problem with Jet Mini

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schellfarms

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Joined
May 28, 2006
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Location
Holly Springs, Mississippi, USA.
I'm having a problem with my lathe not turning true. The mandrel at the tailstock end is way off--you can see that it's not turning true. I just replaced the spindle and both sets of bearings and tried 2 different mandrels--same result. It makes it difficult to get pens turned to the bushings evenly. I took the rod out of the mandrel and rolled it along the (hopefully) flat surface of my table saw and it rolled in a nice straight line. Is the next place to look the headstock?? If that has to be replaced, is it more cost effective to just replace the lathe and keep my current one for a parts donor? I looked at the Jet website, and can't even get it to pull up the headstock as a part. Is replacing it even an option?
 
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1. Clean out the taper in the head stock. It can get dirty and cause alignment problems.

2. Put a dead center or live center in the head stock and another one in the tail stock and see if they line up when you bring the tail up to the head stock.

3. Loosen the screws/bolts that hold the head stock in place and shim as necessary to align the two center's points in #2 and retighten.

Do a good turn daily!
Don



schellfarms said:
I'm having a problem with my lathe not turning true. The mandrel at the tailstock end is way off--you can see that it's not turning true. I just replaced the spindle and both sets of bearings and tried 2 different mandrels--same result. It makes it difficult to get pens turned to the bushings evenly. I took the rod out of the mandrel and rolled it along the (hopefully) flat surface of my table saw and it rolled in a nice straight line. Is the next place to look the headstock?? If that has to be replaced, is it more cost effective to just replace the lathe and keep my current one for a parts donor? I looked at the Jet website, and can't even get it to pull up the headstock as a part. Is replacing it even an option?
Click to expand...
 
SSS: There is no reason your lathe should not function correctly; but before we can get it fixed, we need a better understanding of exactly what is wrong. Don has given you a couple of quick and dirty suggestions that might help or it may be yours is a more difficult problem.

First question is about your lathe. How old is it and is it still under warranty? Second question is whether or not you have contacted the technicians at JET and discussed the problem with them?

And now for the really important questiion.....what do you mean when you say, "The mandrel at the tailstock end is way off--you can see that it's not turning true.....?"

Are you saying:

1. the centering hole in the end of the mandrel does not line up with the tip of the live center in the tailstock or

2. the mandrel is not rotating perfectly around its long axis and sort of wobbles as it rotates describing a cone shaped path or

3. both of the above or

4. none of the above.

Has this been a problem since you first bought the lathe or is this something that has developed over time? Did you replace the spindle and bearings in an effort to correct the problem or did this problem develop after the spindle was replaced?

And finally, if it is a misalignment problem at the tailstock. how much of a misalignment it there. Up, down, left, right, and how many millimeters or inches or parts thereof??

With this information folks here can get a better idea of your problem and how to go about repairing it.
 
My lathe is about 4 years old. The problem is #2 as described above--mandrel not rotating perfectly along the long axis. This was not a problem when the lathe was new. I talked with Jet last week and they said to clean the taper, which I did using a tapermate. When the problem did not resolve, I ordered new bearings and spindle and changed them yesterday. The large bearing went in fine, as did the small, but when inserting the spindle, the small bearing wanted to pop out freely as if the hole for the seat is the wrong size. I had no trouble at all getting the bearings out--the small one just came out with light finger pressure and one gentle tap with a pen blank. it seated just as easily. the hole for that one seems to be almost the wrong size. the large one needed a very small bit of encouragement getting out and the new one in, but seems to be in properly. the spindle was also easy to replace. I suspect the problem to be something with the small bearing. I plan to call Jet tomorrow, since they have no weekend hours. I'll try the above suggestions in the meantime.
 
Well, that is some puzzling information. I have an initial thought or two but would like to think about your comments for a bit.

One other question I should have asked earlier........do you have or have access to a dial gauge so you could take some runout measurements?
 
