[websrvr]

1ph SCR drives are OK for general purpose use, but the higher end type, KB included, now use PWM drives for smother and quieter control.
Al.

Gate driven SCR drives seem to be the cheapest, PWM seem to offer less harmonic resonance making the motor quieter to operate, IPM, MOSFET and IGBT drives seem to be superior offering zero or almost zero harmonics and significantly less loss however, it's a cost trade-off when a $600.00 drive is needed to get the torque performance you want.

There's got to be a relatively inexpensive solution, there has to be some kind of product that can be had, surely the DC motor market can't solely exist on expensive solutions.

[Al_The_Man]

For a while I have been playing around will a PIC project for DC T.M. motors that would be bi-dir PWM use feedack and use the Mach Modbus plug in for control.
Can't give a projected date at this time as it depends on time available.
But if it ever comes to fruition I will post it here.
DC motors are not as popular as they once were, they have waned especially in the spindle market, in favour of VFD's and BLDC motors.
I think it is only the T.M. surplus market that is keeping it going, and economical drive Manuf. such as KB help.
Apart from a few such as Leeson, all the big DC motor manuf in the US are long gone.
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.

[rusmannx]

Sounds like I was just backwards. Whatever I have, they weren't the most expensive. I'm not afraid if I have to upgrade.

[carlowens]

Sounds like I was just backwards. Whatever I have, they weren't the most expensive. I'm not afraid if I have to upgrade.

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.

[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.

[carlowens]

websrvr/dwalsh, i have a g0704 like rusmannx so i know what size bearings it has and asked him if his were capable i.e. upgraded or not, google all you want, i speak from first hand knowledge so mind your own business and quit pretending to know what you are talking about.

[rusmannx]

Thanks websrvr.

I think the main thing here is that this is a cheap mill, which already has cheap bearings and what we can only assume (at best) to be a medium quality spindle. Since OK bearings are cheap, I don't think most people are overly concerned with how perfectly they are aligned, run in, etc. You make some great points and I appreciate the time taken, but I'm trying to avoid spending a fortune on bearings, motor, electronics, etc, for a mill that cost less than $1,500 (shipped). With any luck at all I can get this thing back up and running without pouring tons of money into it, because I plan to upgrade to a larger machine within a couple of years anyway. That said, I am OK with spending SOME money on it to get a bit more power and a higher maximum RPM.

You guys are all great, so keep it coming!

[carlowens]

Thanks websrvr.

I think the main thing here is that this is a cheap mill, which already has cheap bearings and what we can only assume (at best) to be a medium quality spindle. Since OK bearings are cheap, I don't think most people are overly concerned with how perfectly they are aligned, run in, etc. You make some great points and I appreciate the time taken, but I'm trying to avoid spending a fortune on bearings, motor, electronics, etc, for a mill that cost less than $1,500 (shipped). With any luck at all I can get this thing back up and running without pouring tons of money into it, because I plan to upgrade to a larger machine within a couple of years anyway. That said, I am OK with spending SOME money on it to get a bit more power and a higher maximum RPM.

You guys are all great, so keep it coming!

good point, it doesn't make much sense to spend $1500-2000 on a motor upgrade and $500 on a bearing upgrade for a $1200 mill, money can be better spent on something else. one has to keep things in perspective.

[websrvr]

websrvr/dwalsh, i have a g0704 like rusmannx so i know what size bearings it has and asked him if his were capable i.e. upgraded or not, google all you want, i speak from first hand knowledge so mind your own business and quit pretending to know what you are talking about.

Oh my, you really do have an anger issue, you do know they make medication and have doctors to help you with that?

What question about bearings or upgraded bearings are you talking about, is this in invisible text that only you and rusmannx can see???

If you wanted to know if he had upgraded bearings or not then you should have asked him because your post makes no mention of any question regarding his current bearings or any questions for that matter, also, remember, other people are reading this thread and answers to omitted direct questions that your mind-meld can obtain directly with rusmannx aren't helpful to others if they aren't aware of them.

The information I have offered is correct and verifiable, the suggestion to seek professional guidance is sound advice and if such a professional was present it would be great if he would join the thread and offer his knowledge and experiences as mine is limited only to bearings and radial loading, not to spindles.

Your first hand knowledge is based on the lack of or incorrect information as shown by your previous post and I can't comment on your experience as it appears you have very little based on the faulty information you are providing and now implying a question that was never asked or answered.

If your going to quote tolerances and specifications, it would be helpful to do it accurately or don't do it all all, it would be inadvisable for anyone to accept what you have offered as beneficial information or advice since it's basically all based on your knowledge and information and from what you have revealed so far it's not looking good for your knowledge/experience.

All I have done is clarified and corrected the bad information and advice you have given so future readers attempting to perform their own rebuild don't get misled by it.

