[jason_b]

I've been kicking around the idea of converting my MD001 to belt drive for some time and want to do it, but that got me thinking about the quill bearings. As the machine is now, if I run at 1950 rpm ~ 50% for an hour or so the lower bearing area gets up to around 150*. I don't think that's all that bad except that changing hot tools isn't fun. And if I'm going to be getting around 4000 rpm eventually I'm sure it will be quite a bit hotter.

So, I see alot of guys switching to ac bearings and have some questions:

Ac bearings should run cooler, right?

Generally, ac bearings are better? are there any drawbacks to them?

What about installation? Preload etc.?

I gather kluber is the grease to use, what specific kind and where can I get it?

Where should I get the bearings?

Any other thoughts?

Thanks all,
Jason

[jason_b]

Anyone?

[RustedOut]

I've been running a bunch of steel jobs lately using a coated carbide rougher and the tool holder and lower end of the mill have gotten pretty hot. No coolant of any kind. The heat goes all the way up to the top of the draw bar. The gear head isn't that bad though. I'd guess the tool holder to be in the 150 or so range, so hot I can't grab ahold of the tool holder to change tools.

I'm not that worried about the bearing for now though, but I do have a new spares on hand. The spares are low end AC bearings bought for the speed they'll run at. I have the same goal of building a belt drive and the bearings need to cover my top rpm of 6000 when I get it built.

My plan is to run Kluber isoflex nbu15. My bearings came from VBX and are Nachi's. But I don't see a huge difference between tapered rollers and AC if the bearings support the rpm desired.

One thing I want to build before the belt drive is a micro drop coolant system. It's going to be all manual at first, but my cutters need more than just running dry all the time. Increasing the rpm and feed rate will just make that worse.

Bob

[markymarky]

I converted my quill to AC bearings, as I was running the mill at around 3200 RPM and the lower bearing was starting to get hot.

The bearings I got were just nachi ones from VXB, the grease i used was just normal bearing grease, its easy enough for me to relube so i wasnt too concerned about it dripping out. So far the grease has stayed in place. ATM i run my mill at 4000 RPM using the standard gearbox, with just a slightly lower oil level. Heatwise the bearings seem to be performing fine.
The spindle gets quite hot, but it seems that its due to the oil seal at the top of the gearbox.

I think to go any faster, that seal will start to overheat. I am seriously thinking of converting to a belt drive setup, that way I could biff the oil seal and the heat it generates as well as lower the noise of the mill.

[williamsmotower]

did you notice the quality of your cutting improve when you switched to the AC bearings?

My endmill side cutting is so so witht the tapered bearings, and would like to improve it.

[arizonavideo]

TRB bearings are rated at over twice strength of AC bearings. In theory the cuts would have less flex with the stock bearings because they should flex less.

With the machine flex you wont see any difference unless one set of bearings has less runout.

The higher speeds you can run with AC bearings will make all the difference with aluminum for finish quality and in steel with smaller cutters.

Some have run over 5K with the stockers but mine got real hot at 3600 RPM so I changed to AC and a belt drive. The lower bearing still gets hot after long runs but I have a good amount of pre load. The rest of the head runs cool even after hours of running.

The gears make at least 1/2 the heat.

I added drip and a 600 CFM blower (Two bounce house blowers.) and the tools now are cool to the touch and clean after a job and most of the chips go into a trash can, stage left.

[Cruiser]

Very early on I made a manifold to fit the bottom exposed portion of the quil and flowed coolant through it to the fittings for flood coolant to the cutter. This was a big benifit to performance and I still use it that way. The coolant flow will cool off the end of the quil keeping the spindle and bearings happy. My machine is in an enclosure I built and I have a 55 gallon drim on side on floor for my coolant. Even going to an air mist coolant would be of great help to the cutter life. Coolant is a must do !
It could be possible to make a simple collar for the quil and pump a fluid through it to keep things cool. I consistanly run my spindle at max rpm's of 6150 for long periods and it only gets warm to touch. When I cut I splash cooant everywhere within the enclosure, which is the only way to go. I've been on belt drive for a long time. In fact, I think that mine may have been the second one done in a form of belt drive. The first being Aaron's.
If I had the coin to do it, I would build a complete new box assy and a 3 rane belt drive so that I could take spindle to 9,000 in top range and in low range have max torque down in the 80/500 range. But ! No coin !
The adventure is where the interest lies !
Happy adventures !

