Thread: Thiel Duplex 158 Spindle bearings

So I was merrily working away on a little milling project yesterday when the spindle bearings in the vertical head of my Thiel Duplex 158 began to consume themselves.
The lubrication on the Thiel vertical head is a total loss system so before running I usually give a few pumps of oil to the different lubrication points and a few drips come out through the bottom of the spindle every now and then during use. The first indication that something was not right was when it caught my attention that the oil drips were not the usual clean oil colour but much darker bordering on black, I gave them a quick wipe and made an alarming discovery:

Thiel Spindle Bearing 01.JPG

I have been doing a bit of cast iron machining lately and while I use a vacuum cleaner to control the CI dust my first thought / hope was perhaps this was just a bit of dust that got past the vacuum and had collected on the quill where the oil comes through. I gave everything a good clean and another oil then started the machine again but alas the oil continued to come out with the little metal passengers. A close inspection with a loupe showed that the chips were not the grey of CI but the shiny silver of steel so I knew something was very not good.

The spindle did not sound noticeably noisier than usual when running at higher revs but spinning it by hand it did feel a bit lumpy where it was usually perfectly smooth. I removed the head and began to strip it down for a closer look at what was going on. My concerns that the gears might be damaged were soon alleviated as they all looked perfect. The intermediate shaft bearings and as best I could tell the upper spindle bearing all appeared to run smoothly by hand and there were no metal chips anywhere to be seen, although there was grease which I'm pretty sure shouldn't be there.

I removed the quill which contains the lower spindle bearing and it definitely felt lumpy when turning by hand so I suspect the lower spindle bearing is the source of the problem.
The issue I have now is that I have not been able to remove the lower spindle bearing retaining ring. I replaced the quill in the head and removed the small locking screw then made up a pin spanner which I hoped would do the job but the retaining ring is much tighter than I expected and I have not been able to budge it. The holes in the ring showed signs that it had been tinkered with before as there was a bit of distortion which I peened back to as close to original as possible before they got any worse but the ring stubbornly resists any attempt to remove it either clockwise or anti-clockwise.

Before and after peening the holes.
Thiel Spindle Bearing 03.JPG Thiel Spindle Bearing 04.jpg

This is my improvised spanner which started out as just a bent piece of 6mm rod with the ends machined down to 5mm to fit the holes in the retaining ring. Given that the top ring was only hand tight I thought this would be sufficient. It soon became apparent that some reinforcement was needed hence the braces but the arms were still not strong enough and started to bend under load. (They really bent when I did the lolly and threw it on the floor in disgust but let’s never mention that again.) I cut off the arms beyond the bracing and was planning to improvise something stronger but came to the decision that rather than persist and possibly make things worse I would try asking a grown up, hence this post.

Thiel Spindle Bearing 05..jpg

Thiel Spindle Bearing 02.JPG

Looking at a drawing of the head it looks like this ring retains the lower bearing and also acts as a labyrinth seal. Given the presence of a locking screw I am guessing that Locktite or similar is not usually used in this situation. I don’t know if the thread is right or left handed and so have not wanted to monster it in either direction. If anyone out there has worked on something similar and can offer any advice it would be most gratefully received (help me Phil).
Cheers,
Greg.

I would make a guess at a lefthand thread, opposite to the spindle rotation.
The spindle bearings look to be UKF bearings...solid inner ring split outer ring.
Google them they are a rather unique construction and unfortunately do fail.

What size/ centres are your pins? Do you want to borrow a proper pin spanner?
LH does make some sense
On my mill there is a similar arrangement but the ring is locked with a grub screw - has yours got one that has been painted over?

Michael

G’day shedeng, good pickup, the main spindle bearings are indeed UKF type, UK60 up top and UK55 at the bottom.
Manufacturers site is: UKF Angular Contact Ball Bearings
I haven’t looked into a supplier yet but no doubt the price is going to make my bottom hurt.

G’day Michael, the pin centres are between 77 & 78mm or 3.050”, it’s a bit difficult to get an exact measurement with the spindle nose in the way. Thanks for the kind offer to borrow a pin spanner, I might take you up on it yet but my concern would be there is only 6-7mm between the centre of the 5mm pin holes and the side of the spindle nose which doesn’t leave much room.
The quill isn’t painted and there’s only one retaining grub screw which I’ve removed, I guess it’s possible the brass plug might be stuck and still bearing against the thread but I would think this unlikely.

