New Lathe - acceptable run-out?

[matt_southward]

Hi all,

After phil.p introduced me to the top of the very slippery slope that is electrical woodturning - I come from a pole-lathe background - I moved to the dark side and bought myself a lathe and extension bed from Axminster a week and a bit ago, It's a midi 1218VS.

I've already been on to them about excessive vibration, and my conclusion that the spindle isn't running true in the main bearing, which I discovered when turning my first bowl - as when I'd trued the outside of the bowl, I realised that the bowl wasn't round, but very slightly out of round. I then did my best to check the spindle - low tech with the tip of a pencil which on just touching gives intermittent contact (I've just ordered a dial gauge from Axi so that I can get a better reading).

So, the question is - what is an acceptable amount of run-out? Both on a new lathe, and then on a used, worn lathe i.e. at what point do you start to run into trouble with your work? I realise that some run out is acceptable due to engineering tolerance, but I'm pretty sure that mine isn't right!

On another note regarding my lathe, how significant is the flatness of the bed? The reason I ask is that the cast bed on mine is out front to back - that is it's about 0.5mm lower on the front than the back (looks like the casting is twisted too after looking at it with winding sticks).

So all in all it looks like a 'friday afternoon special' but I just wanted some feedback from you guys with more experience as to what I should expect, and what I should be prepared to live with etc I might then sound like I know what I'm talking about when I speak to Axminster next

 

[CHJ]

There should be NO run-out on the spindle beyond the tolerance of decent bearings.

How are you holding the piece, faceplate or chuck? is it either of them not seating true on the spindle.

Has your turning to date just been between centres? there can be subtle differences with bowl turning and associated end grain bounce that if you have basic vibration problems may just be the associated amplification of the two.

Lathe bed out, as you will be aware from pole lathe work of no relevance for spindle turning but if it's enough to throw your tailstock alignment out in relation the headstock spindle alignment in areas you are likely to be drilling in, then that could be a problem.

 

[Blister]

Its a new lathe and should have NO FAULTS

 

[sunnybob]

If its a chuck on a thread, its quite possible for the thread to be minutely off. I used to work in an engineering shop and one of the lathes was used for making template moulds for metal spinning. They had to be PERFECT.
Sometimes when the chuck was swapped on that lathe the thing had a run out on it. i have seen the chuck loosened and retightened with a scrap of paper between the low point and the spindle.
You must check the spindle with a dial gauge, checking both from the side and from head on before calling foul. Holding a pencil just wont do the business.

 

[NazNomad]

A week old? DEMAND a replacement that isn't out-of-true or twisted.

Make sure you don't get one that goes 'thump-thump-thump' when you use it... I'm sure they have one of those in the warehouse now.

 

[selectortone]

Before everyone goes mad blaming Axminster and their crappy lathe, bear in mind that there are many factors that can cause a chuck, and what is mounted in it, to not run true.

I'm a relative turning newbie too (although someone who has worked with wood for much of his life). The first few attempts I had at turning a bowl the thing NEVER ran true after reversing it to do the inside. After some lessons, I discovered that this was down to me... I wasn't cutting the tenon right, I wasn't mounting it in the chuck properly, I was so slow at turning that the blank was moving overnight as the stresses in the wood were relieved, my lathe wasn't bolted down securely enough... yadadadada....

The lathe MIGHT be faulty, but you won't be the first one here who had a "faulty" lathe, returned it, and had the same fault on the replacement.

Just saying....

 

[matt_southward]

Evening chaps - thanks for the feedback so far.

I am perfectly aware that the 'fault' as it were may well lie with this user and be down to poor technique! But I've done my best to try and work out what is going on before I go further. I realise that the tip of a pencil isn't much to go on (hence ordering a dial gauge), but it seems to confirm my suspicion so far. (FYI my 'test' was putting the tool rest up close to the spindle and rested a pencil/dowel on it right up close to pivot inside the spindle with the lathe on low - and I got an intermittent contact).

Anyway, as to what I was doing: spindle turning between centres seemed to be working ok, with a definite vibration at certain speeds - which I initially put down to my bench, or characteristic of the machine/set-up (lathe was levelled). The bowls I have turned where standard flat(ish)blanks mounted on a screw chuck and held in a brand new Axi SK100 chuck (which certainly had no debris on the spindle nose etc to start with). After turning the first and suspecting something was up (me most likely!), I did a few checks on the spindle (as above) and phoned Axi about the noise - vibration and squeaking from the belt. The belt, upon inspection was kinked - so Axi supplied a new one. I can't say I was reassured by their tech saying that he thought the belt might cause the kind of problem I was getting, but went along with it for now. Anyway, the new belt turned up - was straightish (how on earth can they make those plastic belts so cheap and they not snap straight away!? - awful quality) and I gave it a try.

