Lathe Tailstock to Headstock Alignment

[James Combs]

Periodically I pull the H&T-stocks off mt Jet 1642 for a little general maintenance, today was one of those times. I lightly scrape the undersides of the H&T-stocks and the tool-rest to remove the normal build up of gunk. I then oil all the moving parts, apply a layer of Boeshield T-9 to the undersides of the stocks and to the lathe ways.

With this all completed and the lathe reassembled I check alignment of the H&T-stocks using two dead centers. Today was no exception on the alignment meaning nothing had changed. However, ever since I have had the Jet there has been a slight, just perceptible misalignment in the vertical(TS slightly lower than then HS), I am guessing maybe .005-.010", nothing that hurts any thing I do. It does not change alignment between minimal and maximum TS arbor extension so I know the TS is straight to the HS

However, I was just wondering and just for the sake of discussion, if it was out farther and a person wanted to correct it what could reasonably be done. I am thinking of something like shimming the tail stock would be the most logical because there is way too much "meat" on the bottom of the HS to do anything to lower it, besides that would cut into the swing:rolleyes:.

Lets hear some thoughts on what could reasonably be done and/or what you may have done to correct the problem.

As an aside I also have a Griz G0658 12x20 which lines up perfectly at min and max TS arbor extension so I know it is possible to have great alignment.

[Bruce Stilwell]

The way to line them up is to raise or lower the one leg that is racking your bed.
This is the way Jet told me to do it and it works. Your floor can be off level and a small move of your lathe will change the bed.

[James Combs]

The way to line them up is to raise or lower the one leg that is racking your bed.
This is the way Jet told me to do it and it works. Your floor can be off level and a small move of your lathe will change the bed.
Thanks for commenting Bruce. I can see where that could/would correct horizontal misalignment but what about significant vertical misalignment. Keep in mind I am not looking to make any corrections to my lathe, the few thousandths that it is out has no discernible effect on my turnings, I only posted this for discussion purposes.

[Roger Chandler]

I agree with Bruce.........first of all make sure your bed is level both end to end and across the ways.......use a level........preferably one at least 3 feet long for the end to end.

Shimming can be done, but it needs to be checked for level both ways as a starting point. If it is still off a little then a shim on the tailstock, or filing the inboard side of the headstock a little can bring it back into alignment. Of course, this means unbolting the headstock from the ways and flipping it upside down. I would take a good measurement first..........and make sure I did not take off but a smidgen at a time! Also, tighten down the legs to the bed connections.......you might just have enough vibration over time to let the legs splay out or get the bed out of level.

Good luck JD!

[John Keeton]

It is possible for the legs to splay slightly causing the ways to sag ever so slightly. That can cause vertical alignment issues. I had this happen on my 1642, ang corrected by wrapping a heavy tie down strap around the bottoms of the legs and tightening it, pulling the legs together.

[Dan Hintz]

James,

Despite leveling it several times, my Robust had a 15-20 mil misalignment... negligible to most, but I was not getting good results center-drilling non-symmetric stock (final pattern matters, so it must be centered). In the end, it required filing the headstock so I could twist it ever so slightly. It was not recommended, but it solved my issue and it's dead on now. For vertical alignment, shims are the easiest (attach them to the tailstock with some JBWeld, then file, as necessary).

[Thom Sturgill]

The bed being level is not important, but true is. With the H&T removed, use a pair of winding sticks to check for rack and a long straight edge to check for sag or bowing. Accurate straight edges in 3' lengths are available, but pricey (a 36" Starett straight edge lists at $188 - note this is not a rule, just a straight edge & highland woodworking sells several for under $100 including steel ones from Veritas)

The problem with checking point to point is that the tailstock is moved up close to the headstock. Tells you little about where the point is when its a foot or more away. I suppose some kind of laser rig could be made, but it would have to be very precise to be of any use.

[Roger Chandler]

The bed being level is not important, .....The problem with checking point to point is that the tailstock is moved up close to the headstock. Tells you little about where the point is when its a foot or more away. .

Thom..........I disagree with your saying the bed being level is not important...........here's why....

When I got my Grizzly 18/47 lathe [the length between centers is 5" longer than your Jet 1642 evs] it was crucial for me level the bed end to end and across the bed ways in order to make the centers align perfectly. It took several attempts at getting the feet adjusted to the floor of my shop to get it just right........once I got it perfectly level.......with a quality level [cost about $30 from local hardware, not a machinists straightedge by any means] then the centers lined up dead on. [I just happened to have levels as part of my tool collection, so no special purchase was needed]

The comment about the tailstock being up near the headstock is true, however.........on my lathe, even with its length the centers line up perfectly no matter where along the bed I put the tailstock or headstock. It is true the entire length of the bed.......which I think is important with a sliding headstock lathe like we both have.

