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.

[tekfab]

I assume this 10" shaft extension runs in a support bearing of some description ? because if not you really are fighting an uphill battle !

Right, now for the lecture, If you've gone to all the trouble to buy a lathe then at least spend some time installing it and aligning it before trying to use it ! And whats all this crap about waiting until you can afford a milling machine ? There's no point in having a machine that you cant go and switch on and use with some degree of accuracy is there ?
And finally you show up as living in the North East there are some very very experienced machinists on this Forum who are local to you why dont you try PMing them and see if they can come and offer some advice it would be a dam sight easier than the rest of us trying to guess what you've got and what you've done

RANT OVER !

Good Luck !

Mike

[Fergus OMore]

Consett? Ah yes! Was offered a couple of llamas or was it alpacas, the other night from a guy near there.
Not sure, it was one of those nights. About 70 of us, 17 courses and a lot of alcohol in Chinatown.
Best giggle since I was offered a quarter scale Tornado bomber- to stick in my garden.

However, I'd ask Chronos about your duff chuck. As it reads, no one in business today wants people to receive  adverse criticism here or anywhere else.  You know the old adage 'It takes 10 years to create goodwill and 10 minutes to lose it' Inthis climate, it has never been truer.

Let's know how it works out.

Norman

As a sort of reply to Mikes comments. Sadly, I have only had a couple of evenings off since March. Wife had hip op. It went wrong- injections and paralysed. Now it is cataracts for her as well. I can scribble a few words of possibly constructive advice.

N

[AdeV]

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!

Ugh Both sound like they are likely to cause your problem.

eg. when you clamp a bar up, the jaws will try to tilt, nose up or down, that's going to reduce the clamping pressure on your bar & allow it to move around. For the front to be that far out of kilter, it does sound like the back of the chuck is buggered. Between the two, yeah, you're SOL looking for any accuracy.

Since it sounds like you got stiffed by Chronos, I'd give 'em a call - be all nice about it, but basically try to get them to at least take the thing in to have a good look at it. As they are in stiff competiton with RDG, Arc Euro & Gloster (at the very least), getting a bad rep is the last thing they want...

Meanwhile, scour eBay for 2nd hand chucks of about the right size. Go looking for those pokey looking 2nd hand tool shops, it's surprising how much engineering stuff you'll find within. If you're NE based, there's bound to be one somewhere, so many old machine shops & hobbyists closing down. Or just hang around outside Norm's place, sounds like his skip is worth a rummage through...

[S. Heslop]

I assume this 10" shaft extension runs in a support bearing of some description ? because if not you really are fighting an uphill battle !

Right, now for the lecture, If you've gone to all the trouble to buy a lathe then at least spend some time installing it and aligning it before trying to use it ! And whats all this crap about waiting until you can afford a milling machine ? There's no point in having a machine that you cant go and switch on and use with some degree of accuracy is there ?
And finally you show up as living in the North East there are some very very experienced machinists on this Forum who are local to you why dont you try PMing them and see if they can come and offer some advice it would be a dam sight easier than the rest of us trying to guess what you've got and what you've done

RANT OVER !

Good Luck !

Mike

I think you're right about the support bearing. It's something i've been thinking about.



The spindle fits through the hole in that mounting block. This assembly is held vertically, it's part of a spindle sander i'm building, and the motor slides back and forth along the rods constantly. Despite taking care in laying it out, the hole is off by a small amount so i'd have to turn a bushing eccentric. Or make it an undersized top hat and fill the space with epoxy.

As for the lathe, it's one of many things i've needed to 'fix' but I tend to leave problems until I really need them fixed. I haven't required the lathe to be that accurate until now. I've got so many things I could and probably should improve on that i'd never find time for anything else if I really started pursuing them.

Plus those machinists in the north east have their own things to worry about. I don't want to impose on them, but with a thread like this people are free to answer or ignore it as they see fit. (and by the end of the day i'd like to solve these problems as much on my own as possible.)

As a sort of reply to Mikes comments. Sadly, I have only had a couple of evenings off since March. Wife had hip op. It went wrong- injections and paralysed. Now it is cataracts for her as well. I can scribble a few words of possibly constructive advice.

Sorry to hear that about your wife. Old age isn't treating my grandma very well either, but it always seems like it's harder on my grandad than her.

But don't feel you have to come over and fix my problems for me.

Since it sounds like you got stiffed by Chronos, I'd give 'em a call - be all nice about it, but basically try to get them to at least take the thing in to have a good look at it. As they are in stiff competiton with RDG, Arc Euro & Gloster (at the very least), getting a bad rep is the last thing they want...

It was a couple of years ago now and i've never been a big fan of returning items. It's a big hassle, they make you pay the postage, and then there's no guarentee the replacement will be any better.

