Making an accurate spindle with an innacurate chuck.

[S. Heslop]

I've spent the last 3 days trying to solve this problem and everything has failed, so i've given up on trying to figure out a solution on my own.

I'm making a 250mm extended spindle that screws onto the end of a tile saw motor. This probably wasn't the best way to go about the problem but i've been trying to build this thing in a way that doesn't depend on a lathe (even if I was using one for convenience), but with the huge spindle wobbling the whole thing vibrates too much.



There's a shoulder on the motor that's accurate enough that i'm trying to register the spindle on to, but I figure my problem is that my 4 jaw chuck is too wobbly. I was reading a 0.10mm wobble over 90mm of the bar.

Here's the offending chuck.



The bar diameter is too large to fit on the smaller 3 jaw that came with the lathe.

So far I've tried shimming the part in the chuck (i don't have any shim material thin enough), grinding the chuck jaws (I did it very carefully and very slowly, marking the jaws with a pen and feeding so fine that i'd only see about 1 spark per pass, which then increased that wobble to 0.12mm wobble over 90mm), machining an aluminium 'collet' in the 4 jaw chuck (which I really thought would work, but the bar wobbled more still).

I have checked with other ground bars so I don't think the bar i'm using is bent.

I'm really stumped so any suggestions would be appreciated.

[Fergus OMore]

Taking the shortage of shims bit, I would suggest that you have a thous or so in the toolmakers traditional tool- cigarette paper. Again, you can use aluminium oven foil or cut up drinks cans. I like the drinks can one

I would, however, not go down the 4 jaw route but traditionally work between centres in spindle making. Basically, this means that you can pull the lot out and measure or whatever and get it all back together accurately and  without too much effort. Others may disagree but you will find that many motor spindles  are 'popped' so that commies etc can be skimmed. You'll obviously need some method of centreing a centre and having a driver and either a catchplate or faceplate. Probably you could 'fiddle' a bit by using a three jaw chuck to hold a bit of bar, centre it  and put a ball bearing in between the female centres.

By the way, I'm assuming that you haven't got a lot of accessories.

Regards

Norman

[S. Heslop]

Taking the shortage of shims bit, I would suggest that you have a thous or so in the toolmakers traditional tool- cigarette paper. Again, you can use aluminium oven foil or cut up drinks cans. I like the drinks can one

I would, however, not go down the 4 jaw route but traditionally work between centres in spindle making. Basically, this means that you can pull the lot out and measure or whatever and get it all back together accurately and  without too much effort. Others may disagree but you will find that many motor spindles  are 'popped' so that commies etc can be skimmed. You'll obviously need some method of centreing a centre and having a driver and either a catchplate or faceplate. Probably you could 'fiddle' a bit by using a three jaw chuck to hold a bit of bar, centre it  and put a ball bearing in between the female centres.

By the way, I'm assuming that you haven't got a lot of accessories.

Regards

Norman

The trouble is is that I need to bore the end of the bar, so that rules centres out. In all honesty i'm not even that convinced my lathe bedways are level. The lathe has been neglected since I bought it, but i've been holding off adjusting it all till I can afford a milling machine.

I am sort of short in terms of accessories. I did think that a steady rest might help keep the bar parallel to the ways but I'm also short in terms of money. I could attempt making one but without a milling machine it'd be a whole project in itself.

I could maybe try cigarette papers but it was such a fiddle trying to fit the pop can shims in that I'd rather avoid that unless I was sure it'd eventually work. They might still be too coarse.

[Stilldrillin]

Steve (?).

You really need a fixed steady, for that job. Though, I'm sure someone else will disagree...... 

David D

P. S.

Amadeal, £19......    http://www.amadeal.co.uk/acatalog/Fixed_Steady__Rest.html

[S. Heslop]

Steve (?).

You really need a fixed steady, for that job. Though, I'm sure someone else will disagree...... 

David D

I'm Simon! I'm just not used to the idea of signing posts, it's really frowned on on some forums. Internet etiquette is a funny thing.

