Twin Engineering’s heavy mill/drill quill removal

[Martin of WickParticipant @martinofwick]

Is there anyone on the forum with lived experience of Twin Engineering’s Twin Mill (mill/drill) ‘heavy’?

Having just acquired one, running the spindle  for more than a few minutes at 1000 rpm causes the spindle nose and bottom of the quill to overheat significantly within 4 to 5 minute (as in ‘Ow xxxx that’s xxxxxxx hot!’).

I was wondering if anyone with that type mill could advise whether it is possible to detach the quick action drill assembly and drop the quill/spindle assembly out from the head, or is it likely to need the complete head removed?

I’m hoping the bearings just need the old grease removing, cleaning and re-lubricating. Replacement only if evident signs of wear. Either way, the only way to get to the bearings for inspection is by taking the quill out somehow.

ps. lathes.co does not have much useful info on this mill.

[Peter Cook 6Participant @petercook6]

No experience but there are a series of You Tube video’s by someone called Guernsey Submarine which purport to show head removal and bearing change on one.

[old martParticipant @oldmart]

Having had a look at what there is in lathes UK, I would raise the quill to max height and look to see if there is anything like a nut or circlip at the top of the spindle. If there is nothing to stop the spindle passing through the pulley set, then things should be simple. Take out the drawbar.

Remove the rear quill locking bolt both sides first and then unscrew the hex bolt/bearing from the lever which moves the quill. Have a block of wood ready under the end of the spindle to stop it dropping onto the bed. All that should be holding the quill should be the depth stop adjusters which need to be unscrewed upwards bit by bit until they are removed.

Hopefully the quill should come out. You might have to drop the knee for enough clearance. Also, you might have to tilt the whole head if the quill proves too long to remove vertically.

Keep us informed of your progress and see if others agree with my proceedure. Good luck.

 

[bernard towersParticipant @bernardtowers37738]

I would generally suspect that hot means tight

[Martin of WickParticipant @martinofwick]

Thanks for the replies. Apologies for slight pause while I moved house. It was both painful and terrifying to watch a bunch of general movers shift the mill.  I have no idea what it weighs but guess around 200 Kg, enough to ruin some-ones day if they are underneath it.

Actually, it was seeing the submariners video that prompted me to ask for more information. To my mind he seemed to make a bit of a production of the quill removal, only to end up just tapping it out of the head in the end! Was looking for a possible confirmation that it could be a relatively straight forward job. For an allegedly ubiquitous mill, there is very little info available.

I agree with Old Mart since there is no obvious retaining mechanism on the quill there may be no need to take the head off (head can be rotated 90 degrees about the vertical if the table is in the way). Once the ‘scotch yoke’ drill actuator and return spring guide / clamp plate are detached from the quill body, I believe the quill will either drop out or can be gently tapped out.  After that, the bearing preload nut is removed and the spindle can be pressed out in the usual way.

I will update when I have investigated more. First thing to find will be my imperial allen keys somewhere in a huge pile of boxes!

Interestingly,  price range for 32206A taper bearings is from £8 to £280. Even the same make and spec bearing can have a price range of over £50! I will settle on some mid price made in Europe/USA, SKF or Timkens at between £15 to 25.

 

[PeteParticipant @pete41194]

I’m not saying it’s your bearing over heating problem, only that it’s another possibility. Depending on the intended design, too much grease can also cause over heating. Some grease lubricated bearings can have very specific brands and consistency of the grease being used as well as the exact amount of CC’s used to repack the bearings. Fancy and expensive German made Kluber grease is one of the better known brands used world wide. Sometimes too much grease is as bad as too little.

The extra heat is caused by not enough available air space inside the bearing, the grease churning and constant re-shearing action. I think I’d want to somehow come up with a user and lubrication manual for your mill, that of course might be very tough to find. Going by the two Guernsey Sub videos, there also seems to probably be a third bearing the spindle pulley might be rotating on? If so I’d also be checking that. But because the videos were so poorly done and without a third part I could find, it’s hard to be sure of how the whole spindle is driven.

[James FranklandParticipant @jamesfrankland41848]

Hi All.

I am the submariner with the Twin Mill in the video.  Interesting to see someone else with one and the same problem.  It was a while ago i did the repair and i must admit i cant remember too much about it.  But one thing i will say is that replacing the bearings did NOT make much difference with the overheating.  It still does it even with the new bearings.

I will try and answer a couple of points.

