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[4]

Bad bearings? Dah Lih circa 1976 Taiwanese

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Ropata

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#1
I was trying to avoid pulling the vertical head apart but now I have doubts about the bearings. Could anyone tell from the video if in fact they are buggered and maybe from the photos how the hell I get in there? 20170809_163210.jpg 20170809_163244.jpg
 

mikey

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#4
That cogging feeling is probably due to "brinelling", where the balls have indented the race; every time a ball engages one of those dents it catches. The excessive axial play suggests the cage for the bearings are excessively worn. This all means the bearings are toast as Ulma Doc said.

Not sure of the screw in the side of the quill but I would guess it is a guide pin for the R8 collet.

Haven't changed bearings in that mill but someone will be along shortly, I'm sure.
 

Ulma Doctor

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#5
i have not replaced the bearings on that mill, but it appears to have a lock ring (nut) that uses a spanner wrench to remove it.
in picture 2 you can see a hole in the lock ring (nut). that's were the pin from the spanner wrench is inserted.
after you get the ring off, the spindle assembly appears to be removed from the pulley side, taking care not to damage the threads.
i hope the information is helpful
 

Bob Korves

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#6
Not sure of the screw in the side of the quill but I would guess it is a guide pin for the R8 collet.
Looks like it is a 30 taper spindle. I also do not see how it comes apart. Perhaps take out the quill lock completely which may let the spindle/quill combination all come out together. Probably would need to remove the feed shaft and pinion as well. Also, what does the ring of socket head cap screws around the upper bearing hold?
 

Ropata

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#7
Looks like it is a 30 taper spindle. I also do not see how it comes apart. Perhaps take out the quill lock completely which may let the spindle/quill combination all come out together. Probably would need to remove the feed shaft and pinion as well. Also, what does the ring of socket head cap screws around the upper bearing hold?
Yeah I'm really not sure about the ring of cap heads, there is a ring of 4 big ones which are really confusing as there is no joint in the casting or anything there. The small ring close to the top bearing must hold the assembly together.

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mikey

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#8
Looks like it is a 30 taper spindle. I also do not see how it comes apart. Perhaps take out the quill lock completely which may let the spindle/quill combination all come out together. Probably would need to remove the feed shaft and pinion as well. Also, what does the ring of socket head cap screws around the upper bearing hold?
Just shows you how much I know.
 

Ropata

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#9
I got the whole quill out. The top bearing I hope to remedy by tightening the spline sleeve. Do you guys think it's worth pulling the top bearings too? I'm just worried they are pressed into the casting and I have no easy way of pressing them in or out.
 

whitmore

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#10
I got the whole quill out. The top bearing I hope to remedy by tightening the spline sleeve. Do you guys think it's worth pulling the top bearings too?
If I'm visualizing correctly, the 'top bearing' longitudinal play doesn't affect the spindle cut
depth, it could be completely normal. Look up the drawings, it's possible there
is a shimmed pair or other take-out-the-play adjustment. It could be a shim got damaged
or backing nut slipped, and bearings are fine.

Considering other damage was found, though, prophylactic bearing replacement is mainly a wallet decision.
 

mikey

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#11
It looks to me like the quill bearings should be straightforward enough. Commonly, these will be tapered roller bearings. I changed mine to sealed angular contact bearings so no maintenance is required for the life of the bearings.

The upper spindle sleeve, commonly known as a drive sleeve, can definitely affect spindle runout. The axial play may or may not be an issue but if there is radial play then that is not good. You've gotten this far so why not change them out? It looks like they are just held in by the housing; that should come loose when you remove the hex screws at the base. Typically, there are two bearings separated by a spacer and there should be a nut to preload the bearings. I would guess once the housing on top is removed, you can push the whole sleeve and bearings out from the bottom. I'm guessing here but its based on rebuilding several drill presses and my RF-31 mill and the construction in your videos is quite similar.
 

Ropata

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#12
It looks to me like the quill bearings should be straightforward enough. Commonly, these will be tapered roller bearings. I changed mine to sealed angular contact bearings so no maintenance is required for the life of the bearings.

