PDA

View Full Version : Lathe Spindle Bearing Adjustment Question



DFMiller
12-11-2010, 06:11 PM
I have got my Colt headstock partially apart. :-)
http://i560.photobucket.com/albums/ss47/ve7pke/Colt%20Lathe/IMG00096-20101211-1340.jpg
They look like taper roller bearings. They are marked BOWER Japan
I quick search of the web seems to show they are very inexpensive.
Is Bower a OK brand? I don't think I am going to change them yet. Unless I find a problem with them.
Should they be greased or Oiled?
What would be the suggested technique to adjust or set the pre load on them?
How much of a sin is using this type of bearing in a lathe head stock?
Thanks
Dave

Greg Q
12-11-2010, 07:36 PM
Whats the number on the bearing? 60205? If so, thats a cup and cone bearing not unlike a wheel bearing. You find them in drill press quills among other places.

DFMiller
12-11-2010, 07:53 PM
Its 30205.

Greg Q
12-11-2010, 08:15 PM
If you google "30205 bearing" you'll get lots of hits. It is a tapered roller bearing, and I think any quality 30205 will be the same, but I'm sure a real expert will chime in. I cannot recall right now if these are rated like ball bearings, ie with an ABEC rating. If so, the higher the number the better.

What kind of bearings are at the other end of the spindle, and why are yu going to replace this one?

Greg

DFMiller
12-11-2010, 08:23 PM
Greg,
I assume a similar one is on the other end.
I am only going to replace if needed.
The bigger question is how much preload is required.
The Headstock/ spindle currently has movement in and cuts a taper.
I need to adjust the bearings then go on to finding other issues.
Thanks for feedback. It does look like a real common bearing.
Dave

Greg Q
12-11-2010, 08:28 PM
Does that mean you can grab the spindle and move it in and out of the headstock a detectable amount?

Was the spindle noisy before?

Greg

lane
12-11-2010, 08:54 PM
Snug it up tight and back of the net about 1/8 turn . Run lathe and see what happens may need more are less . Just play with it . Feel for heat in head stock around bearing area . If it gets hot loosen up some . Those bearings will last the life of the machine . Longer than you will live . No big deal. These little machines are not high precision . But will do all you are ever capable of.

doctor demo
12-11-2010, 09:51 PM
Dave, I don't think Your oil or grease question has been answered yet.
Yes the bearings need oil. On My import machine with tapered bearings there is oil holes in the top of the headstock casting and a sight glass in the front that shows when the oil level is sufficient. Your machine will probably be slightly different.

After further review of Your picture, it appears that there is grease in there now.
Steve

DFMiller
12-11-2010, 10:40 PM
Lane,
Thanks for the procedure. I will give that a try. I have not been able to snug it up yet. I will have to try again. I think I will have to make a adapter as the adjustable face pin spanner is rather small and hard to tighten down.
Its a little harder than setting a wheel bearing since it does not have the same flywheel. If I recall on a wheel bearing you would snug up until it started to drag then find the next notch in castellated nut.

Greg,
The issue is the 0.010" taper over 1 inch I get when I turn. No noise.
If I chuck a bar in chuck I can get +_ 0.005" deflection without much effort on a DI.
Yes it has grease in in now. It has grease fittings. On a real Myford you need to oil the grease fittings.
Steve,
I think I will leave the grease in for now until I know otherwise. I checked a bearing spec says its rate to 7K oil 5K grease or something like that. Should be fine for this. The bearings seem to be used in trailers so grease should be good.

Thanks you all for the good stuff.
Dave

darryl
12-11-2010, 11:35 PM
There should be no detectable play in the spindle with that type of bearing. .005 is way way too much. You do need to adjust it, basically once you are able to alter that play you can at first tighten it to eliminate the measurable play, then run it for a few minutes. There should be some heat generated, but the headstock should never get more than warm. You should never find that, even after extended running, you can't keep your hand on the headstock. If it even approaches that temperature, it's too tight.

