PDA

View Full Version : Another headstock alignment question



lbhsbz
10-06-2011, 02:34 PM
POS old "Dar-Sin" taiwan 13x40 lathe...machined something the other night that was 6 inches long, and saw that one end was .012" bigger than the other...time to align it..again. I made a bunch of test cuts over a 8" piece of tube, measured both ends, and adjusted as necessary. Once I got the diameters at both ends within .0005", I stopped and called it good....then I started thinking...On the surface, it would seem as if I've got the alignment pretty good...but what if I have misaligned the X axis to compensate for a Z axis misalignment. Theoretically, if I was out in both axes just right, it would still turn the part straight. I have absolutely no idea how to determine whether this condition exists or not. I suppose I could get a 4 foot long piece of material that fits through the spindle and face it off very near the chuck, blue it and mark it with a center in the tailstock, then pull a couple feet through the chuck, reclamp it, mark it again with a tailstock center...then see if the marks are in the same place or not, but I imagine there must be a better way. Thoughts?

Jaakko Fagerlund
10-06-2011, 02:43 PM
You can get accurate enough with just clamping a nice and about straight bar in the chuck that is long and stiff. Then mark a line along the bar. Measure the TIR of the bar at both ends and mark down on paper the readings taken from the line. This shows you how much difference the bar has comnpared to the rotation axis.

Now measure along the bar with a DTI along the line in both lateral and vertical and mark these readings on a paper. Now take the first readings off from these and you have your error amounts on paper, both vertical and lateral.

P.A.R.
10-06-2011, 03:07 PM
Sir most tail stocks are at least .001 or so higher than the center line of the headstock Z axis.I use a piece of true stock in my four jaw and measure/adjust the headstock for parallelism to the ways separately before I adjust the tail stock for taper.The higher tail-stock is not an issue unless you are using it for reference in a precision set up as in line boring.

DICKEYBIRD
10-06-2011, 03:22 PM
I'm thinking this thread will gain traction and carry on for awhile.;)

I will be watching it carefully as my little Emco C8 clone has a similar problem, ie: .003" out in 2".:eek:

My plan is to use the "Rollie's Dad's Method" and use measurements (like Jaako's advice, if I understand his post correctly) as I believe my lathe is too flexible to use its cuts to determine correct horiz/vertical spindle centerline alignment. Hopefully jumping off into it head-first this weekend.

Forrest Addy
10-06-2011, 04:47 PM
Obvioulsy you wish t ensure the spindle axis is parallel to the carriage motion. Cut tests don't prove this very well because it's almost impossible to separare tool and part deflections caused by cutting forces from alignment error.

Stick a !" piece of cold roll in a three jaw so that 6" stick out and you have a limber grip on a slender workpiece. You can move the end of the workpiece 0.002" with thumb pressure alone. Also how much of the taper is atributable to heat expansion of the tool, built-up cutting edge, drunken carriage motion, etc.

You might correct your lathe for dead nuts zero taper for turning and discover a new problem: tapered boring. You have to conduct tests that separate factors. Thus turning and boring tests are often flawed because of the many variables of cutting.

The simplest test for a home shop lates is a two collar test where you select a piece of stock about 2/3 as long as the swing sized to clear the compound rest. This gives the test piece sufficient length and stiffness. Turn two collars 1/4" wide; one at the end of the test piece and one near the chuck jaws. Relieve the diameter between them.

Fine tool finish the collar diameter by separately turning them serparately to a common size. This is not a cutting test, You are preparing a gage use for a subsequent test. Make sure the collars are to eual sized to better than 0.0005". Polish a little if you have to.

Mount your best (0.0001" preferred) indicator on the carriage, Crank the carriage to scan the collar along horizontal plane at center height. Note the reading. Crank back to the first diameter (this is called a "repeat zero test") If the indicator reads zero on the scan and the repeat sero your taper problem is NOT caused by spindle axis misalignment.

Regardless, align the spindle axis if your lathe allows you to do so by simple wrench adjustment. Double check the two collar gage to ensure it's dialed in concentric. Re-scan the collars at center height and repeat sero. If all is well re-clamp the headstock and double check. Go back and forth several times checking collar concentricity and axis alignment. Once you arrive at 0.0000" on the collars with the headstock properly clamped, stop. Never change it again. All future taper problems are tooling, tracking, and if the tailstoc is usef tailstock offset.

