Thread: Headstock to Tailstock alignment

If a lathe is not sitting perfectly flat, I don't mean with no wobble, but so that there is no twist in the bed as you move the tailstock away from the headstock it will move slightly to one side of the centre line.

You need a level placed across the bed and as you move it away from the headstock the bubble must not move.

If it does then shim the feet of the lathe until it is flat. The actual position of the bubble is not important as long as it is always in the same spot.

Thanks @Bohdan

I hadn't thought of that. Checking now it seems good, at least to within the accuracy of my eye on a spirit level. However i might also try doing the test at two lengths. One with wood as I described and then again just with centres. If I centre it at a distance, when i move the tail right up so the centres are almost touching, the points should align. If it aligns near and far then i should be good.

Well this can be a tricky one, for example, I have a very good friend of several years who is an accomplished turner who bought a well known brand of lathe on getting it home to his horror the tailstock was 1mm too low, straight out of the box. He had to pack the headstock up 1mm and to say he was annoyed would an understatement.
So start with the possibility that its a manufacturing issue and therefore its gonna be hard to correct, with some very accurate lathes ie VB 36 the floor its bolted must be flat, very flat to the point you may have to shim the feet and this lathe far from being a lightweight lathe, but mounted on a uneven floor will throw it out.
Steinert(R) VB36
But try this
There is a double ended morse taper set up you can use to align the head and tail stock from Carbatec
Nova Morse Taper Aligner | Carbatec

My centers line up near enough spot on but I can get alignment issues at times from the chuck itself as the jaws themselves dont always hold the work perfectly strait. When the jaws grip one side of the wood may be a bit softer than the other. If using the chuck and tailstock I bring up the live center while the chuck has a loose grip. When the tailstock is tightened up then I tighten the chuck jaws. I usually expect there will have to be some truing up required if the piece has to be reversed.
Regards
John

You need to eliminate the chuck from the equation so take it out and check the alignment using fixed centers in both the headstock and the tailstock. If the centers align your issue is in the chuck; and that's not uncommon in the slightest. Precision machining on a metalwork lathe is always done between centers where the workpiece is ever expected to be removed and replaced or rotated end to end.

If you have access to them and your lathe bed is long enough you can use MT shanked drill bits instead of centers; their extra length magnifies any misalignment (providing they themselves aren't bent or incorrectly ground).

Originally Posted by hughie

But try this
There is a double ended morse taper set up you can use to align the head and tail stock from Carbatec
Nova Morse Taper Aligner | Carbatec

These are good for when you know that the points are vertically aligned and have swivelled your headstock 'out of true' for some job but now want to return to using a tailstock.

What I want is a MT-mounted laser pointer that shoots straight along its' axis.

Then this could be mounted in the head- or tailstock and the alignment checked for true with the tailstock at various positions along the lathe bed. I've found out the hard way that not all lathe beds are machined flat or parallel or truly aligned.

I keep looking, but I haven't found one yet...

Originally Posted by Bohdan

If a lathe is not sitting perfectly flat, I don't mean with no wobble, but so that there is no twist in the bed as you move the tailstock away from the headstock it will move slightly to one side of the centre line.

You need a level placed across the bed and as you move it away from the headstock the bubble must not move.

If it does then shim the feet of the lathe until it is flat. The actual position of the bubble is not important as long as it is always in the same spot.

Do that first to ensure that you aren't getting twist from an uneven floor or legs.

If OK, then do the kiss test with two Morse tapers, checking for both vertical and horizontal alignment.

If they kiss you might be good, however, not necessarily. As the tailstock moves away from the headstock you can get the following....

Kissing centres but not coaxial to bed.jpg

Until Skew gets someone to produce that Morse taper mounted laser pointer, I just sight through the headstock looking from the backend towards the tailstock positioned at the far end of the lathe. You have to reduce the aperture at the back of the headstock for this to work. Turn a small plug and drill a hole through it. I do the sighting at night (in the dark) with just a small light shining on the tailstock end.

You may also need to do the same from the tailstock end.

If all of the above checks out then you probably have a chuck or chucking issue.

Thanks for the ideas all! I will keep you posted how I go.

