# Lathe alignment problem.



## mcostello (Mar 23, 2019)

Grab a cuppa of Joe or some popcorn as this is a bit long.

I have a 15" x 50" Clausing Colchester lathe that has a prblem that has Me stumped.
Since when I bought it used it has been out of alignment and I cannot figure out what the problem is.
It turns a taper of .002 in 2" and I cannot seem to adjust it out. It happens no matter how long the shaft is or where it gets turned. I have a Starrett precision level and the lathe levels up like it's supposed to. I have tried shimming up one corner to bias the lathe with no success.
All the gibs have been adjusted. The compound could use being scraped in as some wear is evident.
Locking the compound and cross slide down produces no change.
I can put a 2' bar in the chuck and with about 50 lbs. force no change is evident.
 The lathe has a set of springs with 24 holes provided, and only 20 springs installed when I got it. I bought a new set of 24 and installed them. The taper was .012 in an inch and this bought it down to the present value of
.002 per 2 inches. 
The only thing left was to adjust the headstock to be angled towards the bank. The taper in the part is such that the part is bigger towards the headstock. This is true weather turning or boring a hole.
I adjusted the headstock at 3 different times with no result. I have kept notes and move the headstock .002 at a time with a dial indicator ona ground shaft. The movement makes no change.  I have moved it a total of .022" with no improvement with the result being the tailstock is no longer aligned and I could not drill a hole correctly. 
I thought the chuckmight be in error as it was in bad shape so I bought a new 4 jaw. Since then I have added a collet set up.The 3 jaw and 4 jaw chucks and collet setup all make the same error. 
When I use the tailstock with a live center the problem seems to go away and the error can be dialed out.
It seems like the problem is with the spindle bearings and I have removed the spindle and inspection revealed no apparent problems. No signs of damage apparent. Spindle is not bent, nor any signs of a wreck
visible.
Any suggestions or tips are gratefully appreciated. 
Spindle bearings are around $3000 if purchased from the factory. I am trying to avoid that.


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## goldstar31 (Mar 23, 2019)

My guess is bed wear and possibly the mating saddle.  Remember that  wear of a 3 thous in the first shear near the spindle conceivably  results in  6thous taper in a machined part.

I hope that this is constructive advice

Norman


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## Anatol (Mar 23, 2019)

Norman's advice is from lifetime experience, mine isn't. But I have a similar issue but the runout is on the opposite direction (should yours be called run-in?). See "3jaw chuck alignment problem" thread, many wise suggestions.

 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! That implies the point, floating in space, is a fixed point.

"The 3 jaw and 4 jaw chucks and collet setup all make the same error."
So its not misaligned chuck jaws. Just like my problem. I believe I've narrowed my search to spindle nose. Have you tested there?

One nagging question I have is: is there a possibility of misalignment of spindle axis with the plane of the ways? You're measuring from the cross-slide. 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? (Not the one you have, probably.) If your lathe is like the pics I saw, it has a vertical flat face on the chuck side of the  headstock. Can you/did you indicate from there?


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## mcostello (Mar 23, 2019)

Spindle alignment seems to be the problem. If I move the spindle with a dial indicator, the dial shows it moves as wanted. Taking a cut shows the problem remains. Moving it again shows no improvement. Taper remains the same after biasing the spindle a total of .022. Then the tail stock does not line up at all. Had the spindle out with nothing amiss, but there has to be a piece of rubber in there somewhere.


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## Hopper (Mar 24, 2019)

mcostello said:


> ...
> The lathe has a set of springs with 24 holes provided, and only 20 springs installed when I got it. I bought a new set of 24 and installed them. The taper was .012 in an inch and this bought it down to the present value of
> .002 per 2 inches.



Which springs are you referring to here? The ones in the headstock bearing? If so, sounds like the source of your problem is bearing related. The new springs have brought your problem down from 12 thou per inch to 1 thou per inch. Pretty good improvement there.  Could it be that the bearing components are binding and not moving that last little bit to eliminate the last thou of misalignment? Might pay to pull the bearings and clean and lube and make sure all parts are moving freely. You can inspect races for wear at the same time.