Here's a Golder Rule: If you have problems, blame the machne last.

topct
10-06-2011, 05:01 PM
Obvioulsy you wish t ensure the spindle axis is parallel to the carriage motion. Cut tests don't prove this very well because it's almost impossible to separare tool and part deflections caused by cutting forces from alignment error.

Stick a !" piece of cold roll in a three jaw so that 6" stick out and you have a limber grip on a slender workpiece. You can move the end of the workpiece 0.002" with thumb pressure alone. Also how much of the taper is atributable to heat expansion of the tool, built-up cutting edge, drunken carriage motion, etc.

You might correct your lathe for dead nuts zero taper for turning and discover a new problem: tapered boring. You have to conduct tests that separate factors. Thus turning and boring tests are often flawed because of the many variables of cutting.

The simplest test for a home shop lates is a two collar test where you select a piece of stock about 2/3 as long as the swing sized to clear the compound rest. This gives the test piece sufficient length and stiffness. Turn two collars 1/4" wide; one at the end of the test piece and one near the chuck jaws. Relieve the diameter between them.

Fine tool finish the collar diameter by separately turning them serparately to a common size. This is not a cutting test, You are preparing a gage use for a subsequent test. Make sure the collars are to eual sized to better than 0.0005". Polish a little if you have to.

Mount your best (0.0001" preferred) indicator on the carriage, Crank the carriage to scan the collar along horizontal plane at center height. Note the reading. Crank back to the first diameter (this is called a "repeat zero test") If the indicator reads zero on the scan and the repeat sero your taper problem is NOT caused by spindle axis misalignment.

Regardless, align the spindle axis if your lathe allows you to do so by simple wrench adjustment. Double check the two collar gage to ensure it's dialed in concentric. Re-scan the collars at center height and repeat sero. If all is well re-clamp the headstock and double check. Go back and forth several times checking collar concentricity and axis alignment. Once you arrive at 0.0000" on the collars with the headstock properly clamped, stop. Never change it again. All future taper problems are tooling, tracking, and if the tailstoc is usef tailstock offset.

Here's a Golder Rule: If you have problems, blame the machne last.

Forrest has nailed it again.

DICKEYBIRD
10-06-2011, 05:41 PM
Relieve the diameter between them. Is this done to lighten the test piece to reduce sag from the effects of gravity or just enough material removed to clear the indicator?

Also, it seems to me that one would check the collars in the vertical plane as well as the horizontal, no?

Great advice as usual Forrest, thanks.

PeteF
10-06-2011, 09:32 PM
Before doing anything with the headstock alignment the lathe should be checked to confirm that the bed is not twisted and the easiest way to do that is to ensure it is level. The headstock should be accurately aligned at the factory, and on a quality lathe there is no good reason it should ever need to be adjusted for the life of the lathe. Indeed many lathes have headstocks scraped or ground to alignment at the factory and then that's it, set for life. If a lathe is turning a taper it is FAR more likely to be an error elsewhere in the lathe's installation rather than the headstock alignment.

At the end of the day, you can hang all the dial indicators you like off a lathe, however there are only 3 measurements that matter; whether it will turn, face, and bore accurately. If somebody is at a stage of their learning and understanding that they don't know how to turn collars accurately (ie consider deflection) then I'd suggest they have no place screwing around with headstock alignment and will most likely only misalign an otherwise perfectly good, but poorly installed, lathe.

Pete

tdmidget
10-06-2011, 10:05 PM
Before doing anything with the headstock alignment the lathe should be checked to confirm that the bed is not twisted and the easiest way to do that is to ensure it is level. The headstock should be accurately aligned at the factory, and on a quality lathe there is no good reason it should ever need to be adjusted for the life of the lathe. Indeed many lathes have headstocks scraped or ground to alignment at the factory and then that's it, set for life. If a lathe is turning a taper it is FAR more likely to be an error elsewhere in the lathe's installation rather than the headstock alignment.

At the end of the day, you can hang all the dial indicators you like off a lathe, however there are only 3 measurements that matter; whether it will turn, face, and bore accurately. If somebody is at a stage of their learning and understanding that they don't know how to turn collars accurately (ie consider deflection) then I'd suggest they have no place screwing around with headstock alignment and will most likely only misalign an otherwise perfectly good, but poorly installed, lathe.