The thought crossed my mind that a left hand thread would work with conventional CW spindle rotation but the spindle also goes the other way so this is not really a hard rule. I tried pushing pretty hard in both directions but there was no movement of the ring before the arms on my flimsy spanner started to flex.
It’s possible that if someone had it apart previously they might have thought Locktite would be a good idea but the top ring had no signs of this so I’m hoping this isn’t the case.
Cheers,
Greg.

Is there perhaps another set screw under the first? A bit like a lock nut.

-russ

G'day Russ,
I did think of that but it appears to be just a brass plug with no slot , hex or other means of removal.
The top ring has a simple brass plug under the set screw so I figure the bottom one will be similar.

I've just been out pondering things and noted that the top ring only has two holes for a pin spanner while the bottom ring has four which makes me think they're expected to transfer higher torque.
I've started work on a more robust pin spanner which will have four pins and will have the ability to be clamped against the face of the ring to prevent it from being forced out while being turned.
Hopefully I'll get it finished tomorrow and will see if it works any better.
Cheers,
Greg.

I'll be defying the public holiday rule, if you wanted to bring it down tomorrow. (Mon) I can cast an eye over it. Call me first.

(Greg & I are about 3 miles apart, when I'm at work.)

A bit of progress this morning, the lower bearing retainer is now loose although I haven’t removed it yet. The head is reassembled hand tight ready to let Phil cast his expert eye over it when he can. Here’s the improvised pin spanner made from a piece of 6mm plate that got the job done, I made it to have four pins but they were a bees dick off and wouldn’t quite fit properly so it was back to two.

Thiel Spindle Bearing 06.jpg

The spanner fits over the spindle nose and flat against the retaining ring. A stud from a hold down kit was clamped in a collet and a calibrated piece of pine used as a spacer with the whole lot clamped down so the spanner was held firmly against the retaining ring.

Thiel Spindle Bearing 07.JPG

I set up a mitre square so I could track if there was any movement then gave the spanner a couple of judicious wacks with a dead blow hammer in the clockwise direction. The clamping system worked well and the spanner was as solid as a rock but there was no movement so I tried a few wacks going anti clockwise and bingo, the ring loosened slightly. Another wack and it turned quite freely, giddy up.

Thanks everyone for your suggestions, I will keep you updated as things progress.
Cheers,
Greg.

If others face this situation, instead of a pin spanner I can recommend turning an appropriate disk (relieve the centre if you need to for clearance) and drill the BCD holes. I normally use silver steel for pins. Braise/TIG/Loctite them in and then similarly fix a hex to the back of the disk. You will then have a hex that is very securely locked to the ring with which to try the usual "persuasion methods". As Greg suggested, the pins need to be accurately located. A bodge is probably to drill slightly oversize holes, locate the whole works on the nut, and then just give the back of the pins a touch with the TIG/MIG. There's enough thermal mass there to not be too concerned about heat unless you get stupid.

I would have expected this to be conventionally threaded, and from what I understand it was? Given it had seen some previous love it's always possible somebody has used Loctite. A little gentle heat rarely goes astray in these situations.

A bit of an update on this one, I called in to see Phil on Wednesday arvo and we stripped the spindle down completely. Sure enough the bottom spindle bearing was the source of the iron filings and was definitely lumpy when we got it out. Phil gave it a good clean in the parts washer, a blow with the air compressor and fifteen minutes in his ultrasonic cleaner and it came up much improved.

Phil suggested Action Bearings in Reservoir (Action Bearings) might be able to help source a replacement so I gave them a call yesterday and spoke to Charlie who was very helpful. Like me he had to google the bearing type having never seen one before, but promised he would do his best to get one for me. I got a call back today to say he could get one special order from Germany, it would take around two weeks and would cost $570.00. It'll be the most expensive single bearing I've ever bought but I do love the Thiel so I gave the go ahead to order one in. A big thumbs up for these guys, no need for a deposit or anything, they'll give me a call when it comes in and just settle everything then, I suspect dropping Phil's name might have helped smooth the way bit.