The taper you are speaking of- seems to me that the headstock is out of alignment. Play in the spindle might give a poor finish to the work, chattering, etc, but I see no reason why it would cause a taper of that magnitude. But don't try to correct that before getting the spindle pre-load set properly. You should be able to take a skim cut and a spring pass, then the cutting tool should quit cutting. Then you should be able to adjust for another half thou and the tool should take off that much. With the spindle play as it is now I would expect that every spring pass you take, you'll be taking off material, and it won't be coming off evenly. As the spindle bounces, the workpiece will randomly move towards the cutter- pretty hard to get precision work done this way.

oldtiffie
12-12-2010, 12:40 AM
Snug it up tight and back of the net about 1/8 turn . Run lathe and see what happens may need more are less . Just play with it . Feel for heat in head stock around bearing area . If it gets hot loosen up some . Those bearings will last the life of the machine . Longer than you will live . No big deal. These little machines are not high precision . But will do all you are ever capable of.

+1

Thanks Lane.

A simple solution to a simple problem on a simple machine done easily.

Lane's "rule of thumb" is as good as it it gets.

Its also and excellent reason to run your machine up to temperature before using it - plus it gives all the bearings and working surfaces a good "work-through" and lubrication before applying a cutting load to them.

The principal is not a lot different at all - if any - from adjusting the bearing "cones" on a bicycle or the bearings in a car (non-driving) wheel or trailer wheels.

This is a classic case of looking for a "difficult" solution to what is really a simple matter and a simple "fix".

A look at the manufacturers hand-book/manual will be a good start (or a manual for a similar machine).

DFMiller
12-12-2010, 01:33 AM
Oldiffie,
Manuals seem to be very hard to find. I have been checking around without success. I understand this model was sold in you your neck of the woods. The only one I have seen referenced on the net was for sale a couple of years ago in NZ. My manual is some where around my place but to date is still elusive.

They were for sale in the later 70's early 80's.
If you know where a manual is it would be appreciated.
Dave

Forrest Addy
12-12-2010, 04:08 AM
That's a Bower ball bearing made in Japan the "205" in its envelope designation. I don't see the prefixes and suffixes normally found on precision grade bearings but I understand lately that bearings are supplied with this information only on the packaging. The only way to determne of this particuar bearing is a precision grade is to open it up enough to see if it's marked with eccentricity burnishes. I don't know if this is a geared headstock or step pulley but I'll procede as id it was geared.

The photo shows the rear spindle bearing on the index end of the headstock? Have you examined the whole spindle inside the headstock? The front bearing may duplexed and its preload is set with shims or spacers between the races. The outer races are held in compression with the spindle retainer visible behind the spindle nose and the inner races with a bearing nut on the spindle itself. Look for a bearing nut assocated with the front spindle bearing and the spindle gear. If this nut has backed off for some reason you'll have to snug it up and re-set the tab in the lock washer. Snugging up the rear bearing nut may have no effect if the rear bearing functions as a "float bearing".

Rant time:

There is so much utter BS and damn fool advice circulating on the topic of spindle bearings it's amost hopeless for the bearing noob to differentiate good advise from bad. The lesser fora seem to attract shade tree grade mechanics no better than yokels full of tales how they use trailer bearings ect as spindle bearings and "it worked just fine" - until you inspect a part they made.

I know my stuff. I've worked on spindles, compiled bearing course materials, taught classes, and toured spindle shops and interviewed their experts. I was on a NavSea technical board concerned with electing and grading equipment bearings for submarine noise reduction. Machine tool spindles do NOT contain inexpensive bearings. The single most critical attribute for a spindle is the quality of its axis of rotation. The bearing grade has been selected by the design engneer as the minimum necesary for the machine to perform to specifications.

Even though a spindle bearing may have the same envelope designation as a wheel bearing you buy at the auto parts store its precision grade is determined by its component parts selected from the production line, inspected, re-worked, graded, and assembled with special attention to the quality of the axis of rotation, the accuracy of their TIR and the squareness of the shoulders to the axis of rotation etc. Also they may be selected in pairs with specific race offsets to assemble as matched pairs for preload, concentricity error, and marked for the eccentricity highpoint.

The quality of a spindle i, among other things, dependent on the accuracy of the axis it generates. All spindles no matter how accurately made exhibit aome error. A spindle containing rolling element bearings will exhibit the irregularities and cyclic errors expected of them. Outer race out of round, inner race out of round and eccentricity, rolling element (ball or roller) out of round and size distribution. The result instrumented and displayed on a polar chart with a radial exaggeration of say 50,000 to 1 shows axis error as what I call a "potato shape" with a wiggly outline - the sum of the many error sources in the bearings and spindle.

The net size of this potato axis error in a good machine tool spindle is 20 to 40 millionths - well within reach of grade 7 angular contact bearings and an accurately made spindle. In a jig boring machine the axis error needs to be about 1/10 of this and the spindle bearings are specially asembled just for this service and cost astronomically.