Additionally, regarding cylindrical roller bearings (tapered or straight), people have the misconception that they are not capable of high RPM and this just isn't true, hybrid bearings consisting of two angular contact bearings separated by one straight (or two tapered) cylindrical roller bearing can achieve +200K RPM (look at BELL and military turbine engine designs) and, you can make your own hybrid bearings using three (or four) individual bearings, they don't have to be in a single outer race.

Here's more information, VXB is a bearing supplier, they buy the bulk of their bearings from the cheapest supplier they can find in china, I advise all to accept any claims of tolerances and specification as reference material, the bearings will fall short of their class specifications and tolerances, this I speak of from first hand knowledge and experience of buying and measuring bearings from VXB, unless you buy a known brand quality bearing and pay for it, you're not getting one.

The information I give is confirmable, I don't give advice based on speculative information and it's certainly not your place to tell me to mind my own business when it is my intention to help the OP make his build/rebuild as successful as possible, including but not limited to correcting faulty information and bad advice if I know it to be.

If rusmannx would prefer I don't participate in his thread he is more than welcome to privately ask me to stop participating and out of respect for him and his thread I would most likely comply.

[websrvr]

Thanks websrvr.

I think the main thing here is that this is a cheap mill, which already has cheap bearings and what we can only assume (at best) to be a medium quality spindle. Since OK bearings are cheap, I don't think most people are overly concerned with how perfectly they are aligned, run in, etc. You make some great points and I appreciate the time taken, but I'm trying to avoid spending a fortune on bearings, motor, electronics, etc, for a mill that cost less than $1,500 (shipped). With any luck at all I can get this thing back up and running without pouring tons of money into it, because I plan to upgrade to a larger machine within a couple of years anyway. That said, I am OK with spending SOME money on it to get a bit more power and a higher maximum RPM.

You guys are all great, so keep it coming!

Don't under estimate the power and performance the machine can provide, it's as good as it's weakest link, choice improvements like bearings improve performance and productivity, replacing the stock bearings with angular contact bearings will make a definite performance improvement, replacing the rear tapered bearing with a pair of 7005 bearings can be extremely beneficial and the height of two bearings is 24mm for 7005 and 18mm for 7905, to use the 7905, you can make a sleeve 47mm OD x 42mm ID.

There's more than enough room to fit either pair of them in and, this will allow a lower preload which will increase the RPM capability of the spindle even if you retain the lower tapered bearing.

The pair of 7005's are yours for $50.00 if you want them.

[rusmannx]

Don't under estimate the power and performance the machine can provide, it's as good as it's weakest link, choice improvements like bearings improve performance and productivity, replacing the stock bearings with angular contact bearings will make a definite performance improvement, replacing the rear tapered bearing with a pair of 7005 bearings can be extremely beneficial and the height of two bearings is 24mm for 7005 and 18mm for 7905, to use the 7905, you can make a sleeve 47mm OD x 42mm ID.

There's more than enough room to fit either pair of them in and, this will allow a lower preload which will increase the RPM capability of the spindle even if you retain the lower tapered bearing.

The pair of 7005's are yours for $50.00 if you want them.

Thanks. I've already got all the spindle bearings (bought almost a year ago and never got around to upgrading). The only bearings I need are the 6007 and 6209 for the quill.

I was about to pull the trigger on an automation direct 56C size 2hp AC 3ph today, and of course they are out of stock. The 1.5hp is in stock, but I really want 2hp or better. I'm still considering using this water cooled high speed spindle, but getting a high ratio reduction via pulleys is not going to be easy. 4:1 would get this spindle in the 2k-7k RPM range, but I would need to go with a comically large 6" zinc 4L V-pulley that I found at McMaster. SDP/SI doesn't have anything in stock that will get me that close.

I also checked the run out of my large DC treadmill motors, and the one that has the least amount (about .004") has some weird tapered shaft.... which I would need to machine to fit a regular pulley. I'm not sure how I would go about that, so these motors are likely OUT. This process is getting to be pretty annoying.

[LeeWay]

I use DC motors on my 80/20 mill and lathe. The drives I like to use are these.
90/180 VDC SPEED CONTROL W/POT

They work pretty well. Better when I used a 2HP motor and 220 VAC. I also use the heat sinks.
I burned the brushes on my original DC motor and could not get good replacements anywhere. I know I could have fabbed my own, but went with a motor from Automation Direct. It is an Iron Horse motor and works very well. It is larger than the original, so puts extra weight on the Z. Not a problem on the mill and would be no problem on a lathe.
I did have to buy a larger pulley for it and that was not cheap either. It works well though and has pretty good low end torque. Still, no comparison to the 1.2KW AC Servo Spindle I have on the Torus. It would be about $1K to replace it and the drive.
The new motor, pulley and controller wound up being about $600.00, so not really that far off. The motor was obviously the biggest cost on that. Since you already have the motors, that is the direction I would go.

You are going to have to precisely balance any pulley on the water cooled spindle. Otherwise you might see some self destruction. It's bearings are designed to use a small fairly balanced tool. With a pulley, you will get centrifugal force also applied and at speed, that can be destructive. Especially on small bearings.