I wrote up a bunch of comments about your problem and then needed to go back and reread both of your messages for reference and decided I had misunderstood what you were saying. Soooooo............​
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If I am now correct, you have a problem with a mandrel that wobbles as it rotates and after installing a new set of bearings and a new spindle, the problem still exists. If that is correct, then the most likely cause of your problem is a bent mandrel or a damaged arbor. We need to know what kind of arbor/mandrel setup you are using. Are you using one of the adjustable mandrels or a setup where the mandrel is threaded and screws into a MT arbor or one of the Berea High Precision Units? If you are using the threaded arbor/mandrel, do you just install different mandrels in the same arbor or do you have an arbor for each mandrel?

Hang in there, SSS. Between the folks at Jet and the guys, here we will get you back on track......it may be a struggle; but we will get it done!!

(I left my original comments below even though I don't think they really apply to your situation, any longer. They may be of interest others for future reference,)





First, we need to clarify one point. It is not clear to me whether you did in fact get the new spindle and bearings installed and still have the problem or whether you gave up on the installation because the bearings were a problem?

OK. I've had some time to gather my thoughts. I have not come to any firm conclusion; but will ramble a little and hope that something I say might push you in the correct direction.

I would like to respond first to your concern about the bearings. The bearings on my JET mini slide in and out and on and off without a lot of effort; but there have been postings in the past from people who had to drive them in or out or use a bar clamp to press them in. The fact that your small bearing won't slip onto the spindle easily could just be a manufacturing tolerance. I difference of as little as 1/1000th of an inch could make the difference between a tight fit and a snug fit. This would probably be a good thing to ask the JET technicians about. I would be interested in what they have to say.

Next point is I wonder if you tried the new bearings on the old spindle to see how they fit. You should be able to tell if your problem is an undersized bearing or an oversized spindle. Obviously, either or both are possible.

I suppose there could be other causes for your problem; but the obvious ones are:

1. Spindle

2. Bearings

3. Arbor/mandrel

For the moment, I am going to assume the arbor/mandrel is not the problem; but this might have to be revisited if other efforts don't pan out.

At four years of age, the bearings could definitely be worn; but bad bearings typically make noise or heat up excessively or just feel loose so we will let that by for the moment, too.

The most likely cause of your problem is debris in the spindle taper. There have been a number of reports about the tapers not being machined properly and this is something that one should always check for; but since you say the lathe was originally good, then a badly machined taper does not seem likely.

My first thought (and it has not changed after a little reflection) is that, as the JET guys suggested, you have accumulated some crud in your spindle taper and the mandrel arbor is not seating properly. It is quite possible that there is something on the taper that the plastic Tapermate was just not aggressive enough to remove.

First thing I would do is give the taper a close examination under strong illumination just to see if there is any visible contamination. Then, I would try a more aggressive method to clean your taper bore. First thing that comes to mind would be an appropriately sized brass-bristled brush like used for cleaning the bores of rifles and shotguns. At this point I would give the mandrel arbor a close examination as well. Perhaps you have damaged it somehow and it has a nick or burr or some other defect that causes it to seat improperly. If you have more than one arbor/mandrel setup if would be helpful to see if they all spin poorly or whether it is just one that has the problem.

The next thing to consider would be the purchase of a MT reamer which is the same thing as a tapermate but made out of steel so it will remove the difficult debris that the Tapermate won't. They are not easy to find and some of them are fairly expensive; but you should be able to find one for about $20 if you are diligent in your search.