I'm looking at the prices of fixed steadies and at ~£30 I may as well buy one. There have been a few jobs in the past where i've wished I had a steady as well. Now I just need to decide which shop I want to order from.

[S. Heslop]

P. S.

Amadeal, £19......    http://www.amadeal.co.uk/acatalog/Fixed_Steady__Rest.html

Not bad. I was looking at Axminster since Arc euro trade has them out of stock, and they were charging about twice that much with delivery. I'm not sure if it'd fit a Seig C2 though.

[Stilldrillin]

P. S.

Amadeal, £19......    http://www.amadeal.co.uk/acatalog/Fixed_Steady__Rest.html

Not bad. I was looking at Axminster since Arc euro trade has them out of stock, and they were charging about twice that much with delivery. I'm not sure if it'd fit a Seig C2 though.

Give 'em a ring. They're very helpful...... 

David D

[S. Heslop]

P. S.

Amadeal, £19......    http://www.amadeal.co.uk/acatalog/Fixed_Steady__Rest.html

Not bad. I was looking at Axminster since Arc euro trade has them out of stock, and they were charging about twice that much with delivery. I'm not sure if it'd fit a Seig C2 though.

Give 'em a ring. They're very helpful...... 

David D

Thanks for the tip but I went with SPG tools. I sort of wanted to order from them to see if they're any good, since they stock the milling machine I might buy if I ever learn how to save up money.

Thanks for the advise in general! Hopefully this won't take too long to arrive.

[AdeV]

but I figure my problem is that my 4 jaw chuck is too wobbly. I was reading a 0.10mm wobble over 90mm of the bar.

That's a hell of a wobble... have you got a bit of swarf trapped between the lathe spindle & the back of the chuck perhaps?

Was it a brand new chuck? i.e. any chance of returning it as not fit for purpose?

[Fergus OMore]

Checking a lathe for truth moves this topic into another ball park.  I would suggest that you have a look at what people like Gadgetbuilder contributed on small lathes.

I'm twixt and between with a Myford on one side and a little Unimat clone on the other

However, if I was faced the question, I would still avoid a suspect 4 jaw and probably remove the poppet from the tailstock-- and use it as a fixed steady. If it is too small , I would make a fixed steady out of wood.

I'm going off at a bit of a tangent but you might have to do this. The ideal fixed steady( And I can get shot down) is not a steady with three or four silly little brass points. Me, I'd go for a something called a fixed bushing steady- Obviously, it would have spacers or bushes to accommodate other round bar sizes.

I recall an account of a guy who held some 11 feet of round bar in his ML7 and this had a hole drilled in his workshop to steady the final bit. He wrote the book on Screwcutting in the Lathe, if you want the reference.
Probably your lathe is bending under the weight and strains- like his was.

Whatever, I wish you every success

Norman

[Fergus OMore]

It is some time since I accessed Mr Morans's site but he goes into how he made a couple of spindles- using two different techniques. He used ball races but I notice that he was also making something more solid- on the lines of the Cleeve steady which I have mentioned.

N

[The Steamer]

Is the 4 jaw self centering or independent? 

[S. Heslop]

but I figure my problem is that my 4 jaw chuck is too wobbly. I was reading a 0.10mm wobble over 90mm of the bar.

That's a hell of a wobble... have you got a bit of swarf trapped between the lathe spindle & the back of the chuck perhaps?

Was it a brand new chuck? i.e. any chance of returning it as not fit for purpose?

No swarf as far as I can tell. It's been this way for a while.

Come to think of it, one of the first things I made on the lathe was the 4 jaw backplate. I should probably take a closer look at it to see if I made any obvious mistakes like leaving a burr on or if any of the cap head screws are sticking out. But after my attempt at grinding the thing, i've probably already messed the chuck up enough to make that pointless.

Probably your lathe is bending under the weight and strains- like his was.

There's a good chance the bed is twisted. The lathe isn't mounted very solidly for starters. I bought a precision level at a car boot sale so if I ever get around to making a proper stand for the lathe I should hopefully have everything i'd need.