The vibration was still there, and the squeaking - and the eccentric (IMO) spindle. So I gave another bowl a try - mounted the same way. I trued up the outside and shaped it, a final light continuous cut, followed by a light shear cut to finish. Then without taking it out of the chuck (tight on the spindle, tight on the screw chuck) I attempted to draw a line on it in different places around the outside with a pencil on the tool rest, and didn't get anything like a continuous line (about a third around the rim). My conclusion was that there is a definite chance the spindle bearing is out, but also a definite chance it's my technique! :shock: oh, and I also thought I could see ghosting of the edge after I'd done the outside.

I shall have a closer look when I receive the dial gauge and get something like an empirical measurement, but I was interested to know what a typical run-out from this type of machine might be. What is the typical engineered tolerance for the sort of bearings used in these headstocks? I'm not concluding that the machine is faulty just yet, as it could be me of course, but I can't say I'm optimistic so far!

 

[Paul Hannaby]

What doesn't make sense here is that if you mount the bowl on the lathe, then take some cuts to true it, even if the spindle or chuck is running out, the part of the bowl you have just cut will be concentric with the axis of rotation. If your cut was consistent the pencil test will be a complete circle. This is why they always say that the lathe is the only machine that can produce things more accurate than itself.

One way to achieve the eccentric circumference you describe would be to have the chuck running out (possibly caused by either the chuck or spindle) and then rotating the work piece on the chuck after truing it up so you multiply the eccentricities. The only other possible scenario I can think of would be if the bearings were introducing a "wobble" on the spindle but I guess this is unlikely.

 

[matt_southward]

Yes, that's what I thought, and it's been bugging me that I can't work out what's going on. I've not had time this week as work is crazy busy, but I nipped out to the garage last night for some more head scratching.

Apart from potential user incompetence :shock: and assuming the spindle bearing is in tolerance, my next best guess is vibration caused by out of alignment pulleys (they are all tight). I ran the motor last night without the belt on and it ran sweetly with no vibration - belt on, back to squeaking and vibrating. Watching the machine with the pulley housing open at low rpm it looks wobbly (but I could be imagining that!) - but the belts are so crappy you can't rely on a visual check on them in motion. When I get the dial indicator I'll hopefully be able to pin it down - otherwise any other pointers would be gratefully appreciated!

 

[woodpig]

A wobbly pulley could cause all kinds of problems but it should be obvious if it's damaged or badly made.

 

[sploo]

Yes, that's what I thought, and it's been bugging me that I can't work out what's going on. I've not had time this week as work is crazy busy, but I nipped out to the garage last night for some more head scratching.

Apart from potential user incompetence :shock: and assuming the spindle bearing is in tolerance, my next best guess is vibration caused by out of alignment pulleys (they are all tight). I ran the motor last night without the belt on and it ran sweetly with no vibration - belt on, back to squeaking and vibrating. Watching the machine with the pulley housing open at low rpm it looks wobbly (but I could be imagining that!) - but the belts are so crappy you can't rely on a visual check on them in motion. When I get the dial indicator I'll hopefully be able to pin it down - otherwise any other pointers would be gratefully appreciated!

NazNomad's "Thump" comment refers to a 1416VS I had (so a different model).

Are the motor and spindle pulleys in alignment?

When you remove the belt is there any play in the spindle (does it do anything other then just spin)?

Belts generally need to be only slightly tight. Depends on the length, but you should be able to deflect the middle (between the pulleys) with moderate push from a single finger; too tight can cause problems.

 

[matt_southward]

NazNomad's "Thump" comment refers to a 1416VS I had (so a different model).

Are the motor and spindle pulleys in alignment?

When you remove the belt is there any play in the spindle (does it do anything other then just spin)?

Belts generally need to be only slightly tight. Depends on the length, but you should be able to deflect the middle (between the pulleys) with moderate push from a single finger; too tight can cause problems.

I did take a reasonably close look at the spindle for play/noise and couldn't find any either in the spindle or pulleys. Now as to pulley alignment, no I haven't checked that thoroughly yet - I suppose the best way is with a small straight-edge? It's obviously a bit awkward getting into the head stock - is there a particular knack to it?

As regards belt tightness - interestingly the Axminster tech told me to tighten the belt when I complained about the noise it was making. I was a bit perplexed as I didn't think a bearing so affected by the belt would be up to much! Though to be fair to him he did tell me to check the pulleys were all tight too. The first belt they sent me was badly kinked, but I'm now wondering whether the kink was caused by the alignment issues?