I wish I knew of some second hand tool shops. You never find anything in the yellow pages, or their website, so the only way to find out is by word of mouth or just stumbling on them.

[awemawson]

I wouldn't write off Chronos on a single issue. I've had very good service from them recently - admittedly only on small stuff but the service has been very good and amazingly prompt.

I still wonder if your chuck is actually sitting flat on your backplate as that's the most likely place for errors. As I understand it you've clocked the face of the backplate - can you clock the rear of the chuck body ? It seems very unlikely that the back and front of the chuck body would not be parallel as I'm sure they are machined at the same mounting in manufacture.

Andrew

[Joules]

If you have a short length of silver steel or other ground stock.  Mount it in the three jaw chuck, clock the run out and mark it on the shaft.  Now clamp the four jaw chuck onto the shaft and clock the body run out, then the rear (that should have been set the body so it has the same runout as the shaft, set true to it)  This will give you a rough estimate of it being parallel, as the run out should be constant from the three jaw chuck.  Is the three jaw chuck also running out much ?

I hand scrap machined!!! faces to get them as accuratly as I can measure.  Had to do this with a cheap ER collet holder that fitted on the lathe spindle and had horrendous runout.

Just make sure the bar you use is stiff so it doesn't flex under load. 

[S. Heslop]

I wouldn't write off Chronos on a single issue. I've had very good service from them recently - admittedly only on small stuff but the service has been very good and amazingly prompt.

To be fair I did get a box of cheap drill bits and a box of taps from them on the same order, both of which are serving me well.

I've also removed the chuck from the back plate and placed it on a piece of plate glass to check the error with the indicator, and got a similarly large reading. I also took care to clean the bottom and make sure no swarf got under it. I also checked the float glass before doing so and it was as flat as I could measure.

It does surprise me that it'd be so far off kilter. Can cast iron shrink that much as it settles?

[lordedmond]

 Have you blued the mounting face of that chuck to your surface plate?
is it flat?

Stuart

[awemawson]

If you are measuring the front and rear faces as significantly none parallel then even after this period of times I'd get in touch and open negotiations as that situation would suggest that the chuck is not fit for purpose. If you explain that you've only just got round to mounting it then you never know they may take pity on you .....

Andrew

[Fergus OMore]

Simon,
            Whilst Stuart is right in seeking important answers, I think that a further lecture is called for.

The first is 'cast iron' and by the very nature of the substance, both it and rolled steel can be very unstable.
If you cut into either, the stresses will start to release. Correctly, cast iron should be rough cut to almost size and put out to weather in the factory yard. This what happened only a few miles from you when the 'Tyne' had factories. Again, when steel was red hot going through the rolling mills and came out, it had received built in stresses to be released later. Bright steel is worst whilst black steel is less unstable.

Steel will do a lot of funnier things than that- but enough for the day.

The next bit of the lecture is Pythagoras and the Euclidian propositions of straight lines which your lathe should adopt. Again, I question whether yours runs parallel to cut correctly. Others have expressed similar points- but much the same really.

The final point is whether your lathe is sufficiently 'man' to support a 5" disc and to machine it- by hand.

This all suggests that you have a lot of testing and alignment  before you commit tools and so forth to a replacement chuck.

I can only apologise but I feel that you should begin to grasp these concepts.

Again, my best regards towards your future success

Norman

[Fergus OMore]

I was wandering about my hard drive and found that I have still got my copy of 'Spindles' in the Nexus Workshop series. I'd made a Quorn and a Kennet and so on and have a couple of lathe spindles made by a Mr G.Potts when he lived over in the Lake District. His other spindle was sold by Woking Models which is now Hemingwaykits. This brings me to cast iron and its behaviour. Woking when it was in North Queensferry sold plans and kits for Edgar Westbury's milling machine. I had all the bits except the head unit- the rest had been cast at Gateshead Tech where I later did my City and Guilds on retirement. Anyway, I bored the casting on a lot bigger lathe than my Pools there. All went well until I had split it so that it would clamp on the round column. So I split it- and it wouldn't go on. So I had to scrape it round- again.

My later escapade was the George Thomas Universal Pillar Tool. Like most of us, I started on George's words and music in the forerunner to Workshop Techniques called 'The Universal Pillar Tool'. His mark 1 arms did exactly the same and GHT designed a Mark2 set which were not split and did not distort.
So we come to none more advanced that Prof D H Chaddock and the Quorn. My first set of castings 'nipped' but I made cottars for the second set-which I have today.

So you have chapter and verse now!

N

[The Steamer]

If your struggling to find good toll shops I suggest a trip down to Sheffield! there is quite literally hundreds of tool shops selling anything you can imagine! some have everything behind the counter so you have to ask for what you are looking for, others are just massive rooms FULL of every kind of tool you can imagine! I have literally spent hours sifting through chucks ect!

