Loading quill bearings

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Mike Ginn

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The top roller bearing (type 30205) on my Warco Minor/Grissly G1005Z mill failed do to lack of lubrication (I was told it was sealed but it isn't). Quite easy to replace but I could get no advice on the procedure of loading the bearing. It needs to be tightened on the bench before final assembly. Can anyone advise on the correct torque to apply?

A secondary question concerns the spindle adjustment on my Sieg KX1 CNC mill. Again can anyone advise on the correct loading torque?

Many thanks in advance
 
I replaced the bearings in my Arboga Mill a while back - the lower spindle bearing is a roller the preload is applied with a castellated nut locked with a tab washer, I tightened it enough to take up the slack and then a fraction more so I could lock the nut with the tab washer, after the first weeks of use I noticed that I had a fraction of play in the spindle, everything had bedded in so I repeated the tightening process, this time going one extra tab space, I noticed the roller bearing getting quite warm after running for a while at top speed 4000rpm so I backed off the nut the extra tab space I had previously applied. It has been like this for over 18 months, been run at top speed and I haven't detected any temp rise in the bearing.
 
Do you mean tapered roller bearing or cylindrical roller bearing. I'm not familiar with the specific Grizzly mill but but there are two possibilities
 
retailer said:
the lower spindle bearing is a roller the preload is applied with a castellated nut locked with a tab washer, I tightened it enough to take up the slack and then a fraction more so I could lock the nut with the tab washer, after the first weeks of use I noticed that I had a fraction of play in the spindle, everything had bedded in so I repeated the tightening process,
Click to expand...

In a tapered roller bearing the rollers are 'wedge' shaped and when you install them statically the roller tends sit in the bottom of the raceway. When they are spun the rollers migrate their way to their actual running position further up the raceway and this increases the clearance within the bearing. Any time you are installing tapered rollers you need to be spinning them as you set the clearance or as you discovered there will be free-play when they are run. On bench tests with front-wheel sized tapers using a dial indicator (we were training fitters to install taper rollers) resulted in something ridiculous like 40 thou of extra end float once we spun the wheel with a bearing that was tightened statically.
 
If it’s taper roller I would be going for 1 thow preload on a spindle but hmm castle nuts can be a pain to get right 😣 ( I hate them )
 
Thanks for the comments. The top and bottom bearings are taper races which can only be adjusted with the quill on the bench. Access to the load nut and castle washer is not possible when installed. In a perfect world I would like to use a torque gauge to load the bearings BUT "Cogsy's" advice has thrown me a bit. I guess I could adjust, spin with a motor, adjust etc but my main question remains - how tight to nip up the bearings. With auto wheel bearings it is usual to finger tighten then add 1/4 turn but I think a quill should be tighter. "Retailer" comments on warn bearings and I suspect that should be the aiming point. However it takes around 2 hours to strip the quill so I would like to get this correct first time.
Thanks guys
 
Hi, been lurking around here a little while.

Doesn't answer your question, but you may find this video useful:



(I didn't believe that I would sit down and watch all 90 minutes of it either, but I found the lengths that he went to fascinating.)
 
Wow - that's a very comprehensive video which uses the correct bearings which are loaded by virtue of their design. Unfortunately my Chinese mill makes use of bearings designed for the steering columns of motor bikes which is never a good place to start. My thoughts are to tighten until I feel resistance which will generate heat. I'll then try to find a way to lubricate the bearings when assembled into the mill - without the need to dis-assemble. However I would really like a ftlb/NM number to work with. I expected the suppliers to have that info but Warco has no info.
 
The down side to per load is will heat up the bearings.

My self I give no per load for longer bearing life. Tighten so it free spins

Dave
 
I replaced the bearings on my RF25 several years ago. I took up all the play turning the shaft as I adjusted the nuts then just gave it about 10 degrees more .Refitted the quill assy and let it run for a good half hour checking things were not getting hot
The nuts on my mill are junk with more slop than thread and you are limited by the position of the lock washer in relation to the castle
Iv not had to redo them so guess I was lucky although all the other bearings sound like Edmondo Ross and his band and need doing
I would need to check but I think if you remove the front plate you can get restricted access to those nuts.It is a long time ago Im not sure
 
Mike Ginn said:
The top roller bearing (type 30205) on my Warco Minor/Grissly G1005Z mill failed do to lack of lubrication (I was told it was sealed but it isn't). Quite easy to replace but I could get no advice on the procedure of loading the bearing. It needs to be tightened on the bench before final assembly. Can anyone advise on the correct torque to apply?

A secondary question concerns the spindle adjustment on my Sieg KX1 CNC mill. Again can anyone advise on the correct loading torque?

Many thanks in advance
Click to expand...
 
I don't think there is any 'correct' pre-load to apply to taper roller bearings. How long is a piece of string?
I reckon the best advice might be from automotive sources, where pre-loaded taper rollers have been used in front wheel hubs since the advent of the car: well, almost! The 'amount' might vary with the size of the bearing and 'or its manufacturing tolerance(s). So called 'precision' bearings are, for instance, made to tighter tolerances than the common variety, with a price to match.
 
It is mill quill using ball bearings.
On a lathe or horizontal mills I per-load since the spindle will heat up and expand and tapper roller bearing.

Dave


wazrus said:
I don't think there is any 'correct' pre-load to apply to taper roller bearings. How long is a piece of string?
I reckon the best advice might be from automotive sources, where pre-loaded taper rollers have been used in front wheel hubs since the advent of the car: well, almost! The 'amount' might vary with the size of the bearing and 'or its manufacturing tolerance(s). So called 'precision' bearings are, for instance, made to tighter tolerances than the common variety, with a price to match.
Click to expand...
 
There is a benefit to a very small amount of pre-load on tapered rollers and angular contact bearings which extends load carrying ability and bearing life, and of course adds to the precision of the spindle. But the amount of preload is very small and the load capacity and bearing life drop off incredibly steeply after this point. When I worked in bearings we sold precision matched sets of tapered rollers and angular contacts for spindles that came with matched spacers and torque settings - but there were very expensive.

For off-the-shelf bearings fitting to a spindle I personally would adjust to zero clearance with no pre-load as it's too easy to put too much on them and have them fail prematurely.
 

Active Atom did a video series on spindle rebuilding.
You will need the better part of a day to watch it all. :)
 
Looks like good mill
But the low speed belt will slip.
Unless tighten the belt to near breaking point it will slip.

I fix this on mill which is close copy by making the center smallest pulley larger and the largest bigger too. This gives a great belt rap on small pulley so does no slip it also gave slower speed.
Note can just make new center pulley just for low speed work too.

I am very happy with low speed and no slipping

I posted drawings and photos of modification here in the downs

Dave
 
I think the price might have a lot to do with it also. How much can you expect from 10 dollar bearings. They are less than ideal when brand new. Of course a set of class 5 bearings would about double the price of the machine. It is what it is!
 
Yes I agree. For a "hobby" mill I guess the bearing is OK but it still needs to be set up in the best way possible. I also accept that the bearing will have a limited life
 
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