Spindle not lining up

[Christopher Knight]

I am having trouble getting the headstock and tailstock to line up properly. I am new at turning so my terminology may be incorrect so I hope I can correctly convey my issue.

The “pointy” piece that is inserted into the tailstock is not revolving around the axis, but rather is rotating in an oval pattern. I have taken out the spindle and mounted it on my woodbench and it is revolving about the axis correctly. But when the “pointy” piece is inserted, the point is rotating in an oval. It is enough that it is causing the work to be non-symmetrical.

Is the solution to get a new “pointy” piece, or whatever it is called, or could it be an issue with the spindle? Attached is a pic of the two spindles. You can see that they are off by just a fraction, but you can really tell it when you get a piece of wood and start spinning.

[John Shuk]

I've found this to be pretty nice. It was a gift suggested to my wife by the previous owner of my jet 1236. I found it really useful and easy to use. Just takes a second and never a problem. I always use it after returning the head to being "in line" It is just a double ended Morse taper and it lines things up perfectly.

http://www.packardwoodworks.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=packard&Product_Code=113121&Category_Code=lathes-acc-mrstool

[Jim Becker]

Christopher, what make and model lathe do you have? Assuming your centers are themselves not defective, knowing what machine will help us suggest a solution.

[Bill Boehme]

The amount of misalignment that you have is a nit and I would not waste my time worrying about it. If the point has a set screw or is spring loaded, that may be the reason that it is not concentric with the cup center.

It may appear to you that it is moving in an elliptical path, but it is inscribing a circle about the true axis of rotation. Also, having the point off the axis of rotation will not cause the turning to be elliptical UNLESS it is a pen or something similar where you have a metal bushing on a mandrel that is wobbling. Otherwise, the spindle will be rotating about the true axis of rotation regardless of where the point is or isn't. In fact, the point could even be removed and things would still work just fine.

There is more to alignment than just getting the points to touch. There could also be angular misalignment which is more difficult to measure and correct. When I first saw the double ended Morse taper a couple years ago, it seemed like a good idea, but after some reflection, I believe that it is an idea with good intentions, but potentially disastrous results. The surfaces of a Morse taper are machined to about .0002" accuracy, but it is not possible to align the headstock and tailstock to such precision, especially in the vertical plane because there are no provisions for up and down adjustments. Even a minute amount of misalignment can cause scoring and binding on both the headstock and tailstock spindle bores. If you would like to make a "safe" double-ended Morse taper, then just turn one out of a medium soft wood. Tweak it until it gives a snug fit on each end and now you have something that is better than the metal one because it can't damage the spindle bore on either end. You can also make it long enough to match the distance between centers.

Bill

ps -- if you are turning pens and are getting elliptical results, the most likely cause of the problem is too much tailstock pressure. The pressure should be just barely enough to get the live center to rotate.

[Robert E Lee]

Spin the live center by hand. If the point does not stay in one place and then yes you need a new live center for the tailstock. If you are going to make pens then you need a 60-degree live center.
Bob

[Stu Ablett in Tokyo Japan]

If this is a Nova, it is a common problem, usually caused by the stand not being flat, and cranking the bolts down on the lathe to stand too tight, and not in the recommended order, I had this problem with my DVR when I first got it, a new flat stand, and the correct order in tightening the bolts to the correct torque solved it.

Take a look at the Nova homepage for details.

if it is not a Nova lathe, sorry, I don't know :D

Cheers!

[Frank Kobilsek]

Stu brings up a good point. On my Jet 1642 if I am doing small work where misalignment is most noticable and I detect a problem the first thing I do is put my level on the ways. Usually I'll find re-leveling the machine straightens things out. Why does in change? Big unbalanced piece dances the lathe a little or the big crack in the concrete moves with the seasons.

Frank

[Paul Engle]

Christopher,
You can take the live center to a machine shop and have them chuck it up to see if it is true... they can turn the point true if it is out. if it is true then maybe bearing / shaft is out of round and they can true the shaft but not the bearing. If these are ok ( which when I got mine it was not true and I cleaned it up on our companys lathe) something in the tail stock is throwing it off . if the point is too high you will need to shim up the head stock to match and vice a versa , this only if the shop says the point / shaft is ok. there are two axis in alignment to be concerned with 1: side to side 2: face. If they are both off you get the " oval " and you will never get the smooth cut, it will keep changing as soon as the bit moves. The cheaper live centers made in CHINA PRC typically are so mass produce in a hurry their Quality control leaves something to be desired. As a marine machinist at Long Beach Navy Yard in my younger days , alignment on board the Navy's war ships is very critical and watched closely by the QC people. All rotating machinery needs to have an alignment when first setting up and after you " bolt er down" it needs to be check. This along with doing dynamic balance on your chuck will be the two biggest concerns you need to deal with first. I just bought a NOVA G3 chuck and balance wise it was off .35 oz's , which translates into a lope at the outter rim, I used stick on wheel weight to counter balance . if you have a belt drive lathe take the belt off set the chuck so the # 1 jaw is on top and see if it rotates by it self, then #2 ... etc. the heavy one will roll to the bottom , mark the top 180 degress out from the bottom , using wheel weight on the out side start with small amout of weight untill you find the amout which will stop the roll and attach inside the chuck body, add small strip of duct tape as cover and giver er a spin, i some times counter larger blanks to get less vib at the start of turning until they are smoothed out then take it off.
email me if you have more questions I can walk you thru the process.
Paul:D

[Christopher Knight]

Bill, you where right. I took it down to the local Woodcraft store and had two of their instructors look at it. They showed me how it is inscribing a circle about the true axis, not about where the point is. They even took a new spindle off of the shelve and showed me how it also rotates around the true axis. The $100 dollar spindle did just a little better job than mine did. Thanks for all of the input. You guys are great.

