New lathe arrived today : The ongoing saga

[HopperParticipant @hopper]

Brian, I could drop around sometime Thursday or on Friday morning with a dial indicator and have a look at it for you if you want to give me a call.

[Brian JohnParticipant @brianjohn93961]

I tried what John suggested but I could not detect any difference from one end to the other. I also put a 300mm bar in the chuck to see if I could feel any movement in the lathe chuck and I could not.

I called the company today and they suggested that I should be running it on high gear(320-3000) for aluminium….around 1500 RPM or even higher. I was using low gear(160-1500) at about 800 RPM. So I have spent the afternoon raising the workbench to standing height; now I can access the gear box door more easily. It was blocked by the side bench supports before. I changed the V belt to high gear (page 28 of the manual) and I will give it a go tomorrow.

The WD 40 did not seem to help much. I was going to try kerosene but there was none in the cupboard. (I was sure that there was !) I will buy tomorrow.

Can I use light machine oil for turning brass and stainless steel ? I do not want to stink up the living room if I can avoid it. I do not mind the smell of machine oil. Canola oil and other edible oils like lard are likely to go off in this hot climate as well as attract cockroaches and ants.

For the time being (until Hopper has a look at the lathe) I am going to assume that the problem is me and not the machine. Yes, it seemed to be going well for a few days but perhaps this was a fluke.

My diamond file arrived today. Can I give HSS tools a touch up with this or would I be wasting my time ? (No, I do not have a grinder as yet.)

[john carruthersParticipant @johncarruthers46255]

Yes, I use a diamond file to touch up tools, works well on carbide so HSS should be no problem. It's worth making a jig so the faces are flat not dubbed over or rounded. Use plain water for lube.

Edited By john carruthers on 16/09/2015 08:32:29

Edited By john carruthers on 16/09/2015 08:32:52

[Peter HallParticipant @peterhall61789]

This chap lives and works in Cairns. http://www.clickspringprojects.com/ . He admits to picking the brains of other machinists and clockmakers, so he may answer a few of your questions if you ask nicely. I haven't looked closely yet but he seems to have some very helpful stuff on his blog.

Pete

[Anonymous]

Posted by Peter Hall on 16/09/2015 16:12:17:

This chap lives and works in Cairns. http://www.clickspringprojects.com

Good grief, he's good.

Andrew

[Brian JohnParticipant @brianjohn93961]

Thanks for that link ; it is very interesting. The man has a Sherline and a Sieg C4  and he has very high praise for the Sherline. This is an extremely useful website. I am surprised I have not stumbled onto it before !

Edited By Brian John on 16/09/2015 18:26:33

[Peter HallParticipant @peterhall61789]

Posted by Brian John on 16/09/2015 18:17:47:

The man has a Sherline and a Sieg C4

That's why I thought it might be interesting to you. He's producing stunning work on essentially low-end equipment. No Swiss machinery costing tens of thousands. Just looks like a slow, deliberate approach and an understanding of exactly what he is doing. Lovely stuff.

Pete

[Peter HallParticipant @peterhall61789]

Don't get sidetracked by the Sherline. They're nice, but expensive for you and very small. Concentrate on using your existing lathe to produce good results and you can always trade up later. Everything you learn from your current difficulties will be useful later on. Persevere. Don't be tempted to buy another lathe because yours "doesn't work properly". It will be possible to make it work properly, but you badly need some help from someone else who knows what they are doing. Tap up Hopper, or, frankly, anyone else you can find in the area who has some experience. If you reach out locally I'm sure you will find some like-minded souls who will be pleased to help you along. Good luck!

Pete

[Jeff DaymanParticipant @jeffdayman43397]

Brian John – At risk of being called lazy, I will state that I have not read all 15 pages of this thread, but get the gist that the surface finish on the "optimum" lathe is not as good as is desired.

Going back to basics –

1.have you checked that your headstock is not moving relative to the lathe bed during the cut? It should not move at all.

2. have you checked that your spindle is not moving with excessive front/back or up/down play relative to the spindle? if there is much more than 0.03 mm free play, that may explain some of the transient cutting finish issues.