How you could possibly pivot the headstock by 22 thou and not see a change in the taper being turned is beyond me. Unless you are using a tailstock centre to hold the far end of the job? This of course should not be done when testing spindle to bed alignment. Job should be sticking out of the chuck with no tailstock support at all while taking test cut. Job should be at least 1" diameter and stick out no more than 4" to maybe 6". 

Unless of course your adjustment is moving the headstock over by 22 thou, but parallel to the bed axis, which I think is impossible if the headstock pivot dowel pin is intact.


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## mcostello (Mar 24, 2019)

The problem makes no sense to Me also.  The adjustment nut is tight. The races and bearings look in excellent shape. I am not using the tailstock center when doing the test. I am wondering about the pivot pin but the headstock probably weighs in the neighborhood 0f  300-400 pounds. Would have to get the engine hoist in to move it. Does not run hot or anything else. If You read about these lathes on the Internet everyone says they are a great machine. I am thinking that the only thing doing this problem might be a mismatch in the bearing and it's race such as one having the wrong angle. Happened to a friends Jeep, it wobbled slightly going down the street, He thought it was the tires, Some one seen the tires wobble then He found the problem. I had the spindle out but did not think to check to see if the angles matched.


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## deeferdog (Mar 24, 2019)

OK, I'll show my ignorance. What are lathe springs?


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## petertha (Mar 24, 2019)

mcostello said:


> The only thing left was to adjust the headstock to be angled towards the bank. The taper in the part is such that the part is bigger towards the headstock. This is true weather turning or boring a hole. I adjusted the headstock at 3 different times with no result. I have kept notes and move the headstock .002 at a time with a dial indicator ona ground shaft. The movement makes no change.



Just to confirm, if the test cut taper results in larger diameter at the head stock end vs tail stock end, that would infer the head stock is pointing to the operator side of the lathe. So to correct it would have to be rotated to the opposite side of lathe. And you say you did that & no change? Where is the 0.002" referenced from? Are you putting a DTI on the end of the test bar to observe this deflection while adjusting & confirming its actually locking on this new position? 

Do you have jacking type set screws that displace the head stock over once hold down bolts are loosened or how is the new position secured? Assume you are working of a manual but maybe there are more set screws that work opposite to one another (loosen one tighten the other type deal). I have jack screws & found them to be uber sensitive. I would think it would be easier to radically change the HS noticeably out of tolerance but you are saying the opposite - its muted. I wonder if for example your tightening bolts might be in contact with their through holes & you don't have sufficient rotation travel so to speak before the bolt pattern prevents it from going any more?

Another potential source is the head stock is pointing in an up or down inclination relative to bed ways. So maybe the HS was shimmed to compensate that orientation & that  has been disturbed during the adjusting phase?


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## mcostello (Mar 24, 2019)

Yes it seems like the head stock is pointing towards Me. I have referenced the .002 with a dial indicator, the dimensions have been observed and written down so the mistake is not with a faulty memory. Done this 3 times. It does have adjusting screws on the back that are very sensitive and locked down against each other when done. I can move the headstock .022 out of alignment and then it will not drill a hole on center because the drill  makes a circle in the part. If the part was out of tram vertically I could not center drill a shaft that sticks out a foot or two.


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## Hopper (Mar 24, 2019)

mcostello said:


> ... I have referenced the .002 with a dial indicator, .



Again, I'm a little confused here. You should be measuring the .002" taper per 2" with a micrometer, not a dial indicator. How are you measuring the amount of taper on the test piece after turning it?



mcostello said:


> a) I can move the headstock .022 out of alignment and then it will not drill a hole on center because the drill  makes a circle in the part.
> 
> b) If the part was out of tram vertically I could not center drill a shaft that sticks out a foot or two.




a) The circle confirms you have moved the headstock over, but if the lathe is still cutting a taper, it means you must have moved the whole headstock over in a roughly parallel manner instead of pivoting it at an angle.  Put a dial indicator on both the left and right hand ends of the headstock and check how it moves when you play with your adjusting screws. 

b) But you say you can't drill a centre hole, it makes a circle, so should check vertical alignment too. Easy way is to turn a 60 degree point on a short piece of bar in the chuck and then bring the tailstock centre up to meet it. Big errors you can see by eye between the two points. Smaller errors you put a thin  steel rule between the two points. If correct, the rule should sit straight up and down and straight across.