Pete


+1 Headstock alignment is the least likely except for one thing. OP said it was time to align it again. So he's messed with it before. If this lathe's headstock flops around like a fish out of water then that problem probably can't be solved except with a real lathe. It was almost certainly originally located by the vee ways or dowels. Find out why it has moved if indeed it has.

Chris S.
10-06-2011, 10:24 PM
snip

Before doing anything with the headstock alignment the lathe should be checked to confirm that the bed is not twisted ....
Pete
I'm surprised that this thread went to 8 replies before this was even mentioned. It's the first subject covered in lathe setups and should be periodically checked. Hell, some cheap Taiwanese beds may have never been stress relieved or aged and may go through contortions for its entire life.

Chris

Forrest Addy
10-06-2011, 10:33 PM
Peter you are right that the major function of an engine lathe is to turn, face, and bore accurately but in order to do that you do have to "hang indicators off it." Technical problens are detected and defined by the collection of datas in terms of numbers and units. "Wobbles around" means nothing. 0.003" TIR near the jaws and 0.005" TIR 5" from the jaws is information you can work with.

When the lathe is first assembled on the factory floor the bed is leveled using its built-in reference surfaces, the flats of the ways. Then bit by bit the other parts are added with each alignment references to the ways leading up to the spindle axis which is generally proved by a spindle test bar stuck in the spindle's internal taper and dialed in to verify the concentricity and straightness of the cylindrical portion. Only then is it used to verify the spndle axis alighment to the bedways.

In Connelley's "Machine Tool Reconditioning." there's a whole chapter on inspection of engine lathes and the tools and equipment used to perform it. Every active machine tool used for precision work should be fully inspected periodically for level, wear, alighment, linearity, accuracy of axis movements, bering adustment, operation of all parts, controls, features, and safety equipment, electcial integrity, leaks, lube systems, etc and this period should be no more than once every two years. A full survey should be performed on each machine when purchased new or used and immediately before the decision is made to overhaul or re-build it. This is not a lick and a promise procedure. Depending on the complexity and size of the machine it may take one man three hours sor a millwright and his helper a week.

If you as a home shop owner have not conducted a survey of the precision machines in your inventry when you first acquire them you are stabbing in the dark. A problem with taper comes up so what do you do? Immediately blame the machine? Are you justified in blaming it? If you have a written survey of the machine you can refer to, you can rule out - or in - the likelihood of machine fault.

The final test of a machine tool are machining tests where the functions of a machine are demonstrated on real life machining problem involving (in an engine lathe) turning boring, and facing. Also threading, Max HP cuts, roundness specimens, taper turning (if an attachment is fitted) and so on through all the feds speeds and TPI. With each verified against the chart by travel indicator. But that's only after you remove the hanging indicators.

Most people I know have machine history files without knowing it. Somewere they have the machine manuals, the receipts for sale and shpping invoices, the slips for tooling purchases, attachments, etc. Telephone notes to service people, the manufacturer, and these days copies of eMails and message board thread of spedific interest. Gather all this together and stuff it in a file (I use pleated accordian folders) bada-bing you have an equipment history file.

Survey results and problem notes, sketches and plane for improvements go in this file as well. When a real problem comes up (like sudden inexplicable taper cutting) you can dig through the file to see it's the culmination of a trend or delayed result of damage. Schlessinger in his "Testing of Machine Tools" (if you can find a copy) has worksheets for machine tool surveys that can be copied and filled out as the survey progresses.

A question on the purpose of the relief between collars is sensible. It's to isolate to collars so the tool has only a short cut to make instead ot full length thus preserving the cutting edge to the maximum expent possible. You don't really need the relief but I've always included it for the reason stated.

Finally a precsion ground test bar is quite expensive. I've seen a few for $120 but usually they run $200 to $600 depending on size. It's pretty much a one-use tool. You use it then preserve it and store it on a shelf next to the other white elephants. A two collar test costs the time it takes to machine it and is as handy as the material in the remnant rack.