These checks using a dial test indicator and some wiggling of parts relative to each other would be worthwhile to do as they will verify the lathe's basic relationships are OK, If they check OK then there is probably an issue with feeds and speeds, tooling geometry or sharpness, or excessive free play in the cross slide / carriage assy somewhere. As others have said, go through everything methodically and you will track it down eventually.

My lathe is old and worn out in areas but through a series of dirty tricks, guile, and trial and error I have learned to get acceptable work out of it. Fundamentally though and all humour aside it was a well designed and made piece of equipment from the start. Good luck JD

[AjohnwParticipant @ajohnw51620]

There is something decidedly odd going on Jeff. I almost feel like saying stinking fish. Most things have been covered. There is only one other that I can think of. Brians adjustment of the saddle so that it does rock !!! Rather hard to imagine what some on might do to achieve the results he has had.

I can't really imagine how some on can have this much trouble using a lathe as I used one for the first time at the age of 11 at school. Did I receive any instruction – yes a bit, on things like this is how you turn it on. Teach watched from a distance for a while and noticed that I tightened up the belt drive and he loosened it again after class – he was very keen on keeping the bearings in good order – me I wanted to take a bigger cuts. It seems I was the only person that did that. It was the first time I had even seen a belt drive but it was obvious why the chuck stopped turning even though I couldn't see the belt – I had to look under the guards and behind the machine. Perhaps it's my parental black country genomes. No one round here could survive without them so natural selection rules etc.

John

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[Brian JohnParticipant @brianjohn93961]

Hopper will be here this morning with a DTI and somebody competent can finally have a look at it.

Peter : I do intend to get this machine to work. I do not intend to buy a Sherline anytime soon but I have noticed that it is one of the few lathes that everybody is happy with right from the start. Even some of the big name machines can give experienced people problems. The Sherline is small…yes, but highly accurate and with the riser blocks you can do some pretty big work with it.

I have only had this lathe a short time and I have learnt a lot in that period. You can read as many books as you like but there is no substitute for having a lathe in your hands. A lot of things in books did not really make sense until now ; you have to have the ''hands on'' experience to see what the writers are talking about.

Jeff : those things have been checked already and they will be checked again this morning. Also, it would seem to me that the older lathes were often much better quality than some machines being made today.

John : ''adjustment of the saddle so that it does rock''. I really do not understand that ? I have adjusted the saddle and now there is NO movement whereas previously there was a lot of movement/rocking in the saddle.

[Neil WyattModerator @neilwyatt]

> Also, it would seem to me that the older lathes were often much better quality than some machines being made today.

Something of a myth, because people compare apples with oranges.

You can't compare a your lathe with a Super 7 lathe that would cost six or seven times as much second hand, let alone new.

In the past small entry level lathes at price points comparable to yours were poorly finished and considerably less sophisticated.

Neil

[Ian S CParticipant @iansc]

WHEN I first used a lathe, I was at school, the lathes we used were old in 1962 (pre WW1). They were Harrisons, driven from the workshop line shaft, some of us could do some quite good work on them, the rest of the kids could turn out scrap metal, same lathe, same tool.

Ian S C

[Brian JohnParticipant @brianjohn93961]

Hopper has been today and sorted out the problems (thank you Peter). Some problems were due to operator error (I had missed two adjustment screws) and some were due to equipment faults. Hopper will give a more detailed explanation later concerning the results of the DTI.

[HopperParticipant @hopper]

Well, we had a truly enjoyable afternoon at Brian's place, playing with his lovely new lathe. As is usually the case, the big problem was really an accumulation of small variances. Both in equipment and operating procedures, as Brian has said.

The biggest contributor was a revolving tailstock centre that was not staying on centre. In fact, initial DTI reading revealed 0.30mm up and down movement at the large diameter of the centre itself. Hmm. A bit of exploration found a hitherto undiscovered tailstock quill clamping Allen screw on the far side of the tailstock body. Nipped that up and things improved drastically. But still there was 0.20mm up and down movement measurable at the centre.

Turns out (no pun intended but all kudos accepted) the MT1 taper was a gnat's bicycle too small for the hole in the tailstock. So the taper was not seating. Instead the unmachined shoulder at the large end of the taper was hitting the tailstock quill and allowing the whole centre to flop about loose. Solution: chucked up the centre body and machined off the shoulder so the taper could seat properly. The lathe does its first ever piece of useful work and fixes its own problem. For now. DTI is showing just 0.02mm movement at the centre. Quite acceptable and about as good as you are going to get it with ball bearings that always have an internal clearance of maybe that much.

