3jaw chuck alignment problem

[Anatol]

We can only do so much. The rest is really up to you.

Norman

thanks Norman, I know. This community is very knowledgable and generous.
I have Schlesinger
I was jut confused about your reference to 'mikes'

 

[Anatol]

if this is a new error I can't see it being a bent spindle without some major event occurring. My money is still on the chuck/backplate/spindle interfaces as the problem.

No major event, I'm with you on the diagnosis, that's where I'm going next.
I'm not near the lathe for a week or so, currently my shop is 50 miles from my house, that's living in LA!

"You mentioned you have ordered a ground bar, hopefully it has an MT taper you can fit directly to your spindle."

sadly no, its just bar. Its a big spindle, manual says #5 morse taper. That would be a big bar! I guess I could get a morse taper reducer, MT5-MT4 for about $35 on amazon...

 

[Anatol]

I am curious if this lathe was purchased used.
Is there a possibility that your lathe was dropped during transport?

Your only solution may be to shim the head stock to get it close enough.
.

It was bought used but from a local hobbyist, never dropped afaik.
But one can never be sure which is why I'm trying to be very methodical and measure and level everything in a logical order.
"I'm sure that we would all like to see this issue resolved"
thanks for your kind thoughts, I'm working on it

 

[goldstar31]

thanks Norman, I know. This community is very knowledgable and generous.
I have Schlesinger
I was jut confused about your reference to 'mikes'

For mike read micrometer

 

[Anatol]

The 2 important surfaces that the camlock system registers to a corresponding mounted accessory on are the tapered cone (end of red arrow) and the rear face (end of green arrow). The nose front (orange arrow) doesn't contribute anything. Notice this back plate adapter is just a hole, it is not in contact with the lathe spindle. So when back plate & spindle are mounted together, cones coincide with one another and the faces are maybe 0.001" apart constant offset. Tightening the cams then bring the faces together. Ideally in a nice fitting arrangement the back plate has just a teeny bit of 'stick' &then pops off. Its a delicate fit.

So as pointed out ^above^ it matters not where you mount the DTI when checking the lathe as long as it is fixed. You are rotating the spindle & looking for deviation. For example if the spindle cone is not circular the DTI will wander in & out showing this deviation. Same thing with the nose flange face.

Again, thankyou for such a helpful and knowledgeable description, and the always helpful pics.
So, if I understand correctly, the sides of the 'hole' in the backplate (red arrow in second pic) are conical. I had not noted this. I now understand the cone sections function like a slice of morse taper. Tightening the camlocks brings the faces together, but the cones are doing the centering/alignment. Makes brilliant sense. Thanks again.

 

[Anatol]

For mike read micrometer

I know. What I was confuse about was how to use a mike in this particular test process. I did not see reference to using a mike in Schlesinger. He always shows DTIs. Are you suggesting using an inside mike for greater accuracy?

 

[goldstar31]

I know. What I was confuse about was how to use a mike in this particular test process. I did not see reference to using a mike in Schlesinger. He always shows DTIs. Are you suggesting using an inside mike for greater accuracy?

Instead of asking all the time Schlesinger has such pretty pictures showing how to set up tests. Somewhat wryly, he's enough to get your job done-- once as he rightly says - Level your machine FIRST.

'Nuff said?

N

 

[Anatol]

'Nuff said?

N

until I have something to report. Hopefully good news.

 

[petertha]

Its a big spindle, manual says #5 morse taper. That would be a big bar! I guess I could get a morse taper reducer, MT5-MT4 for about $35 on amazon...

MT5 spindle is quite common for lathes like this. Same as my 14x40. You should get a reducer if one didn't come with your lathe, it gives you tooling options. This is what I was referring to when I said get a straight test bar with MT3 end. So in the head stock you insert the MT5/MT3 reducer sleeve, then the MT3 end of the test bar. Now you are accurately concentric & you can test spindle without any chucks or back plates involved. Likely you also have MT3 tailstock so the same test bar can be used there.

Is your test bar that you have coming accurately center drilled? That also adds additional functionality. Mind you you need a headstock center. So either you have an MT5 shank center (I'm guessing probably not likely) or you would be using an MT3 center in conjuction with aforementioned adapter sleeve.

