Spindle/bearings fit query for X2 type mill

[John MC]

On John MC Said:

.   I think the idea that “rubber” oil seals can cause an overload of the electrics is a red herring.

 

It can and does happen. I’ve seen it more than once.

 

 

[Michael GilliganParticipant @michaelgilligan61133]

Here’s a very sensible comparison between rubber seals and metal shields

Shielded vs. Sealed Bearings: Differences, Types, and How to Choose

MichaelG.

[Graham MeekParticipant @grahammeek88282]

A few posts ago the talk was about the play in the Needle Roller bearing used on the Emco and the temperature variation of Oil Films when compared to Taper Roller bearings.

When faced with the actual tolerances, (micrometre’s, or millionths of a metre), used to select the Spindle for the FB2 Quill assembly. We get a diversionary tactic onto the Geometric Tolerancing on the run-out of the spindle.

Clearly the exceptionally close examination of the Drawing did not reveal the “MK 2″ taper just above the Quill Centre-line. That is how the taper is designated on the Continent along with the angle.

Just remember the quoted run-out Tolerance is a maximum run-out, and that it equates to the Morse Taper (MK 2), being 0,005 mm, (0.0002”) off centre. On the machines I have had the Dial indicator, (0.002 mm / div clock) did not even flutter.

Anyway, we were, I thought talking about Hobby machines at one time. Clearly I have missed the post where the Topic was moved on to encompass Societe Genevoise Jig borers??

(I would have thought that the more bearings there are, the less play there can be, simples.)

Regards

Gray,

 

 

 

 

[Howard LewisParticipant @howardlewis46836]

Graham is right. For nearly all of us, our machines are either fairly lightweight hobby machines or old machines showing signs of wear, not Calibration Room equipment. You are not going to be able measure any departure from stated size for gauge blocks (Unless something has gone SERIOUSLY wrong).

In neither case are you going to have micron capability. If you aspire to that; budget for at least £30K or more, not £700!

Nor are you going to make spares for the fuel injection equipment on your car. For that you need, at most, 1  or 2 micron capability, and lapped fits, most probably in an environment that is closely controlled for temperature and humidity.

Sensibly, you should be thinking in terms of 12.5 microns maximum as the limit to which you can work, without a lot of scrap going in the bin.

I shudder when I read posts, effectively saying”I have just bought my first lathe, and my first project will be a pacific locomotive” Disillusionment looms on the horizon.

A skilled operator can produce good work on an old, worn machine, A total amateur can produce scrap on the best machine available.

Learn the trade first, and be aware of the limitations of the machines, and oneself.

Sorry to be brutal, but someone has to say “Get Real”!

[howardbParticipant @howardb]

“Nor are you going to make spares for the fuel injection equipment on your car. For that you need, at most, 1  or 2 micron capability, and lapped fits, most probably in an environment that is closely controlled for temperature and humidity”

You would be horrified at the prevalence of badly worn, mechanical single element injection pumps still operating, starting and running in old marine diesel engines, having been run on a mixture of domestic heating oil and sea water.

I have personally stripped and rebuilt Bosch single element diesel injection pumps in workshop conditions, and in one instance, on board a boat.

If you work clean, clean hands, clean tools etc with plenty of diesel fuel to flush your work clean it’s ok.

It’s not something that I did voluntarily, only by necessity, if you were up a gumtree and it needed doing to support the brand, you did it.

 

 

[John MCParticipant @johnmc39344]

Michael G.  That information doesn’t say a lot. Sealed bearings will, of course, have more friction, but how much more?  This information, for me, is elusive.    I wonder if its because the friction is insignificant?  Plenty of information on speed though, a significant reduction needed,.

What if there is a separate oil seal, I’d wager there will be more friction from that than the seal built in to a bearing.

Are the motors a control gear fitted to these machines that feeble they have problems with the friction generated by a seal?

As for “diversions”, why publish a picture of the somewhat poorly designed Emco quill assembly.  Were we expected to look at it and not comment?

This thread started out with the OP wanting to improve his machine, what followed was some helpful info.  I suggested the possibility of going a step further with, probably very little, extra work.  Then the “why bother” comments started.  No good reason to go the final (small) step given.

The way this thread has gone is unfortunate.  The purpose of a forum is to, well, google it.  I’m worried that threads like this discourage users.  A load of self appointed experts (I include myself in that description so as not to cause upset), spouting forth can be quite off putting to those less sure of themselves.

I wish the OP well, I hope his work is successful and please let us know how it goes.

 

 

[John MC]

On John MC Said:

Michael G.  That information doesn’t say a lot. […]

 

 

No of course it doesn’t say a lot, John …but clearly endorses the [intuitively-evident] general principles.