PeteF
10-07-2011, 05:46 AM
Forrest I have absolutely no problem at all with what you're saying, and the "2 collar method" as you have described is an excellent way to align a lathe. What you're doing is effectively making your own version of a test bar. However as you said, and I'll say again, the final test of a lathe is whether it turns, faces and bores accurately. It is quite possible, though somewhat more tedious, to align a lathe (at least the components that are capable of being moved without grinding or scraping) without even owning a DTI! You wouldn't, but you certainly can, and I feel the process of why you can and how is important in understanding precisely what is going on with your machine and how it works. I'm quite sure you're aware Forrest, but I feel many others may not be, which components require adjustment can be deduced by which of the 3 final tests is not proving sufficiently accurate. As mentioned, that is not the way they are typically aligned in the factory, but it is the final test; and the only test that really matters.

As far as the 2 collar test, it's not the method I use and I will carefully machine the full length. Yes is takes MUCH longer and I'd only suggest it for the final-final test. Forrest has already outlined the advantage of this method, however the disadvantage is it then only surveys the machine at 2 points. That may well be fine on a lathe that's perfectly level with unworn ways, however that may not be the situation if you're tracking down why an old machine is turning inaccurately. Particularly if somebody is screwing around with the headstock alignment, if that's all you look at, it's possible to adjust the lathe so the machine will turn accurately at those 2 points however is inaccurate elsewhere. Again, I stress the final test is whether the machine turns, FACES, and bores accurately. Before adjusting anything, consider these 3 factors carefully as the answer to the problem is right there.

Pete

philbur
10-07-2011, 06:13 AM
What's the difference between turning and boring with respect to alignment checking, isn't boring internal turning or do you mean drilling (for tailstock alignment?). In order to use these parameters to confirm that your lathe is "OK" wouldn't you have to perform them at multiple locations or run the same risk of missing something, as you pointed out in the two collar test?

Phil:)


Again, I stress the final test is whether the machine turns, FACES, and bores accurately. Before adjusting anything, consider these 3 factors carefully as the answer to the problem is right there.

Pete

PeteF
10-07-2011, 07:04 AM
With a skilled operator, there shouldn't be any difference between turning and boring, and that's the whole point. However if the lathe is turning a "taper" and boring isn't then it could save a person chasing a "fault" that doesn't exist, or exists in another area. Maybe even with the operator!

No I did not mean drilling, which is quite a different, indeed my comments weren't even directed at tailstock alignment. I have never heard of the equivalent of a "2 collar test" for boring so of course you would check for accuracy at numerous points along the bore.

Pete

RussZHC
10-07-2011, 07:52 AM
Believe me, I enjoy a "theoretical" discussion more than most but I am not sure I would go chasing this one.

Not saying the advice and thoughts so far are wrong/inappropriate but has not the discussion, in a larger sense, been that a true machinist is capable of working with the faults of the machine to still produce the exactness needed with said machine? i.e. you are limited by the machine but can work right to the tolerances it is capable of...

IF each end is the same (truthfully I would do a few in the middle to...but the theoretical there is that should not be needed?) and the faces are flat to the degree you need/want, have you not arrived at the cylinder shape called for? and at that point what does it matter how you arrived there? Assumption being, on that occasion anyway, other sizes could be turned to the same tolerances.

Slightly off topic but I throw this out there...I've got micrometers that are capable of some pretty fine tolerances, to the point where I have difficulty deciding if the "pull" needed at each measure is the same but those numbers are way past "good enough" for what I do most often...I would also point out, as have others in previous discussions, at some level the run out of a chuck say or the flexibility of the equipment make some tolerances sort of moot, you could be chasing something a lean/push the "wrong" way put back into spec...sorry, also question, if you determine those variables of the original post whether the machine in question can hold itself there anyway

J Tiers
10-07-2011, 08:38 AM
It is pretty common to place an additional "collar" halfway between. That checks for "nod" that may occur due to wear on the front way a bit in front of the headstock. Certainly the use of "two" is not a reason to disregard the test, which is a practical turning test, showing the behavior of the actual "system" as the parts move, and is not a "theoretical" measurement made under ideal static conditions.




If you as a home shop owner have not conducted a survey of the precision machines in your inventry when you first acquire them you are stabbing in the dark. A problem with taper comes up so what do you do? Immediately blame the machine? Are you justified in blaming it? If you have a written survey of the machine you can refer to, you can rule out - or in - the likelihood of machine fault.



With home shop machines, purchased out of another home shop, it CAN get simpler...... "OF COURSE IT IS THE MACHINE".... maybe, or at least in part....

I can think of only ONE machine I have purchased from a "home shop" that was essentially without faults. That "home shop" was actually a commercial screw machine operation located "at home" in an outbuilding up in quad cities.