 

[cds4byu]

It seems to me that the first step is to establish the device that is causing the runout.

Put the bar in the chuck. Use your dial indicator away from the chuck jaws (out along the bed where you have the larger runout). Spin the bar and observe the runout. Now mark the bar (using a sharpie) where the dial indicator is reading the maximum value. You can tell which is the maximum value by lifting the indicator probe away from the bar and observing the direction of the needle.

Now remove the bar from the chuck and rotate it 180 degrees so the mark you just made is on the opposite side from the dial indicator contact. Check for runout again, and see where the maximum value on the indicator is. If the maximum value is where the bar is marked, the runout is due to the bar not being true. If the maximum value is opposite the mark, the runout is due to something in the chuck/mounting system.

If the runout is in the chuck/mounting system, clean the mark off the bar, and check for runout. This time, when you get the maximum reading on the indicator, mark the chuck and the D1-4 camlock ring to indicate the high side. Now remove the chuck and rotate it relative to the spindle nose, then remount it. Mount the bar back in the chuck, and do the test with the indicator. If the maximum reading is at the same location relative to the chuck, it's most likely a problem with the chuck and/or the chuck mounting plate. If the maximum reading stays with the D1-4 ring, it's a probem with the spindle nose and/or the camlock system.

Since you've seen in on multiple chucks, I'm pretty sure it's something wrong with the spindle nose and/or the camlock system. But in just a few minutes you should be able to confirm this 100%.

Carl

 

[Anatol]

It seems to me that the first step is to establish the device that is causing the runout.

Put the bar in the chuck. Use your dial indicator away from the chuck jaws (out along the bed where you have the larger runout). Spin the bar and observe the runout. Now mark the bar (using a sharpie) where the dial indicator is reading the maximum value. You can tell which is the maximum value by lifting the indicator probe away from the bar and observing the direction of the needle.

Now remove the bar from the chuck and rotate it 180 degrees so the mark you just made is on the opposite side from the dial indicator contact. Check for runout again, and see where the maximum value on the indicator is. If the maximum value is where the bar is marked, the runout is due to the bar not being true. If the maximum value is opposite the mark, the runout is due to something in the chuck/mounting system.

If the runout is in the chuck/mounting system, clean the mark off the bar, and check for runout. This time, when you get the maximum reading on the indicator, mark the chuck and the D1-4 camlock ring to indicate the high side. Now remove the chuck and rotate it relative to the spindle nose, then remount it. Mount the bar back in the chuck, and do the test with the indicator. If the maximum reading is at the same location relative to the chuck, it's most likely a problem with the chuck and/or the chuck mounting plate. If the maximum reading stays with the D1-4 ring, it's a probem with the spindle nose and/or the camlock system.

Since you've seen in on multiple chucks, I'm pretty sure it's something wrong with the spindle nose and/or the camlock system. But in just a few minutes you should be able to confirm this 100%.

Carl

thanks Carl,
Advice understood. I've done all of what you suggest, but not quite as methodically. I'm away form the lathe but will get back to this and follow your advice ...on April fools day!

 

[Anatol]

Is your test bar that you have coming accurately center drilled? That also adds additional functionality. Mind you you need a headstock center. So either you have an MT5 shank center (I'm guessing probably not likely) or you would be using an MT3 center in conjuction with aforementioned adapter sleeve.

Just a raw bar. I can probably get it center drilled though, at a nearby precision shop.
Headstock center...same as a tailstock center right? Fixed or live ? - I've got both. But will need the adapter... Hang on, this is instead of a MT on the bar for the headstock end? Thanks.

 

[goldstar31]

I don't think that you appreciate just how precise test equipment is required and 'clocking or miking' or whatever you call it demands simple but precise measuring equipment. Somehow, I think that recommendations for cheaper and less accurate materials would have been suggested if they compared favourably

 

[Anatol]

"I don't think that you appreciate just how precise test equipment is required"

I'm learning.