In all honesty I don't use the lathe that much. Not enough to justify spending so much time getting it working perfectly. It's even rarer that I require much accuracy from it.

Is the 4 jaw self centering or independent?

It's independant.

[lordedmond]

bingo
what did you make that back plate of ? 
I will bet its warped/stress relieved itself

pop off the chuck and reface your back plate and mark it some way as to get it back on the same position


I bought some back plate for my myford big bore from the new myford machined them up all good about six months later chuck run out did the face again ( it was out ) they did it again six months on this this they are OK  . They do not age the castings in china or wherever they get them from

Stuart

[S. Heslop]

It's made from 5 inch diameter EN8 steel. It took me two days to saw through it! I didn't imagine such metal would warp.

So I took the chuck off and measured the runout on the backplate and it was about 0.02mm, which was a fair bit. So I refaced it, put the chuck back on, and chucked something in the jaws...

...and now the bar wobbles 0.37mm over 90mm! That might be the result of my stupid grinding attempt. I'd say lesson learned but I think my only option now would be to try grind the jaws again. Or I could try reversing them to see if that improves any.

[PekkaNF]

Looking your first picture...do you have a undercut at the end of step? That shoulder on the motor shaft is crisp and if it leans against burr or such it might prevent even very well fitting collar to sit straight. Micrometer blue would give you an idication where it is bearing.

Just a tought.

My experience says that you really need a some type of fixed steady and to tweak the bar straight/consentric on the four jaw...

PekkaNF

[AdeV]

It's made from 5 inch diameter EN8 steel. It took me two days to saw through it! I didn't imagine such metal would warp.

So I took the chuck off and measured the runout on the backplate and it was about 0.02mm, which was a fair bit. So I refaced it, put the chuck back on, and chucked something in the jaws...

...and now the bar wobbles 0.37mm over 90mm! That might be the result of my stupid grinding attempt. I'd say lesson learned but I think my only option now would be to try grind the jaws again. Or I could try reversing them to see if that improves any.

Can you run a dial gauge against the chuck body to see if that's running true? May as well eliminate the obvious first...

2nd, yes, reverse the jaws & see if that makes a difference. You can always buy new jaws if you've stuffed this set up.

Another thing to check, is there any discernible "wobble" of the jaws when they are not clamped on something?

You should probably check the headstock alignment as well; I believe this can by checked between centres - google "rollie's dad's method" for the easy way to do it.

[S. Heslop]

Looking your first picture...do you have a undercut at the end of step? That shoulder on the motor shaft is crisp and if it leans against burr or such it might prevent even very well fitting collar to sit straight. Micrometer blue would give you an idication where it is bearing.

Just a tought.

My experience says that you really need a some type of fixed steady and to tweak the bar straight/consentric on the four jaw...

PekkaNF

There's a considerable undercut on the motor's spindle, and a slight one on the spindle I made, but I should maybe try the blue idea. I might've mucked up the other shoulders and it's catching somewhere else before those shoulders mate.

I have ordered a steady but it might take a while to arrive.

Can you run a dial gauge against the chuck body to see if that's running true? May as well eliminate the obvious first...

2nd, yes, reverse the jaws & see if that makes a difference. You can always buy new jaws if you've stuffed this set up.

Another thing to check, is there any discernible "wobble" of the jaws when they are not clamped on something?

You should probably check the headstock alignment as well; I believe this can by checked between centres - google "rollie's dad's method" for the easy way to do it.

Just checked the face of the chuck and the wobble is pretty huge. With the jaws in place I could only turn it about 40 degrees but the dial moved about 0.15mm in that small arc. I then checked the backplate face (it overhangs a bit so I can check without removing the chuck) and thats still running perfect. I dont think headstock alignment should be a problem for this though, any misalignment would just lead to a tapered shoulder on the spindle.

The jaws themselves are very loose in the chuck body's tracks.

I guess I just bought a rubbish chuck!