EVERY other machine has had a problem of some sort. In many cases they were just stupid assembly, and really didn't affect operation, in other cases they were things which would directly cause problems.

The following photo I have posted before.... it is the "blue-up" test of the column ways on a mill I got used from a shop of which it was said "he could buld or fix anything, and always kept his machines in tip-top condition".
Good thing I knew otherwise in this case.... and did not "believe in" the "flaking" visible on ways etc. Not a whole lot of contact with the granite flat..... borne out by the wear on the knee, which showed contact only at matching points. Even this poor contact was not present over the entire height of the ways. "Tip-top condition"? Righty-ho.

The knee was about 3 thou in 6 inches "off" from aligned with the spindle (horizontal mill), and "nodded" significantly as it was moved up and down the column. That would be about 10x the misalignment Connelley suggests as a maximum.

it's mostly fixed now, but summer is not a good shop work season, so I have work to do yet. Also had to make some tools (scraped squares) in the mean time.

http://img.photobucket.com/albums/0803/jstanley/benchM_spot.jpg

gizmo2
10-07-2011, 09:09 AM
One thing that also screws up alignment are screw on back plates. If your spindle nose is threaded, chucks will seat slightly differently each time they are screwed on and off, changing the amount of runout on the machined part.

PeteF
10-07-2011, 09:09 AM
Jerry I agree, there is nothing "theoretical" about a 2 collar test, nor I'd suggest Forrest's version of it. They are both time and tested legitimate tests of a machine. Yes a machinist can work with an inaccurate machine and produce excellent work, however that was not what the OP asked. The question was regarding headstock alignment, not how to work with an inaccurate machine. I see this question come up regularly and my point is to be sure it is indeed actually the headstock that requires "realignment" to correct a lathe that is inaccurate.

Pete

lbhsbz
10-07-2011, 01:04 PM
OK...a little more history on this thing...it was given to me by the company I work for. It's a 20 year old Taiwanese machine, ergo, it's a hunk of crap....but it's the only lathe I've got, so I'd like to try and fix it. The main issue lies in the fact that the bed surface where the headstock sits is finished BY HAND with....no, not a scraper, but an angle grinder...yep, you read that correctly. The bottom of the headstock is finished in the same manner. The tailstock sat about .040" low, and in taking that apart I discovered that all the "critical" surfaces on the tailstock were also finished in the same manner. I Just finished getting the tailstock squared up...I remachined/squared up the tailstock base and body such that now I've got flat surfaces to shim it correctly.

I guess I'm trying to polish a turd here, for lack of a better term. I can't afford a good lathe right now, and this is many times better performing than my last one, so it'll have to do.

I've leveled the bed as best and straight as I can about a year ago...but that doesn't mean it didn't move. I'm borrowing a level this weekend to go at it again, then will try the 2 collars method, along with several others to see if I can't get this thing dialed. I'm sure it's possible....somehow.

Forrest Addy
10-07-2011, 02:01 PM
PeteR: If you have another way to verify spindle alignment I would like to hear it. I described two methods of verifying an engine lathe's spindle axis parallelism to the bedways and cited two authrities whose book go into the prodecure thoroughly with diagrams and illustrations. These two authorities while writing of methods used 50 years ago are still recognizzed and used even today. Alexander Slocum is his recent "Precision Machine Design" cites Connely and Schlesinger as source material.

If you have another simpler, less equipment intensive way to quantify spindle axis alighment please elucidate. There's a whole industry yearning for better methods. If there's an advantage to your method, peer review and general acceptance will prevail in the end..

I'm trying to understand why you are agreeing with other posters yet you cite contrasts with your preferred method.

PeteF
10-07-2011, 09:21 PM
Forrest, by PeteR I presume you mean PeteF ie me?