A plain vanilla engine lathe spindle still needs to make round diameters whose roundness error is 1/4 to 1/10 the minimum size tolerance anticpated. In a Monarch ee or equivalent thi error might be 20 mllionth. A general purposed engine lathe 80 millionths. I have no figures of inspetion experience with import consumer grade shop machinery but I wouldn't set my sights too high.

OK Rant off.

Lane offers the best advise. Run the bearings working in gradual steps up to the highest speed. Run it at high speed for about 20 mnutes. Look for about 20 degrees F temperature rise over ambient. Adjust accordingly. Even the best and most sophisticated spindle shops use this technique or something very simlar for final acceptance.

As for lubrication, most ball and roller bearings need only a seep of oil to lubricate the cages and provide the molecules thick boundry film needed to mitigate the inevitable scrub present in rolling element bearings. Very high speed bearings were once lubricated with open cycle oil mist systems but now high adhesion greases are doing the same job. The 205 bearing in the photo shows traces of grease. I wouldn't mess with it unless it started making noise.

.RC.
12-12-2010, 04:29 AM
I am surprised it does not have Gamet bearings in it, with it being a colchester and all..


All I will add is this.... When tightening them spin the spindle at the same time to seat the bearing properly.....

Upon startup do not start in top speed... Spin it at a low speed for half an hour to let the bearing settle in again...

I am wondering if someone has been into that headstock before...Japanese bearings in a British lathe? I would have expected hoffmans or RHP or even a brit made Timken...

Greg Q
12-12-2010, 05:55 AM
That's not a Colchester, RC. It's an Asian made Myford look-alike.

philbur
12-12-2010, 06:55 AM
The OP might want to post a general view photo so people know what a "Colt" lathe actually looks like.

Phil:)

.RC.
12-12-2010, 07:06 AM
That's not a Colchester, RC. It's an Asian made Myford look-alike.


ahhh OK, I thought it was one of these http://www.lathes.co.uk/bantam/page3.html


If it is a small asian lathe then it won't have precision bearings in the spindle anyway, it will just have standard bearings...

DFMiller
12-12-2010, 01:04 PM
Here is a picture of the lathe in question.
http://i560.photobucket.com/albums/ss47/ve7pke/Colt%20Lathe/ColtLathe2.jpg
Its a late 70's early 80's Taiwanese clone of a Myford Super7B I believe.
I bought its used from a friend who was the original owner. It's been lightly used. I have all the attachments, Taper turning, Steadies and Milling attachment.
Its pulley driven with some type of clutch arrangement in the headstock itself.
http://i560.photobucket.com/albums/ss47/ve7pke/Colt%20Lathe/IMG00088-20101129-1828.jpg
Forrest.
I have had a good look at things and cant seem to locate any other adjustments. I am reluctant to take the the headstock apart without a manual as there is more going on than just a pulley mounted in the middle. The spindle does not freely move with the rear end dissembled. Some gentle nudging with a dead blow will move the spindle toward the tailstock.
From what I can see there are just two bearings and a simple nut to adjust things.

Has a nice feel to it and I think just needs some TLC to get it working fine. Its miles ahead of any off shore machine that I have seen new.

Thanks for all the help. I am sure I will get it tuned up soon.
Dave

DFMiller
12-12-2010, 08:03 PM
Forest and Lane,
I have taken it apart and put it back together.
It is as I suspected two roller bearings a simple spindle and a single nut that adjusts preload.
For some reason I am not able to tighten up to get any drag on spindle. I have bent my Pin spanner. I guess I need to make a new one so I can apply more leverage.
One thing I noticed is the races has some visible wear. Is it possible that the wear in preventing the bearing from tightening.
http://i560.photobucket.com/albums/ss47/ve7pke/Colt%20Lathe/HeadstockBearingChuckEnd2.jpg
http://i560.photobucket.com/albums/ss47/ve7pke/Colt%20Lathe/BearingDriveend1.jpg
Running it a high speed for 10 minutes generates some warmth but it not hot.

I still have the same movement when I chuck up a bar. and put a dial on it.

How much force should you need to apply to preload the bearing?

Thanks
Dave

oldtiffie
12-12-2010, 10:13 PM
The adjusting nut may be "hard up" on the soulder of the spindle.