MichaelG.

[JasonBModerator @jasonb]

Are the motors a control gear fitted to these machines that feeble they have problems with the friction generated by a seal?

We have seen it mentioned by the likes of Ketan and JS that too much friction due to preload can on some versions with less overload protection cause problems. Ketan has also posted about being wary of fitting big chucks to the mini-lathes as again the start up loads are increased. Overload protection does vary between makes and even paint colours on what look to be the same machines.

I learnt the first time I used my Warco on large diameter work I found out when it would stall, I now keep within those limits. Similar on the Sieg mills though they don’t stall they just trip the overload, which is preferable to a stall.

So certainly a possible weakness, may not go bang on the first press of the button but if you were doing something that required a lot of stop start work then parts could heat up overtime an dpossibly fail.

I feel a forum should allow all members to give their opinions. I particularly tend to take on board posts by those that have been there and done it and note their findings particularly if they are about similar sized machines as what works (or does not) on them may not be the case when applied to large industrial ones and vice versa.

As for the practicallities of going with wider taper roller bearings I’m not sure if the lengths of the other components could accomodate an aditional 6mm or so of length (2x bearing thickness increase + 2 x sealing plates/covers) you may end up with no exposed thread for the lock nut(s).  Though it is possible to get the same 16mm width which would just need the addition of covers/seals but at £250 a pair probably not something many would consider a good way to spend their money particularly of the gains are marginal. Lets face it the column/head is likely to deflect more than the spindle.

But the OP now knows what to watch out for when doing his bearing change and if that does not give a marked improvement he could always try TRB or go back to original spec possibly just with a better make bearing.

 

[IdlerParticipant @idle1]

My lived experience with rubber sealed bearings is they have enough friction to prevent an older British-made 6″ bench grinder from starting up when the original steel shielded bearings  were replaced with rubber sealed jobs. It would just sit there and buzz until you gave the grinding wheel a nudge to start it. A less robustly built motor could have easily suffered damage.

I had the same experience on a large, heavy Chinese drill press.16mm chuck and I believe IIRC a 3/4hp motor. All the original steel shielded bearings were replaced with rubber sealed jobs. It too would not start from standstill,just sitting there buzzing until you gave the chuck a spin by hand to get it started. Again, a less robust motor or electronic controller would likely fail under such conditions.

At the time,  I looked into it and learned this is the reason manufacturers of electric motors and machine tools use steel shielded bearings and not the more swarf resistant rubber sealed ones. It is common knowledge in the industry.

My original point in mentioning rubber seals was to confirm that starting torque is so low on many machine tool motors that it takes very little friction to stall them at start up. So the problem with excess taper roller preload doing similar and damaging delicate motors and boards seems very plausible.

And back to the OP’s post, my lived experience has also been that bearing brand can be critical. I now only use quality brands such as SKF from a reputable supplier. No-name or cheap Chinese bearings simply are not as good in too many instances. Good bearings  are not expensive and you don’t have to do the job a second time.

 

 

[John MC]

On John MC Said:

[…]

The purpose of a forum is to, well, google it.

 

[…]

 

I’m still struggling  with that assertion of yours, John ^^^

 

My understanding was that a forum was a place where individuals contributed their opinions/experience/questions/rhetoric/whatever … for the greater enlightenment of the group.

MichaelG.

[Graham MeekParticipant @grahammeek88282]

The drawing was published due to the dis-belief on “Selective Assembly”. The comments concerning the “Run-out” were a distraction to move away from the fact that there was very little play in the assembly.

As regards the design being rubbish, that is only one persons opinion. If you feel that strongly I suggest you write to Emco and tell them where they are going wrong.

Given the size and diversification of this company. I would not want to make myself look like a fool by such an action.

This may come as a shock but the FB2 is a sought after machine. My last machine sold for more than double what I paid for it. In fact even disposing of this machine through a dealer I got the same price as I paid for it.

When a person comments from a position of having done that, points out the pitfalls, and has got the T-shirt, I tend to listen. Also if I can see from published data that something proposed offers no significant advantage, then I have a right to comment about it. It may go against the grain but other forum members have a right to know, and understand why the suggestion is no better.

Regards

Gray,

 

 

 

[Michael Gilligan]

On Michael Gilligan Said:

On John MC Said:

[…]

The purpose of a forum is to, well, google it.

 

[…]

 

I’m still struggling  with that assertion of yours, John ^^^

 

My understanding was that a forum was a place where individuals contributed their opinions/experience/questions/rhetoric/whatever … for the greater enlightenment of the group.

MichaelG.

Michael, I wrote “google it” to save me the bother!  Not intended to be an assertion.