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## Hopper (Mar 24, 2019)

deeferdog said:


> OK, I'll show my ignorance. What are lathe springs?



Colchester uses a circle of springs to set preload on the tapered roller headstock bearings. This allows for take up for wear and also thermal expansion of the spindle etc.


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## deeferdog (Mar 24, 2019)

Thank you Hopper. I suppose everyone else knew that!


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## john_reese (Mar 24, 2019)

_I am not familiar with Colchester so regard my remarks accordingly.  If it has jacking screws to adjust the headstock you are not moving the headstock enough.  You need to know, at least approximately, the distance from the headstock pivot point.  The amount to move the headstock, measured at the jacking point, is the error on the radius x the distance between the pivot and jacking point  divided by the distance over which error was measures.  Another way to look at it: consider the taper as an angle.  The angular movement of the headstock has to be equal to 1/2 the angle of the taper._


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## mcostello (Mar 25, 2019)

All I know for sure is if I move the 1' long bar in the headstock .022" the drill will not start on the center of the part and will make a circle. The tailstock marks are aligned on the center mark. If I turn a bar between centers then I can dial out the taper by the usual methods, or make it much less, it's been a while since I have done it so don't have exact numbers on that process. Also it faces stock flat with a scale across the face. Have not checked with feeler gauges but no gross error there.


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## john_reese (Mar 25, 2019)

If you shift the headstock the tailstock will be out of line with it.  You need to shift it as well.
Start by aligning the headstock to get rid of taper.  Next, turn a piece between centers and adjust the tailstock to eliminate taper.  I just got my Nardini running and it is time for me to do the same tests to make sure it is properly aligned.


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## mcostello (Mar 25, 2019)

I don't want to deviate from the lines scribed at the factory as I would think They basically are right. It seems like there is rubber mounted in there somewhere and things are flexing, moving a measured .022 is a heap. Everything I can put an indicator on seems to say things are solid. I have been trouble shooting this for 3-4 years and have not seem to found it yet. Wondering if Some one replaced the front bearing and race and did not get the race in squarely. Going to bed now will check in tomorrow about 2:00 pm EST.


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## Hopper (Mar 25, 2019)

mcostello said:


> I don't want to deviate from the lines scribed at the factory as I would think They basically are right.



Not necessarily, especially after all these years.  Disregard the scribed lines and set the tailstock by turning a test piece between centres AFTER you are good and finished with setting the headstock spindle parallel to the bed ways.

Meanwhile, you need to set two dial indicators on the headstock, one at each end, so you can tell how the headstock is moving when you adjust those jacking screws, ie pivoting vs moving over but remaining parallel to the bed. Just measuring what the end of a 1-foot bar is doing is not telling you the full story.

If you want to set your headstock spindle parallel to the bed it is essential that you first know for 100 per cent sure how and where that headstock is moving when you adjust it.

Once you know how the jacking screws are in reality affecting the headstock position, you can then make a plan to use that adjustment to bring the spindle back in line with the bed.


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## TonyM (Mar 25, 2019)

Have you checked to see if the bearings have been fitted correctly in relation to the max runout marks.


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## mu38&Bg# (Mar 25, 2019)

If you are measuring taper with an indicator, you aren't actually measuring taper. Measuring taper is turning a length of bar and measuring diameter along it's length to determine cylindricity.

Correcting this step will allow you to continue with setup.


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## mcostello (Mar 25, 2019)

I am measuring the taper with a micrometer on the shaft. I have been only using 1 dial indicator though. I have pulled the spindle out but did not think to see if the bearing race was fully set square in it's bore. I can dial the tailstock in and get something like .001 difference in 12". Maybe should not have called it taper as it is only a difference. I will get on it soon as possible but a friend needs some work done.


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## mu38&Bg# (Mar 25, 2019)

.002/2 of taper is rather large. Even if bearings were totally shot, I'd expect moving the headstock to change the taper on a turned shaft. I'm uncertain why the tailstock comes into the discussion when trying to sort headstock alignment.


