# Question About Headstock Alignment



## ddickey (Mar 21, 2017)

I bought a MT3 precision alignment bar a while back. Decided to try it out today. I ran an indicator along the 13" length and showed .003" taper. I had a .075" shim under my far TS foot. I reduced it to .045" and the indicator now showed zero taper. On the vertical plane it was .00039" (.01mm). I think I'm good there as I'm sure there is some sag in the bar.

Anyway I remember reading an article about Rollie's dad's method so gave it a try. Let me know if I did this correct. I zeroed my indicator at the low point  and got .001" movement at the HS. Did the same at the TS and got .0055". After doing the calculation I get a delta of .0025". Figured I'd try to shim my HS like the instructions say but in the process I found a couple small jack screws used to align my HS. I decided to abandon the shim and just make a HS adjustment. No matter which way I moved the HS the delta on the indicator didn't change. I did get a nice big taper though which I aligned back out.

Any thoughts on what I did? Does shimming the HS do something else rather than just aligning the HS?


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## 4GSR (Mar 21, 2017)

Dicky,

Without knowing the overall condition of your bed in means of wear, I would leave well enough alone.  Adding the shims as you have indicated leave me to believe, you have serious wear issues in the major components of your lathe including the bed.  Not familiar with your lathe, but common with all lathes, they wear after years of use regardless how well you take care of the lathe.
What you have to do is start from the foundation and work up until the problems are solved.  So starting with the foundation, the bed, do you have a straight edge of known accuracy that can be used to determine flatness of each bearing surface or shear.  Feeler gages can be used for this exercise.

Don't get me wrong, you are doing a good job determining areas of wear such as under the tailstock, and that's good.  The headstock should be the last thing that should not have any wear under it.  It  should be correct as it left the factory.  I think it has told you there is wear on the bed, the 0.003" you're chasing, wanting to add shim under the headstock and don't do.


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## Dave Paine (Mar 21, 2017)

When I tweak something to try and fix a problem and it makes things worse, I try to go back to basics to find out where I went wrong or to find the root cause of a problem.

The fact you measured a taper means something is out, could be due to wear, could be twist in the bed, etc.

I would recheck the lathe level.  A good video by Keith Rucker.  Try and mount the level on the carriage.






Keith shows machining a short test adapter which is exactly the same OD as the quill, then mount the adapter in the chuck and test the height from the carriage with an indicator at the headstock, then the top of the quill.   I thought this was a good way to check alignment.

If someone added shims in the past you need to try and assess what issue they were trying to fix.  You may want to try and confirm the axis of the headstock and tailstock are parallel to the lathe bed.  Can you mount the MT3 test bar in the headstock and separately the tailstock, then run an indicator down the bar?  The bar may have some sag, but at this point it is worth trying to find out the present state of the machine before doing any more tweaks.


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## ddickey (Mar 21, 2017)

Yeah that's what I did. There were no shims when I bought the lathe. At first I tried taking the twist out by using leveling casters which worked some but when I realized I only had 2 of the 6 casters touching the ground I knew I needed to try something else. I decided to shim under the feet of the lathe on the TS end with .075" shim and got all the taper out. This was confirmed by using the two collar test bar method. That was a while ago so checked again and saw the taper. This time using a MT3 test bar. I reduced the shim to .045" and then the indicator showed no taper over 13". I did not take any cuts however. Since I had the alignment bar in the HS tried Rollie's dad's method. According to what I read my spindle is misaligned .0025"


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## ddickey (Mar 21, 2017)

After some reading I will abandon the RDM method. Will put things back together. I have a project to do.


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## oldscouser (Mar 21, 2017)

Hello Dickey.

The RD method of lathe alignment is very powerful.  You can use the method to align the headstock in both horizontal and vertical planes.  And then the tailstock with its ram retracted and then the TS with its ram extended, again in both planes. 

As you know, for a constant diameter test bar, the RDM calculation uses high and low gauge readings at 2 locations (1 and 2).

The misalignment is given by

dA = (G21 + G22)/2 - (G11 + G12)/2

Once the dial indicator has been set it at one position it should not be reset at the second.

