Help identifying X2 spindle wobble

There should be an adjustment for the preload on the spindle bearings. I'd check it. Also could be a pulley or belt issue including alignment. Unless the bearings are very worn I don't see them as being the wobble issue unless its a cracked or broken ball/needle. Heat maybe, but most likely whatever is causing the wobble is causing the added friction and heat. Do the pulleys have a good fit on the spindle shaft? I've seen set screws tightened and moving the pulley off center enough on aluminum pulleys that weren't a perfect shaft fit or out of round cause such a wobble. I had an LMS mill for a while but didn't have issues so never checked into the bearing preload. I put a belt drive on a grizzly mill I cnc converted and I had spindle heat issues prior to the belt drive and after. Decent angular contact bearings aren't too expensive and when I upgraded the bearings everything ran much cooler FWIW.
 
coherent said:
There should be an adjustment for the preload on the spindle bearings. I'd check it. Also could be a pulley or belt issue including alignment. Unless the bearings are very worn I don't see them as being the wobble issue unless its a cracked or broken ball/needle. Heat maybe, but most likely whatever is causing the wobble is causing the added friction and heat. Do the pulleys have a good fit on the spindle shaft? I've seen set screws tightened and moving the pulley off center enough on aluminum pulleys that weren't a perfect shaft fit or out of round cause such a wobble. I had an LMS mill for a while but didn't have issues so never checked into the bearing preload. I put a belt drive on a grizzly mill I cnc converted and I had spindle heat issues prior to the belt drive and after. Decent angular contact bearings aren't too expensive and when I upgraded the bearings everything ran much cooler FWIW.
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The preload is adjusted with the nut on top of the pulley. I have played with it to no change. If tried just snugged down a bit up to "any more and this thing is going to snap". The thing that has me confused is that the spindle taper is only out .0005" but the wobble is still present on top. The spindle pulley isn't a perfect fit. It probably has .005" or so play in it before it gets tightened down. I could see that causing it to rotate eccentricly, but I don't see how that could cause the wobble I am seeing.

I plan to go ahead and swap the bearings out. I have also seen people have faced off the nut to square it up. I will try that too.

I think I probably have more than one issue going. Its not 1 problem causing the wobble, the grinding, and the excessive heat. Ill see what happens with new bearings and squared up hardware.
 
shooter123456 said:
I think I probably have more than one issue going. Its not 1 problem causing the wobble, the grinding, and the excessive heat. Ill see what happens with new bearings and squared up hardware.
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It could very well be that the headstock bearings are the sole cause of this. Bad bearings will cause wobble, grinding and overheating. It could also be that the spindle needs replacing, too. Let us know what you find with this one.
 
mikey said:
It could also be that the spindle needs replacing, too. Let us know what you find with this one.
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It would be kinda rare to have the spindle get damaged and cause this with normal use but I suppose severe overheating or a drastic "crash" could cause issues. Since you're pulling it out to change the bearings, roll it on a piece of glass and any issues (bend or warping at least) should be evident. Good luck and hope you get the issue resolved.
 
In order for the spindle to wobble like this one does, I would guess the top spindle bearing is more shot than the one at the bottom. It is also possible that the spindle is damaged at the top so that there is play between it and the upper spindle bearing. I doubt the spindle is bent in the middle unless it is a two-piece affair but I haven't seen a two-piece spindle before. I agree that you can pick up very small amounts of bend by rolling it on glass or a surface plate but I'm anal enough to use V-blocks and a DTI to check it.
 
Hello Coherent. I have a G0704 mill and I plan on a belt drive and then on to CNC conversion. Will you mind if I direct some questions to you when I begin my quest?
Bill


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When a ball or roller bearing starts to go bad or is of inadequate quality there is a good chance that the inner race will turn on the shaft. This creates heat. In one case I had the inner race actually welded to the shaft.

Or the shaft wears away and clearance between shaft and bearing increases. As the shaft knocks about inside the bearing it makes noise. Also causing the shaft to wobble. Under these conditions, the higher the speeds the worse it gets. If the shaft is not worn too bad a new bearing would have to be glued to the shaft. (ex: using Loctite retaining compound).
http://na.henkel-adhesives.com/us/content_data/356776_9294_LT5021_Retaining_Brochure_F.pdf

The only way to get a clear picture of the problem with the bearing and spindle on your mill is to take it apart and inspect it.
 
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Hello,

Balenceing would probably be a good thing to do with it running over 4000 rpm, I would imagine that the oil/grease in the bearings has probably warmed up a lot and left the bearings, i used to have a slight issue with dripping oil from my mill spindle when running over 2k rpm , if they actualy dry out that would add to the heating and be a viscious cycle of heating and ware.

I belive the pre tension is often a little less for high speed spindles but i dont have vast experience with that so dont take that as gosple.

Stuart
 
mikey said:
I would suggest taking careful readings for run out at the spindle. Un-do the belt from the spindle up top and turn the pulley by hand. Put the tip of a good DTI inside the spindle taper and first check concentricity by marking the pulley with a Sharpie. Make one full revolution and note the run out. Then push and pull the pulley in all directions, looking for movement of the indicator needle. If you see excessive run out, either with the static concentricity check or with pushing/pulling on the pulley then your bearings are likely the issue.

Just looking at the upper spindle running at low speed, you can see it wobbling. To me, this suggests that the bearings are shot or the spindle, if it is one piece, is bent. The grinding sounds and high temps also suggest the bearings are shot.

If your bearings are original Chinese bearings then getting more than a year or two out of them is about all you can expect. I suggest replacing them with high quality angular contact bearings or deep groove ball bearings. It is also a good idea to use sealed bearings that are lubricated for life and typically require no run in time. It might be a good idea to consider using ABEC-5 or equivalent bearings in your spindle; they cost more but will last longer at the speeds you're running. Going for more precision in a bearing might not be cost effective on a mini-mill.
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I am shopping for replacement bearings, and am completely lost on what I should be getting. I can't tell quality beyond the price really and have seen them from $10 to $500.

My question now is:

What makes a bearing high quality and how can I figure that out without spec sheets?
How much should I expect to spend for either angular contact bearings or deep groove bearings?
Would it be better to get a very high quality deep groove bearing or a mid range angular contact? Those seem to be about the same price.

Also, you suggested high quality bearings but then say going for more precision in a bearing might not be cost effective. That sounds contradictory, but maybe I just don't understand.

I appreciate your help with this.
 
coherent said:
It would be kinda rare to have the spindle get damaged and cause this with normal use but I suppose severe overheating or a drastic "crash" could cause issues. Since you're pulling it out to change the bearings, roll it on a piece of glass and any issues (bend or warping at least) should be evident. Good luck and hope you get the issue resolved.
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I haven't had any major crashes. I think the worst one was when I was fly cutting and broke the plastic drive gears. But even so, that was a small crash. Ill inspect the spindle when I get it out to change the bearings.

I have a granite surface plate, would that work to check the spindle or do you recommend glass specifically for some reason?
 
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