As to your comment about needing a new headstock, that seems like an extremely remote possibility. According to your comments, the lathe performed just fine when it was new. I don't see any way the HS could have been damaged to cause the current problem.​


 
I'll try to answer the quetions posed above. I purchased new bearings and a new spindle. I replaced all 3 parts and the mandrel still wobbles. I have 3 mandrels--one is the adjustable type and the other 2 are not. The mandrel at the tailstock end spins in an elliptical pattern around the tailstock. I replaced the mandrel initially because I figured that I'd bowed the mandrel by running the tailstock up too tight, but all 3 do this. When the headstock and tailstock touch, it looks like the rotation is perfect. My dial indicator is a really cheap junky one, and is not accurate. I would estimate that the lathe is out about 3 mm with the mandrel in place. This is making the pens difficult to turn down to the bushings all around. It will be perfect on part of the pen, but on one side it will be proud of the bushings, and then I have to turn very carefully to allow the tool to only remove the material on the proud side--very tough. I called Jet, and the person I spoke to thinks it's an alignment issue. The MT on each of the mandrels appear to be ok--no pitting or rust. We normally store them in the box or baggie that they came in and keep them in a drawer in the lathe cabinet to protect them. I did notice that when we removed the bearings, there was some very fine sanding dust around the bearings in the bearing seat, and the small rear bearing popped out when I put the new spindle in place. It went right back with a little tap with my palm. Could there be too much play in the seat where the rear bearing is placed?
 
OK, I think I am stumped. I emailed a couple of guys and asked them to look at this thread for their thoughts. Will see what their thinking is.

schellfarms said:
.....The mandrel at the tailstock end spins in an elliptical pattern around the tailstock.....
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The mandrel would spin in its elliptical orbit whether it were near the tailstock or not so the problem is "NOT" one of alignment of the HS and the TS. You mentioned that the JET tech thought the problem one of alignment. What type of alignment problem was he talking about?

Was this comment made today during your second call to JET or was the opinion expressed during your first consultation??


schellfarms said:
.....My dial indicator is a really cheap junky one, and is not accurate. I would estimate that the lathe is out about 3 mm with the mandrel in place......
Click to expand...
Even an inexpensive dial gauge can be useful. You are not so much interested in absolute measurements as you are in relative measurements so even a modestly priced dial gauge can be helpful and definitely better than nothing. The 3mm measurement that you mention, is that the estimated width of the ellipse the end of the mandrel is traversing or some other measurement?


schellfarms said:
.....I did notice that when we removed the bearings, there was some very fine sanding dust around the bearings in the bearing seat, and the small rear bearing popped out when I put the new spindle in place. It went right back with a little tap with my palm. Could there be too much play in the seat where the rear bearing is placed?
Click to expand...
The bearings on my lathe slide in and out fairly easily so I don't think that is a problem. The bearing would have to be extremely loose to cause a 3mm problem at the TS end of the mandrel and that much looseness would be quite obvious. Other problem is that the bearing seat is not something that you would expect to wear out over time so, if it was good when the lathe was new, then it should be good now as well.

I guess one thing you might try is to grab the nose of the spindle and shake it back and forth and see if you feel any play or looseness in the inside bearing. Then do the same thing with the handwheel and see if you feel any play in the outside bearing.

I hope another set of eyes or two will throw some light on the problem as I am totally puzzled.

Another comment from your earlier post.

sss said:
.....I took the rod out of the mandrel and rolled it along the (hopefully) flat surface of my table saw and it rolled in a nice straight line.....
Click to expand...
Since you say all three mandrels do the same thing, it is a little unlikely that all three mandrels are bent; but the test of a bent mandrel is not whether or not it will roll in a straight line on a flat surface. If the mandrel is bent you will hear a slight clicking sound when it rolls over a flat surface....a glass coffee table top is a good surface to use.....and if it is bent enough to cause a 3mm ellipse, you should actually be able to see part of the mandrel lift off of the flat surface at some point in the roll.:confused::confused::confused:
 
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Randy_ said:
Even an inexpensive dial gauge can be useful. You are not so much interested in absolute measurements as you are in relative measurements so even a modestly priced dial gauge can be helpful and definitely better than nothing. The 3mm measurement that you mention, is that the estimated width of the ellipse the end of the mandrel is traversing or some other measurement?
Click to expand...