I have not said it is a preferred method, please read my posts again. What I said is that it is POSSIBLE to accurately align a lathe without using a DTI. Indeed I specifically said that is NOT the way it is done in a factory, however the important point is to understand the geometry of the machine and the three final goals of what we're aiming to achieve; a machine that turns, faces, and bores accurately. No I'm not going to sit down and write a 40 page post on machine geometry, I will leave you to research that for yourself. However knowing your background in this area I'm quite surprised you're implying otherwise. The traditional "2 collar method" doesn't use a DTI and instead uses a micrometer to measure the finished turned sizes. That was the way the "old timers" would check and level a lathe, go back far enough in history and they probably didn't even own a DTI or precision level yet still could have accurate lathes! How could that be? Indeed the 2 collar method is the method that some manufacturers still recommend as the final test to level their lathes. What I have said is that if one properly understand the lathe it's also POSSIBLE to check other alignments without using a DTI. What does it imply if the machine faces quite accurately but turns with a taper? What does it imply if the machine turns accurately, but only at two points? So it goes on. I am NOT talking about machine rebuilding here Forrest, simply looking carefully at precisely where the errors lie in an otherwise serviceable machine and using an understanding of the machine's geometry to narrow down what may be causing the errors instead of willy-nilly starting to adjust things! The OP has now provided additional information that suggests why the headstock was adjusted, however this topic comes up relatively regularly and there are many times I have the impression that the headstock was adjusted first in an attempt to correct taper, when it hasn't even been determined if the lathe is properly level, never mind whether or not it's facing accurately!

It is possible that you have derived my "preferred" method from my comments about turning full length and not simply collars. As I have already said, I do this because the method you're suggesting (using 2 collars only), it is possible to have both the headstock misaligned and the bed twisted such that when the headstock is "realigned" you will measure the collars accurately, yet it will only be these 2 points that are accurate. I similarly like Jerry's suggestion to turn 3 collars, as the third will determine if that is the case. The last time I did this on my worn lathe it was to try to find a point where a compromise could be found in terms of "relatively" accurate turning over the portion of the bed I normally use. 2 collars simply wouldn't cut it. Excuse the pun.

Hopefully that clarifies what I actually said.

Pete

J Tiers
10-07-2011, 10:48 PM
Yes a machinist can work with an inaccurate machine and produce excellent work, however that was not what the OP asked. The question was regarding headstock alignment, not how to work with an inaccurate machine. I see this question come up regularly and my point is to be sure it is indeed actually the headstock that requires "realignment" to correct a lathe that is inaccurate.

Pete

...... well I was pointing out that in most cases one has a pretty good idea that it IS the machine........ or at least that it is a significant possibility..... Depends on the machine.

Possibly "Bubba" has been using the machine, for unknown purposes, OR "Bubba" "fixed" it (mebbe he fixed it like a dog), with whatever he had on hand.

In teh case of the mill in the pic, apparently "Bubba" fixed it, since I doubt Benchmaster let it out the door with that sort of slide contact and alignment. Then ol' Bub went and purty'd it up with some "flaking".

Well, DANG......

PeteF
10-08-2011, 12:13 AM
Jerry, I'm not entirely sure why you quoted me in your post. I have been referring all my posts back to the OP's position with lathes and similar posts I've seen from other members over the years. I don't feel I'm in any position to pass comment about mills and I'm sorry if the impression I've given was to the mill example you provided.

My whole intent was to simply illustrate that there is more than one way to skin a cat ... handy if cat skinning is your forte ;) For those going down this path I would suggest reading Forrest's advice carefully as he has an enormous amount of experience in this area. Having said that, also be aware there are other ways to approach a problem, being aware of what they are, and HOW and more the point WHY they work will go a long way to saving a lot of wasted time, possibly screwing up a perfectly aligned headstock in the process! Relying on one single method of checking a lathe for accuracy is completely flawed, I have already given an example of how a lathe may have a misaligned headstock AND a twisted bed, yet turn 2 collars perfectly accurately. Simply being aware that the lathe needs to also face and bore accurately will indicate that all is not well in this situation.

Pete

Forrest Addy
10-08-2011, 01:40 AM
PeteF: It's all to easy for the noob to over-intellectualise the simple and practical. It's clear you are more concerned with forcing your message than understanding a few pretty basic principles. I suggest you go out to your shop and try a few of your solutions and alternatves. Report back only when you're done and have conclusions to present.

PeteF
10-08-2011, 03:01 AM
Forrest can you please explain why you are attacking me like this. I have suggested an alternative solution and for some bizarre reason whenever this topic comes up you seem to adopt the attitude that it's "my way or the highway" and nobody else's opinion counts in your eyes. Rather than the cheap shots, perhaps you could clearly state what it is that I have written that is incorrect? The "2 collar method" is a tried and true way of checking a lathe's turning accuracy, I'm sorry you don't believe that. A straight edge and feeler gauges is a tried and true way to check a lathe's facing accuracy, I'm sorry you don't believe that either. I have spent time in my shop doing both, and unremarkably both worked as advertised.