[websrvr]

Thanks. I've already got all the spindle bearings (bought almost a year ago and never got around to upgrading). The only bearings I need are the 6007 and 6209 for the quill.

I was about to pull the trigger on an automation direct 56C size 2hp AC 3ph today, and of course they are out of stock. The 1.5hp is in stock, but I really want 2hp or better. I'm still considering using this water cooled high speed spindle, but getting a high ratio reduction via pulleys is not going to be easy. 4:1 would get this spindle in the 2k-7k RPM range, but I would need to go with a comically large 6" zinc 4L V-pulley that I found at McMaster. SDP/SI doesn't have anything in stock that will get me that close.

I also checked the run out of my large DC treadmill motors, and the one that has the least amount (about .004") has some weird tapered shaft.... which I would need to machine to fit a regular pulley. I'm not sure how I would go about that, so these motors are likely OUT. This process is getting to be pretty annoying.

Deep Groove bearings are not really suitable for heavy forces exerted by simultaneous radial and axial (thrust) loads under milling conditions unless your mainly working with soft/light material and taking minimal cuts at very low feed rates.

Yes many people use them as a really cheap solution and because it appears to work they assume it's great but there is a reason manufacturers don't use them in spindle heads, they're not designed to take thrust loads and since radial precision is not a serious concern, you'd be better of using the cheapest china angular contact bearings you can find.

dwalsh62 has a stock pile of small dia high speed air-cooled router stators (77mm) and rotors for 3HP 220V 3-PH motors that will operate from 450 RPM (15Hz) to 9000RPM (300Hz) with a 2:1 belt system if you want to try your hand at making a body and shaft.

I purchased one for $45.00 to make a motor for someone and configured the VFD for 2HP that seemed to operate with good results without overheating from 900 RPM (15Hz) to 15000 RPM (250Hz) and the body was made from a 3-1/2in aluminum tube and wasn't all that difficult to make, a used 110V round fan I got off of ebay to cool it finished it off, of course it looked home made and the spray paint didn't want to stay on the aluminum as it kept flacking off it turned out to be a real work horse.

I also recall speaking to someone about 1.5HP motors who repairs electric motors for a living, he recommended buying a 1.5HP 4-pole 56C or 63C motor as a better option because the plate material in a 4-pole motor is commonly 50W350 which has an operating bandwidth of 10Hz to 235Hz (300 RPM to 7050 RPM) and a 2-pole motor most likely is made with 50W800 which has an operating bandwidth of 40Hz to 70Hz (2400 RPM to 4200 RPM) or an operating bandwidth of 25Hz to 90Hz (1500 RPM to 5400 RPM) if it's 50W470 or 50W500.

He said you can't tell by looking at the stator or rotor what the material is but when operating it at 30hz the temp should not exceed 160deg if it's a 2-pole motor with 50W470 or 50W500 running under a no load condition for 5 to 10 minutes.

He further suggested for the 4-pole motor that by adding an external fan to cool the motor and removing it's internal impeller blade (if it has one), you could operate it at these frequencies without overheating the motor or run it at 40% of the low to 60Hz and 75% of the 60Hz to max for passively cooled motors (no fan).

I haven't been abler to confirm all his claims and statements, only that wire and plate material does have an effect on the operating frequency range and that 50W800 is commonly used in motors of 40Hz to 70Hz (one supplier gave 35Hz to 75Hz), 50W350 10Hz to 300Hz and 35W270 2Hz to 600Hz so I can't say with any certainty the remaining information is 100% accurate as I also found some unsubstantiated reports that people were operating 50W800 2-pole motors at 20Hz to 125Hz without causing any damage.

I see the MTR-002-3BD18 is in stock and fairly cheap at $166.00 plus free 2-day shipping so I'm gonna give it a shot since I've got a 3HP china VFD collecting dust and I'm tired of the DC motor issues.

My current motor project involves a case damaged 4HP YVF100L motor in which I want to rob it of the rotor and stator so I can remove the shaft from the rotor, enlarge the rotor bore to 55mm so I can press in a lathe spindle shaft which has a 1-3/4in through bore so I don't loose bar feed capabilities and end up with a direct drive lathe spindle but KMMP-USA is slow in getting back to me with the needed information to determine if the modification is possible.

There seems to be enough clearance inside the aluminum end rings of the rotor but the amount of clearance from the aluminum bars is in question since magnetic flux/density will be greatly reduced if insufficient material exists and motor performance will be severely degraded.

[carlowens]

boy websrvr you argue and condescend just like dwalsh and are still trying to sell him stuff, how about that, the deep groove bearings you are pi$$ing on that rusmannx asked about DO only take radial loads in this application, so using ac bearings to replace them is complete nonsense, there is no way to apply a preload to them and the assembly they are on MUST handle a radial load, why don't you get what rusmannx keeps telling you, he's not looking to spend loads of money just to get his hobby mill back up and running and understands it doesn't require ultra precision parts to get the acceptable performance needed.