[DavidA]

Just wondering,  Have you gone right back to basics ?  is there any run-out on your lathe mandrel nose.

Does the backplate fit comfortably on the mandrel egister ?

Dave.

[S. Heslop]

If you are measuring the front and rear faces as significantly none parallel then even after this period of times I'd get in touch and open negotiations as that situation would suggest that the chuck is not fit for purpose. If you explain that you've only just got round to mounting it then you never know they may take pity on you .....

I keep making excuses but I really just don't want to deal with the hassle. I'm a little busy at the moment and it'd probably cost me half the price of the chuck just to ship it back to them. But I do appreciate the suggestions though.

The first is 'cast iron' and by the very nature of the substance, both it and rolled steel can be very unstable.
If you cut into either, the stresses will start to release. Correctly, cast iron should be rough cut to almost size and put out to weather in the factory yard. This what happened only a few miles from you when the 'Tyne' had factories. Again, when steel was red hot going through the rolling mills and came out, it had received built in stresses to be released later. Bright steel is worst whilst black steel is less unstable.

There's a place at the bottom of the Team Valley trading estate with big stacks of what look (to me) like unmachined cast iron pipe fittings. I wonder if they're being left to season.

Still though, I'm aware that this stuff shifts a bit as it settles but i've never heard any real numbers to put it into perspective. I didn't imagine that cast iron could settle enough to make a 0.4mm difference on a large lump.

If your struggling to find good toll shops I suggest a trip down to Sheffield! there is quite literally hundreds of tool shops selling anything you can imagine! some have everything behind the counter so you have to ask for what you are looking for, others are just massive rooms FULL of every kind of tool you can imagine! I have literally spent hours sifting through chucks ect!

I think my dad sometimes heads down that way for work. Maybe I could hitch a lift down some morning and take the bus about. Got any addresses for places worth going to?

[Fergus OMore]

I've been retired( from TVTE) longer than  I have ever worked  so I haven't a hint about what there is, However, I 'm sufficiently with it ( Quality control-wise) to say 20thous in what? Without going into the realms of engineering, you could have attempted to cut the chuck blank almost to size- and then heated it up to red hot- and let it stew until most of the stresses were relieved. Then you do your finish to size thing.
However, I recall you making hats out of tin or something and stretching and shrinking with heat and cold is part and parcel of sheet metal work. For all practical purposes, it is the same thing.

As a simple analogy , a central heating radiator or boiler will rattle and bang with expansions and contractions- after being in use for perhaps 20 years. A bit of railway line will alter in length with heat. If you are getting into fine measurement of precision tooling, you measure at a given temperature and that goes for viscosities as well. If you have a car you have a windscreen with tempered glass on both sides and normalised glass in the middle. If you damage a tiny bit of the outside, the inbuilt stresses will smash the screen.

However, I still think that you might have a lathe that is trying to cope with poor alignment and or a chuck too heavy for the design. With a model makers lathe, you can throw it out of alignment by simply leaning on the tailstock.
I'd better apologise but these are cold truths and perhaps are unwelcome.

[S. Heslop]

I went and stole back a gift i'd made for my grandparents.



I made it to test out the 4 jaw chuck when it was new. Checking it with the indicator, it's off by a fair bit as well. I remember taking care to ensure it was properly bedded against the chuck body when I was making it. (I'll make a new stand for it before I give it back. The last one went missing)

I also found that the mounting face of the chuck rocks quite a bit, so that's maybe where the innacuracy is from. The surface of the back looks (to me) like it was flycut, with radial machining marks. Maybe I could try the gripping it on a bar thing, but as Norman has suggested my lathe might not be up to the task, even supporting with the tailstock.

Or I could maybe have a go at adjusting it parallel with shims between it and the backing plate.

I'm still waiting for that steady rest to arrive before I make a move though.

[lordedmond]

Simon

this may help



Stuart

[S. Heslop]

Simon,
            We've reached the stage of 'workarounds' rather correct machining. So please don't get at me -anyone- I'm trying to help!

I appreciate the help and I don't mean to sound ungrateful, but I don't want you thinking i'm stone ignorant either.

I'm aware of what the 'correct' methods are, and have done plenty of reading on the subject (with access to a university libary). But with the budget, time, and equipment I have available I have to find compromises and alternative ways to solve problems. Plus by the end of the day that's what I really get out of this hobby. It's like a puzzle. It'd be unsatisfying having all the ideal equipment and following the instructions in a book.

I am aware that my lathe isn't very rigid, and have done tests in the past, but it doesn't account for all the error in the chuck and it can be worked around. I've also done tests available to me on the chuck, its backplate, and the lathe register (feeler gauges, felt tip pen as machinist's blue, dial indicator, surface plate, etc) to pinpoint the problem (that being that the chuck is all warped and none of the faces are parallel or even flat).