SSS; You replaced the bearings and spindle. I would next use the Dial Indicator and touch the probe to the INSIDE of the spindle taper while hand turning the hand wheel. The taper should vary less than .001". I'm not sure what the actual limit for this should be. On metal lathes there will be an inspection record with tolerances specified, and a measurement test listed. I went and looked at my metal lathe inspection record and the tolerance is .0007" (.02mm) and measured .0004" (.010mm).


I guess one thing you might try is to grab the nose of the spindle and shake it back and forth and see if you feel any play or looseness in the inside bearing. Then do the same thing with the handwheel and see if you feel any play in the outside bearing.
Click to expand...

This is a good test for severe problems.
The following applies to the Jet 1014 lathe only!
You may want to make sure the spindle and bearings are set correctly after you replaced them. The adjustment process isn't obvious.

  1. Run the lathe without a mandrel at high speed for 15 minutes. Feel the headstock around the spindle while doing this.
    1. If it is cold, tighten the hand wheel.
    2. If it gets hot, loosen the hand wheel.
    3. The temperature you are looking for is slight warmth. You should be able to lay your forearm on the headstock without discomfort.
  2. To adjust, loosen the two set screws on the hand wheel and tighten (warmer) or loosen (colder) the hand wheel. The adjustment is very slight, only a few degrees of rotation. Then re-tighten the set screws.
BTW; My Jet was set MUCH too tight and the headstock got too hot to touch.



Since you say all three mandrels do the same thing, it is a little unlikely that all three mandrels are bent;
Click to expand...

I think you are correct Randy. I would remove the tailstock and shine a light into the headstock taper. Any ridges inside the head stock taper may prevent the mandrel from seating properly. When inserting the mandrel, it should seat evenly. If it seats with a "click" (sound of metal on metal), it isn't seated entirely.
 
Ok, done a quick read of the post here. All good suggestions on checking out your lathe. And like Randy said, this type of problem won't have anything to do with alignment, so.... When you replaced you mandrel, did you replace just the mandrel. If not, you might look at the tapered part as well. These machines aren't built any whaere near the tolerance specs of a metal lathe, although that is what most of us want, I think! If you did replace the whole thing, then checking the tapered hole is a good place to look, if you haven't already. Last thought is to remember we are relying on two threaded parts to run true. If the threaded hole in the taper part is off at all, that will magnify out on the end of the mandrel. I have said before, most of the time my mandrel does not run dead true with the center out, but the whole thing runs well with the center in, so that is the main thang, ain't it? If the mandrel runs pretty true at the headstock end, and the tail stoc end with the center in, I'd think you were good to go. I hope I haven't added to the ' mud'!
Another thought. When I run between centers, my dead center is not dead true. I had to rotate it and re-incert it a couple of time before the tip ran true. I have put a mark on the center to line up with a mark on the spindle so I don't have to go through that each time. Might be something to look at as well with the mandrel assembly.
 
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Well, the results are in and all indicators point to the mandrels as the culprits. The spindle is slightly warm after 15 minutes of running. Runout on the spindle--measured just inside the spindle--was <.001 per rotation. Just out of curiosity, I also measured runout on the handwheel and got about .004. But the real trouble came with the mandrels--each of them had lots of runout--the worst one was about .060--terrible!! The other 2 were not much better. I don't know how accurate my dial indicator is, as it's a cheapie from HF, and has been known to give different readings in the same spot on a flat surface--maybe operator error. When I turn a pen, I usually get the tailstock close to the end of the mandrel and then use the handwheel on that end to snug it up just until it turns the live center. Is this too tight? I have to belive that I killed the mandrels rather than getting 3 lemons. The question now is are they fixable? If not, who sells the best ones? One or 2 of them came from HUT, and the adjustable one from a local ww shop in Memphis that is now a Rockler affiliate, so it is probably from Rockler. Thanks to everyone who took the time to read and/or reply. It really makes me appreciate this forum even more!!

sarah
 
Did you check the run out with the center in or out. And are you checking up and down the mandrel in various spots? Sixty thou with it in is pretty bad. Are you running the factory live center? If so, they are not true 60 degree. The point hits the bottom of the 'dimple' before the angle sets in. You can get away with this by filing the point off the tip about 1/16". It does work, as this is the way I run mine and always have. I do have a 'real' live center, but only use it when turning between centers.
 