>he seemed to make a bit of a production of the quill removal, only to end up just tapping it out of the head in the >end!

Indeed.  I had no manual and no instructions.  Just figured it out as I went along.  It could well be possible to do it without taking the head off, but I remember that bit was easy, you just need to tram it all in again after.  I will have to re-watch the video to see what I did.

>probably be a third bearing the spindle pulley might be rotating on? If so I’d also be checking that. But because the >videos were so poorly done

There is not a 3rd bearing.  I would have changed it if there was.  Sorry if the videos are “so poorly done”.  I was concentrating more on trying to fix the mill, with the camera just floating about in the background.  Plus im not a professional film maker.

Anyway, let me re-watch the videos to jog my memory and ill get back to you in the next day or so.  It would be really interesting to try and find the source of the overheating.  In fact, I might do another video and get the laser thermometer on the machine to see how quick it heats up and to what temp.  I do think its a “bit” better after the bearing change, but not much.  Still seems to overheat.

Kind Regards
James

 

 

 

 

 

 

[Clive FosterParticipant @clivefoster55965]

Overheating in that sort of application can be due to insufficient clearance in the bearing. Whether, as previously mentioned, due to too much grease or excessive interference fit.

But excessive interference fit seems unlikely as the bearings tap out cold.

I wonder if the spindle bearings are actually supposed to be greased at all. Many mill spindles use a simple total loss system with a low rate drip feed of an oil heavy enough to hang around for a days work after filling an oil cup first thing in the morning. Seemed to work well enough for Mr Bridgeport.

An oil lubricated bearing runs cooler than greased one.

But this does pre-suppose there is some means for regular oiling. The Twin appears to be a simply engineered and robust machine. It wouldn’t be unreasonable to find that the (long lost) instruction sheet advised “poke an oil can in here and pump once every morning”. Conceptually crude but economical and undoubtably effective alternative to ball oilers or oil cups.

Clive

[Martin of WickParticipant @martinofwick]

Thanks for your updates and apologies to James for my ‘helpful’ observations! Those that are safely ensconced in their armchairs watching the struggles of others often lose sight of the fact that pioneers have to resolve their problems on the fly.

Interesting to learn that the replacement bearing is still heating up. My observations on my mill are that it is just the the lower bearing that gets hot, the upper one has no temperature change.

For speeds below 1300 RPM, the lower bearing becomes warm but acceptable, at 1300 it starts to get hot, but seems to stabilise, at 2000 and 3000 RPM the heat build up is very fast and to a level that I would be concerned about heat shrinking the spindle onto any taper in use! A major design flaw of this mill is the lack of any means of ejecting a taper (MT2) other than hammering the bejabers out of it (which can hardly benefit the bearings).

My previous WM16 would run for long periods at 2400 RPM without any heat build up. So I would have thought that as the TwinMill was designed for speeds up to 3000 RPM, there should be no problem.

Type of lubrication may be an issue as Clive suggests. The top bearing is visible and easily lubricated with a drop of oil, you would struggle to apply grease anywhere, so oil would be the obvious go to and it looks well oiled! Lubrication of the lower bearing is via a grease nipple on the side of the quill. And as we all know, grease nipples seem to attract grease in quantity (because some is good, therefore more must be better). This which will drop on top of the bottom bearing, no doubt building up in sedimentary layers as the years go by burying the poor bearing completely.

Unfortunately, it is going to be a few weeks before I get the new workshop together, but when I do, I will update with further investigations. May well try Clives advice to remove and clean bearing, give a minimal smear of grease, replace and then try a squirt of EP90 to top bearing and via grease nipple to bottom bearing periodically, as required.

I notice that the lower bearing does appear to have an oil seal on the bottom, which may be a clue?

 

 

[DiogenesParticipant @diogenes]

Sealed bearings can get hot at those speeds with iffy lubrication, aren’t shields usually recommended instead?

Someone here ?Old Mart? might have had some similar issue once? Memory is a bit treacherous..

Also try a suitably heavy hydraulic oil instead, ep oil stinks/is startlingly unpleasant and if it starts to leak and get flung out it’s a miserable experience..

[Martin of WickParticipant @martinofwick]

The seal is more like a rotary shaft oil seal, but I can’t really get a good view of it peering at it through a 4m gap. I suppose it is possible that someone could have substituted an incorrect bearing in the past.

Hadn’t considered the stink of EP, thanks for the reminder!

[Clive FosterParticipant @clivefoster55965]

Martin

Grease nipples aren’t necessarily for grease!

