Thread: MMD-45 Mill Tight Spindle

Hi Dean,

If you find a "sweet spot" in-between the gears which would serve as a neutral then you can turn the spindle by hand to get a feel for how smooth and how tight/loose the spindle bearings are. It may take a bit of jiggling (especially if it's new and a bit stiff) to find an unofficial neutral.

So, the reason it stalls in top gear but just manages to turn in the lower gears may indicate that the spindle bearings are tight. It may also be one of the shafts from the gears that is also tight but given what you have explained, i'd be inclined to think it's the spindle or the final drive before the spindle or the final gear that has the slip shaft that drives the spindle.

Either way, it sounds like you will need to either take the mill back or (if you would rather) take the gear head apart, clean it, adjust whatever is not properly adjusted and re-assemble.

Be interested to see what others suggest.

Good luck.

Simon

Thanks Simon.

If you find a "sweet spot" in-between the gears which would serve as a neutral then you can turn the spindle by hand to get a feel for how smooth and how tight/loose the spindle bearings are. It may take a bit of jiggling (especially if it's new and a bit stiff) to find an unofficial neutral.

Yes that is what I did.

So, the reason it stalls in top gear but just manages to turn in the lower gears may indicate that the spindle bearings are tight. It may also be one of the shafts from the gears that is also tight but given what you have explained, i'd be inclined to think it's the spindle or the final drive before the spindle or the final gear that has the slip shaft that drives the spindle.

I have no idea at this stage how it operates internally. That is the main reason for asking for advice, along with some suggestion as to what form of bearing I am likely to encounter.

Either way, it sounds like you will need to either take the mill back or (if you would rather) take the gear head apart, clean it, adjust whatever is not properly adjusted and re-assemble.

I will have to dismantle the head, which will enable me to do a couple of other things I have in mind including checking the inside for foreign matter.

Most results I have found on the net show tapered roller bearings at both ends. My top bearing is not a tapered bearing (visible on the top of the head) which leads me to believe it is different to these other mills. I should point out that there are many types of mill produced of this type and I have no illusions that any of this information is the same as mine. Having said that, the only parts breakdown document I have found is for a Grizzly G0463_pl mill and as they use a totally different naming convention I don't even know if it is the same size. For a start it is belt driven. This mill does use non-tapered bearings. They appear to be deep groove, and thrust bearings.

My first step will be to remove the lip seal from the top bearing and inspect it.

Dean

HI,
It does sound like the Spindle bearings are a bit tight, but the upper gear shafts may also be tight. I have a DM-45 Mill it is harder to rotate the spindle in the lower gears, because of the low gearing. It is however easy to rotate the spindle in the higher gears. These Links may help in Dismantling your Mill's Gearbox
http://www.graetech.com/index_files/Page878.htm http://www.metalworkingfun.com/showthread.php?tid=405 Good luck.

Originally Posted by Oldneweng

My top bearing is not a tapered bearing (visible on the top of the head) which leads me to believe it is different to these other mills.
Dean

Not necessarily. The top bearing that you see may in fact be the bearing of the shaft of the final drive gear. It has an internal spline to match the spindle. The spindle slides in and out of this when it moves up and down and transfers the rotational power to the spindle. I doubt you will see the spindle bearings from the top but I could be wrong.

Bare in mind, when you take the top off, it houses about 4 bearings for the shafts for the gears. Depending on how tight a fit, the shafts will either pull out from the bottom or from the head. They are pretty easy to put back when re-assembling. Easier than first expected.

Simon

Originally Posted by steran50

HI,
It does sound like the Spindle bearings are a bit tight, but the upper gear shafts may also be tight. I have a DM-45 Mill it is harder to rotate the spindle in the lower gears, because of the low gearing. It is however easy to rotate the spindle in the higher gears. These Links may help in Dismantling your Mill's Gearbox
http://www.graetech.com/index_files/Page878.htm http://www.metalworkingfun.com/showthread.php?tid=405 Good luck.