So, for example, say your gauge shows +0.0005" and -0.0005" at position 1 (the headstock) and +0.0025" and -0.0025" at position 2 (the tailstock) then 

dA = (+0.0025 - 0.0025)/2 - (+0.0005 - 0.0005)/2 

i.e. dA = 0

the headstock is perfectly aligned in the plane you are measuring.

Hope this helps.


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## ddickey (Mar 21, 2017)

I monkeyed around with it some more but gave up as I could not get the difference <.0018". 
I think I did it wrong as I was adding the two then dividing not thinking one number is a negative. Oh well.


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## oldscouser (Mar 21, 2017)

A way to avoid negative numbers is to zero the dial indicator at the lowest position and then the other 3 readings will all be positive.


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## ddickey (Mar 21, 2017)

Good idea. Was just not sure if I was supposed it leave it alone.


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## Zoltan (Mar 25, 2017)

That's not how I do the RDM method.

RDM compares the averages of the two measurements. For the headstock measurement I'll adjust the DTI so the needle moves the same amount above and below zero. Then I'll move the DTI to the tailstock end. If the needle travels the same amount above and above zero (even if it's a lot more movement)  then the headstock is aligned. If the needle travels further on one side of zero, then the headstock is out of alignment by half of the difference. Honestly, I'm not sure how I'd be able to do it by setting zero to so all travel is positive.


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## astjp2 (Mar 25, 2017)

If you have a .0001 dti, build the tools to check your bed first, then you know what you are working with.  My rockwell was out .008, the new bed is .0006.  Big difference in what your other measurements would be if the bed is out that much.  Tim


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## Happycamper (Mar 26, 2017)

DD, got the same problem, at the spindle using the test bar, it's dead on. At the end of the test bar I show 3 thou off. I leveled the bed and it didn't change so I ground the jaws. Didn't help. Can't figure it out. I have 6 levelers on the base, 4 on the head stock base and two on the tail stock base. There are 4 levelers on the bed at the head end and 2 on the tail stock end. I am only checking the Y axis though, not up and down. The problem is that if I chuck up a long bar, because of the misalignment, it will bend when the tail stock center is locked in to the end of the bar. You can see a visible out of round movement then in the middle of the bar. I always thought RDM was to check alignment of the tail stock to the center of the spindle. I also thought that grinding the jaws would cure the problem but it didn't. Comments would be appreciated. DD didn't mean to hijack your thread but since we both have similar problems I thought I'd add mine to yours to see what kind of answers we get. I'm leaning toward adjusting the levelers on the head end of the Lathe.


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## astjp2 (Mar 27, 2017)

OK, so your bed is worn, you need to check your bed for how much wear you have.
http://www.hobby-machinist.com/threads/dovetail-tolerance.43355/

Also look up the King way alignment tool for more examples


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## terryw123 (Mar 28, 2017)

I have a Clausing late and if I put a precision ground shaft in the chuck and an indicator on the saddle and ran it down the shaft, by the time I got 18 inches from the check I was about .020 off.  I found out that my whole head stock is adjustable.   I could adjust it and it would take all taper out.  Worked great.


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## ddickey (Mar 28, 2017)

Then turn the stock a quarter turn and try again. Does it stay true?


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## chips&more (Mar 28, 2017)

terryw123 said:


> I have a Clausing late and if I put a precision ground shaft in the chuck and an indicator on the saddle and ran it down the shaft, by the time I got 18 inches from the check I was about .020 off.  I found out that my whole head stock is adjustable.   I could adjust it and it would take all taper out.  Worked great.


Hi, just curious, what model Clausing lathe do you have?


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## terryw123 (Mar 28, 2017)

I have a clausing/colchester 8000 series 11 inch.


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## oldscouser (Apr 3, 2017)

A few thoughts to end on.

Starting with the obvious.  The spindle of the headstock rotates about its axis.  We want the spindle axis to be parallel with the bed of the lathe and also in line with the bed ways.

The spindle will probably have a Morse taper machined at the chuck end.  This Morse taper will have its own axis that may, or may not, be aligned with the spindle axis.