So we whiled away several pleasant hours then with a bit of tutorial on general lathe work, locking the cross slide, and so forth, and testing speeds and feeds on some sample pieces of ally and steel. All were turning quite nicely. Feed rate was measured and confirmed at 0.05mm per mm and giving a nice finish. We found the spindle high range speeds (300 to 3,000 rpm) was a bit hard to finely judge the exact rpm in the lower range. So we changed it to the low range, 150 to 1500 rpm and found much finer control over the rpm. A digital tacho would be real handy.

BUT THEN … we stopped for a cuppa and a chinwag. When we went back to the machine with a view to trying out some of the carbide toolbits etc the bloody thing was turning rough as guts again, chattering and squealing its head off. Great diagonal striations across the surface. Same pieces of material, same toolbits, same speeds and feeds. And nothing we could do seemed to make any difference.

Put the clock on the tailstock centre again, and found 0.20mm movement again. WTH?? This time it seemed the bearings had heated up and got looser. Put the dead centre in, nipped it up just so and all was good again. Problem solved!! Turning beautifully on ally and steel, and taking up to 1mm cuts on either, with both HSS and Carbide tools. Problem Solved!!!

Partly. The other part is that the headstock spindle had some measurable movement at the chuck mounting flange. No endfloat, but about 0.02mm at the flange with some gentle hand pressure on the end of a 100mm long bar grasped in the chuck. Not bad, for a spindle running on ball bearings that by nature have internal clearance. But by pushing with my fingers on the end of the 100mm long bar about as hard as I could, it was easy enough to get a reading of 0.08 or even 0.10mm at the chuck flange.

For us old duffers, that's three to four thou of spindle movement. Certainly more than I would like to see on the larger lathes I am more familiar with. But having no experience on these small lathes, with their small diameter spindles and light-on cast headstock and bed, I am not sure if this sort of movement is normal? IT could not be felt as "slop" but could have been some flexing of the spindle and bed/headstock unit? Perhaps those more experience with mini-lathes can enlighten us on that one. (Neil??)

I have seen on the ARCEurotrade site that with some of the Sieg small lathes, many owners choose to replace the standard ball bearings with angular contact bearings that can then be run with a small pre-load and therefore zero effective clearance. So perhaps the problem is the plain ball bearings? I know from experience that Chinese bearings can sometimes leave much to be desired compared with a good brand name such as SKF etc. Perhaps someone with mini lathe experience can comment on this?

So it seems that for any work more than 25mm from the chuck, the tailstock centre is essential for stability to stop the headstock spindle movement/flex etc getting out of control. So for most work, it is good enough. A fixed steady would be helpful for long jobs that can't take a centre, such as boring a long cylinder etc.

But as it stands, using the dead centre, the lathe performs beautifully for a little unit of its size and type.

The pre-ground HSS toolbits seem to work ok when fresh and sharp. The Hopper-ground toolbit likewise. There was a bit of trouble running in the high speed range and knocking the edges off, but using the low range and careful control of speed cured that. I am not sure the speed increase is linear per graduation on the control knob so care must be exercised (or digital tacho fitted!)

Overall I think Brian is pretty happy with the machine now and was turning away like a champion on the test pieces.

He is going to buy a better quality MT1 revolving centre. The one he has now is a "light duty" job. It does not have the screwed plate on the front of the body that allows large bearings, something like a 6203, to be used. It does not appear to have any bearing retainer visible, so I can only conclude that it is a solid lump with hole up the middle about the same diameter as the OD of the actual centre. IE about 16mm or so. So the bearings must be tiddlers of 16mm OD and perhaps 8 or 10mm ID. Not at all up to the job. The centre was an internet cheapie, not part of the lathe kit itself.

[HopperParticipant @hopper]

PS, (post too long you bloody windbag)

And then we had a lovely time playing with Brian's stable of wonderful little PM Research steam engines and the boilers he has built for them. I have to say, if Brian gets his turning work practiced up as good as his silver soldering skills, we'll be being seeing some top notch model engines coming off the little Optimum in the future.