I see regular comments and warnings on Practical Machinist forums concerning machines gummed up with grease pumped by the unlettered through grease nipples that the maker actually provided for heavy oil.

Clive

[Martin of WickParticipant @martinofwick]

I can update, unable to bear the torment of not knowing any longer I found some suitable looking tools and just went for it.

In fact it is a surprisingly simple process to remove the quill from the Twinmill and it does, quite literally, drop out of the head once the the rapid feed arm and spring return plate are released. I will post pictures and full description later tonight.

As I tilted the quill upside down to look at the spindle nose I was astonished, in many ways, to find I had tipped about 10cc of grimy looking oil out of the quill onto my foot! The oil wasn’t particularly thick about the same as you put in old cars, it was rather dark and turbid but no evidence of metal flakes. No grease in sight, whoever owned it previously was clearly using oil as maintenance. Judging by the amount, the lower bearing would have been submerged in medium oil.  Perhaps too much oil is as bad as too much grease?

Getting the spindle out of the quill required the press, but was straight forward. The bearings were clean, bottom bearing was only oiled and only a little residual grease on the top cone. Both looked undamaged, no sign of brinelling, deformed cages or untoward wear. There is a bit of polish on some rollers to about the same degree on both bearings. The shells looked perfect to my eye. There was no sense of any roughness when manually turning the spindle in the quill. Even with the oil removed, the bearings feel smooth when fully seated in their shells and rotated by hand. The shells look properly seated, the cones were not loose on the spindle and the spindle is perfectly straight. The spindle oil seal was in good condition.

I have no idea how to assess what is unacceptable wear on cup and cone style taper roller bearings, but they look OK to me. The bearings are SKF 32206A, not particularly expensive but don’t want to spend £40 unnecessarily (particularly as James reports that replacing his bearings has not solved the heating issue). Also, it will be a bit of a task to extract the bearing shells. So for the time being I shall put a thin smear of grease on both bearings restore everything to original condition and hope for the best.

It’s a mystery.

 

 

 

 

 

 

[James FranklandParticipant @jamesfrankland41848]

Hi Martin\All.

Good to hear you took it all apart.  Will be interesting to see how you get on with the thin smear of grease.

I tried mine today and did an update video.  I’m just updating it now and will post shortly.

I had overheating issues….It seems to be bearable at 600 – 1000ish.  After that it gets hot.

Regards
James

[James FranklandParticipant @jamesfrankland41848]

Hi All.

I did a new video.  Im just really discussing the issue and take some temperature readings.  I should really have done all the readings on the spindle itself, rather than the body.  But I did do some on the spindle eventually.

[Martin of WickParticipant @martinofwick]

Thanks James, set out below are steps to remove quill.

 

 

 

 

First remove the quill rapid feed lever by undoing the two large nuts, then loosen off the quill clamp nut at bottom right of head giving a slight tap to ensure split collets are not stuck with congealed grease etc.

By the way, if you feel compelled to oil or otherways lubricate the bearings, use the grease nipple for the lower set and pull down the quill rapid lever and this will expose the top of the upper bearing for you to point the oil can at. The grub above the slot I suspect has something to do with the spindle pulley bearing assembly – a battle for another day.

 

 

Next slacken clamping allen bolt at rear of quill clamp return collar,  seen here on the black plate directly below the left side of the quill clamp lock nut.

 

 

 

 

Then, with your 3 hands, simultaneously slide a screwdriver into the slot in quill clamp return collar to loosen its grip on the quill while pulling down on the quill clamp collar and pushing up on the spindle so the collar can be pulled clear of the spindle and rotated forward out of the way. At this point, the quill and spindle will drop like a bunker buster and hit the piece of wood that that you thoughtfully placed on the table before you started. If you happen to have a fourth hand, you may able to catch it, but it is heavy and oily!

Picture shows the position of quill clamp plate after quill has dropped out (and been recovered).

 

 

 

The quill and spindle, freely dribbling oil everywhere, showing bearing pre load collar, need to unscrew grub and unscrew  collar using C spanner.

 

 

Extracting the spindle and bearing cones using press (Hangs his head in shame at the dodgy set up but it did the job).

 

The spindle and bearing cones, oil seal and quill body.

Note no grease, just oil.

 

 

 

 

 

Lower and upper bearing  cups. They are perfectly smooth despite the appearance of marks, no ridges or scoring evident just burnish from some use.