[Bill Boehme]

Bill, you where right. I took it down to the local Woodcraft store and had two of their instructors look at it. They showed me how it is inscribing a circle about the true axis, not about where the point is. They even took a new spindle off of the shelve and showed me how it also rotates around the true axis. The $100 dollar spindle did just a little better job than mine did. Thanks for all of the input. You guys are great.
I am glad to hear that everything is working out fine. There is a lot of misundersanding in woodturning concerning having the drive and tailstock centers both perfectly on the axis of rotation. Mostly this is caused by taking metal turning requirements and applying them to wood. In metal turning, the head stock end is held securely in the jaws of a chuck and the tailstock center must align very closely. In woodturning, when turning between centers, the rotation is about the axis of rotation which is not necessarily exactly along a line between the points. The turning will be round regardless of where the points are located -- they are the simply as a reference point. NOTE: If you remove the spindle and then remount it, that CAN have an effect on the turning as the true axis of rotation may have moved in the process.

Bill

[Frank Fusco]

Bills comments are confusing. A lathe is true or it is junk IMHO. I do a lot of turnings with mandrels (duck calls, pens, etc.) and do not need eliptical items. With larger items, I would agree that the degree of variation may not be too noticable. But when we spend bigo bucks on a machine it should be right or returned.

[Stu Ablett in Tokyo Japan]

Bills comments are confusing. A lathe is true or it is junk IMHO. I do a lot of turnings with mandrels (duck calls, pens, etc.) and do not need eliptical items. With larger items, I would agree that the degree of variation may not be too noticable. But when we spend bigo bucks on a machine it should be right or returned.

Frank, did you read AND understand what Bill wrote?

Perfectly clear to me.

But, I have to ask, if a cheap live center is a tad off, you would return the whole lathe?

:D

[Frank Fusco]

Frank, did you read AND understand what Bill wrote?

Perfectly clear to me.

But, I have to ask, if a cheap live center is a tad off, you would return the whole lathe?

:D

Yep. I used "confusing" in an attempt (apparently a failed attempt) to be diplomatic. I don't agree with him at all. Eccentric turnings are made by putting one side out of alignment with the other. Yes, it would be prudent to eliminate all factors other than the lathe as a whole first. I still believe that a lathe that isn't in alignment is junk.

[Robert E Lee]

As Bill said as I take it, Please jump in and tell me if I got this wrong. If you are turning between centers it dose not matter. This I agree with. If you have a mandrel, chuck or even a faceplate and using the tailstock and live center then I would think it would put it in a bind every rotation that it makes. More so if the center is not running true.
Bob

[Frank Fusco]

With non-alignment, what you have is as shown below, albeit to a lesser extent.

[Bill Boehme]

Yep. I used "confusing" in an attempt (apparently a failed attempt) to be diplomatic. I don't agree with him at all. Eccentric turnings are made by putting one side out of alignment with the other. Yes, it would be prudent to eliminate all factors other than the lathe as a whole first. I still believe that a lathe that isn't in alignment is junk.

Frank, In a previous post I mentioned that this does not apply to things like pens and game calls that are turned on a mandrel. This is the case because the mandrel is a chuck and holds the turning rigidly at the headstock end. In that case, the tailstock end would be inscribing a circle about the point and when the mandrel is then held by the off-center point, it will force the motion to become elliptical towards the tailstock end.

This is in contrast to a spindle turning between the centers turning where there is a spur or stebcenter or similar drive at the headstock that allows relative movement similar to a universal joint. The same thing holds for the tailstock end. The axis of rotation will be about the spindle true axis and the live center axis and this not necessarily where the points are located although it is always better to have a drive center and live center that do line up.

Another minor point that woodturners are sometimes not aware is that there is more to alignment than radial alignment which is what we are talking about when we get the points to match. The other thing to consider is angular alignment. It would be rare to find a woodturning lathe in which the tailstock axis and the headstock axis both fall on the same line. The good news is that it is normally not that important unless we have the turning firmly mounted in a chuck in the headstock while trying to drill a straight hole with a drill mounted in a chuck on the tailstock. It may be less of a problem if we swap the positions of the chucks, but if there is angular misalignment, the hole will be along the drill axis and not the center of rotation.

I mentioned angular misalignment, not because of its importance, but because it is a very similar situation to spindle turning between centers where the points are not perfectly aligned. The axis of rotation is neither the spindle axis nor the tailstock axis, but the line between the points. The turning will be round because it is rotating about a fixed spin axis.

Bill

[Bill Boehme]

With non-alignment, what you have is as shown below, albeit to a lesser extent.
Frank,

Your picture of the elliptical chuck is good to partially illustrate what I was talking about in my previous post. Instead of mounting a piece of wood on the chuck for face grain turning, suppose that you took a long piece of wood (not too long for obvious reasons) and screwed the end grain onto the chuck -- some thing like a 4 X 4 block that is 5 inches long. Next, take a spindle roughing gouge and turn it as you would any spindle. What you would end up with is a round spindle in which the center is along the axis of rotation and not the screw (think of this as a faceplate with only one screw). I don't actually recommend doing this, but it is fairly easy to visualize.

BTW, I did not consider any of your posts to be undiplomatic. Your questions are very fair and reasonable. Some things seem counter-intuitive and are not readily visualized. When I am trying to do a multi-axis turning, it takes some serious headwork for me to keep from getting things backwards.

Bill