The bar I have purchased and awaiting for is
"1045 Precision Shaft Steel Round Bar 1" Dia x 12"Long
Turned, Ground, Polished Precision Shafting Tolerance is (-.0005/-.002)"

not good enough?

"'clocking or miking'"

I don't know what that is

 

[Cogsy]

Hi Anatol, I'm replying here so I don't clog up mcostello's similar alignment thread. In that thread you made the comment "Its difficult (for me) to imagine a mechanical situation that would result in the bar drawing a cone where the point of the cone is at the outer end and the 'base' off the cone is in the chuck!" and also "Various folks have said it doesn't matter where you indicate from. But if the spindle and ways are not parallel in both planes, surely this would introduce an error?" which leads me to believe you don't have a good handle on these types of errors yet.

Basically, mcostello's error is that his machine is cutting a taper. This means that if he puts a nicely round, straight bar in his lathe and puts a dial indicator on the saddle at some point down the bed his reading will be zero (or close to it) run out of the bar. However, when he machines the bar, the misalignment between the axis of rotation and the travel of the saddle means the diameter of the bar changes over distance. It means his depth of cut is increasing the further away he gets from the spindle and eventually it will cut to a point and make the bar into a cone. This means to measure his misalignment, a dial indicator needs to travel along a known (non-rotating) straight bar down the length of the lathe.

For your machine, as you have descried it at least, the bar is being held misaligned between the axis of rotation and the bar itself. This means, no matter where in space your indicator is placed at a stationary point, the bar will measure run out as the end 'wobbles'. The alignment between the bed and the axis of rotation is irrelevant to this measurement (effectively you could remove the headstock entirely and run it mounted in a vise and the same problem would remain). If you measured with an indicator mounted to the saddle as you traveled along the lathe with your bar not rotating, your reading would be dependent on the relative position your bar had ceased rotating and would tell you absolutely nothing about the problem.

In simple terms, mcostello's spindle centreline is not pointed directly in line with the lathe bed/saddle travel, but your workpiece is not in line with the your spindle centreline. Very different things.

 

[goldstar31]

Your PGMS bar has no place in Schlesinger tests. A couple of them would be delightful as the bed bars on a Quorn tool and cutter grinder. I hav e a pair on mine but that is not what we are about- is it?

Schlesinger uses a Morse taper to suit the internal taper of the specific spindle in. Sleeves simply add dimensional errors.

Again, Schlesinger specifies a minimum of TWO - do you call them dials for reading the deflection or what ever comes from very high precision centres. The resolution of them is possibly half a thous minimum and usually they have the indicator end changed to 'an elephant's foot' rather than a spring ball. Mine came from a Boxford tool and cutter grinder- and are more accurate.

Again, the levels are precision levels.

In the case of a possible worn lathe, there are 'references 'of high precision. I have a very decent cast iron surface plate, Johansson blocks which ring together, microscopes and so on. It may look like a scrap yard but I have quality stuff capable of measuring very accurately.

The sad thing is that I am getting very old and I have macular degeneration in both eyes- one 'wet' and the other 'dry' and even reading and typing are now a real chore.

Time will soon come when all of it will go into the rubbish bin and in the meantime, I have to consider whether I am continuing on my own projects. Trying to help others now is becoming increasingly nigh impossible.

You have the sources better than I can describe and in the circumstances might I suggest that you avail yourself of what is priceless information.

I wish you good fortune

Norman

 

[Anatol]

Cogsy, Norman, dieselpilot, petertha and others:

It is with respect, humility and gratitude that I thank you for your generosity with your knowledge and experience. I am not unaccomplished. I have achieved substantial things in several fields. I was remarking to a friend that learning the art of precision machining and really understanding the procedures, is one of the most challenging things I've ever attempted. I find two things especially interesting and important.

That the trade/art/craft combines rigorous intellectual work - reasoning - with highly sophisticated and attuned 'sensorimotor' practices (what we used to call hand-eye coordination, manual dexterity, etc).

That in cooperation with sophisticated tools and instruments, we can 'sense' minuscule variations beyond the ability of our senses. A DTI or a mike or a precision level is like a telescope or a microscope. But a telescope or a microscope only 'look', while with this machinery we also 'act'.

