3jaw chuck alignment problem

Initially, I'm delighted that you are working your way through 'Connelly'. There is an enormous amount of valuable information which will take more than one reading to really appreciate. Nevertheless, I'm sure that you will get there eventually. My suggested use of a wet towel, aspirins etc came as a result of my own experiences. It's tough going.

Of course, the book is dated especially about the use of scraping tools and diamond pastes and carbide scrapers are a great improvement to constantly honing hss and carbon steel scrapers. Again, you will eventually find that things are not flat FLAT! Also, there are now things like Moglice and Turcite that can build up wear rather than having to scrape a long run of otherwise nigh perfect straight and unworn metal. So before you venture to correct things, think whether a dollop of filled resin might be the easiest alternative. So the saddle of my Myford has had a layer of Turcite building what was as rough as a badger's nether end!

As another idle thought, you might consider a more accurate way of measuring tenths of thous instead of thous.

As the late and lamented George Thomas said 'No hairs are too fine to split!'

Above all, I wish you well

Norman

Anatol said:

Thankyou Norman, Lloyd, dieselpilot for helpful advice. ................
...............
I am a beginner and am keen to learn. The exactitude of the machinist's art is something mere mortals cannot comprehend, and I must admit being a bit awe-struck by the precision that can be achieved by skill, precise method and concentration, using simple, but accurate, tools. I am also thoughtfully impressed by the fact that diagnosing such seemingly simple geometrical problems in the metal objects right in front of me can be as intellectually challenging as anything I've ever done.
thanks again.

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Anatol,
I quoted your last paragraph because it really struck a chord with me, especially your first sentence. Even though I have been doing this as a hobby for 10 years and consider myself very mechanically inclined compared to the "general public", I am totally humbled by the skill and knowledge of the participants of this forum. It IS intellectually challenging, and anything that is such, always presents a stage for lively interpretation and discussion. Anyone not familiar with the art probably doesn't understand that, but ask me about literature or music and I am totally clueless.
Visualization of alignment issues is, for me, difficult, because they are so complex and there are so many variables to assess. Machinists who have dealt with these issues can visualize it effortlessly and have their own self taught, self learned tricks. If Norman or dieselpilot were there with you, I bet the problem would be solved in short order. Verbalizing and interpreting it is a lot tougher, just like literature and music, LOL. But that is one of the reasons we love the challenge of machining.

One somewhat related anecdote I'd like to share about visualization, if you will indulge me. I was installing trim around the roof of a small shed and my 6 year old grandson was over "helping". I had cut 2 identical rake boards for the gable end, and they were both setting on the saw horses, parallel to each other, so that they both looked the same. I installed one of them onto the left hand slope. I could see him studying the other rake board, which was laying totally in the wrong orientation for installation onto right hand slope. I asked him, "Khayden, I don't know if I cut this one the right way, I am not sure it will fit." He immediately said, "Sure it will grandpa, just do this." He held his arms straight out in front of himself and twisted them into a funny "X". He got it. I was proud.

Time to introduce that young man to what some of us call the Seven Liberal Arts!

goldstar31 said:

So before you venture to correct things, think whether a dollop of filled resin might be the easiest alternative.

As another idle thought, you might consider a more accurate way of measuring tenths of thous instead of thous.
Norman

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I've spent quite a lot of time with (epoxy) resins, as a boatbuilder. I've begun to experiment with custom composites, such a epoxy filled with graphite and short class fibers - this seems useful for self lubricating, non-corroding machinable bushings.
I can. probably come up with a decent Moglice-like product, probably using bronze powder or aluminum powder.

"measuring tenths of thous" I've got a tenths indicator, didn't use it yet on this problem.

Lloyd-ss said:

Anatol,
I quoted your last paragraph because it really struck a chord with me, especially your first sentence. Even though I have been doing this as a hobby for 10 years and consider myself very mechanically inclined compared to the "general public", I am totally humbled by the skill and knowledge of the participants of this forum. It IS intellectually challenging, and anything that is such, always presents a stage for lively interpretation and discussion.

I asked him, "Khayden, I don't know if I cut this one the right way, I am not sure it will fit." He immediately said, "Sure it will grandpa, just do this." He held his arms straight out in front of himself and twisted them into a funny "X". He got it. I was proud.

Click to expand...

Thanks Lloyd,
I've been designing and building for years, and am challenging myself to learn old school machining - no DROs. Not till I really understand it anyway.
Regarding the "X", this is a subject of great interest to me. "Embodied Cognition" or more colloquially, knowing through the body. Its a way of knowing that is less and less valued as we become more dependent on more sophisticated technologies. Hence "no DROs" .

goldstar31 said:

Time to introduce that young man to what some of us call the Seven Liberal Arts!

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That 'young man' is approaching retirement age.

I was talking about the grandson!

goldstar31 said:

I was talking about the grandson!

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yeah, sorry of course you were. I laughed!

Back to lathe chucks and inaccuracy.

