Thread: Changing the top quill bearing to a taper one on a HM52

Originally Posted by Dave J

That one is a plain bearing, but is not the quill bearing. That one just supports the drive hub that drives the spindle by the look of it.

When you move the quill up and down does the spindle splines slide though it, if so it's not the quill bearing.

Dave

Yes you are correct , the splines slide up/down through it ...

I would say yours are tapered bearing both ends, as all the ones I have seen are. It only takes 5 minutes to take the quill out of the machine and inspect it. It would probably be a good idea to take it apart and give it a clean and preset the bearing preload yourself, as I wouldn't trust how the Chinese have done it.

If you do this you can then get the bearing numbers and store them away for latter if you need them, that way there is no down time chasing bearings. To replace them with SKF it will only cost you around $50 for the pair.

I did a right up on the forum for removing the quill, yours will be very similar to mine, so if you want I can chase it up for you.

Dave

Originally Posted by Dave J

I would say yours are tapered bearing both ends, as all the ones I have seen are. It only takes 5 minutes to take the quill out of the machine and inspect it. It would probably be a good idea to take it apart and give it a clean and preset the bearing preload yourself, as I wouldn't trust how the Chinese have done it.

If you do this you can then get the bearing numbers and store them away for latter if you need them, that way there is no down time chasing bearings. To replace them with SKF it will only cost you around $50 for the pair.

I did a right up on the forum for removing the quill, yours will be very similar to mine, so if you want I can chase it up for you.

Dave

Roger that ... that would be handy to know .

They have packed some grease around the bearing pictured ... I'm not sure what grade of grease it is . But, yes it would be worthwhile repacking the bearing with wheel bearing grease of good quality .. Do the tapered spindle bearings run in the oil inside the gear box ?

I am rather gentle with the machine , I don't stress it as I want it to last. MIKE

You will find the oil in the gearbox is totally separate from the quill. The quill will have grease in it and when I rang the bearing places (after ringing ever tech line) eventually told me that if you could place your hand on the bearing while running just use wheel bearing grease.

Below is a picture showing inside your head with the covers off. There is a wall between the quill and gear box. So the quill is totally separate and you will have no oil coming out if you remove it.

Dave

Hi Dave!

First of all, congratulations on another well thought out and executed project. You are an inspiration, especially to new, less experienced people like myself.

Thanks!

I must concur about the 45 size mills from my experience, my mill has tapered roller bearings top and bottom. The user manual states 7208 and 7206 tapered roller bearings. Having said that, I would not order new bearings based on that alone. The Chinese tend to make slight alterations in their products without updating the manual from time to time! I would still pull them out and eyeball them.

The bearings are greased and kept separate from the oil bath by way of a double oil seal that can just be seen from the top where the drawbar tightening nut is.

One question, did you not put precision bearings in ie one with a P6, P5 etc? I don't understand why lathe spindle bearings are precision bearings (mine had P5 and P6) but mill bearings tend to just be standard automotive bearings. Can you or someone else explain why? Surely the run out of the bearings and therefore the spindle is just as important?

PS I think my mill only has standard bearings too. Cheap as chips compared to my lathe!

Cheers,

Simon

Hi Simon,
Thanks for that , I did a lot of research and planning for this and it ended up turning out as planned. As you have probably read Ray changed his bearing over as well and said he is happy with the change as well.

With the bearing, I think we are to low of class with our machines to get good grade bearings. I did price around for high grade bearings for mine but they where $800 odd dollars for my 4 (horizontal and vertical spindle) and needed to be ordered from overseas as no one carried them here. I decided to leave them at that price and just fitted standard new SKF quality bearing back in. I use all Chinese and Taiwanese tooling so it probably has more run out than the bearings have, so you need to think about that.

Thanks for clearing that up about the tapered bearing, every mill I have seen in that size has tapered top and bottom, but you never know they could change, my size mill missed out for some reason.
I found all my bearing numbers to be true to the manual, but I had to go online and convert the Chinese part numbers over to our standards. If you type in your bearing number it will show you the number from different manufactures. I have the link here somewhere if you want it let me know and I will chase it up.