Cut some shims to go under the nut to restore some adjustment.

J Tiers
12-12-2010, 10:21 PM
Ball or roller races should NEVER have "wear"...... They fail when the surface fatigues and starts to shed pieces..... after which they fail fairly rapidly from the effects of the bits circulating in the grease/oil.

But aside from that, they don't "wear" unless they get dirt or chips in them.

darryl
12-12-2010, 10:30 PM
Seems to me you've run out of room for the bearings to move either on the spindle or in the bores. With the amount of tightening it seems you are applying, you should have been able to get the spindle to be quite resistant to turning, let alone eliminate play.

Something is not right. Just a bit of thought should tell you that a tapered roller bearing will lose all axial and radial play when the inner race is pushed into the outer race, with roller cage pinched between. If play still exists, it has to be between the spindle and the inner race, or between the outer race and the bore in the headstock. Hmm- be sure the headstock isn't moving on the ways- maybe you are getting the pre-load just about right, but are being fooled by the headstock moving slightly.

Some of what I'm saying is plain logic, some is guesswork since I don't know that lathe. It's not rocket science though- the answer is there mechanically. One of the bearing elements has to be free to slide to allow a pre-load adjustment to be made, and this range of motion should not be used up- unless the design called for a precision fitting to shoulders where the play should be down to zero or so. Normally you'd see this in back to back bearings, where a precision spacer does the job, or precision machining and matching of bearing components does the job. It doesn't appear that this is the case here.

If the pre-load is supposed to be right when all the bearing elements are perfectly seated, then they have relied on selected bearing parts initially to achieve the right pre-load with no adjustment possible after that. If that is the case here, then the replacement bearings have not been properly selected for that particular lathe- and how could they be unless the lathe had been sent back to be factory re-fitted. That's highly unlikely.

I will offer a gut feeling- that is that you will have to add a spacer behind one of the outer races to allow you the adjustment range to get pre-load.

J Tiers
12-12-2010, 11:43 PM
I am starting to see the problem here, and it could explain a couple things.......

1) are the bearings the original type and number? If NOT, their dimensions may be different enough to cause an issue of not being able to apply preload. Since you say these seem to be cheap ones, odds are they are a replacement type, and may be considerably different in dimension. They might not even be the right type, although tapered roller bearings are reasonably common for lathe spindles.

2) if you GOT the machine in that condition, then there is a fair chance it has been that way for a while..... if that is the case, then the 'wear" you see may stem from the spindle rattling around to some extent when used.

3) it might have seemed OK for a while..... I once replaced a logan bearing with a Logan replacement, and didn't realize for some time that it was bad.... was supposed to be internally preloaded, but it wasn't. However, the tail bearing was hung up in the headstock bore, and there was an "inadvertant preload" that persisted until I had to take out the spindle for anotehr reason... when I put it back, I naturally cleared out the hang-up, and immediately got problems.

in your case, shipping, or moving it, might have removed a condition that covered up the preload problem.

Are you certain that you have all the parts? Do you have a parts sheet for it?

Can you confirm the type and dimensions of the original bearings?

Can you get them, in case these turn out to have been damaged by running loose (if they were)?

Do you have means to make some spacers in case you do need them to make up the required distance between the bearing faces?

doctor demo
12-12-2010, 11:50 PM
That's a Bower ball bearing made in Japan the "205" in its envelope designation. with the front spindle bearing and the spindle gear. If this nut has backed off for some reason you'll have to snug it up and re-set the tab in the lock washer. Snugging up the rear bearing nut may have no effect if the rear bearing functions as a "float bearing".

Rant time:

There is so much utter BS and damn fool advice circulating on the topic of spindle bearings it's amost hopeless for the bearing noob to differentiate good advise from bad. The lesser fora seem to attract shade tree grade mechanics no better than yokels full of tales how they use trailer bearings ect as spindle bearings and "it worked just fine" - until you inspect a part they made.

I know my stuff.

Even though a spindle bearing may have the same envelope designation as a wheel bearing you buy at the auto parts store its precision grade is determined by its component parts selected from the production line, inspected, re-worked, graded, and assembled with special attention to the quality of the axis of rotation, the accuracy of their TIR and the squareness of the shoulders to the axis of rotation etc. Also they may be selected in pairs with specific race offsets to assemble as matched pairs for preload, concentricity error, and marked for the eccentricity highpoint.
OK Rant off.