I'm wondering if this is a common fault where the Number 1 shear is worn about 6" from the spindle nose.

I've had this on several Myfords

Regards

Norman

Anatol,
Your interest of embodied cognition prompted me to do some reading on the subject and although I found it intriguing and very plausible, I found the subject extremely difficult to sort out in such a way that I clearly understood the concept. The individual body-mind metaphors made sense to me, but I, because of the way my mind works I guess, was unable to assemble "the big picture" of the concept. It is in the realm of what I might call (for myself) philosophical thinking, which I have always found to be very difficult to decode. For me, visualization seems to be necessary for full understanding of almost any subject, and although I can visualize various examples of the concept, I cannot visualize the concept itself. I hope this explanation of my struggle and inability to understand makes sense. Something in my brain can't process that sort of structure. But, on the other hand, I am glad that my grandson's body-mind processing of the puzzle might have further gelled your understanding of the subject.
And just to stay on task for the forum guidelines, do you think there is something of the embodied cognition that makes some people intuitively better at machining and conceptualizing the projects that we make?
Lloyd

I am getting the lathe going again after many years of inactivity and my first purchase will be a DRO. Old eyes don’t work anymore on teeny little inscribed lines and numbers. Give me those big glowing numbers. Same with micrometers and calipers. All digital. So much easier these days. It all makes me want to choose the lathe over the TV in the evenings.

goldstar31 said:

I'm wondering if this is a common fault where the Number 1 shear is worn about 6" from the spindle nose.

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First, please explain what "Number 1 shear" is ?

Second, early on in Conelly, he talks about "the Three Plate Method utilising Symmetrical Distribution of Error (See Sec 21.5)"
I went to 21.5 and comprehend the Three Plate Method, but, sadly, he makes no further mention of "Symmetrical Distribution of Error" . Do you, or anyone, know what this is or where can learn more about it ?
thanks!

Number 1 shear is the first shear as you face the lathe. In an ordinary flat bed it is fairly obvious but in a Vee bed, it is the first bit of the vee which faces the operator. The wear is caused by the predominance of working near the chuck/ collet/ faceplate.

The Three plates are ground with abrasive rubbing each face alternatively at random which progressively flattens each face until ANY face will ring to ANY other face-- or as some describe it, if glass is being used, three optical flats are created.

Is this any clearer?.

Norm

NB. Moving on somewhat, a 'reference ' is created on which to build up verticals and whatever. Happily, I broke off a note to Lloyd to go to a Masonic first degree( Entered Apprentice) rehearsal at one of my lodges.
Of course, what I'm prattling about is what was 14 year old 'schoolboy Euclid'
N

I am not familiar with your lathe but I Googled Grizzly model G4003 because you suggested the similarity. If your head stock is separately mounted to the bed, then any rotational misalignment viewed from the top would explain what I think you are seeing. ie. if the DTI was mounted to the apron, registered to a test bar at an inboard position close to the spindle nose & zeroed. Then traverse the DTI/apron down the test bar (no spindle rotation). If it reads something different at the end of the test bar it could be purely related to the entire head stock being yawed. This has nothing to do with chuck centering, jaw grip, lathe twist or even spindle rotation. If you can get hold of a cylindrical test bar with matching MT# socket, stick that in the spindle with no chuck, eliminate all the middlemen & just traverse down the bar. If you measure discrepancy, this is a strong clue.

Typically on these Asian lathes there are bolts which secure the head stock down to the bed & there are also some lateral set screws which micro-adjust the head alignment. If during moving or just not set up properly the head has shifted and spindle axis is pointing inward or outward relative to bed axis, this is the issue I'm describing & needs to be corrected. Strangely, the G4003 manual does not discuss this & I cant quite see such screws on the parts diagram. It just talks about checking taper cutting via the tailstock offset which is a different matter down the road when the headstock alignment is first dealt with.

Now if your particular lathe is an all-in-one meaning the head stock is integrally cast with the bed, then disregard all the above. You have no means to adjust this other than what people have suggested - bed twist, chuck issues etc. Let us know what you see & better yet, some pics!

.

Now that you have a precision level , read the instructions that came with it. The level has adjustments. You will find that this level is not comparable to a carpenters level. Much more sensitive. This level will indicate twist in the bed , if there is any. The level is place across the ways , NOT parallel to the ways. Thin shims , paper etc under the bed casting in one or more corners is done til the bubble is dead center. This can take hours , I spent most of the day leveling a friends Standard Modern lathe he got from a school in Canada.
After the lathe is leveled to the best you can get , then do the two ring test. You tube probably has a video on this, I haven't done it in years and do not want to describe it for fear of making mistakes.
The ring test should show the lathe is level across the ways. Now test the bar in the chuck. Hopefully the chuck problem is solved, just an out of aligned lathe bed.

mike

As everyone is still assuming Anatol read a misalignment vs runout on his test bar. I will ask, What exactly was observed?