If one does not have a true starting point, [level] then there might be one place the centers line up, but if the bed is bowed [sagging] or racked just a bit, then at other places the centers will be off a little. The most accurate starting point [level both ways and even moving the level around to several locations on the bed when setting up and getting it as close as you can, will make for a much truer setup and also if there is sag in the bed then tightening the leg/bed connections and winding sticks if needed [ metal fatique?] to re-level is a good way to go.

[Dan Hintz]

The bed being level is not important, but true is.

Let me revise my verbiage... I jacked up each side and let the legs extend until they made solid contact with the ground, preventing the bed from twisting. I doubt my bed is level, but it's not twisted.

[charlie knighton]

should you use shims instead of the little adjustable feet ////I have the 1642 and have added weight/////if I took off the adjustable feet it would be a more solid base/////have issues with multi-axis turned off the end??????????????????

shims vs adjustable feet

[roger oldre]

I have to second Thoms comment. the lathe does not need to be level but in order to be precise it needs to be true. In other words the ways need to be coplanar not level with the earth. the lathe will turn round parts standing on end? Now, what effect does the centers being off have on a wood lathe? it is possible for the lathe to be way off and the centers to line up in only one particular location. where the center axis' of the headstock and tail stock coincide. The head stock can be skewed in X or Z and so can the tail stock. There are lots of things that need to be checked and adjusted to really have a lathe that is true, but is it necessary? I have purposely set my centers off over 3/8" to show that it has NO effect on turning between centers such as a spur drive and a live center. It does however make a difference when chucking the work and using the tail stock for support.

[Roger Chandler]

It seems to me that level.........is a plane.........regardless of whether or not the ground is level. A concrete floor could have a low spot where one leg sits, so adjustment of the leveler on the foot will compensate for that. To have co-planar surfaces means on the same plane.......either side of the ways can rack if the plane is off on either end.........up on rear right more than the front right...........small amounts translate to larger gap on the other end.

The best solution to start with seems to me level.........it is a plane..........not necessarily parallel with every point on the ground surface, but a plane that will put you in the best place to get centers matched up.

Some folks may not care a whit about machine accuracy........me.......I am particular about it. The fence on my table saw is within 1/2 of .001 from front to rear as measured by a dial indicator........took me a while to get it there, but I wanted it that way........some folks may think it is overkill, but that is the way I roll. I want my lathe bed dead level ........my centers match up at all points on length of my bed ways.......and that is just the way I like it...........

Your mileage may vary and that is perfectly fine by me! ;)

[Thom Sturgill]

Roger, my point was that level is just ONE example of TRUE or co-planer. If your level is not up to snuff, reversing it end for end will give a different reading and rack could go unnoticed. Winding sticks are a cheap easy way to check for rack. I use two aluminium 1" angles about 36" long. I painted one black. banacne them centered crosswise on the bed on at each end and sight from the black one to the light one. The length of the arms exaggerates any rack making it visible. This is an old cabinet makers trick. Also a level is not a good enough straight edge to check for bow in the tolerances that the OP stated.

However, I do not think this answers the OP which was concerned with minor vertical mis-alignment.

Since my centers have damaged tips, I probably would not even be able to detect .005":eek:. Machinists use offset to create tapers. This works because the cutting tool is ridgedly held and moves parallel to the bed. Since we work by hand, the only issue I see is that a true running piece might not be quite true when reversed, but what with normal wood movement, .005 or even .010 is probably insignificant, even compared to a 1/8" (0.125") thick form.

[Roger Chandler]

Roger, my point was that level is just ONE example of TRUE or co-planer. If your level is not up to snuff, reversing it end for end will give a different reading and rack could go unnoticed. Winding sticks are a cheap easy way to check for rack. I use two aluminium 1" angles about 36" long. I painted one black. banacne them centered crosswise on the bed on at each end and sight from the black one to the light one. The length of the arms exaggerates any rack making it visible. This is an old cabinet makers trick. Also a level is not a good enough straight edge to check for bow in the tolerances that the OP stated.

However, I do not think this answers the OP which was concerned with minor vertical mis-alignment.