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## mcostello (Mar 25, 2019)

I am hoping that it shows the lathe is actually of turning a straight shaft, and not some other undiscovered problem. It was .012 in 2" when I started. Installing new springs seemed to help but I cannot make it any better.


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## mcostello (Mar 25, 2019)

.002 in 2" is miserable to work with.


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## goldstar31 (Mar 26, 2019)

I wonder whether there is a very simple explanation that has yet to be explored.  I was re-reading George Thomas in one of his books called the Model Engineers Workshop Manual and was plowing my way through his discourse( s) on alignment.  I wonder if tool height or a worn base on a tool holder might be or contribute to cutting a waisted cone of metal.

Again, I was wondering whether  tests should be carried out with the additional and problematic top slide instead of a more rigid tool station utilising the boring table.

And then there is the story of 'points per square inch'- the story of those who can scrape and those who ---well, cannot.

Perhaps enough to get on with- methinks?

Norm


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## Hopper (Mar 26, 2019)

mcostello said:


> .002 in 2" is miserable to work with.



So get two dial indicators and set the headstock spindle parallel to the bed, without that .022" offset,  as already discussed.  It's really not that hard once you have a second indicator telling you exactly what that headstock is doing when you turn the jacking screws.

You are right that the fact that your lathe will turn a parallel shaft when between centres, after suitable "dialing in" of the tailstock centre indicates the source of the problem is not bed wear or low tool position or loose gibs or anything else like that.

So the problem must be headstock to bed alignment. Buy a second dial indicator and spend some time and care getting it just right.


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## mu38&Bg# (Mar 26, 2019)

I think some photographs of what is being adjust and how things are being inspected would be helpful. Something is being lost in communication. It's simply not possible to change the angle of the headstock relative to the bed and not see a change in taper.


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## mcostello (Mar 26, 2019)

That's what I thought also. The adjustment screws are buried and hard to get to. It will have to wait for a while as I am swamped with work and need the lathe for it. Thanks for the ideas and I will continue  this post when time allows.


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## petertha (Mar 26, 2019)

mcostello said:


> I am hoping that it shows the lathe is actually of turning a straight shaft, and not some other undiscovered problem.



I made this suggestion on another post regarding head stock alignment. Any chance you can get hold of an accurate test bar with taper profile on one side? Its the best 50 bucks I ever spent. For example if you have MT5 spindle, insert a MT5-MT3 adapter sleeve, then the MT3 ended test bar. Now you have temporarily completely eliminated chucks and cutting forces & stock overhang... you can focus on alignment as step-1. Mount the DTI to apron  & traverse down the side of bar to detect any headstock yaw rotation in or out. You should also put DTI ball on top of bar, repeat & detect if the headstock is pointing up/down for whatever reason (which will also cut a taper).

But getting back to the headstock rotation, putting a DTI on the end of the bar should be showing you movement as you adjust the jack screws & re-lock down the headstock. Goingto the end of the bar is maximizing this sensitivity. The rotation point is somewhere inside the headstock, but we dont care. We are looking for confirmation of movement direction & amount at some consistent poisition for test purposes. Note that some lathes actually specify a permissible amount of 'point in'ie to operator side of tailstock. I had a somewhat similar issue adjusting my tailstock in/out. Even though I could displace the axis with the 2 adjusting screws to a target zero position with DTI in constant contact with a test bar, turns out the torquing effect of securing down the position clamp bolt could make it wander off zero again. So it was a bit of an iteration. But point is I would have never known this unless I had a direct reading dial giving me constant feedback. That's why I wonder if your headstock hold-down clamping mechanism is possibly somehow over-riding your jack screw setting.

Something is not adding up because the amount of discrepancy you are seeing by cutting a coupon should stick out like a sore thumb on this basic alignment test. Now if the alignment happens to show its within accurate tolerance, then we proceed with work holding & cutting related issues. But cutting stock to ascertain taper is practically a waste of material if the headstock orientation is questionable at this time. Introducing the tailstock over & above this is a recipe for chasing your tail. Maybe the HS is out & TS is in, but how would you ever know?