I guess I started off with the assumption that it was my fault - being inexperienced with mechanical lathes - and gradually started to realise that it might not be me after all. After my brief look last night, I'm going to take a closer look at the pulley alignment as I think that's where the vibration seems to be coming from.

 

[sploo]

I did take a reasonably close look at the spindle for play/noise and couldn't find any either in the spindle or pulleys. Now as to pulley alignment, no I haven't checked that thoroughly yet - I suppose the best way is with a small straight-edge? It's obviously a bit awkward getting into the head stock - is there a particular knack to it?

As regards belt tightness - interestingly the Axminster tech told me to tighten the belt when I complained about the noise it was making. I was a bit perplexed as I didn't think a bearing so affected by the belt would be up to much! Though to be fair to him he did tell me to check the pulleys were all tight too. The first belt they sent me was badly kinked, but I'm now wondering whether the kink was caused by the alignment issues?

I guess I started off with the assumption that it was my fault - being inexperienced with mechanical lathes - and gradually started to realise that it might not be me after all. After my brief look last night, I'm going to take a closer look at the pulley alignment as I think that's where the vibration seems to be coming from.

Straight edge yes - but it's rarely easy in the confined space.

Overtightening a belt won't do much good - more likely to damage bearings and the belt (and transmit motor vibration to the spindle). Essentially, you don't want it to slip or flap about, but if it's transmitting power it's doing its job.

 

[AndyT]

Matt, when you get your gauge and measure your lathe, you will need something to compare it with.
My lathe is pretty basic. It's a Chinese one, from the 90s, bought from Axminster who described it at the time as having improved bearings compared to similar models.

Intrigued by your question, I got out my dial gauge, put a drive in the headstock and took some measurements.

I pressed the stem of the gauge against the side of the drive and zeroed it.

I then rotated the headstock by hand. As it happened, I had started at one extreme of the runout. The other was at four thou.

So on my example, the runout is plus or minus two thousandths of an inch.

I should say that although it's a basic model, there's nothing wrong with the lathe, and it's been fine for my needs.

I should add that having done this test, I realised that the drive was not inserted quite as tightly as it would have been in use, with the tailstock run up tight. Any way, it could give you a reference point to say that up to 2 thou, measured in this simple way, is perfectly acceptable in practice.

Also, on this model, the belt is slack, with working tension coming just from the weight of the motor, which is on a pivot.

 

[Blister]

Andy

You could be measuring some deflection in the 4 prong drive ?

 

[sploo]

Andy

You could be measuring some deflection in the 4 prong drive ?

Indeed. I'd also worry that even by turning it by hand you'd introduce a fair bit of error (at least, that's my experience with dial gauges).

Still, a few thou sounds more than fine for a woodworking lathe.

 

[AndyT]

Agreed - it's a rough and ready approach to the measurement, but I hope it gives some sort of basis for comparison. If Matt does a similar test and finds say, 20 thou each way, he'll know he's got a lathe that's not even as good as my old cheap one.

 

[CHJ]

Just checked run out spindle on my Wood Lathe which is 20 years old:-

Internal Morse taper close to nose 0.00075" (new unused Blank Taper fitted)
Chuck register 0.0012"
Periphery of 100mm chuck 0.0025" (just as one time seating no retries for best fit)

 

[woodpig]

Still, a few thou sounds more than fine for a woodworking lathe.

Yes, I agree, a couple of thou is nothing to worry about on a wood turning lathe.

 

[Keithie]

I have an opinion here, fwiw. I may not know a heck of a lot about woodturning, but I know some stuff...

1. Axminster have an ebay shop for their 'seconds', returns, ex-demo lathes and other equip
2. They recently sold a return as the customer was moaning that the headstock/tailstock was out of alignment (I was thinking of buying it). Turns out it was less than 0.5mm out (or so they told me) but that this was within spec for a wood lathe.
3. It sold no problem at not hugely far off the new price (not to me)
4. My guess is that if 0.5mm misalignment could be described as a fault, then it was probably in the headstock..but given it was only a small lathe then its probably not a major issue for everyone (I'd be delighted if my work was so consistently good that I'd notice..presumably only in thin walled stuff?)
5. Axminster have a very good reputation and make a lot of good kit...if you're not happy, even if there's really not much wrong with the lathe, have a chat with them. You may find that after a bit of 'umming & arring' they just swap for a new one. If they do & your happy with the new one then tell folk on here. That way if Axminster do right by you, you do right by them.

I wasnt sure about my record dml320 when I first got it, turned out it was me being a twit (no change from normal) ... I can now reverse pieces as much as I like and its all fine....even long hole bore pieces no prob either way round.

good luck