[Michael GilliganParticipant @michaelgilligan61133]

Excellent News

Well done Hopper & Brian

Thanks for the detailed info.

I'm sure it will be useful to future visitors.

MichaelG.

[HopperParticipant @hopper]

Posted by Neil Wyatt on 17/09/2015 07:57:41:

> Also, it would seem to me that the older lathes were often much better quality than some machines being made today.

Something of a myth, because people compare apples with oranges.

You can't compare a your lathe with a Super 7 lathe that would cost six or seven times as much second hand, let alone new.

In the past small entry level lathes at price points comparable to yours were poorly finished and considerably less sophisticated.

Neil

Yes, it is often forgotten that Myford and Drummond lathes and the like were expensive bits of kit in their day. Very expensive. In 1948 when the ML7 first appeared, it cost about 40 pounds. The Drummond cost a little more. The average weekly wage was about 7 pounds. So a good lathe then was worth about six weeks' wages. Today the average UK weekly wage is over 400 pounds. So six weeks' wages would be over 2,400 pounds. Enough to buy a pretty nice mid-sized lathe I think. Or put another way, enough to buy six mini-lathes.

[HopperParticipant @hopper]

Posted by Michael Gilligan on 17/09/2015 14:48:32:

Excellent News

Well done Hopper & Brian

Thanks for the detailed info.

I'm sure it will be useful to future visitors.

MichaelG.

Thanks. Yes. I guess the "take home" point is: Spend the extra money and buy good quality tooling and accessories for your lathe. (Something I learned myself the hard way.)

Edited By Hopper on 17/09/2015 15:13:53

[JasonBModerator @jasonb]

Well done Hopper, its so hard to sort ouit a problem over the net, nothing to beat an experianced hand.

J

Ps I suppose Brian will be starting a new thread now – how do I make pistons?

[Ketan SwaliParticipant @ketanswali79440]

Well done Hopper,

I am glad you managed to sort things out for Brian. From what I can read, most of the problem came from a poor quantity MT1 revolving centre, some from user inexperiance, and some from machine itself.

Regarding your points about Headstock bearings and mini lathe. I revisited the Optimum manual link which Michael Gilligan provided earlier. **LINK**

Great manual by the way. After looking at point 8.2 and 8.3.1, it states parts located in the headstock. The two spindle bearings are slim section ball bearings 6003-zz – part 17. Provided this is the correct manual, then this machine cannot be really classed as a mini-lathe. The same bearings are used in a C0 Baby lathe. So, it would be wrong to draw a comparison with any mini-lathe. You can compare properties vs a micro or baby lathe, but not a mini-lathe.

6003-zz are classed close to being slim section bearings 17mm bore x 35mm OD x 10mm wide. I would not put too much pre-load on these, as far as possible. Secondly – and this is my opinion only – I would not fit a standard 3-jaw self centering chuck on such a spindle supported by slim section bearings. This load of this type of chuck on such a spindle is too heavy. This is again, my opinion. It is same as asking to put such a chuck on the C0 Baby lathe, which I think would be wrong. The C0 baby lathe of similar headstock specification, closer to Unimat, has a smaller and lighter lever scroll chuck, which is more in proportion in line with the bearings used.

On mini-lathes, the ball bearings are much larger – 6206ZZ – standard – not slim section, size 30mm bore x 62mm bore x 16mm wide. Ballbearings are not designed for accepting pre-load, but you can and do pre-load them to a small extent. They do not suffer from or behave in the same way as observed by Hopper on Brians baby/micro lathe. For general use, on a mini-lathe this is fine. But for improved accuracy and/or larger diameter 100mm chucks, we suggest and propose the change to use of angular contact bearings(ball) or taper roller bearings on such lathes. However, we do not regard this change to be critical.

Coming back to Brians Optimum – micro / baby lathe family machine, after some use of the machine, and after gaining some experience, if he might want to consider changing the ball bearings to angular contact bearings (ball), such as 7003 B which is dimentionally the same as the ball bearing 6003 zz which he has at present. Dont know at present how easy it will be to get with seals (2RS). This is also provided that there is some way to put on the pre-load, which I cant see clearly from the drawing. There probably is a way.

It is probably a good machine for light work. Hope Brian makes some good progress here on.