 

 

 

 

 

Lower and upper bearing cone with oil wiped off. Looking pretty good to me, just some slight burnish.

 

If both ends of the quill had been getting hot, I would consider too high a pre load, but only the lower end gets hot, specifically the spindle nose and the heat build up is very rapid at 2000 RPM and above. This and the fact that the heat dissipates very rapidly may point to another hypothesis. Someone might suggest it too, far-fetched though it may be…

 

 

 

[Martin of WickParticipant @martinofwick]

Thanks for the Vid update James, comments are:

The motor on high speed does sound alarming, how old is the belt, is it slipping at all or is the motor loosing torque? If you have a clamp on ammeter does the current go sky high as it slows down indicating binding somewhere? Try a more flexible segmented belt perhaps. The motor looks lke a bog basic capacitor start with centrifugal switch cut out. As it starts ok we assume the capacitor is OK but you may want to check connections or that there isn’t a run capacitor as well in the ‘hump’ (unlikely). If the centrifugal switch has failed leaving the capacitor in circuit, I would have thought the start capacitor or start winding would have failed long ago.

Its a bitch that they only put a half horse on these mills as they are well capable of handling more power, but I guess most of them were sent to schools and half was good enough for the spotty oiks to use.

You are right, The quill return spring is at the front of the head, the small grub at the bottom locks the lower spring retaining collar in place. I suspect the spring has become a little tired with age, if you could find something similar then maybe replace it. It is an issue on my mill too but it doesn’t stop me using the rapid for drilling – you just have to ‘help’ it a little on the return!

I don’t seem to have any trouble with my split collar quill clamp, maybe need a good clean and oiling, possibly check the bolt isn’t bent causing the collars to bind slightly.

I have exactly the same heating issue, tolerable up to middle pulley or 1300 RPM. Very rapid at 200 and 3000. An issue for me because I like to use high speeds with carbide cutters. Haven’t used 3000  for a trial as concerned about the heat build up.

After you replaced the bearings, did you replace the shaft oil seal on the bottom of Quill? Only asking as there is a nagging concern that the seal friction may be contributing if not possibly causing the problem.

I did ask AI to calculate the loss of a 30mm oil seal and it came up with friction dissipation of between 50 to 70 Watts! Not inconsiderable, but I have no way to check how it came up with that result. But that rate of heating is not inconsistent with your observations.

As it is so easy to get the quill out I shall reassemble without the seal in place and report back. If the heating is much reduced with no seal then possibly try a costly PTFE seal. For use some sort of seal needs to be in place to prevent swarf entering the bearing.

 

[DiogenesParticipant @diogenes]

Before it goes back together you could make some enquiries to see whether there are any lower-friction seals on the market – technology has moved greatly..  ..’old’ seals also lose suppleness over time..

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Martin, regarding your motor and the way it performs when in top speed, I’m wondering if a single phase motor has been fitted to a three phase machine, as it is acting in a very similar way to my Boxford lathe when I try it in top speed, which has a one horse single phase motor in place of the original three phase one.

Regards Nick.

[Martin of WickParticipant @martinofwick]

Mill quill now re-assembled, bearings greased relatively lightly in the best vintage Castrol LM, all rollers coated but but void space not completely packed. In any case, with this type of cup and cone arrangement over packing  probably wouldn’t matter much as excess will just get squeezed out top and bottom of the bearing.

Bearings pressed into place with the last mm left for the pre-load nut. Tightened down until all play removed but smooth rotation to the spindle maintained. Timkens suggest you crimp ’em down till they squeal and cant move, then back off a quarter turn – macho stuff from the good old days eh! but not for me.

The shaft oil seal WAS NOT replaced in order to test the effect of omission on spindle running temperature.

Just to recap, before all this rigmarole, at middle speed or 1300 RPM, the spindle nose would become too hot to hold after 5 to 6 minutes, but at least seemed to stabilise at this high-ish temperature. At 2000 and 3000 RPM within a couple of minutes the spindle nose became alarmingly hot as in capable of giving a nasty burn.

Testing without the seal gave the following results:

All 3 speeds up to and including middle speed, ie 300 600 1300 RPM, minimal temperature change after running for 6 to 7 minutes and stable.  At 2000 RPM, very slight warming of both bearings, but temperature stabilises below blood heat.

At 3000 RPM there is a temperature build up over 5 minutes to what I would guess to be about 45C ie, at the level of a hot bath. The  temperature seems to stabilise at at that level beyond 5 minutes and both bearings are equally affected.  This seems quite acceptable for 3000 RPM.