I think this 'barbell' or 'Rollie's dad method' are the go-to diagnostics where people have 'cast in place' headstocks. In other words they are presuming the factory alignment must be pretty close to begin with. But when you have a lathe with the ability for the HS to be rotated & reset into a yawed position, all bets are off. Its a different machine. You need to nail this down first.


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## Hopper (Mar 26, 2019)

dieselpilot said:


> I think some photographs of what is being adjust and how things are being inspected would be helpful. Something is being lost in communication. It's simply not possible to change the angle of the headstock relative to the bed and not see a change in taper.



+1 on pictures. We seem to be going in circles otherwise. 

+1 on impossible to rotate headstock without changing taper -- unless the pivot pin is missing, broken or otherwise fubared, or not fitted to this particular model etc. A dial indicator placed each end of the headstock would reveal what is actually going on.


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## mcostello (Mar 27, 2019)

When I can get to it this will be the first thing I will try. I have not thought of up and down as being important in this problem, but I will research this also. I am planning to see if I can pull the pivot pin but it might involve pulling the headstock which is probably in the neighborhood of 300-400 pounds. I don't have a test bar but I do have a collet setup and some ground stock which would work. Nothing makes sense at this time, but I will keep on it. Thanks, Mark.


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## john_reese (Mar 27, 2019)

Mcostello,
You need the pivot pin to remain in place. Just back off the hold down bolts a bit, then go after the jackscrews.
I am not in favor of test bars.  You don't know how true they are and a little dirt or a burr in the taper can throw them off.  Instead, chuck up a heavy bar.  It needs to be chucked the full length of the chuck jaws.   Make it as long as you can get away with without chatter during light cuts.  Starting about an inch from the end reduce the OD of the bar up to about an inch from the chuck.  There are two reasons for reducing the OD: it eliminates the potential for tool wear between the ends of the bar, and it saves time because you don't have to machine the whole length of the bar.    Take a cut off the raised bands to true them up.  Take a light cut off both raised bands without disturbing the cross slide or compound between cuts.  Measure both both diameters.  Ideally they will be the same.  If not, adjust the jackscrews and repeat the test until the cut diameters are equal.

Use a large diameter bar to reduce the effects of deflection.  Thick walled tubing is OK.
Use the longest bar that is practical to increase the sensitivity of your measurement of taper.
No tailstock or steady rest support.
Get the headstock running true before you even think of messing with the tailstock.


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## mcostello (Mar 27, 2019)

What You have suggested I have done many times, it shows the headstock  end bigger than the tailstock end. Adjusting from there does no good. I have not used two indicators yet to see what that shows.


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## goldstar31 (Mar 27, 2019)

If the bed is not in twist, you have wear in the front shear or wear or mis-adjustment in the saddle.

I hope that you have  not been using a damn fool top slide which is another variable that can cause trouble

Cheers

Norm


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## petertha (Mar 27, 2019)

Lets say hypothetically the HS was aligned 100% parallel to the way axis viewed from the top. But you had microscopic grit or burr or casting warp or whatever between the underside of the HS block & the mating face of the lathe bed such that the head stock was pointing net up or down slightly viewed from the side. Even assuming perfect cutting finish, nil cantilever bar deflection under tool load, stress relief, material skin effect... etc. two 'different' barbell diameters would not point you to the correct HS misalignment diagnosis. Worse yet, you 'interpret' this resultant taper cut as a 'typical' deviation in the horizontal plane and now start rotating the HS to compensate. Now you have 2 problems instead of just 1 and they are somewhat masking one another. If you ran a DTI along the top of a test bar, it would indicate this.

There are ways to measure test bars to get a sense of accuracy by rotating them to different marked quadrants, at different length positions, remove & re-insert to different clock position. Counting on a lathe to cut to the +/- degree of center-less grinding operation on a test bar seems like a stretch to me. Never say never with an import, but I would hope it should be as good or better unless a completely botched job. Actually that's not even true. The ground finish allows you to compare diameters all the way down the test bar in opposing orientations using your same best micrometer. So if that checks out the remaining deviation to validate is banana effect which should always hilite the same under spindle  rotation. For sure the tapered surfaces have to be spotty clean. But if we are going to second guess that then we may as well include mounting anything to our tapered spindle nose, or dead centers into the tailstock etc. The fact that things are not adding up on this makes me think its something outside the normal box.


