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View Full Version : Replacement bearings for an X2 spindle?



sansbury
01-21-2009, 02:28 PM
I've recently finished a CNC rebuild of an X2 mini-mill and now that I am using it the problems with the stock spindle bearings are coming back into focus.

I put a belt-drive kit on the mill shortly after I got it, and any time I ran much over 2000RPM the spindle would start to heat up, and if I ran it at the higher speeds the belt drive allowed, the spindle would become what seemed like dangerously hot, as in uncomfortable to touch for more than a couple seconds. I went through a lot of bull at the time--swapped bearings, polished the spindle so they were more of a slip fit and less of a hard press-fit, etc., none of which did any good. Tried both rubber sealed and metal shielded bearings, no difference.

In a fit of desperation I pulled off the lower seal and found if I left it off the lower bearing, then it only warmed up a little, and after some hours it doesn't seem to warm up at all. I put the plastic spindle cover (not the bearing shield) back in place and decided to work on other problems for the time being.

Anyway, that bill has as expected come due as the rattling noise continues to get louder. It's always been there but I suspect contamination or other non-good things are contributing to premature wear. Now that I have the CNC part mostly done and the machine otherwise making (seemingly OK) parts, I figured it was high time to tear it apart on another wild goose chase.

The bearings are deep-groove 6007 and 6206 series. I got replacements locally, Nachi brand about $8 each. As the last series of remove-replace-recheck (I can't tell you how many times and configurations I tried) did no good, I am wondering:

1. Did I not give the originals/replacements enough time to wear in? I ran them for at least 30-40 minutes at speeds sufficient to throw off what seemed like too much heat to be good for anyone.

2. Should I try better (more expensive/rated) bearings?

3. Do a lot of these spindles make a lot of noise, and if the parts are coming off OK should I just leave well enough alone until something starts to smoke?

Thanks in advance.

sansbury
01-23-2009, 12:19 PM
93 views and not one opinion, on a bearing question no less?

Bruce Griffing
01-23-2009, 12:33 PM
Try here:

http://www.littlemachineshop.com/products/product_search.php?critFast=bearings&B1=Product+Search

derekm
01-23-2009, 12:53 PM
70c or 158f is a "normal " stable temperature for bearings running at speed under normal load/preload. Thats just about too hot touch for more than a second or two. Dont believe me? go visit the SKF site.
In fact one approach to setting preload is to do it to temperature and the temperature often quoted is 70C. Measure the temp. if its not much above 60C dont worry.
Your bearings probably werent too hot.


Derek

aboard_epsilon
01-23-2009, 01:00 PM
Youre not over-packing them with grease are you .

They are suposed to have half as much in them as you think it needs

You could also wash them out and put synthetic grease or another called Kluber grease in them .

Kluber isoflex supertel ART,-NR.004025/221

*IR 529993

this stuff is recomended for deckel spindles ..but is low temp 70 degrees .....so how it behaves ..who knows.........perhaps it's so good that it wont reach 70 ..it costs a fortune anyhows

all the best.markj

derekm
01-23-2009, 01:03 PM
see this thread

http://bbs.homeshopmachinist.net/showthread.php?t=31242

I go into this in excruciating detail but basically 70C is not hot

sansbury
01-23-2009, 07:04 PM
OK that's more like it--thanks everybody :)

The original replacements I used were based on P/Ns from the LMS site, so that's what I tried.

I have a second X2 spindle and housing which has stock bearings and all as they come straight from the mfr--I think I might swap that one in and flog it for a while and see how it behaves. HF is offering a non-contact thermometer for $12 so might get one.

IIRC this is the same basic setup as the mini-lathe headstock, and supposedly upgrading that to taper roller bearings makes it a lot nicer machine. Is there a reason that wouldn't be a good idea here? I haven't compared the spindle sizes though so maybe they wouldn't be a drop-in replacement...

lakeside53
01-24-2009, 01:20 AM
I don't know anything about an X2, but hot spindle bearing in a few minutes sounds very odd.

How do they set the preload on the bearings? Are you sure the orginals weren't ground for preload?

sansbury
01-24-2009, 12:53 PM
I don't know anything about an X2, but hot spindle bearing in a few minutes sounds very odd.

How do they set the preload on the bearings? Are you sure the orginals weren't ground for preload?

:D It's a $500 Chinese benchtop mill--the table is ground, but I suspect that's more for appearance than anything else. The preload is set by tightening a nut on the top of the spindle. I experimented with it a lot without it changing the heat output, so I don't think that was the issue.

The machine had been used very little when I bought it, and then I slapped new bearings in, so I'm wondering if there was a running-in issue at work in this, along with my perception of the heat output being excessive.

aboard_epsilon
01-24-2009, 01:07 PM
Running in would be sort of like this

5 mins at 200 rpm ......let cool

5 mins at 500 rpm ...........let cool

5 mins at 1000 rpm ...let cool

5 mins at ......top speed...let cool

then

repeat above with 10 mins running time

let cool

then give it 25 mins at top speed .

it should then be ready for cutting.

all the best.markj

derekm
01-24-2009, 03:01 PM
Running in would be sort of like this

5 mins at 200 rpm ......let cool

5 mins at 500 rpm ...........let cool

5 mins at 1000 rpm ...let cool

5 mins at ......top speed...let cool

then

repeat above with 10 mins running time

let cool

then give it 25 mins at top speed .

it should then be ready for cutting.

all the best.markj

Skf recommended running in see

http://bbs.homeshopmachinist.net/sho...40&postcount=17

aboard_epsilon
01-24-2009, 03:06 PM
link doesnt work

all the best.markj

Bill Pace
01-24-2009, 04:09 PM
Yeah, do get one of those thermometers ---

I went ahead and sprung for one of those that'll go over 1000deg, but most any of em will do. I was very surprised in going around checking different spots for temp. Had just finished a rebuild of my little shaper with new bearing on the pulley shaft and the load side was noticeably hotter than the other, sorta like you describe as being to hot to really touch and also residual oil on it would give off light smoke. Checking it with the thermometer showed 145-150 degs!!, I was really surprised. And as already mentioned, that really aint all THAT hot.

FWIW, I kept messing with the shaft and figured out it was in a slight bind, and on getting it trued - which was a pill - the temp went down.