Since my centers have damaged tips, I probably would not even be able to detect .005":eek:. Machinists use offset to create tapers. This works because the cutting tool is ridgedly held and moves parallel to the bed. Since we work by hand, the only issue I see is that a true running piece might not be quite true when reversed, but what with normal wood movement, .005 or even .010 is probably insignificant, even compared to a 1/8" (0.125") thick form.

Thom .......your method will certainly work........no issue with that. I have 2 quality levels........and a couple of laser levels for that matter as well, but since I was able to use the 4 ft. level and get my centers aligned at any combination of points on the bed I put the headstock and tailstock, then I know mine is true.

I think we go at the same issue with different methods, but it gets the same result in the end! Winding sticks are a good way to get level.......I saw David Marks make a torsion box assembly table with that method...........likely one is not able to do much better than with that old trick........one just needs a good eye!

The level I used is not a wooden one........it is a high quality machined aluminum, and was guaranteed to be accurate when purchased......at any rate, the results I got with my lathe prove it is plenty accurate for most jobs. If I recall correctly it is a Starret or perhaps a Johnson level, but it is a good tool.

[Thom Sturgill]

Roger, just to be accurate, I have no problem with using a level for a wood lathe. I'm sure it is probably 'good enough'. In fact I used my level to get the lathe 'approximately level' (that's the engineer breaking out) and used winding sticks to verify and adjust one leg a hair. I did not use a straight edge though I do own one, as I had not considered that to be an issue. Nor had I considered using either a spreader or tension cable to correct any bowing. The Jet is thicker in the middle to help prevent such. I have seen several lighter designs that I would worry more about.

On the other hand, James seems to be a precisionist, so I was responding to that. Shimming would seem to be his best solution if the difference were great enough to worry about.

I would also like to see some method of testing at different settings on the bed that was easy to set up and check. A MT2 mounted laser comes to mind, but it needs very accurate machining and a sharp image. I would probably also want a 'target' MT2 piece for the other end so that you have something to check to. Might be a good item for a club to own and lend to members if it were rugged enough, probably to much for most turners to invest in. Someone like JT Turning could probably make it for a decent price.

[Dan Hintz]

Since my centers have damaged tips, I probably would not even be able to detect .005":eek:. Machinists use offset to create tapers. This works because the cutting tool is ridgedly held and moves parallel to the bed. Since we work by hand, the only issue I see is that a true running piece might not be quite true when reversed, but what with normal wood movement, .005 or even .010 is probably insignificant, even compared to a 1/8" (0.125") thick form.

I think you would see it, too, if you were looking for it in the right place. When turning a bowl, it's imperceptible... when turning a pen that's only 1/2" in diameter, that is a very large change in center. Segmented pens almost always need a dead-center mark, else the pattern will be lopsided... because of this, I had to tweak mine.

[roger oldre]

Roger, A level defines or compares two points of contact. the highest of two points contained in a line. a plane although defined by three points is made up of all points on that plane. to be coplaner all points of both ways would be on the same plane. this would preclude sag ,twist or rack. The ways could be coplaner and still the lathe could be off. the only way to check if the centers are lined up would be to fix the cutter and follow the ways exactly to see if there is taper. as Thom has stated not many wood lathes have that option. if you push the tailstock up to the headstock and the ram of the headstock is retracted and the centers line up does not mean that they will line up with the tailstock extended. of the tailstock is not parralell in the z axis then the tailstock center will be high or low when it is extended. if the tailstock is not parallell with the ways in the x axis then it will move wither fore or aft when the ram is advanced. the same goes for the headstock if it is not parallel with the ways. Roger how did you check to see that your centers lined up throughout the full range of motion for the lathe? I have seen many many lathes that people have spent countless hours getting perfect only to find that they aren't really. I have heard many people blame the equipment for faults that fall squarely on the shoulders of the operator. I get into this because i have been at this for a while and have built several pieces of equipment from scratch, some of them happen to be wood lathes. I am fully aware of what out of line centers can cause again as I mentioned I did it on purpose to prove a point in another forum. out of line centers are often blamed for things that they cannot possibly contribute to. Again as has been mentioned wood turning with hand held tools is not in the same ballpark as a metal lathe with a fixed cutter that follows a path that is described by the ways in two dimensions and by movement along those ways for the third. I am glad that you enjoy your equipment to the point of putting in the effort to be more precise than even the wood can maintain overnight. I enjoy working with wood too. I am not competitive or perfect but people like the stuff I do whether one off or long runs. I did the bar rail for Cesars palace, and the cross and crosure for the Papal processionals here in the USA. I guess I can hold my own even on homemade lathes. and they are FAR from perfect!