Thanks heaps for those links Stewart. They should make things easier to understand. I will study these carefully.

Simon

Not necessarily. The top bearing that you see may in fact be the bearing of the shaft of the final drive gear. It has an internal spline to match the spindle. The spindle slides in and out of this when it moves up and down and transfers the rotational power to the spindle. I doubt you will see the spindle bearings from the top but I could be wrong.

Bare in mind, when you take the top off, it houses about 4 bearings for the shafts for the gears. Depending on how tight a fit, the shafts will either pull out from the bottom or from the head. They are pretty easy to put back when re-assembling. Easier than first expected.

Some more pieces of the puzzle to help me. Thanks again.

Now I have some concept of what I can expect to see inside.

Dean

Ok. So the plot thickens.

I just went to have a quick (I'm watching tea cook) look at the top bearing above the spindle thinking to remove the lip seal. I forgot a torch as the light is not quite good enough that high. I did clean off some dirt and stuff. I tend to forget to replace the cover. Maybe I should put it on the table when I remove it so I see it before I continue.

Anyway I thought I should remove the milling cutter and the ER collet chuck before proceeding. I then turned the mill on. It was still in H-1 (Fourth gear). It took off without any hesitation. Switched to H-2. Same thing here and in top gear.

This is something I need to ponder. Tomorrow I will experiment with various attachments and see what result I get. The ER collet chuck was not over tightened. The mill was in H-1 as stated above and I did not hold the spindle. The draw bar released just with a quick twist of the spanner.

Dean

It would seem from your own results that something you have put in the spindle is the cause of your problem.
Have you used this collet chuck and drawbar assembly before?

Originally Posted by pipeclay

It would seem from your own results that something you have put in the spindle is the cause of your problem.
Have you used this collet chuck and drawbar assembly before?

The collet chuck was received in a fairly large order shipped from CTC on 28/12/12. It has seen extensive use. The drawbar was made by me shortly after receiving the order as the one that came with the mill had a 14mm thread which fits nothing I have seen except for what was supplied with the mill.

I have not used anything else in the spindle in the last couple of days.

I will have a look inside the spindle. It seems like it is pretty easy to remove.

Dean

Today I first checked that the problem still existed (desperation I know). No Change. I tried varying the amount of pressure on the drawbar and found that this made a difference. Keep tightening it and at a point it stops turning in 2 top gears.

I then tried the drill chuck and 14mm drawbar, both of which were supplied with the mill from new. The same result. This at least confirms that the problem is in the spindle.

I have removed the spindle. Checking the taper, it looks and feels fine except it is not the finest finish I have seen. What one would expect. I have examined the MT4 tapers that have been used in the spindle and could not see or feel any imperfections. I have not dismantled the spindle, but I did check that the locking tab is engaged on the top adjusting nut.

I could just back off the adjustment a bit and see what happens, but I can't help thinking there is a problem further down. The spindle laying on the bench is still pretty tight. I struggle to turn it with my finger/thumb from the slots at the bottom. Gripping the spline it is quite firm to turn. It wouldn't hurt to clean it out and check the bearings while I have it out although it was a pretty easy job.

Dean

How tight should it be to turn?

Hi Dean. I think you should be able to turn it with your fingers reasonably easy. Based on the info you have given, I would suggest its way too tight. Its a bit late now but I should have suggested you run the spindle in a mid range gear for 15 mins and check the temp with your hand. I shouldnt be anymore than warm to the touch. In fact the owners manual for both my lathe and mill said to run the machine in each gear for 20 mins when new.

I would take the spindle apart since you got it out and clean and repack the bearings with grease. In fact I would replace them the quality japanese bearings and be done with it but thats just me and it could be unnecessary.

Simon

Originally Posted by simonl

Hi Dean. I think you should be able to turn it with your fingers reasonably easy. Based on the info you have given, I would suggest its way too tight. Its a bit late now but I should have suggested you run the spindle in a mid range gear for 15 mins and check the temp with your hand. I shouldnt be anymore than warm to the touch. In fact the owners manual for both my lathe and mill said to run the machine in each gear for 20 mins when new.