[RustedOut]

Very early on I made a manifold to fit the bottom exposed portion of the quil and flowed coolant through it to the fittings for flood coolant to the cutter. This was a big benifit to performance and I still use it that way. The coolant flow will cool off the end of the quil keeping the spindle and bearings happy. My machine is in an enclosure I built and I have a 55 gallon drim on side on floor for my coolant. Even going to an air mist coolant would be of great help to the cutter life. Coolant is a must do !
It could be possible to make a simple collar for the quil and pump a fluid through it to keep things cool. I consistanly run my spindle at max rpm's of 6150 for long periods and it only gets warm to touch. When I cut I splash cooant everywhere within the enclosure, which is the only way to go. I've been on belt drive for a long time. In fact, I think that mine may have been the second one done in a form of belt drive. The first being Aaron's.
If I had the coin to do it, I would build a complete new box assy and a 3 rane belt drive so that I could take spindle to 9,000 in top range and in low range have max torque down in the 80/500 range. But ! No coin !
The adventure is where the interest lies !
Happy adventures !

Don,

I'm guessing you replaced the original cast iron ring, what was that a quill stop? I never gave much thought to coolant cooling the lower bearing, but it makes sense. And the bottom of the quill is a real handy place to dispense coolant from.

I'm liking the less mess of a micro drop system, but still need to be able to aim it from both sides of the cutter and a ring like that might work for a collector and mount. I'll have to give that some thought. Not sure how much heat the mostly air coolant will cool the lower quill, but it certainly wouldn't hurt anything. And if the micro drop doesn't work out, I'd have that part already in place.

Long ago I had a crazy thought of plumbing and pumping the gear oil through a cooler, but decided to go the belt drive route instead. But even that wouldn't have dealt with the lower bearing.

Good idea
Bob

[Cruiser]

That iron ring with the threaded stem was indeed a settable stop. Mine has been off for so long that I didn't recall what you were referring too for a moment !
My Quill cooling collar has a rather large channel inside for the coolant to flow around the Quill, but, if the channel was reduced to say a very course thread then air could flow around and around the thread from the in to the out port and effectively cool the quill as well. I bought a pkg of O-rings when I made my collar, actually I made two and replaced the first one. But using something to seal it is imperative.
I'm not familiar with the micro drop but I have and have used an air siphon nozzle from "Cool Mist" from time to time and it works good at cooling and lubricating the tool as well as blowing away the chips. Facts is as facts is that you just can't beat full flood coolant, except for the cost and maintenance ! My coolant tank smells bad and I can't afford to change it out, I may go back to the cool mist'r system.

[DarkStarMedia]

I just finished running in my AC bearings... sorta... I ran it at 1000rpm for an hour and a half and then at 2000 for about 1/2 hour.


I took various temp measurements and based on where the heat is I think I have gearbox bearing wear as that is where most of the heat came to... the max temp I got was around 145 degrees F. most of the heat was near the top of the gear box.

The part of the quill that hangs out maxed out at about 100 degrees and the area just above the bearing on the taper was around 130-ish.

It may just be me but I think the gear box got to around 130 before the spindle got to 120. I just measured various parts of the side and top of the head to determine gearbox temps.

My gearbox is also rather loud.

I really need to get some stuff out so I think I will leave it as is and just square everything and then switch to belt drive.

I used NSK Explorer series AC bearings.

Richard

[Cruiser]

It appears that your spindle is doing good, periodically after a run, like at tool change, Grab the tool and see if you can feel any shake at all from the bottom bearing. If you do then of course you will need to take up one more lock position with the nut.
The noisy gear box can and should be addressed by replacing all the bearings in the bottom, and any that run in the oil. their is an Idler bearing pack in the lid that has two bearings in it, I found that by adding a third bearing and a thin shim that I could make it more rigid, I don't recall the specifics, it was too long ago and CRS is fully engaged.
I wouldn't assume it is gear noise as both gears and bearings will have very close resonance frequencies.
I would advise strongly to try to salvage the gear box intact before going belt drive. Having shift-able gear ranges is just plain too advantageous to discombobulate it forever !

[duwayne.]

I've been kicking around the idea of converting my MD001 to belt drive for some time and want to do it, but that got me thinking about the quill bearings. As the machine is now, if I run at 1950 rpm ~ 50% for an hour or so the lower bearing area gets up to around 150*. I don't think that's all that bad except that changing hot tools isn't fun. And if I'm going to be getting around 4000 rpm eventually I'm sure it will be quite a bit hotter.

So, I see alot of guys switching to ac bearings and have some questions:

Ac bearings should run cooler, right?

Generally, ac bearings are better? are there any drawbacks to them?

What about installation? Preload etc.?

I gather kluber is the grease to use, what specific kind and where can I get it?

Where should I get the bearings?

Any other thoughts?

Thanks all,
Jason

I went to my local bearing house and explained to them my requirements for grease and the application. They carried the Klubbers at about $130.00 a tube. They also carried and recommended the Timken's ultra high speed high temp spindle bearing grease. I bought a tube of that at $26.00 a tube. It works just fine. As far as the bearings go, I agree that althought taper roller bearings may not have as high a speed rating. They will carry a heavier load than the AC bearings. I just took my spindle apart a few days ago and cleaned and repacked the bearings. I also set the bearing preload a lot lighter than what they were from the factory. I ran it wide open for about 3 hours straight and the quil was only warm to the touch. My gear box was much hotter.