[lordedmond]

Simon

is the chuck sitting correctly on the back plate i.e. is the correct face in contact with the back plate?

have you got the spigot on the backplate to long which will not allow it to sit down correctly on its mounting flange

have you tried to blue the back of the chuck register to check for bumps

Stuart

[S. Heslop]

Simon

is the chuck sitting correctly on the back plate i.e. is the correct face in contact with the back plate?

have you got the spigot on the backplate to long which will not allow it to sit down correctly on its mounting flange

have you tried to blue the back of the chuck register to check for bumps

Stuart

I just checked and yeah it seems to be contacting the back plate fine. With the chuck off the backplate I decided to get out my surface plate(of glass) and i'm getting the same measurement from that.

[lordedmond]

am I correct in thinking what you are saying

with the chuck on its back on the surface plate, the top face where the jaws fit is not parallel to the register face

looks like its duff if it is  but it could be remachined to make it correct  , but now its a whole new ball game

looks like you need someone with a bigger lathe to mount your chuck ( when griped to a known bar ) between centres and true up the rear face to the jaw axis ( but you have ground them but it could work out )

if you go for a new chuck get a bison they are not cheap


Stuart

[Fergus OMore]

Am I correct in now assuming that this is a second hand chuck? And continuing the same theme, am I correct in thinking that the jaws  are loose in their guides?

True, you can tart a worn chuck up-------------------a bit but you'll never achieve any accuracy worth mentioning other than ONE diameter.


I would like to be wrong- but that's show bizz.

Regards

Norman

[S. Heslop]

Am I correct in now assuming that this is a second hand chuck? And continuing the same theme, am I correct in thinking that the jaws  are loose in their guides?

Brand new when I bought it, and yeah the jaws are pretty loose in their guides. There's burrs all over it too. I bought the thing from Chronos at about the same time as getting my lathe, and I remember being a bit surprised at how rough the thing looked considering i'd spent something like £50 on it (I can't remember exactly what I paid). I wouldn't buy from them again.

if you go for a new chuck get a bison they are not cheap

I think if I ever start to get real money (i'm currently living off of a small student loan) i'd just spring for a real lathe second hand.

But at the same time I keep hearing stories of people just flat out throwing perfectly good lathes away. The folk at the school my mom works at did the whole 'ohh if only we knew you were into this stuff a few months ago! We didn't have the space when we moved to the new school so we just threw everything into a skip!', a fella my grandad knew died of cancer and the first thing his Scottish relatives did when they inherited the house was sold all of his carefully collected equipment and instruments for scrap. Real tragic, but it makes for a frustrating situation when it comes to the price of second hand tools.

[Fergus OMore]

2 years ago, I found a almost perfect Myford ML7 with a gearbox and long saddle for £400. It needed a set of chucks but it had been slideways ground and would have served someone for the next 1000 years. No one was interested yet the box alone was worth more than that. I was too old to be interested as I had a lathe bed done- by the same local firm.
A guy got interested in my little Unimat clone which I 'd bought for £250 and it came almost unused with two chucks, faceplate, tool posts etc and a set of ERX 16 collets. He spent a day 'kicking my tyres and my temper and took it home -and brought it back -because he didn't know how to check the speeds. That was his story!

On Monday, I put had a Quorn- for all of a ton(£100) and the guy has showed no further  interest. A few weeks ago, I offered a freebie of information- and a bloke here -couldn't be arsed to collect.

A few weeks ago, I had a call and someone wanted a Myford tray and expected that it would be cleaned, delivered and probably fitted for the Square Root of Bugger All.

So I can understand why 'the skip' is so popular. My kids are not bothered for a few quid from me- and a skip is written into my Last Willie and Testicles.

We live, young Sir , in a situation where  we can all play the same silly, selfish and  indifferent game.

Meantime, I wish you luck

Norman

[S. Heslop]

I can never understand people who take the mick like that. But then i'm the kind of person that can't browse a small shop without feeling like I have to buy something.

Speaking of that Myford though, I've never been too sure where to even look for second hand tools in this area. There's one second hand shop on the way to Consett that very occasionally gets tools in but the guy likes to use ebay as a pricing guide.