Making an accurate spindle with an innacurate chuck.

[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