The upper spindle sleeve, commonly known as a drive sleeve, can definitely affect spindle runout. The axial play may or may not be an issue but if there is radial play then that is not good. You've gotten this far so why not change them out? It looks like they are just held in by the housing; that should come loose when you remove the hex screws at the base. Typically, there are two bearings separated by a spacer and there should be a nut to preload the bearings. I would guess once the housing on top is removed, you can push the whole sleeve and bearings out from the bottom. I'm guessing here but its based on rebuilding several drill presses and my RF-31 mill and the construction in your videos is quite similar.
Yes! exactly. Thanks heaps Mikey. I now have the top bearings out and you are dead right. The bearings are pristine, no sideways play at all and I think I have found what is causing the axial play. If you can see in the photos, it looks like someone has been in there before. The spacer between the 2 drive bearings looks newer than all else and has chuck marks on it. The spacer is half a millimetre bigger than the inner bearing seats as I've drawn in the photo. Do you think the last guy just made a mistake? He got the bore spot on. I just can't imagine mass produced parts having chuck marks on them.
20170810_120548.jpg 20170810_120957.jpg 20170810_121044.jpg
 

mikey

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#13
In most cases, there is a nut that allows you to preload the bearings. This makes the length of the spacer between the bearings non-critical. However, if there is no nut then the spacer length becomes critical. The OD of the spacer normally should allow it to touch only the outer race, while the preload nut would apply tension to the inner race of the bearing it is adjacent to. Your spacer looks like it would contact the area between the two races, which makes no sense at all. Maybe the previous owner got it wrong?

Is there a preload nut? If so, where is it? In most cases, it is on top but I don't see it there. If it is on the bottom, I cannot see how you would adjust it. If there is no nut then the length of the spacer needs to be adjusted but I'm not sure how to figure that length out.
 

Bob Korves

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#14
What are the part numbers of the upper bearings? I cannot read it in your pics. Two upper bearings? Same part number?

You do not want axial end play in a spindle/quill doing drilling and milling.
 

Ropata

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#15
What are the part numbers of the upper bearings? I cannot read it in your pics. Two upper bearings? Same part number?
6208 I think. Have just gone back to work so will confirm when home and also explain the preloaded nut to the previous post too.

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Bob Korves

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#16
Could be 6208. They are 40 mm I.D. and 80 mm O.D. 6200 series bearings are very common and inexpensive radial bearings, and are not meant for thrust loads. Assuming they are the original spec bearings. What make and model mill is this, anyway?
 

Ropata

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#17
Could be 6208. They are 40 mm I.D. and 80 mm O.D. 6200 series bearings are very common and inexpensive radial bearings, and are not meant for thrust loads. Assuming they are the original spec bearings. What make and model mill is this, anyway?
It's a Dah Lih circa 1976 Taiwanese. I can't find any info at all on it and can't get a reply from the company.

The locking nut has one of those washers with the bendable tabs and key to keep locked (see photo) 20170810_154528.jpg . It goes inside the spindle sleeve side as per the first couple of photos. As mentioned, the only play is up and down because the spacer is larger than the outer race seat.
 

Ropata

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#18
Also, what grease would you guys use for these bearings? It has a top speed of 2500 but I'm thinking of a VFD to get a bit more out of it.
 

mikey

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#19
Okay, I think I see the layout now. It looks like the spacer is sitting between and bearing against the inner races and the nut is on the bottom of the lower bearing and presses against the lower inner race. I'm not sure if that spacer is the correct length; because it is longer than the bore it sits in, it might prevent one of the bearings from fully seating in the bore. If that is so then one of the bearings will be floating and that might be why the drive sleeve has play. I could be wrong about that but it makes sense to me.

Those bearings are shielded bearings. There is some controversy about lubing shielded bearings because getting grease inside a shielded bearing is difficult. Rather than grease them, it is usually suggested that you replace them. Also, if those bearings are original then they are likely past their usual service life. They may spin okay but may behave differently under load. The bearings are cheap and I would consider changing them while the machine is apart. If you do, I would change them to sealed, permanently lubricated Nachi deep groove bearings that require no ongoing maintenance until they wear out.

I would also change to sealed angular contact bearings in the quill. They do not require maintenance either. Tapered bearings are okay but they are all un-shielded, must be lubed periodically and must be preloaded correctly.

EDIT: Okay, check my thinking here. If the two drive sleeve bearings have a spacer that mechanically separates the inner races of the bearings and it is preloaded then the only axial play it can have will be the internal bearing clearances, right? I mean, the outer races are supposedly seated in their bores and the inner races are preloaded and are effectively solid. If the shaft is moving vertically then the only thing that should allow that are bearing clearances and this should be very small (micron range small). If this is true then the axial movement you are seeing suggests those bearings are shot.
 
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Ropata

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#20
Okay, I think I see the layout now. It looks like the spacer is sitting between and bearing against the inner races and the nut is on the bottom of the lower bearing and presses against the lower inner race. I'm not sure if that spacer is the correct length; because it is longer than the bore it sits in, it might prevent one of the bearings from fully seating in the bore. If that is so then one of the bearings will be floating and that might be why the drive sleeve has play. I could be wrong about that but it makes sense to me.