In our digital age, we are encouraged to think that abstract thought is all that is needed, because there are machines to do the 'work' - just press 'print'. In my opinion an entire generation, at least in the 'west', is being hoodwinked and deskilled.

It seems to me this knowledge - the basis of the industrial revolution - is precious, and is disappearing rapidly. I hope to play a small role in preserving it. I'd also like to make some projects Thankyou for your patience.

 

[DJP]

My first home shop lathe was a 75 year old Soutbend with some wear. It drank oil and it required a slow approach to the final cut but for my needs it worked and provided value. I have since upgraded to a newer (still old) and tighter Myford but my approach to precision hasn't changed and I accept the limits worn into the machine. I'm sure that there are many levels of higher precision available to me if I upgrade.

My thoughts for your consideration are that perhaps this old lathe either needs to be rebuilt or used for less accurate work. Keep going in your quest but you may discover that running with tail stock or using a 4 jaw chuck are the only ways to minimize the errors due to wear and the best solution is a new machine. CNC and 3D printing require digital programming skills so that eventually our lathes and mills will be museum pieces. If you visit a small machine shop producing product you will see the future of our hobby. There may still be a rebuilt Southbend there for a specific job but the precision work is done by new digital machines in high volume.

 

[goldstar31]

In my perhaps warped view of things, it was partly recalling a ridiculous offer of a tool and cutter grinder- which attracted no takers. The dedicated motor alone would have cost at least £100- the offer price for the whole thing. There were no takers!

Again when my turn comes, my children/my executors/ attorneys have been instructed to literally scrap my workshop rather than waste their precious lives in trying to find buyers who are prepared to put their hands into their wallets/pocket books to find realist prices. None of my stuff is CNC or 3D printed. To put that onto the market would be even more of a fools errand.

Certainly in the UK, the closure of 'model shops' and such are an indication of what can only be an indication of wealth or the the willingness to pay a realistic price. Somewhat scurrilously, there is an ability to buy a phone for £40 a month or £480 a year which is almost 5 times my teasing price of £100. I bought a virtually unworn SiegC4 for £350- delivered which was- and I'm an accountant( retired) a whole tenth of the new price.

For DJP's delectation, a slideways ground bed for a Myford Super7 was a mere £200 and my rather more rough and ready Blancharding was a mere £25 and - being somewhat of a accountant etc, I noted that both firms went into liquidation which is more or less a euphemism for 'Gone down the Swanee!'

What will happen when China is forced to put up its prices- I'm a political animal and able to play the Stockmarket- is anyone's guess but it will not be a benefit to the model engineer and his one off.

My thoughts- of course.

Norm

 

[petertha]

The bar I have purchased and awaiting for is "1045 Precision Shaft Steel Round Bar 1" Dia x 12"Long
Turned, Ground, Polished Precision Shafting Tolerance is (-.0005/-.002)"

Well....
- It doesn't have centers on either end which means you cannot put it between centers as-is to dial in tail stock at some point as an example. So somewhat reduced utility.
- Its hardened so not exactly easy for a machine shop to do that job for you at reasonable $$ just as a guess. Now you have to be concerned how they are gripping it & center drilling it etc.
- Re tolerance, actually not that great but I guess relative to what you paid. Hard to know based on that info. Do they mean could be 0.9995" - .9980" anywhere along the shaft? Across one direction vs another on the same part of shaft? Compare to el-cheapo MT test bar from India below. The one I got tested favorably to the 10-thou mic in my arsenal FWIW. Any further testing I don't have capabilities myself.
- it doesn't have MT taper on end so cant be plugged into head or tail stock taper, so again a bit reduced utility. About all you can do in your issue is to chuck it & make measurements on that basis as already discussed. However you also just chuck the cylindrical portion of an MT ended test bar & accomplished the same thing.

https://www.ebay.ca/itm/3MT-Lathe-A...877671?hash=item3d2f053da7:g:ac4AAOSw8gVX2ZxK
Accuracy within 1 micron. Max.run-out :0.0001". Overall length : 335mm (13-3/16")