I rotated it by hand without the center. Even with the center, the same thing is happening, although I haven't measured it with the tailstock in place. My center has had the end filed down and has worked in the past. I'll check the mandrels with the tailstock in place and at several points along the length. It is the factory live center that came with the lathe, but I can try with the heavier one from Little Machine Shop--but the center point on that one has not been filed down.
 
Here's the next trial:

NOTE: distance given is inches from where the mandrel screws into the MT (from the headstock end)

Mandrel 1: (using factory live center with filed down point)

Tailstock in place tailstock not in place
1" .0015 ish .006
2" .006 .013
3" .008 .018
4" .002 .0275--worst reading
5' .010 .015
end at tailstock .003 .020

Using little machine shop live center--tip not filed down--tailstock in place for all measurements:

1" .001
2" .005
3" .005
4" .004
5" .003
end @ tailstock .001

Bear in mind that my dial indicator is a cheapie and not always inclined to be super accurate, but hopefully it was having a good day!!
 
Did you replace the mandrel and taper assembly, or just the mandrel? If you haven't tried replacing the taper part, I would try it, or try knocking it out and rotating it a bit and check again. If you have acess to a 1/4-28 tap, you could put that in a drill chuck in the tail stock, and run it into the taper part (carefully, turning by hand, let it feed itself in) to clean up anything in the threads. Assuming yours is that size. Some have a smaller threaded part. (10-32, I believe). Also make sure the factory tip on your center is still in good shape. It will wear 'funny' since it is not true 60 degree, but normally will wear even. I have only replaced mine once is about 10 years, but I only turn about 10-15 pens a year right now.
As for the 'good' center, you will not need to knock the tip off as it is a true 60 degree center.
 
I have 3 mandrels all with dedicated tapers for them so that we don't have to change out the rod each time. Where can a replacement tip for the center be gotten? Is that a Jet purchase? Also, how can I prevent excessive wear on the tip of my "good" live center? It's not been used much (I usually use the factory one), but has a ring from where the outbard end of the mandrel seats against it. I'm just getting it snug enough to make it spin freely to try to prevent bowing the mandrel rod.

thanks!
sarah
 
Ok , now this may be a problem on it's own . You say you are using the stock live center ? That live center is most likely NOT a 60 deg live center . The grove you are cutting into it proves it . You will never get the mandrel to sit right on that centers tip and that will add to any OOR problems you are having .
Get a TRUE 60 deg live center , several people here sell them .
 
You might look to any place the sells the Jet, they may sell the replacement tip. Butch, it will work if the tip is flattened a bit. I can switch between my stock center and the good one with out any troubles.
 
schellfarms said:
I have 3 mandrels all with dedicated tapers for them so that we don't have to change out the rod each time. Where can a replacement tip for the center be gotten? Is that a Jet purchase? Also, how can I prevent excessive wear on the tip of my "good" live center? It's not been used much (I usually use the factory one), but has a ring from where the outbard end of the mandrel seats against it. I'm just getting it snug enough to make it spin freely to try to prevent bowing the mandrel rod.
thanks!
sarah
Click to expand...

Sarah: You probably don't need to replace the tip in your stock live center. As long as it has a reasonably sharp point, the ring/grove that is worn into it won't matter. But you do need to put that puppy away and use it "only" for wood. When turning pens and using a steel mandrel, you need to use the live center you got from the Little Machine Shop. It has a tip that has the angle for a perfect fit with the dimple in the end of your mandrel (standard 60° angle) and you don't need to do anything to protect the tip but for not dropping it on a concrete floor.​


I certainly agree with Paul that you "can" use the stock JET LC with its 30° tip if you file off the end a little; but it is also certainly better to use a LC designed specifically to fit the pen mandrels and that is what you have in the LC from LMS or at least we hope so. Do you remember what the model or stock number is of the LC that you purchased from them??