Those bearings are shielded bearings. There is some controversy about lubing shielded bearings because getting grease inside a shielded bearing is difficult. Rather than grease them, it is usually suggested that you replace them. Also, if those bearings are original then they are likely past their usual service life. They may spin okay but may behave differently under load. The bearings are cheap and I would consider changing them while the machine is apart. If you do, I would change them to sealed, permanently lubricated Nachi deep groove bearings that require no ongoing maintenance until they wear out.

I would also change to sealed angular contact bearings in the quill. They do not require maintenance either. Tapered bearings are okay but they are all un-shielded, must be lubed periodically and must be preloaded correctly.

EDIT: Okay, check my thinking here. If the two drive sleeve bearings have a spacer that mechanically separates the inner races of the bearings and it is preloaded then the only axial play it can have will be the internal bearing clearances, right? I mean, the outer races are supposedly seated in their bores and the inner races are preloaded and are effectively solid. If the shaft is moving vertically then the only thing that should allow that are bearing clearances and this should be very small (micron range small). If this is true then the axial movement you are seeing suggests those bearings are shot.
I think we're getting somewhere Mikey. The 2 bearings have open backs which face into the bore where the spacer sits. The grease zerk points directly into this cavity too. The outer races are not a press fit and they slide up and down what looks like half a mm which is how much longer the spacer is than the area for it. This makes me pretty sure that someone has home made this spacer again to a slightly longer size for some reason. I know it's hard to explain and I'm probably not doing a good job of it but **** it helps a lot going through it with you guys. I may look into sealed bearings if they aren't too expensive. Onto the bearings in the quill later tonight so no doubt I'll have a few questions about the taper roller ones in there.
 

mikey

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#21
Oh, okay, those are Z bearings instead of ZZ (single vs double-shielded). Normally, drive sleeve bearings are a close slip fit and not a press fit. It sounds like you're right in that if the spacer is too long and the axial play is however much longer the spacer is, then that accounts for the axial play you're seeing. Too bad you can't find the manual; it would help confirm if the bearings are the correct ones.

The quill bearings should be tapered roller bearings and should be light press fits. There should be two preload nuts on top, separated by a tabbed lock washer if yours follows the typical Asian pattern.
 

Ropata

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#22
So I turned the spacer down to be about .005mm shorter than the bearing seats and started on the quill. Does anyone have a similar nut at the end of theirs? I guess I'm going to have to make a pin spanner. Wish I had a mill!
I'm still not sure what the philips head machine screws are for? Pretty sure they are for oiling or greasing the inner quill. There is also a grub screw that has a grub screw inside that turns with the spindle.
20170810_183359.jpg 20170810_183411.jpg 20170810_183429.jpg 20170810_183507.jpg 20170810_183515.jpg 20170810_183613.jpg
 

mikey

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#23
I'm going to guess that the end cap at the lower end of the spindle threads off and that should expose the lower bearing. A strap wrench should get that off. I would also guess that removing the cover at the top end with a pin spanner will reveal the preload nuts and upper bearing.

Once you get the covers off and press the spindle out of the quill, the function of those screws will become evident.
 

Bob Korves

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#24
The upper bearings are designed for radial loads. They only keep the upper end of the spindle located radially. The lower bearings are in the quill and are probably tapered roller bearings. They take all the working loads from the spindle, and contain radial and axial runout there. They should be cleaned, lubed with light grease, assembled as clean as possible, and lightly preloaded. Spindle bearings are often a precision grade that has etching marks on them to show the high/low spots, and those need to be properly oriented at installation for best accuracy.
 

4gsr

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#25
That's an odd arrangement a set screw with a Phillips head screw in it, if I'm looking at it correctly.
 

Ropata

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#26
I've had absolutely no luck getting the end off this quill. I made a heavy duty pin wrench but even that is starting to bend. Any suggestions? soak in penetrating oil? heat? I've bashed and gripped it about as forcefully as I'm comfortable with.
20170813_130749.jpg 20170813_130807.jpg 20170813_130823.jpg
 

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#27

Ropata

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#28
It's probably a left handed thread. Gorton mills have a left handed thread on this nut. You never know.
I gave a few whacks the other way but didn't budge.

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Ropata

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#29
Well I just broke the wrench that took me 2 hours to make so I'm really at a loss.
 

mikey

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#30
Are you sure all pins are out? While unlikely, what about that hex headed screw on the end of the cap?

If all else fails, you might try some gentle warming with a torch.
 
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