I would take the spindle apart since you got it out and clean and repack the bearings with grease. In fact I would replace them the quality japanese bearings and be done with it but thats just me and it could be unnecessary.

Simon

I will check the prices for the bearings as it makes sense to replace them while I have the chance to do it easily. I will certainly check the condition of the bearings if I can get them out. The 2 links provided by Stewart have a lot of useful information regarding disassembly, but there is information missing in both of them. Disassembly of the lower section of the spindle is one of these. There is a large threaded disk which obviously needs some sort of pin spanner to remove, but the holes (3) are tiny. I don't have any sort of tool to fit and don't really know what to use make one. Drill bit shanks? I can make up a disk to suit. The face is not flat, but has a taper. No real problem there. It would be good to have a working mill to position the holes! Can any one tell me if this disk will be tight to remove? (typically that is) I have found a picture. It seems to be only to keep carp out, but mention was made of needing to press the quill out of the bottom bearing so it needs to come off.

Spindle Bottom Threaded Cover.jpg

Photo thanks to Graetech.com

The only info in the links provided regarding adjustment of the spindle bearings is

Install keeper plate and castellated nut. Tighten and back off about 1/8 turn. Set the keeper tab into the nut slot.

I guess that will be enough to work it out.

Dean

I have probably missed something here but doesn't the spindle rotate inside a top and bottom bearing?
And the tooling you use Is held in a taper in the spindle and if required retained by a draw bar?
If the spindle when in the machine was able to rotate in high gear with out tooling there must be something causing it to tighten or jam when the tooling is fitted.
Is there the chance that the spindle may have a small fracture and when you tighten the draw bar the crack is opening causing the spindle to tighten or jam on the bearings.

Originally Posted by pipeclay

I have probably missed something here but doesn't the spindle rotate inside a top and bottom bearing?
And the tooling you use Is held in a taper in the spindle and if required retained by a draw bar?
If the spindle when in the machine was able to rotate in high gear with out tooling there must be something causing it to tighten or jam when the tooling is fitted.
Is there the chance that the spindle may have a small fracture and when you tighten the draw bar the crack is opening causing the spindle to tighten or jam on the bearings.

Yes you are correct PC.

The first picture is the bottom spindle inner bearing race on the spindle and the mating bearing cone still in place in the quill. The thread just outside the bearing cone is where the spindle cover screws in. The second picture shows both bearing inner races on the spindle in relation to where they fit in the quill.

Sorry about the small sizes. Pictures are both thanks to Metalworkingfun.com Forum.



Lower spindle Bearing.jpg Spindle Bearings and Quill.jpg

If the spindle when in the machine was able to rotate in high gear with out tooling there must be something causing it to tighten or jam when the tooling is fitted.
Is there the chance that the spindle may have a small fracture and when you tighten the draw bar the crack is opening causing the spindle to tighten or jam on the bearings.

There is always the possibility of something like this happening which is why I wrote

I could just back off the adjustment a bit and see what happens, but I can't help thinking there is a problem further down.

I do want to pull it apart and examine it carefully. Looking at the diameters it seems that the only place a problem like this can occur is at the bearing mount points. There appears to be a lot of clearance everywhere else inside the quill.

Dean

Hi Dean,

If the spindle when in the machine was able to rotate in high gear without tooling there must be something causing it to tighten or jam when the tooling is fitted. Is there the chance that the spindle may have a small fracture and when you tighten the draw bar the crack is opening causing the spindle to tighten or jam on the bearings.

This would be my guess as well ! I would pull the bearings, and fit the drawbar and a tool, tighten and see if you can see or measure any crack or out of round where the bearing fits. If you have access to someone who has crack testing equipment that may be a better bet. Though I hope that you find something silly such as a spacer that is binding and easily fixed.