Here's a couple of photos of the bearing in question, they are certainly different to anything I've seen before. You can see how the outer ring is split to facilitate the assembly of the internal ring of spacer balls. The second shot is the best I could do to show the spacer balls.

Thiel Spindle Bearing 08.JPG Thiel Spindle Bearing 09.JPG

I've nearly finished giving the head a complete clean out, at least one of the oil galleries for the gears was nearly completely blocked with grease and there was a lot inside the head where it doesn't belong. The rest of the bearings appear to be fine so I will stick with just replacing the one for now.

Many thanks to Phil for his assistance and advice and I will post another update with some photos of the reassembly when the bearing arrives.
Cheers,
Greg.

So my mill is back in action and just for posterity I’ll post a bunch of photos and a bit of a description of the rebuild.

First minor issue uncovered during the strip down was that the screw that retains the drive gear on the input shaft had managed to shear itself somehow. I can only guess that at some point it in time the screw came loose and the continual contact with the transfer shaft over time flexed it until it snapped.

Thiel Spindle Bearing 10.JPG

The break was a bit wonkey and below the surface so into the lathe for a quick clean up with a slot drill, centre and through drill for an easy out and jobs done, I love it when things just work.

Thiel Spindle Bearing 11.jpg

The gear retaining washer needed a clean up, it was a bit mangled presumably from when it came loose and made its way past the drive gear on its way to the bottom of the head casting where I found it. Luckily there was no discernible damage caused to any of the gears. I machined the countersink a bit deeper so the replacement screw now sits just below the surface of the washer.

Thiel Spindle Bearing 12.jpg

The transfer shaft had a bit of galling where the above mentioned screw had been rubbing, a quick spin in the lathe with some fine emery cleaned that up, the shaft is made of some very tough material.

Thiel Spindle Bearing 13.jpg

The components that make up the input shaft assembly.

Thiel Spindle Bearing 14.JPG

The reassembled input shaft assembly, I used a bit of locktite on the retaining screw just to make sure it stays put.

Thiel Spindle Bearing 15.jpg

This is the new bearing that the boys at Action Bearings got for me with the original for comparison. I don’t know where they tracked it down from as the box is marked “Made in West Germany” but I’m glad they managed to get one.
It will remain safe in its box for a bit longer though because I’ve reassembled the spindle with the original for now.
Why buy a new bearing if you’re only going to use the old one you might ask?
Well this is the first time I’ve worked with high precision bearings and while the Thiel spindle is pretty foolproof as far as assembly goes, I figured a safe path would be to rebuild the head using the old bearing first. After Phil’s cleaning job it runs pretty smooth and if I do happen to get something wrong it should become apparent without rooting a $600.00 bearing.

Thiel Spindle Bearing 16.jpg

This is the spindle to which the bearing in question is fitted. It locates on the surface to the left and is retained by the threaded ring in the middle. The drive gear mounts in the upper spindle bearing which is fixed in the head cap and is retained by the ring to the right. The spindle shaft is free to slide up and down inside the drive gear as the quill moves in and out.

Thiel Spindle Bearing 17.jpg

Here the lower spindle bearing is installed and the quill housing and retaining ring is shown below it.

Thiel Spindle Bearing 18.jpg

This is a view of the quill before and after inserting the spindle. Getting the spindle installed was a bit fiddly as everything has to be lined up right for the bearing to go in smoothly. Any slight misalignment and everything locks up.

Thiel Spindle Bearing 19.jpg

The quill and spindle assembly.

Thiel Spindle Bearing 20.jpg

The head casting and the head cap with all grease and old oil cleaned out.

Thiel Spindle Bearing 21.jpg

Some more views of the head casting from different angles.


Thiel Spindle Bearing 22.jpg Thiel Spindle Bearing 23.jpg Thiel Spindle Bearing 24.jpg

The transfer shaft installed.

Thiel Spindle Bearing 25.jpg

The head cap in which the upper spindle and transfer shaft bearings are mounted. Strangely the head cap is an aluminium casting with steel sleeves for the bearings.


Thiel Spindle Bearing 26.jpg

View after installing the head cap with the input shaft ready to go in. The input shaft must be installed with the little oil hole towards the top so it lines up with a mating grove in the head casting to allow oil to reach the input shaft bearings. This is probably the one part of the assembly that you could get wrong if not paying attention. To the right is the input shaft installed, the 66 is the last two digits of the machines serial number and many of the parts are so marked.