Paul has already explained the potential problem that is caused by inaccurate threading of the taper. (I think the correct technical term is arbor.) Preliminarily, I'm thinking that is not the problem. Either that threading is good or it is not right out of the box and it does not change over time except in rare circumstances which don't seem applicable here. According to what you told us this was not a problem when the equipment was new but has developed over time.

The only thing I can think of like that would for the mandrels to have become bent somehow.

There are several different ways mandrels can be bent........some common and some not so common. The most commonly accepted cause, probably, is applying too much pressure to the mandrel with the headstock. To be honest with you, I'm hard pressed to understand exactly how this happens; but that is another discussion. From what you describe you are using the correct amount of pressure on your mandrels so we will eliminate that for the moment. Another (and to me more likely) possibility is that you have tools that are not quite as sharp as they should be and you are putting excessive pressure on your mandrel when you are actually turning your blanks. So what we need to do is try to determine whether your mandrels are bent or whether there is really something wrong with your arbors.

BTW, you may recall that Paul mentioned that some mandrels have a 10-32 thread into the arbor rather than the sturdier 1/4-28 threading. Woodcraft is the company that sells the mandrels with the 10-32 threading. I think HUT probably uses 1/4-28 threading; but don't know for sure. You can tell by unscrewing a mandrel from the arbor and seeing if the brass nut on the other end of the mandrel will fit the arbor thread. Far as I know, all mandrels have a 1/4-28 thread on the TS end.

But I digress………back to the problem at hand. Determining if a mandrel is bent is a little tricky if the bend is small. OTOH, the 3 mm problem you are seeing is pretty large and if it is due to a bend in the mandrel it should be pretty easy to detect. What you need to do first is remove the mandrels from the tapers (arbors) and then roll them on a flat surface. The best surface would be a glass table top like a coffee table or an end table. Failing that, you could take a picture off the wall if you have one with a glass front panel and not a plastic one. A stone or synthetic countertop would probably also be flat enough to be useful for a test. You mentioned your table saw……that should work also. Anyway, roll each mandrel on some hard flat surface and if it has a significant bend you will hear a distinct clicking sound as the bent section lifts off of the surface and then comes back in contact with it. If the bend is more than just very slight, you will probably even be able to see some part of the mandrel coming off of the flat surface. If your eyes are good and you look close. I'm guessing you should be able to see 0.005"± and 0.01"± should be flagrantly obvious. With the 3mm ellipse you have described, I bet you could eyeball the mandrel and see the bend if there is one.

Another thing that just occurred to me is you could just hold two mandrels between your thumb and forefinger right next to each other and kind of roll them between your fingers. If you see a gap develop between the mandrels, you know one or the other or both are bent.

To answer your other question, you can order the LC tips from JET and they are less than 2 bucks; but they will want to charge you postage. When I tried to order one, they wanted to charge me their standard shipping rate of $19.95 ..........no, that is not a typo!! Well, I threw a fit:mad::mad: and they finally came down to $9.95. I told them to forgedaboutit and found one at the local Woodcraft store for $1.75. It is not a stock item at Woodcraft and you can't order them online. It is just a courtesy item that some Woodcraft stores carry and others don't.

If your tip is not terribly beat up, you can take a file and restore the profile without too much effort. It doesn't have to be anywhere near perfect.

Well, all of the above is probably enough to make you cross-eyed so why don't you take a shot at a closer examination of the mandrels and let us know what you discover.

In the mean time, I will search out the link yo Russ Fairfields web page with instructions for dealing with a bent mandrel. It is a very good article and well worth reading!!