When greasing quill bearing, only fill the free air space in them 1/3 with grease, they are not like wheel bearing where you fill them right up.

Dave

Thanks for the warm welcome Dave. I'm tied up Saturday but will have time Sunday to post pics of my mill and lathe. I'll focus on the mill first as my lathe and 4 Jaw seem to be capable of holding acceptable tolerances. I'll probably just break down the head assembly. Maybe the most challenging part will be threading the M40 1.5 nut that you made. I'll also have to ask my buddy to weld in a piece of round stock as I have no TIG or MIG. I will definitely have questions about that operation, i.e. did you use an full profile insert or single point, # of passes, helical angle, etc? But that's all getting ahead of myself. I'll start slow and work up from there posting and pics that might be helpful. Anyways thanks again and I'm excited to jump into the world of metalworking!

Originally Posted by Dave J

Eskimo, haven't you done that yet? LOL

Dave

nope ...not yet .....I guess he has been sick or something

Originally Posted by simonl

One question, did you not put precision bearings in ie one with a P6, P5 etc? I don't understand why lathe spindle bearings are precision bearings (mine had P5 and P6) but mill bearings tend to just be standard automotive bearings. Can you or someone else explain why? Surely the run out of the bearings and therefore the spindle is just as important?

All comes back to the quality of the build... From my experience it is only the more expensive machines that get the precision bearings...

My Turret mill, a bridgeport clone was only fitted with standard off the shelf SKF angular contact bearings... I have modified them to improve them a bit though..

Originally Posted by .RC.

All comes back to the quality of the build... From my experience it is only the more expensive machines that get the precision bearings...

My Turret mill, a bridgeport clone was only fitted with standard off the shelf SKF angular contact bearings... I have modified them to improve them a bit though..

Thanks. If it's good enough for a Bridgeport clone then it's good enough for my 45 size Chinese mill too!

Hi Dave, thanks for the reply. I understand where you're coming from.

Cheers,

Simon

Attachment 196556Well, I had a spare moment and curiosity got the better of me so I removed my quill to take a closer look. Discovered two things:

As I said earlier, I don't fully trust Chinese owner manuals! The owners manual states that the quill has two tapered roller bearings, a 7206 and a 7208. When I took it apart I found the following bearings:

A 30206 and a 30208 tapered roller bearing. Both are a P6 precision tolerance. Yea I know, Chinese precision is very questionable!

I don't know what the differences are between and 30206 and a 7206 or a 30208 and a 7208.

Same same for my lathe. the bearing list stated a 7211 and a 7212 bearing but when I looked at them it had a 30211 and a 30212 tapered roller bearings.

I just going to clean them up real nice and repack with good grease. The outer bearing race on the bottom quill bearing sits inside the quill. You can't knock, press or drift it out so I have no idea how you would remove it to replace with a new bearing. Only thing I could think of would be to split it with a cold chisel and remove it destructively. Not something I would be keen on.

Pics attached show the two bearings and the bottom of the quill where you can see the outer bearing race inside the quill...

Simon

Originally Posted by simonl

Attachment 196556

A 30206 and a 30208 tapered roller bearing. Both are a P6 precision tolerance. Yea I know, Chinese precision is very questionable!

Especially when there is no such thing as a p6 precision tapered roller bearings....

Tapered rollers use a different lettering system for bearing class... Imperial use the Timken system of 4,2,3,0,00,000

while metric use the letters K, N, C, B, A, AA

Also remember the lower the P number with ball bearings the higher the accuracy.... With ABEC it is the opposite with super precisions like ABEC9 is about equivalent to a P2...

ABEC 5 and P5 are about the same...

Interesting and informative

So what is the prefered method for removing the DM 45 quill ? The attachment doesn't open

You might get that bearing cup out with a slide hammer , if there is enough room to get behind it that is.

Mike

To remove a bearing cone in an inaccessible place (like this one or worse - bottomed in a blind bore), just run a bead of Mig or stick weld around the minddle of the roller track and let it cool down. The bearing part will just fall out. The weld shrinks it quite a bit. Obviously this is destructive but does no harm to the shape of the mounting bore, whereas hitting it with a chisel and hammer may deform the mounting bore.
Joe