Pete

Forrest Addy
10-08-2011, 04:51 AM
PeteF. That's not the case at all. I'm not attacking you. I'm trying to get you pointed in a more productive direction. There's a difference between insistance and contribution that seems to escape you just now.

I'm trying to get you out to your own shop to put your own suggestions into practice thereby learning from them. I've done that countless times to my apprentices and younger journeymen over the years. "Go try it" I would say. "Show me your results". It's a wonderful teaching technique if the time involved isn't excessive or the task wasteful. There's a balance that has to be struck between bringing along the younger generation by having them confirm lessons by experiment and getting the effing work out.

PeteF
10-08-2011, 05:15 AM
Well I HAVE tried it and can confirm that a straight edge on a faceplate and turning 2 collars and then measuring them with a micrometer both work, neither required the use of a DTI which YOU actually insisted was required to confirm a lathe in turning accurately. Now once again I ask you to clearly state what it is that I have said that is incorrect? Maybe without the condescending attitude? It seems as if every time this topic comes up and anyone suggests an alternative approach you jump all over them. In the past you jumped all over Jerry and now you're jumping all over me. Simply because it's an alternative, and possibly inferior, approach to that you suggest doesn't make the alternative "wrong". However if it is wrong, then let's have it? Tell me in plain English why it's wrong, I have tried it and it seemed to work just fine. The manufacturer of the lathe I use suggests using it and one would expect they would know a thing or two about lathes. Nevertheless I'm certainly very keen for you to explain why this method doesn't work.

Pete

Forrest Addy
10-08-2011, 12:25 PM
PeteF. Stop posting: Decouple from this thread. Allow your subconcious to to act while you're doing other things. Then after a couple of days return refreshed to this thread and look over preceding posts. Consider how I suggested the DTI be used and what the point was. In particular consider quantitive data collection for record keeping Vs casual acceptance. Also consider tool, part, thermal deflection in the course of cutting tests Vs DTI scans of qualified (in the metrological sense) gagind features.

I've been here before. I've taught a lot of people. Once in a while someone siezes a line of arguement and brings all progress to a halt with endless repetative discussion until he is either driven from his specious arguement or becomes receptive to wider understanding. I predict you will continue to scramble incoming messages to suit your agenda but just once I'd like to be proved wrong.

PeteF
10-08-2011, 09:49 PM
Forrest I'm a simple guy, I asked a very simple question. You seem to have plenty of time to rubbish me and generally talk in circles. I'm not trying to "prove anyone wrong" so if that is what you're concerned about I can assure you you're mistaken. Some seem to consider life one giant Pi$$ing contest, I can also assure you I am not one of those guys, I'm quite happy with my lot in life and see no need for such antics. Indeed I have never claimed ANYONE is wrong, quite the opposite in fact. That claim was in fact you toward me. So, once again, no riddles, no circles, no telling me when I can and can't post; what, specifically, was it that I wrote that was wrong? Maybe I could then question why it was so horribly wrong that you have gone to such extraordinary effort to attack and rubbish me about it?

Pete

Forrest Addy
10-08-2011, 10:32 PM
I give up. Your notion of engine lathe spindle alignment is correct and all alternatives are silly. The only rational perspective is that of a self taught person working in isolation scorning a hundred years of past experience by Whitworth, Colvin, Gisholt, Connely, and other luminaries of machine tool technology. What I have learned from my mentors is incorrect and I am hostile. Pardon my sarcasm. I'm frustrated and needed to vent.

Please, please, PeteF, do as I suggest in post #28. Disengage and give it a rest for a couple of days. Then go back and read through this thread with a fresh perpective. I will be glad to respond to your remarks/questions Wednesday AM by your reckoning of the international Dateline.

I want you to understand how to determine by quantitive means lathe spindle alignment and how a DTI is essentail to the process prior to the cutting tests. If you lack a good DTI. I will send you one I can spare gratis in the hope you might thereby gain understanding. Please send me your snail mail address via PM. Do you have suitable rods and snugs and a means to attach it?

philbur
10-09-2011, 03:57 AM
What was the question?:rolleyes:

Phil:)

Forrest Addy
10-09-2011, 10:10 AM
Philbur: Exactly. Touche