I was thinking of that laser solution today. A battery powered pointer in a M2 taper, with a target for the other end. Only hard part is making sure they are straight. I smell a business opportunity

Ok 50mW laser head is ordered.... $2

So if I take an MT2 taper, and get it machined out to fit the cylinder. I get 4 machine screws taps around it to use as aligners.

Now if I put it in the late and shine it on anything, the further the better, and hand rotate the lathe the dot will not move if it is centred. Adjust the alignment screws till it does

Now I need a target in the tail stock. anything flat scored with a centre dot and rings will do. Put it in the headstock to mark it.

Now theoretically, i should be able to put the laser in the head stock, target in the tail and check alignment over the length of the bed.... Will let you know if the theory check out! Need to find a machinist!

I wonder if I can fit some button batteries and a switch in the rear of the taper??? Checking while spinning would be ideal!

To be honest I would not be too hung up about alignment to the enth degree. By all means get things as close to aligned as you can but remember there are 2 basic kinds of turning. Faceplate and between centers. Between centers or 2 points is a strait line anyway. Both ends have flex on the 2 points then no real problem. A chuck kind of replaces a faceplate by holding the work rigid. Rigid but not always in line with the 2 centers. Chuck and tailstock really shows up things that dont line up. The longer then more so. If something can be done between centers then do it. Things like bowls and platters on a chuck you can use the tailstock for security until its round and balanced. Chucks are very handy and save work but have made us a bit lazy.
Regards
John

Originally Posted by hughie

Well this can be a tricky one, for example, I have a very good friend of several years who is an accomplished turner who bought a well known brand of lathe on getting it home to his horror the tailstock was 1mm too low, straight out of the box. He had to pack the headstock up 1mm and to say he was annoyed would an understatement.
So start with the possibility that its a manufacturing issue and therefore its gonna be hard to correct, with some very accurate lathes ie VB 36 the floor its bolted must be flat, very flat to the point you may have to shim the feet and this lathe far from being a lightweight lathe, but mounted on a uneven floor will throw it out.
Steinert(R) VB36
But try this
There is a double ended morse taper set up you can use to align the head and tail stock from Carbatec
Nova Morse Taper Aligner | Carbatec

Yup. I have, the only, Oneway 2436 is Aus. Not bragging but, they're effin expensive machines!! And you'd think they'd be perfectly set up when sent out of the factory... The head and tail are slightly out to the side, about 1mm. One day I'll get around to aligning them... But it does cause slight issues when grabbing something short in the chuck and also holding with the tailstock.

So never assume a lathe, or other machine, is set up correctly when you get it...

Originally Posted by NeilS

Do that first to ensure that you aren't getting twist from an uneven floor or legs.

If OK, then do the kiss test with two Morse tapers, checking for both vertical and horizontal alignment.

If they kiss you might be good, however, not necessarily. As the tailstock moves away from the headstock you can get the following....

Kissing centres but not coaxial to bed.jpg

Until Skew gets someone to produce that Morse taper mounted laser pointer, I just sight through the headstock looking from the backend towards the tailstock positioned at the far end of the lathe. You have to reduce the aperture at the back of the headstock for this to work. Turn a small plug and drill a hole through it. I do the sighting at night (in the dark) with just a small light shining on the tailstock end.

You may also need to do the same from the tailstock end.

If all of the above checks out then you probably have a chuck or chucking issue.

I thought about making a laser pointer set up but realised it won't work. Need a laser that has a dot >1mm for it to be reasonably accurate. I don't think they work properly trying to shoot them through a small hole.

Originally Posted by orraloon

To be honest I would not be too hung up about alignment to the enth degree. By all means get things as close to aligned as you can but remember there are 2 basic kinds of turning. Faceplate and between centers. Between centers or 2 points is a strait line anyway. Both ends have flex on the 2 points then no real problem. A chuck kind of replaces a faceplate by holding the work rigid. Rigid but not always in line with the 2 centers. Chuck and tailstock really shows up things that dont line up. The longer then more so. If something can be done between centers then do it. Things like bowls and platters on a chuck you can use the tailstock for security until its round and balanced. Chucks are very handy and save work but have made us a bit lazy.
Regards
John

My sentiments exactly after all wood turning is free hand turning. One of my lathes doesnt actually have a tailstock, but then I am not a spindle guy, hollow vessels etc is my main thing

Originally Posted by orraloon

To be honest I would not be too hung up about alignment to the enth degree. By all means get things as close to aligned as you can but remember there are 2 basic kinds of turning. Faceplate and between centers. Between centers or 2 points is a strait line anyway. Both ends have flex on the 2 points then no real problem.