So there it is –  the main culprit all along was the shaft oil seal, which at 3000 RPM was busy converting about 15 to 18% of the motor output into heat for the spindle, if the generative AI analysis is correct.

The cheapest, allegedly low friction PTFE shaft seals of the correct size I have seen are available from about 12 pounds. What I cant determine from the manufacturers gaudy patter is whether they are truly low friction, or actually just high temperature capable.

Note for James the submariner, I have the identical motor to yours and while running at high speeds for an extended period today it was clear that one or both motor bearings are on their way out. (it is usually the one that bears the pulley).  This might be a contributory issue with your motor, if you are lubricating the motor bearings, try oil through the grease nipple rather than grease.

Nick, It is James’ motor that is apparently losing power. I agree that a 370W 3 phase motor would be superior in performance  to the equivalent single phase and going from 3ph to single ph can be underwhelming. I get the impression that Twin were more focused on domestic/educational customers and so generally fitted motors to suit. It is for sure the OEMs motor that has been fitted to both machines.

 

 

 

 

[David George 1Participant @davidgeorge1]

I have had a similar problem with bottom seals causing overheating on a spindle but on a larger mill. It took a me a while to sort it out and eaven with a low friction seal it would return and I kept a spare seal ready to replace as nesesary.

David

[old martParticipant @oldmart]

Those bearings look like that with a good clean and light lubrication with lithium based high melting point grease (from a car parts shop) they should last another 50 years. There was mention of a problem I had with a seal overheating, it was with the Tom senior mill that I converted from MT2 to R8. I bought an oil seal, double lipped with a garter spring on the oil side and even though it ran on an exact size and fine ground surface just above the bottom of the spindle, everything got very hot. I tried everything to get zero endfloat  and minimum preload including removing the quill/spindle assy and setting it on vee blocks with DTI’s to no avail. Then I noticed that the top bearing was not getting hot at all, and the seal became the prime suspect. Removing the garter spring had very little affect, and I ended up by cutting the main seal right off and only having the tiny lip pointing downwards. There is no danger of the grease leaking out and the lip keeps swarf from getting in the bottom bearing. I have a spare modified seal in a bag in the workshop with a note for future users regarding its use.

[Neil LickfoldParticipant @neillickfold44316]

I have come across bearings that ran hot. I initially thought set too tight etc etc. Turned out , it was the rubber seal was creating all the heat. Changed to a different seal, and the over heating went away. The seal was changed to a Viton one, the one I had was nitrile rubber I think.   The other one I came across recently was a router bearing that was replaced with the same looking rubber sealed bearing. It too was over heating. So got another bearing but with the steel side shields. That ran normal temperature and not that hot you could not touch the router collet.

OldMart, I did not try your fix of relieving one of the lips on the seal, but did try removing the spring and that had no effect.

[old martParticipant @oldmart]

If you measure the seal housing diameter and the end of the spindle, it might be possible to get a seal designed to fit a spindle 1mm larger. That would reduce the rubbing friction. The Taiwanese round column mill that sits next to the Tom Senior at the museum has no seal, but a screw in baffle which fits close enough to the spindle diameter to exclude swarf with pretty well zero friction. Backing off the preload nut by about 1-2mm on its diameter would reduce the 45C if you intend to use max speed often.

The ammount of oil that you spilled would mean that the bottom bearing was flooded and that would cause some churning and excess heat. When taper roller bearings are greased, when they run the grease gets pushed out from the parts in contact and all lubrication subsequently is from a tiny ammount of oil that separates from the grease. That size taper roller would be fully lubricated by no more than two drops of oil, and the grease provides enough for years of use. The Tom Senior ended up with about 3ml of grease in each bearing.

[Martin of WickParticipant @martinofwick]

It was a learning experience to me that such a small contact was absorbing so much power. The previous owner must have also  been having problems, as when I took the seal out there was no spring to be seen. As everybody has found spring removal makes practically difference to the friction! The bloody things should come with a health warning!

The mill spindle only needs a dust seal really, not a strangulating oil seal! If I could get hold of some appropriate bits of teflon I’m sure I could make a minimal contacting 3 or 4 leaf labyrinth seal to fit the space as swarf deflector.

Meantime, I will apply Old Marts brilliant solution, get a viton seal cut off the spring seal part, just leaving the wiper which will have minimal contact and exert no pressure against the spindle.

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