Lane offers the best advise. Run the bearings working in gradual steps up to the highest speed. Run it at high speed for about 20 mnutes. Look for about 20 degrees F temperature rise over ambient. Adjust accordingly. Even the best and most sophisticated spindle shops use this technique or something very simlar for final acceptance.

As for lubrication, most ball and roller bearings need only a seep of oil in the photo shows traces of grease. I wouldn't mess with it unless it started making noise.
Forrest, I don't think He has a ball bearing there:)
I do respect the vast knowledge that You have in the machinery trades , but that doesn't mean that that machine does not have a ''trailer bearing'' in it. Remember when and where it is made:eek:

Steve

DFMiller
12-13-2010, 02:28 AM
I believe the bearing are original.
As I have stated before, I think earlier in this thread. I can't find my copy of the manual and unable to locate another copy.
I have had the thing apart. There seems to be some wear on the races.
http://i560.photobucket.com/albums/ss47/ve7pke/Colt%20Lathe/Spindle2.jpg
I will try to figure out why I can't seem to snug it up. I will pull it apart again and see if the gear end bearing is hitting on the shoulder.

Thanks for ever ones help.
Dave

tdmidget
12-13-2010, 12:44 PM
The gear on the outside end of the headstock just doesn't look right. It appears to be a bit out of line with the other gears and there is a space between it and the bearing. Is there anything between the gear and the bearing? There should be something to fill that space and push the cone inward to preload the bearings.
Since we now know that you've had it apart before, when did this problem start? Found any pieces that didn't have a home, possibly about the ID of the small end of the spindle, maybe with a keyway? Might the nut have a recess machined on one side to allow it to slip over the spindle and push the gear and cone further?

DFMiller
12-13-2010, 01:38 PM
I am not sure which picture you are referring to?
http://i560.photobucket.com/albums/ss47/ve7pke/Colt%20Lathe/DriveGear2.jpg
Is in contact with the bearing
Tighten down by collar with holes in.
As far as bottoming out
There is a gap between the collar and casting on both ends when assembled.
http://i560.photobucket.com/albums/ss47/ve7pke/Colt%20Lathe/IMG00088-20101129-1828.jpg
If you look at this picture the flat on the left end is where the collar is.
http://i560.photobucket.com/albums/ss47/ve7pke/Colt%20Lathe/Spindle1.jpg
I will have to check if there is a burr or something preventing the bearing from moving where it should be.

Its hard to see in the pictures but looking at race
http://i560.photobucket.com/albums/ss47/ve7pke/Colt%20Lathe/CloseofBearingRace.jpg
You will see a difference in shinyness on the race at the smallest diameter. I am not sure if this land is supposed to be there are its the issue.



Until yesterday I have never had it apart.

Its possible the previous owner had it apart as that's how you change or install the belt.
I have not used the that much since I got it and only noticed it the issue when I was trying to machine up some leadscrews for bearings. This is when I noticed the taper issue.

Thanks for your thoughts.
I think the thing to do is make up a new Face Pin Spanner while the lathe is together. Then take it apart and look at why the bearing does not slide up to shoulder. Then try assembling without the pulleys to see if I can see more and find the issue.
Then either use it or change out bearings.
To my eye I see wear on the races. I will try to get a better look when I have apart and get a good picture.
I am not an expert on these things but hoping a more experienced eye will either agree or shoot me down.

Thanks again and this is interesting.
Dave

tdmidget
12-13-2010, 03:02 PM
If you can feel a step, regardless how small, in the conical surface of the race then the bearing is worn/damaged and should be replaced. There should still be provision for adjustment of some sort, usually by the nut on the spindle pushing the gear/spacer and ultimately the bearing cone toward the other bearing. This could be fixed by putting a shim behind the race or a shim between the cone and spacer. First make sure that the spacer is free to move and push the cone. If so then shims/spacers can be purchased at most bearing supply houses. In any case I suspect that you are going to pay them a visit due to the condition of the bearing.

DFMiller
12-13-2010, 09:04 PM
You are most likely correct.
Waiting for the rest of the experts to comment on the latest picture?
Dave

darryl
12-13-2010, 11:56 PM
Looking over my shoulder, I see no experts. Looking in the mirror, I still don't see an expert- :)

Yes, do the fingernail test. You should not be able to catch it anywhere on the surface where the rollers run. From the picture- the surface doesn't look good to me. Looks like someone tried to 'clean it up'- but it's hard to tell, even with the close-up. What you're calling the unworn part, and land in question- they look equally 'cleaned up', but not polished. The polishing would be consistent with the bearing having been run for some time. There should be no ridge detectable across that whole surface.