Thiel Spindle Bearing 27.jpg

This is a photo looking up into the head where the quill goes. You can see the upper spindle bearing and the transfer gear towards the bottom of the left hand photo. The right hand photo shows the spindle drive gear installed. Every gear is marked with the alloy it’s made from (16Mn Cr5) a part number and what I think is a date, some of these are just visible in the photo. The bevel gears have additional markings which I think might relate to inspection, I’ll put some clearer photos of the markings in another post.

Thiel Spindle Bearing 28.jpg

The top of the spindle drive gear protrudes out of the top of the head so the upper retaining ring can be installed as seen to the right.

Thiel Spindle Bearing 29.jpg

This is the shaft which controls the quill movement. I plan to make a new one of these at some point with something a bit more user friendly than the simple square shaft for a handle.

Thiel Spindle Bearing 30.jpg

Some photos of the quill going in, the quill is a very precise fit in the casting and needs to line up with both the bore and a keyway to get it in. This is a bit fiddly when your hands and all the components are covered in oil but in the end was a fairly painless operation. The quill is only retained by the quill control shaft and the clamp ring visible in the lower right photo.

Thiel Spindle Bearing 31.jpg

All back together and on the machine ready to continue with the job I was working on when I first noticed the problem.

Thiel Spindle Bearing 32.jpg

As mentioned all grease has been cleaned out of the head now and after pumping in new oil I noticed a lot more came dripping out past the spindle when I first ran it than did so before. After about five minutes running at various speeds the dripping greatly reduced to the point of nearly nothing and everything seemed to be running smooth and a bit quieter than before.

I had previously contacted UKF who sent me some information on lubrication of their angular contact bearings in general. The bearings can be lubricated with either oil or grease depending on application. Most of the information pertained to circulating oil systems and atomizers. It states “With minimal Oil Lubrication, very small quantities of suitable oil are adequate, but it must be carefully distributed, to ensure that the oil moistens the balls and the grooves” and the figure of 1ml/hour per 25mm of bearing diameter is quoted as a generally recommended figure.

The Thiel manual recommends lubricating the vertical head with 7.5 to 8.5E (ISO68 as best I can tell) oil once a week, so based on this I’m guessing that the design of the labyrinth seal will hold enough oil to provide lubrication and allow any excess to pass through hence the initial leakage. I’ve always given each of the oil points a pump of oil before use so I’ll stick with that for now and see how things go.

I used the mill for a good four hours yesterday and it worked fine with no sign of trouble so I’m a happy camper. I’ll continue to run it with the old bearing for now and just play it by ear. Now that I know what’s required I reckon I can strip the spindle and replace the bearing in around an hour without too much trouble.

Many thanks again to Phil (Machtool) for his invaluable assistance and advice.
Cheers,
Greg.

Glad to see that the mill is up and running, minus the expensive spare part. Probably won't need it now for the next 20 years
Kryn

Originally Posted by kwijibo99

This is the new bearing that the boys at Action Bearings got for me with the original for comparison. I don’t know where they tracked it down from as the box is marked “Made in West Germany"

They have this thing called something like bearingnet. I tried to get on it, but its like $1k a year subscription. They find things I cant, odd ball Nardella & Gamet bearings for Huron's and Colchester's. Hollow roller Gamets.

If they quoted you $570, your getting it at my buy price. I would have expected that bearing to be post $1k. There is a UKF agent here, they have no clue and no stock.

Sub story. Lot of years ago. I gave that Action Bearings a Verbal order for $28,000 worth of bearings in a 2 minutes phone call. I was down at Ford Geelong. Z-Z the company I did my time in. We had this 8 spindle gear box. Op 20 on the lower arm steering, plant 5, BMO. Lube pump had imploded, and force feed shrapnel into the bearings. 16 pair of front and rear bearings needed post haste. RHP stock was only down here due to ANCA. I knew some one Ex Z-Z, and got the bearings released.

They have looked after me ever since.

Greg. We need a dumpling intervention, before you fit that new bearing. Most particularly, the over all thickness of it. Despite the $570 bucks, width of that bearing could be all over the place with in 200 micron.