[Roger Chandler]

Roger, A level defines or compares two points of contact. the highest of two points contained in a line. a plane although defined by three points is made up of all points on that plane. to be coplaner all points of both ways would be on the same plane. this would preclude sag ,twist or rack. !

I have no issues with the things you are stating, Roger.......sounds like you are fairly knowledgeable about tools and woodworking. You mentioned level being two points of contact.........well, lets just say one point is the area of the headstock and the other is the area of the tailstock on the ways of a lathe. If one has made sure the bed ways are level front to back and end to end...........the middle point of the ways would be the third point on the same plane.

If one does all the necessary tweaking of the ways to get it level all the way across and end to end [ by duplicating the settings in the factory got in manufacturing] then true is an achievable result. Starting true with the bed, once installed onto the legs and adjusted properly, will get the headstock and tailstock onto that same plane..........at least that is the results I got...........again, your mileage may vary.

All I know is that I used this method and got the desired results everywhere on the bed I tried a headstock and tailstock combination. My centers match up..........that is the result I was after, and what I achieved. Others may use other methods, or feel it is not necessary to get the centers in true alignment.........that is their thing. My purpose in answering the post was simply to attempt to help provide a solution for centers being off.....the same as other posters in this thread. It was not trying to be argumentative with anyone, so I hope you did not think I was being argumentative with you.......:)

Many times a problem can be solved in more than one way, and I am certainly not saying the solution I provided is the only way to do it....but it does work! Each one can take whatever they want from offered input............and hopefully find a solution that suits their needs.

[David C. Roseman]

Interesting thread. I'll add one thought to the "level" vs. "true" discussion. No question that true is much more critical for practical purposes, but I do think that a bed that's out of level end-to-end does experience more distortional force toward the center of the bed than one that is level. In theory, at least, that could cause enough bow to cause vertical misalignment of the HS and TS.

Here is my layman's reasoning. Visualize the lathe sitting perfectly level, end to end. If we were to locate the centers of mass (COM) of both the HS and TS, and then drop a vertical line through each COM down to the ways, the lines would intersect the plane of the ways at point A for the HS and point B for the TS.

Now visualize the lathe out of level end-to-end, say by an extreme 30 degrees for purposes of illustration, such that the HS is now higher than the TS. The vertical lines through the COM of the HS and TS will now intersect the ways at points C and D, further toward the tailstock end of the bed. Since the HS is significantly heavier than the TS (and its COM also likely higher above the ways than the TS's) more downward bending force will now be directed toward the longitudinal center of the bed than when the bed was level. Whether in reality it would be enough over time to cause the heavy cast iron of the 1642's bed to bow a few thousandths of an inch is a different matter. But in theory at least, I think end-to-end level does matter.

David

[Thom Sturgill]

David, you posed a situation that obviously is extreme. I doubt anyone would set up and use a lathe at as much as 2 0r 3 deg out of level unless there was a need. I worry more about the fact that the sliding head is more often at the center of the bed (for hollowing) than at the end over the legs.

While drastically out of level may, over time, cause problems, it does not affect the OP's question about alignment. I stand by my statement that for ALIGNMENT, level is not critical, but TRUE is, and agree that level IS a special case of TRUE. If you own a good quality level, by all means use it. If not, winding sticks are a good alternative to check for twist in the bed. In fact, I believe they will show variation that would be hard to spot with a level measuring across the ways.

To test that, set a level across the ways, and then use feeler gauges to see how many thousanths you have to raise one end before it is noticeably out of level. Then do the same with winding sticks, placing the feeler gauge under one stick on one of the ways. I'd bet that you will notice the difference more quickly with the winding sticks since they amplify the difference and the level does not.

[Thom Sturgill]

Roger, I start everything between centers, get it round and shape the outside while forming either a tenon or recess. For a hollow form larger than about 6" tall I would prefer a dished area with the center marked to mount a face plate. I use a fairly small aluminium faceplate, but then again most of my turnings are relatively small. Once reversed and running true I remove the TS. I was lucky enough to get a Nichols steady rest before he stopped making them and use it while hollowing. Though I have a home-brew captive (and articulated arm) hollowing system, I tend to hand hollow after a day with David Ellsworth. Since I rarely turn anything long, my headstock tends to stay near the center of the bed.

I would assume that any manufacturer making a sliding headstock would make the bed sturdy enough to support it. I guess the difference would not show up (unless there is a pre-existing defect) for many years. Still, a Powermatic 3520 with its beefy bed and additional power is very enticing.