large that go above 8,000 RPM. The fastest I have found are 7,500 RPM.

Also, automation direct is selling the BLDC spindle motors again, which may be a good solution for you.

CNC Milling Spindle | Automation Technology Inc

I was just looking at those larger bearings now. I'm going to need to order some, I can't get mine out though. Maybe a large drift from the bottom of the head?

I'll let you know if I find some, but 7kRPM would be fine I think.

[hoss2006]

I was just looking at those larger bearings now. I'm going to need to order some, I can't get mine out though. Maybe a large drift from the bottom of the head?

I'll let you know if I find some, but 7kRPM would be fine I think.

I have some decent Nachis listed on my site that are good for 7800 rpm from vxb for the upper, 12k for the lower.
Bearing Upgrade
Hoss

[websrvr]

there's not much difference between abec1 and abec7, the cheaper abec1's only have about .0004 or so runout, the expense get higher with the abec number because the runout gets smaller. your cheaper ones should be fine at 8000rpm.

That is misleading information and unsound advice, the runout you state is for a bearing with a BORE less than 18mm, assuming his shaft is 15mm (highly unlikely), two bearings with 0.0004in runout can give more than 0.014in of runout depending on the distance between the bearings, the index of each internal races runout offset and distance from the bearings to the tool.

In ABEC 1 bearings, a 30mm BORE bearings specifies 0.0006in of max runout, I've measured several, the best one had 0.0003in, the worst had 0.0005in and these fall within the specifications for ABEC 1.

In ABEC 7 bearings, a 30mm bore specifies 0.00015in of max runout, the best one had 0.00007in, the worste had 0.00013in and these fall within the specifications for ABEC 7.

A significant difference between 6/10ths and 1.5/10ths.

Cheap china bearings fall far short of meeting the specifications as the pair of ABEC 1 I tested, best was 0.0013in and the worst was 0.0017in and the ABEC 7, best was 0.0009in and the worst was 0.0013in, all outside of the specification so I went with a quality bearing to avoide any problems.

carlowens, please don't imply to the OP that his bearings have a runout of 0.0004in when you don't know the bore size or the source of the bearings or stipulate the runout is for a specific size which you don't state, this will cause many people to fail because you toss this information around as if it were fact, google can help you get your facts right and it would also help if you clarify the information you give because clearly you're not an expert.

Here's a source to confirm the information I have provided is accurate --> Bearing Works.

When dealing with spindles and angular contact bearings it takes time to setup the bearings, indexing inner races, setting the preload correctly and bearing runin procedures (which can take 15 to 20 hours for a 10K RPM spindle if done correctly) are things most people aren't aware they have to do and very few people seem to be discussing these things in their spindle rebuild because they are taking too much advice from self proclaimed spindle experts who really have no clue what is involved in doing it correctly.

Without indexing the bearings so that runout is minimized (you can't just slide them on and expect the best results unless you get lucky) you might get acceptable bearing runout which is compounded over distance to tool and have unacceptable runout, too much or too little preload and you have end-play or premature bearing failure and opting for the quick runin procedure for spindles is not recommended by any (spindle) bearing manufacturer because bearing life is severely reduced forcing you to repeat the replacement process prematurely.



I'm by far no spindle expert, I rely on the advice of professionals who know what they're doing, discussing this with spindle experts or experienced spindle builders is my personal recommendation, unfortunately the man to discuss these things with doesn't frequent this place so his knowledge and experience isn't shared where it's needed.

rusmannx, if you need/want help or sound advice, I would be more than happy to discuss your rebuild with dwalsh62 and see what he advises to optimize your results or you can contact him directly yourself if you prefer, if not him I suggest you find an expert in the field who knows what he's doing before you waste a lot of time and money following false information and bad advice.

It sounds like you have replaced the bearings in your spindle, but have you checked the bearings in the head of your mill? These larger bearings are the limiting factor for your spindle speed. Let me know if you find any sealed bearings that large that go above 8,000 RPM. The fastest I have found are 7,500 RPM.

Also, automation direct is selling the BLDC spindle motors again, which may be a good solution for you.

CNC Milling Spindle | Automation Technology Inc

I've got some NTN 7005ADLLBG1P42 (47 x 25), 7905ADLLBG1P42 (42 x 25), 7906ADLLBG1P42 (47 x 30), 7906ADLLBDBP42 (47 x 30) and 7006ADLLBDBP42 (55 x 30) bearings good for 18K RPM 79LLB series and 15K RPM 70LLB series, these are sealed 25deg angular contact bearings, P4 precision with P2 tolerances specifically designed for spindles.

I ordered and paid for two of each bearings for my rebuild and some (now abandoned) projects and they shipped two sets (four) of each bearing and I only used one set of 7005ADLLBG1P42 and one set of 7906ADLLBG1P42 so I have extras.

I've got a stack of 47G1MP shims for medium preload to fit the 7005-G1 and 7906-G1 bearings, they came in a 50pak for $16.00, and I only needed 2 so extras (47 because I bent one) I have on hand.

The cost of these bearings was $157.00 to $193.00 each, if one or more of the listed sizes fits your needs I'm confident rusmannx we can work something very reasonable out as my way of contributing to your successful rebuild.