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## mcostello (Mar 28, 2019)

This is odd. Nothing makes sense. I do have time to put the collet attachment on and check with a ground bar. Will report back tomorrow night. Another funny thing is when  I turn a shaft and it is bigger on the headstock end, then go to boring out a holeit also is bigger on the headstock end. Seems like it is just the way it wants to go.


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## petertha (Mar 28, 2019)

Actually both attributes make sense if HS is pointing out to operator side I think.


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## goldstar31 (Mar 28, 2019)

I could be wrong but I have this gut feeling that 'something needs to be attended to in addition to fuddling with the headstock.

 I recall tackling a wreck of a lathe and filling the gaps ( which shouldn't really be there) where the badly fitted gib strips  didn't quite fit with metal based polyester.

There is a whole library of comments on badly. fitted gibstrips in  Chinese/Taiwan lathes.
So these things are not unknown.  I think Baz was part of the discussion

Norm


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## goldstar31 (Mar 28, 2019)

On a different quest , I was browsing John Moran's excellent Gadgetbuilder.com site and noted again that he had written up how he had corrected his Far Eastern lathe.

I noted that he included a sample test of alignment checks.

There you have it- or not

Norm


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## ShopShoe (Mar 28, 2019)

I just re-read the original post again.

It seems to me that there may be something in the alignment or tracking of the saddle / cross slide / compound / toolholder area.

If it was my lathe, I would probably disassemble those parts and inspect them carefully, following advice from some of the books mentioned earlier. I would use the same reference material to check the bed again with independent measurements, not using the tailstock, headstock, or saddle assembly as a reference.

I would expect to find some things that need attention in all of this, some of which I might be able to address and some I might have to live with. I would be very careful in deciding to do any scraping or grinding, which could end up creating an additional error that would make the general situation worse.

In reassembling, I would put the saddle together, then test alignment without the cross slide. Add cross slide and re-test, then add compound and test. If I was to try cutting a bar for basic testing, I would try it without my usual toolholding setup (IE: remove the QCTP if I'm using one).

I'm rambling, I know, but I had half-a-cent to add.

My gut feeling, which is totally unscientific, is that there is more than one problem in general, as well as a specific problem causing the basic error.

--ShopShoe


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## goldstar31 (Mar 28, 2019)

ShopShoe
                      Your comments are clear enough. . I suspect that there is saddle problems.
In any case, there should be a  constant maintenance schedule on the lathe ways and the saddle.. 
Regards

N


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## mcostello (Apr 9, 2020)

I would like to put this thread to rest and share the solution if it happens to anyone else. The lathe still turned big at the headstock end. I finally was able to find a roundtoit and tore it down. Loosened all the bolts holding the headstock down and loosened the alignment block. Up to this time moving the adjustment block was all I did. I decided to remove it. I was working off a factory supplied repair manual. The page i was needing was missing and I did not know it. My SIL has a Friend who specializes in research and He found another copy, same front pages and all with stains and all marks being the same including the missing page. The lathe has a pivot pin in the middle of the headstock underneath where it is hard to see. I took the alignment block apart and found one hole was clean and the pin was in contact with the pin. The other hole was half filled with chips and the pin could not press on the pin. I cleaned everything up and greased things to prevent corrosion problems in the future.Someones slackness cost Me more than 20-30 hours work, let alone the extra time to fit parts that I make. At least it is fixed now. I only needed to look 1 step beyond where I was but never had the time. It all makes sense when I got all the facts. Thanks for the help.


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## petertha (Apr 9, 2020)

That's could to hear. Did you take any pics along the way you could post? Alternatively while its fresh on your brain, could you post a sketch or picture of your repair manual page showing the part & pins? You wouldn't believe how many times this same issue comes up on lathes with bolt-on head stocks.


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## Danuzzo (Apr 28, 2020)

Read this thread with interest. I am having taper issues on the 7x mini lathes I have tried. I will start another thread so as to not hijack this one.


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## mcostello (Apr 28, 2020)

I don't know if the page is copy righted and don't want to make problems. If allowed I will post them.


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