Have a look at a trailer wheel bearing somewhere. Compare the finishes- you might well be right that the bearings are damaged. There's little difference between the look of a new tapered roller bearing and one that's been used but is still good. There will be some polishing where the rollers roll, but no pitting, grooving, etc, and no tell-tale 'heat-treat' colors. You've indicated that the rollers look rough- that probably means they already are too rough to be serviceable, especially for a spindle. Do they make noise when spun, and can you feel any roughness at all if you spin it by hand?

Again, it's hard to tell from the picture, but it doesn't look good to me.

As far as getting to the point where you have some pre-load- here's another test you can do- with the spindle assembled into the headstock, but without the pulley or gears between the bearings, check the play with your indicator. Should be what you measured before. Now mount a tailstock chuck with a length of small diameter rod, a 6 inch piece of 1/4 inch rod will do. Sandwich a piece of wood up against your spindle with a bit of pressure- a few pounds maybe. Now check the play at the spindle again. If forcing the front bearing into tighter contact lessens the play by some amount, then it would seem obvious that the pre-load nut action is not actually able to pull the spindle bearing parts into contact. I would expect play to reduce to a sub-thou level with this test. I see nothing in your pictures that would prevent the spindle from moving left to the point where the bearing races would not nest together. If it comes tight but play doesn't reduce- I'd have to say the bearing is shot. If play reduces largely, you're back to square one- almost. You will have learned that a problem exists at the left end of the spindle.

With the nut snugged up, measure the distance from the face of the nut to the end of the spindle. Now remove the spindle and run just the nut on- will it go further than it did before? If so it hasn't run out of adjustment range. Then mount the left side inner race and the gear, put the nut on and see how far it will go. You will find that it either is able to go on further, or that it can only go on as far as it did at first. If it does go on further, that suggests that you have adjustment range left, and if that's true then the bearings are actually taking the pre-load pressure. If they are giving play under that condition, they are shot.

If the inner race and gear are on, and the nut stops short, then one or the other of those two components are hanging up on the spindle somehow. Do the test again with just the gear- now you will have learned all you need to know to resolve the problem.

DFMiller
12-14-2010, 01:48 AM
Darryl,
Some great ideas. I have got my new wrench almost done. I have a plan now after your suggestions and a day of pondering. The strange thing is other than the taper the lathe actually works not bad. I did some facing and boring and did not have any major issues.
Thanks for your insight.
If you ever get to Surrey let me know and stop by for a visit.

Dave

Richard-TX
12-14-2010, 01:57 AM
On my lathe which features tapered roller bearing in oil, the manufacturer says to run it for 30 minutes at the highest speed. If the bearing is warm then the preload is set right. If the bearing temp is uncomfortable, then it is too tight.

J Tiers
12-14-2010, 10:14 AM
The race area of a bearing does not need to have a high "chrome-like" polish. It DOES need to be smooth and within spec for the bearing type. The existence of grinding "marks" (for lack of a better term) is not proof of evil, they need to be out of spec for smoothness to be bad.

That picture does show an area with "marking" but does not give me a good idea whether it is "ground down" by "wear", or if it is just an unflattering angle.

The "land" at front and back could be intentional non-bearing area, or it could be un-"worn" area, can't tell. If there is the slightest raised 'ridge" sliding from teh bearing area onto the "land", that's a proof of *utterly stupid* amounts of real "wear". I'd be surprised, but I've been surprised before.

That amount of "real wear" would indicate crazy neglect, and complete ignorance and machine abuse by the previous owner.

DICKEYBIRD
12-14-2010, 02:15 PM
One factoid I can add to the mix from recent 1st hand experience is that the amount of grease packed into your bearings has a profound effect on the heat generated. I cleaned & packed the bearings on my X-3 mill and packed the bearings *full* of grease. HAH, was I stoopid! I re-set the preload looser & looser at least 3 or 4 times until there was even a small amount of endplay and the heat was still excessive at the upper range of spindle speed (only 2000 rpm)

After reading up on the subject, cleaning and repacking the bearings approx. 40% full, the heating problem was completely solved!

DFMiller
12-14-2010, 02:42 PM
Good Point. I will remember that. Heating is currently not an issue for me.