The below link shows runout of a shaft in a lathe. Is this what was observed? This is not the same as a twisted bed or misaligned headstock. I'm sure more suggestions will help, but let's make sure we're solving the right problem.

I'm assuming an element of wear or misuse simply because of Anatol having chuck problems on the original chuck and then buying a second hand chuck to 'replace it' on e-bay- and finding that it was just as bad.

There is 'something' that we all are unaware of. After all, it is not some ancient old lathe that is being discussed.

goldstar31 said:

The Three plates are ground with abrasive rubbing each face alternatively at random which progressively flattens each face until ANY face will ring to ANY other face-- or as some describe it, if glass is being used, three optical flats are created.

N

Click to expand...

thanks, yes. I found the reference. Although in the text he points to 21.5, the discussion of Symmetrical Distribution of Error is at the beginning of 21.

Lloyd-ss said:

Anatol,
Your interest of embodied cognition prompted me to do some reading on the subject and although I found it intriguing and very plausible, I found the subject extremely difficult to sort out in such a way that I clearly understood the concept. The individual body-mind metaphors made sense to me, but I, because of the way my mind works I guess, was unable to assemble "the big picture" of the concept. It is in the realm of what I might call (for myself) philosophical thinking, which I have always found to be very difficult to decode. For me, visualization seems to be necessary for full understanding of almost any subject, and although I can visualize various examples of the concept, I cannot visualize the concept itself. I hope this explanation of my struggle and inability to understand makes sense. Something in my brain can't process that sort of structure. But, on the other hand, I am glad that my grandson's body-mind processing of the puzzle might have further gelled your understanding of the subject.
And just to stay on task for the forum guidelines, do you think there is something of the embodied cognition that makes some people intuitively better at machining and conceptualizing the projects that we make?
Lloyd

Click to expand...

Hi Lloyd
"I found the subject extremely difficult to sort out in such a way that I clearly understood the concept."
that is probably because we are accustomed to thinking we have a 'mind' an a body' and they are separate and different. Thank Descartes for that. Embodied cognition starts from the premise that this simply isn't true.
"It is in the realm of what I might call (for myself) philosophical thinking, which I have always found to be very difficult to decode."
yers, I find a lot of philosophy pretty abstruse too. But Embodied cognition is based in the common sense understanding of practices and experiences all makers have.
"do you think there is something of the embodied cognition that makes some people intuitively better at machining and conceptualizing the projects that we make?"
All humans and animals cognize in an embodied way - we integrate internal and external senses - proprioception, vision etc. Some people, through inclination or vocation, refine it. Others are more disconnected from their bodies, we call them 'klutzes'

petertha said:

I am not familiar with your lathe but I Googled Grizzly model G4003 because you suggested the similarity. If your head stock is separately mounted to the bed, then any rotational misalignment viewed from the top would explain what I think you are seeing. ie. if the DTI was mounted to the apron, registered to a test bar at an inboard position close to the spindle nose & zeroed. Then traverse the DTI/apron down the test bar (no spindle rotation). If it reads something different at the end of the test bar it could be purely related to the entire head stock being yawed. This has nothing to do with chuck centering, jaw grip, lathe twist or even spindle rotation. If you can get hold of a cylindrical test bar with matching MT# socket, stick that in the spindle with no chuck, eliminate all the middlemen & just traverse down the bar. If you measure discrepancy, this is a strong clue.

Typically on these Asian lathes there are bolts which secure the head stock down to the bed & there are also some lateral set screws which micro-adjust the head alignment. If during moving or just not set up properly the head has shifted and spindle axis is pointing inward or outward relative to bed axis, this is the issue I'm describing & needs to be corrected. Strangely, the G4003 manual does not discuss this & I cant quite see such screws on the parts diagram. It just talks about checking taper cutting via the tailstock offset which is a different matter down the road when the headstock alignment is first dealt with.

Now if your particular lathe is an all-in-one meaning the head stock is integrally cast with the bed, then disregard all the above. You have no means to adjust this other than what people have suggested - bed twist, chuck issues etc. Let us know what you see & better yet, some pics!

Click to expand...

Thanks Peter
"I Googled Grizzly model G4003 because you suggested the similarity."
its pretty close, so is a Jett 1236 and a PM1236
"If your head stock is separately mounted to the bed, then any rotational misalignment viewed from the top would explain what I think you are seeing." "This has nothing to do with chuck centering, jaw grip, lathe twist or even spindle rotation."
yes, I think your analysis is correct
"If you can get hold of a cylindrical test bar with matching MT# socket, stick that in the spindle with no chuck, eliminate all the middlemen"
that would be nice, yers, I'd thought the same thing. But I don't have one so I'll have to use what I can get. I will proceed as you suggest - after rechecking machine level and bed twist -using the biggest straightest piece of bar I can find.
"Now if your particular lathe is an all-in-one meaning the head stock is integrally cast with the bed,"No I believe its bolted on, but I have yet to explore and find bolts. Tomorrow maybe.
"Let us know what you see & better yet, some pics!"
ok, thanks again.