Sorry to be blunt but I just want this to be clear.

this may help

If i'm understanding this right, then I don't think it applies to my chuck. The inner face is a rough machining with 4 holes bored in that parts of the mechanism are pressed into. Thanks though.

[lordedmond]

Ok Simon

that was from my Myford book

the Chronos chuck clearly do not follow the norm

IMHO
you have two choices find someone with a larger lathe clamp the chuck on the car and spin it up between centres and face the rear to the jaws and you will be sorted
or get a new chuck

All my working life I have worked to this principle if its K for not working I cannot make it worse so any repair is liable to improve things

I hope you sort it out with the minimum of fuss

Stuart

PS why don't you PM  double boost  (John ) he is in your neck of the woods to see if he can help sort out the chuck

[PekkaNF]

hmmm....

If we are now on workaround route....and the chuck is expendable?

Because now it is concluded that front, rear and jaws are not to be trusted, only way up is to true everything on jaw ways.

Do you have a some parallels or ground key stock? You could rest the chuck on your surface plate on the jaw ways on the parallels and clock the rear mounting face of the chuck.

Can you mount the chuck on the lathe face plate on parallels touch the jaw ways?

I don't think you can true this four jaw chuck clapped on the arbour, because I don't think you can trust jaws being true to jaw ways.

What do you think?

Pekka

[lordedmond]

Pekka

the jaws are the only thing that the work touches ( unless you knock it back to the body ) so that has to be the datum to machine any fix from ( at this stage not when it was manufactured ) so mounting it on a bar with the jaws is the only way to ensure that any machining will be true to the jaws

If Simon was near to me I would have it fixed in 10 mins ( it would be Ok but with those loose jaws it is never going to be perfect ) but it would be a lot better than it is now


Stuart

[PekkaNF]

...
the jaws are the only thing that the work touches ( unless you knock it back to the body ) so that has to be the datum to machine any fix from ( at this stage not when it was manufactured ) so mounting it on a bar with the jaws is the only way to ensure that any machining will be true to the jaws
....

Stuart

I agree on your logic. That is the standard way of making four jaw chuck workable, but I'm not sure if it enough on this particular case.

Here the jaws are "trued" to wobbly chuck (see opening post). Therefore jaws are not true to jaw ways. I know that this is not normally big issue, but this might be one wonky chuck. Therefore I would first true back of chuck register to jaw ways and then true jaws to chuck body and chuck body front as well. It would make using it so much easier or write it off completely, but this is not a heirloom chuck. Or am I missing here something?

Pekka

[awemawson]

As Simon has ground the jaws, unless Chronos will replace the chuck I think the best course of action is first and foremost install new jaws. Then using those grip a large bar that is centred at each end with the jaws, and run it on centres allowing you to face the  rear to truth relative to the jaws, which is all that is important. This can be done on another lathe. Then re-fit the back plate having trued it on the target lathe.

(If you've taken too much off the back !plate for a good register fit, convert it 'Griptru' style !)

Andrew

[S. Heslop]

or write it off completely, but this is not a heirloom chuck.

I think this would be the way to go with how loose the jaws fit in the tracks. I'll probably be able to find a use for this one for workholding in stuff like welding, or whatever comes up. I've found 4 jaws can get a real good grip on square and round objects without marking them, so it'll be good as a vise for hand tapping the ends of bars as well.

[lordedmond]

Simon

I do think that is the correct thing to do repurpose it for other uses so it is not a complete write off of your cash

keep your eye open for something like a TOS

good luck

Stuart

[kayz1]

 What is the Ali block with the holes in it called please? a mates Dad has a set on a shelf at home, 4 inches down to 1/2 inch in 1/2" drops, all in a row...
Ta!  Lyn.

[S. Heslop]

What is the Ali block with the holes in it called please? a mates Dad has a set on a shelf at home, 4 inches down to 1/2 inch in 1/2" drops, all in a row...
Ta!  Lyn.

They're called turner's cubes, and that's a pretty impressive amount of steps. I remember it being pretty tedious work making one with just 3 holes to bore, carefully counting graduations on the handwheels...

[S. Heslop]

Just to conclude the story. The steady rest eventually arrived after a week and a bit and works great (but if I ever make one of my own, i'd definitely give it 4 fingers so it's less of a fiddle to adjust), but even after that there was still about 0.60mm wobble on the end of the shaft. This was caused by the motor's own spindle that I couldn't grind better than 0.01mm using my plywood setup and dremel knockoff.

So I just scraped the shoulder of the spindle till I got 0.20mm wobble, which reduced vibrations to an amount I could live with.

With that the spindle sander is now working. I just need to pretty it up and figure out the dust extraction because whoa nelly.

Thanks for all your help!