Good Luck Brian.

[AjohnwParticipant @ajohnw51620]

Ball races can be preloaded but they then run as angular contact – one well regarded small lathe the unimat has done this for donkeys years. Not a problem providing that they are good bearings. Angular contact may offer a bigger contact angle than a deep groove ball bearing has. Some more compact angular contact bearings have rather low contact angles. It's probably possible to compare ball and angular by measuring diameters – the less distance between inner and outer the greater the contact angle.

Boxford have an interesting way of setting preload. Wrap rope/string round a face plate and pull string with a spring balance and note the weight it reads. Some find it works others don't. This seems to be down to bearing wear. They always wear oval eventually which seems to mess the setting up and more preload is needed to prevent spindle deflection. It didn't work for me so I used heating. Bearings heat up in use and as the heat is taken away more easily from the outer than the inner they also tighten. What I did was adjust and run the lathe for around 15mins and then checked the bearing temperature on the rear by sticking my finger in the end of the spindle – lathe off of course. I did this because I happen to know that lathe bearings often run at over 100C so expect to feel some real warmth. I did this at medium speed – around 600rpm on a Boxford and then flat out, 1300rpm as a check. Not much difference. Set like this I can see that the finish with very light cuts improves when the lathe has warmed up but due to that it's also more likely to show very shallow problems that are down to vibrations on the machine.

I can't relate either of these to small ball bearings as the Boxford uses much larger taper rollers but it might give people some idea of how they might set them. The problem with setting preloads on bearings is that if it's too high they wont last long at all. None of these types of lathes even from other manufacturers seem to give any info on setting them. – Not the ones I have seen anyway.

John

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Edited By John W1 on 17/09/2015 20:05:40

[Neil WyattModerator @neilwyatt]

Big sigh of relief. It must be good for Brian to know he wasn't imagining the on-off nature of his problems.

Ketan is as much of an expert on bearings as anyone I know so I can't add anything – except to say that I suspect Nut 33 and pulley 60 in the picture on page 62 of the manual could be adjusted to remove the excessive play. Loosen the grub screw in the pulley before making any adjustment and note I say 'remove the excessive play' not 'add preload'.

Neil

[AjohnwParticipant @ajohnw51620]

I wouldn't even suggest Brian adjusts them.

I suspect I am going to have the problem soon. Manual states check bearing heat every 500 hrs. Adjustment states remove free play still allowing the spindle to turn easily by hand plus an over tightening warning. Pity there isn't any info on the heat aspect. My understanding is that there are 2 methods of specify bearing setting. One is dimensionally – a lathe that doesn't have any adjustment and via torque required to turn. Even too much grease can mess that one up. The wrong grease too.

It also states something which I feel people neglect – as soon as any slides show signs of wear – loosening in other word adjust ASAP. Same for the bearings. It is a fact that these all wear more slowly if the adjustments are kept correct. Nearly every small lathe I come across has the cross slide set too loose. The bearings on my Boxford were way too loose when I bought it. I doubt if they had ever been adjusted from new.

John

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Edited By John W1 on 18/09/2015 00:17:09

[HopperParticipant @hopper]

Thanks for the input, guys. Lots of good info there. Ketan, thanks for the bearing info and the tip about the chuck. Nothing like experience to get to the heart of things. I had not even realized there was such a thing as a micro or baby lathe vs a mini-lathe! Yes those micro bearing dimensions do sound pretty small.One can't expect too much of them.

I did not mess with pre-loading or tightening the bearings at this stage. I figured it best now that the lathe is producing a respectable result to let Brian use it for a while and let everything bed down a bit. There was a fair bit of heat coming from both bearings so I was loathe to tighten them up until they have bedded in some more.

We can have a look at bearing adjustment down the road a bit. And even fitting the 7003 bearings Ketan mentions if Brian so chooses at some point.

Ketan, if fitting new bearings with two rubber seals instead of the zz shields, will the little motor on these micro machines have enough starting torque not to be overstressed by the friction of the seals? I've seen Chinese drill presses before that would barely start after being fitted with rubber sealed bearings in place of shielded. It can't be good for the motor.

 

 

 

 

 

 

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Edited By Hopper on 18/09/2015 01:09:06

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