Originally Posted by hughie

My sentiments exactly after all wood turning is free hand turning. One of my lathes doesnt actually have a tailstock, but then I am not a spindle guy, hollow vessels etc is my main thing

Yeah, Nah!

Yes, we are free hand turning, but only in the fact that the tool is handheld. Yes, between two points is a straight line. Yes, there is flex and the tool rest can be positioned to accommodate any misalignment.

Yes, it is not often an issue for "face plate" turning, i.e. bowls, platters, HF's etc held only on the headstock side.

However, the misalignment if present will introduce issues for the turner in plenty of common turning scenarios, notably pen and fine spindle turning.

The issues arise when one, or both ends of the turning / mandrel / jig etc are constrained, that is held securely in place and constrained to spin in a plane perpendicular to the head and / or tailstock axis. A prime example of this is using a pen mandrel on a lathe that has alignment issues, that introduces a bow or curve in the mandrel, which often means a pen barrel turned eccentric to the tube and mandrel.

We are seeing more of these issues arise because turners are employing mounting techniques such as spindle turning with a chuck securing the headstock end of a blank with auxiliary tailstock support via a live center. In the past similar issues were encountered using "cup chucks" - a cylindrical jamb chuck.

The severity of the issue is compounded by the misalignment/s and offset/s of the headstock and tailstock axes.

Firstly, the offsets,

1. vertical offset - the height above the bed.
2. horizontal offset - the axis relative to the centerline of the lathe bedways.

Those offsets can be caused by the quality of the milling of the,

• bedways
• boss on the foot of both the headstock and tailstock castings
• bore of the tailstock quill
• spindle nose thread on the spindle.
• and also on any auxiliary items used cup, scroll & collet chuck/s etc, chuck adaptors, spindle extenders, MT accessories, mandrels, bushes etc. - remember this is by two - for headstock & tailstock.

Then we have the assembly of the lathe components, bed, headstock, tailstock castings. Next is the installation setup issues.

Ideally the bedways, headstock (spindle) axis and tailstock (quill) axis are assembled so that the components are concentric, coaxial / colinear, and co-planar and remain that way for the life of the lathe and the full travel of the headstock (if relocatable) and tailstock over the bedways.

It is also a nicety if they are centered over the center of the bedways, and perpendicular to the vertical plane through the lathe bed centerline / axis. For that to occur the base of both the headstock and tailstock castings must be milled perpendicular to the desired vertical plane through the castings etc.

Others have covered the lathe installation setup alignment - i.e. ensuring the lathe bed is preferably horizontal and in one plane - no twists or bows.

Not really rocket science for quality production but then the bean counters become involved, meeting price points whilst maintaining maximum returns (profits). Quality slips through production shortcuts, lax quality assurance / control (if any - often the customer is the QC), or production snafu's.

As a surveyor I'm very familiar with the errors introduced when all of those conditions are not met - they do indeed introduce errors - often very significant errors. So, to dismiss them as not relevant as we are "hand turning" is not really true.

The severity of the issues are very much dependant on the "size" of the errors and the proportions of the blank being turned. Large architectural turnings between centers are unlikely to present any issues with say a 1mm offset in both vertical and horizontal offsets or non - co-linear & concentric headstock & tailstock axes. I doubt the turner would even notice. However, those same errors would be a nightmare for a turner turning small spindle components, pens, finials etc.

Its all about the magnitude of the errors, how the piece is mounted, and the scale of the piece.

ps. Is it worth getting hung up about fixing the "errors"?

So Yeah, don't get to hung up about them & only if they are or become an issue of concern for the projects you do. Remember wood lathes are NOT manufactured to the tolerances of metal lathes and have more robust castings for a reason.