[Michael GilliganParticipant @michaelgilligan61133]

🙂

[Graham Meek]

On Graham Meek Said:

The drawing was published due to the dis-belief on “Selective Assembly”. The comments concerning the “Run-out” were a distraction to move away from the fact that there was very little play in the assembly.

As regards the design being rubbish, that is only one persons opinion. If you feel that strongly I suggest you write to Emco and tell them where they are going wrong.

Given the size and diversification of this company. I would not want to make myself look like a fool by such an action.

This may come as a shock but the FB2 is a sought after machine. My last machine sold for more than double what I paid for it. In fact even disposing of this machine through a dealer I got the same price as I paid for it.

When a person comments from a position of having done that, points out the pitfalls, and has got the T-shirt, I tend to listen. Also if I can see from published data that something proposed offers no significant advantage, then I have a right to comment about it. It may go against the grain but other forum members have a right to know, and understand why the suggestion is no better.

Regards

Gray,

 

 

 

Well, that’s me put in my place!  How dare I question Emco’s (or whatever they are called at the moment), design.

I was hoping that this thread may have resulted in an interesting discussion, probably best continued as private messaging so as not to bore the thread participants to tears.  I’ve done this before and it has been so very useful.

Instead, its getting unnecessarily personnel.  So I am taking my leave from this particular thread.

If anyone comes up with any good information on the friction in sealed bearings, start a new thread, I’ll be interested to see it.

[fingerscrossedParticipant @fingerscrossed]

Thanks all, OP here again! It does tickle me how threads develop a life of their own (and even have children, it would seem!).

Anyway, an update on progress. The new bearings went in the freezer (-18C apparently) for 24hrs, and the housing went on a radiator to warm up. The bearings pulled in easily, with only a minimum amount of persuasion required. Taking on board Neil Wyatt’s comment that his bearings maybe didn’t seat down fully initially (he used angle iron) I used a steel 60mm disc, with a 30mm (ish) nylon disc stuck on with double sided tape to keep everything aligned. Worked a treat.

The spindle also went in the freezer, and was easy to get through the bearings.

The metal spacer went on (mental note – a nasty fit, to be sorted). On my (later) mill this tube has small protrusions for speed monitoring (I’m not sure if these are magnets or merely reflective). Pulley, then the top ring nut.

With gentle and slow adjustment of the nut I could feel the free spin of the spindle reduce slightly – then I realised I had the nut upside down! Doh…

Then with the nut on the right way (and the mill re-assembled) I ran out of thread on top ring nut. This due I think to the ‘depressing nature’ (ha ha) of the angular contact bearings. There is simply more movement than in the original bearings.

I could make an additional simple washer type spacer but I was always going to make new pulleys for poly-v belts, so maybe I’ll plough on with that. And when I disassemble the spindle, I’ll face the ends of the steel spacer. I’m not convinced that anything is particularly accurate!

So, ongoing. BTW the bearings I’m using are SKF 7206 BE-2RZP – low friction seals. I only want to do the job once, and they should give years of good service.

[Neil WyattModerator @neilwyatt]

First point – the factory fitted deep groove bearings are probably more than adequate, at least for the vast majority of owners.

User experiences have shown that angular contact are just as good in practice as rollers for mini lathes that have the same spindle geometry.

For a mill, the higher speeds used make roller bearings more likely to skid, especially when fitted by those unfamiliar with fitting them who tend to get the preload wrong and use far too much grease.

The effort required to adjust taper rollers correctly is more than for angular contact, where tighten up until there’s no shake, run and then check and adjust if necessary is pretty much sufficient. With rollers you need to run up to working temperature for a while and then check – as it’s possible to over load them far more easily.

As for any changes to spindle diameters … the spindle and housing come finished to fit deep groove bearings with exactly the same dimensional specifications as the other bearings, there should be absolutely no reason to work on the spindle unless its burred, has picked up or some other damage.

It’s easy to over-think this. Changing X2 bearings to angular contact is simple a case of remove the existing ones and fit new ones ‘reassembly is the reverse of dis-assembly’.

Neil

[fingerscrossedParticipant @fingerscrossed]

Thanks Neil. I hesitate to say ‘it’s all your fault’ but I doubt if I would have undertaken the endeavour if it wasn’t for finding your excellent write-up. Many thanks again.

I certainly am guilty of over-thinking things (most of the time!) but also subscribe to the ‘fail to prepare, prepare to fail’ school of thought.

The spindle on my machine was hard to turn by hand. As I understand it these generic machines use the same main castings but the quality of finishing and of the components used varies between different brands.

I do enjoy the technical discussions, although they can make me ‘glaze over’ after a while!

 

[Dave HalfordParticipant @davehalford22513]

Did we not have a thread a while ago about the heating affects of the various types bearing seals?

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