A: If the taper axis is parallel to the spindle axis but offset (we are talking the odd thou or so here) then it will be eccentric and a test bar mounted in the Morse taper will show the same circular motion at both its ends.

B: If the taper axis intersects the spindle axis but is not aligned with it then a test bar mounted in the Morse taper will show different circular motions at its two ends.  But the motion will be in phase (the min and max dial indicator readings at the two ends of the test bar will occur at the same angular position of the headstock spindle).

C: The third case for Morse taper misalignment is a combination of the first two.  The MT is angled to the spindle axis and does not intersect the spindle axis.  In this case the motions at the two ends of a test bar mounted in the MT will be out of phase.

The best way forward is to disregard the MT and mount the parallel end of the test bar in a 4-jaw chuck and adjust the jaws to get a zero total indicator reading adjacent to the chuck.  Move the dial indicator to the other end of the parallel section of the test bar and rotate the chuck noting the min and max readings.  This is the Rollie’s Dad’s method.

The headstock should be adjusted to give equal min and max indicator readings about the zero at the free end of the test bar.  After each adjustment of the headstock the end of the test bar mounted in the 4-jaw chuck should be zeroed before checking the free end.

Hope this is of use.


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## ddickey (Apr 3, 2017)

Thanks. Interesting as I've not thought about the MT and the spindle being two separate axis'.


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## ddickey (Apr 7, 2017)

I tried it tonight and the min max readings at 12" are virtually the same. About .00075" different. I was not able to get zero run-out at the chuck, ~ .0005-.00075. I also took a face cut on a 3" diameter piece and had maybe a thou movement on the outside. 
I guess this means my headstock is in alignment. 
Now if I could figure out why i'm cutting a taper when using center support.


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## oldscouser (Apr 7, 2017)

Sounds like you are making progress Dickey.  I assume you checked both the vertical and horizontal alignment of the headstock?

So now you should check the tailstock alignment.  Your test bar should have centres ground at each end.

Loosely mount the parallel end of the test bar in your 4 jaw chuck and locate the opposite end on a dead centre mounted in the tailstock.  Adjust the jaws of your 4-jaw chuck to get a zero total indicator reading adjacent to the chuck.  Make sure the other end of the test bar is sitting firmly on the dead centre in the tailstock.

Now run your dial indicator along the length of the test bar.  There is no point in rotating the chuck/bar for this operation.  The dial indicator shows directly whether the position of the dead centre in the tailstock is aligned with the headstock spindle.  You should then extend the quill or ram of the tailstock and repeat the measurement with the dial indicator.  This second operation will show if there is any angular misalignment of the tailstock.

The above tests should be repeated for the vertical or horizontal, depending on which you did first.  It all takes time and effort but it's worth it in the end.


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## ddickey (Apr 7, 2017)

Oh no, I forgot to check vertical alignment of the HS. I will try this when I get home.
Thanks.


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## ddickey (Apr 7, 2017)

Over an 8" length there is no movement on the vertical and horizontal plane with bar in the TS dead center. With quill extended vertical did not move but horizontal indicator showed +.0005".
I also tried the vertical alignment for the HS and the results were exactly the same as the vertical or at least appeared that way.
I think I'll leave it now and see how she cuts.
Thanks for the procedure.


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## oldscouser (Apr 10, 2017)

Great.  You are going through things systematically and ticking off the boxes one by one.  A half thou misalignment over 8 inches looks pretty good to me.

As they say, the proof of the pudding is in the eating, so you will have to let us know the results of your efforts.


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## 4GSR (Apr 10, 2017)

ddickey said:


> Over an 8" length there is no movement on the vertical and horizontal plane with bar in the TS dead center. With quill extended vertical did not move but horizontal indicator showed +.0005".
> I also tried the vertical alignment for the HS and the results were exactly the same as the vertical or at least appeared that way.
> I think I'll leave it now and see how she cuts.
> Thanks for the procedure.


ddickey,
I would be tickled pink if my lathe would cut within double the numbers you are getting.  
Call it good and move on and do some machine work. 
You have done a great job on calibrating in your lathe and fine tuning it.  Come to my place next and tune up my lathe for me.
Ken


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