Ciao.:)
​
 
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I'll take the mandrels out and check them on a flat surface. Probably be late next week, as I'm out of town till then. I think the LS from LMS might solve the problem--it's the "medium duty" one (at least that's what's printed on the box, but the LMS label on the box says heavy duty). It took the play down to about .005 on one of my mandrels if my dial indicator can be trusted. I'll try sharper tools too. That makes good sense--I'm probably a little heavy handed with the sanding too, so I'll try to be more gentle. It's just not my nature!! I think .005 is acceptable?? That is 1/200 of an inch, so it can be fixed easily with sand paper if needed. I've just been more into the $$$ pen kits with the last few I've turned and they just cost too much to mess up.
 
Sarah said:
.....I think the LS from LMS might solve the problem--it's the "medium duty" one (at least that's what's printed on the box, but the LMS label on the box says heavy duty)....... It took the play down to about .005 on one of my mandrels......I think .005 is acceptable?? That is 1/200 of an inch, so it can be fixed easily with sand paper if needed......
Click to expand...

Sarah: Be sure to report back and let us know what you find out. The information you supply will be useful to others in the future with similar problems.

Here are pictures of the two live centers that the LMS sells. The one on the right is the HD LC. Is that the one you have?

80.1189.jpg
....................
80.1592.jpg



The LMS live center really doesn't solve your problem, it just camouflages it. If the mandrel wants to rotate with a 3mm ellipse at the TS end, then when using the LC you are just forcing the LC to spin closer to true; but whatever is causing the mandrel to spin elliptically is still in [play and needs to be identified and corrected. When things are right, the mandrel will should spin pretty close to true without any support at the TS end and that should be your goal. To force it to spin true with the LC is merely putting a bandage of the problem and not solving it. Over the weekend, I will put a dial gauge on the "UNSUPPORTED" TS end of my mandrel and see how true it spins. If RandyS and Paul see this message maybe they can do the same to see what one might reasonably expect.

0.005" doesn't seem like a lot; but it is about the thickness of two sheets of newspaper. I once read that the average human finger could feel a step with an offset of about 0.003" so 0.005" is pretty significant; but you are certainly correct that sanding could easily repair that kind of discrepancy.

Enjoy your trip and and give us a shout when you get back.
 
Sarah

I have on all the lathes I own metal or wood checked the alignment between the tail stock and head stock using a dead centre in each end bringing them close together and holding a thin feeler guage between. Locking the tail stock wind the tail stock end to the other tip, the feeler guage will divert if there is an error in 360 degree movement to show which way it is out, if it is dead true the two points hold the guage square.

Using two dead centres also gives you a gap between the head stock and tail stock roughly the distance between that approximates where the tail stock would be to turn half a pen. This I do ie half a pen at a time to eliminate colley wobbles, I also did away with the primitive 60 degree point into the live centre from that small hole in the mandrel.

The only way to truly check alignment is at the real distance apart the head and tail stock would be with the mandrel in the head stock and the two blanks would be fitted in place, that is where the action takes place.

This info is common practice followed by metal lathe users since I was young and before and since I am now 75 in a couple of weeks I have no evidence to disprove my practice.
When I commenced wood turning I must say I have been dissallusioned with the manufacturers of wood lathes in that for the same price comparison metal lathes are far more accurate. I do see a trend with the upmarket pens to turn between bush to bush in which case a small metal lathe would take away errors and make pen making far more simple.

I wish you success with your lathe and happiness when turning pens.

Peter.
 
When I saw this post I decided to run right out to the shop and measure the spin on my mandrel.........just couldn't stand the suspense any longer. :eek::eek: I didn't clean the arbor or the spindle taper or try to seat the arbor for the best position. Just jammed that sucker in there and measured it to see how it compared with Sarah's. Total variation of the orbit of the mandrel was 0.42mm so it was a lot better than the 3mm that she mentioned; but not as good as I expected. (Sarah: Was that 3mm actually a measured distance or were you just estimating it by eyeball??) When I get some more time, later this WE, I will clean everything up and try different arbor positions to see if I can do any better. Will also make a few measurements with the mandrel supported by the LC and I will also make some measurements on a mandrel held in a Beall collet chuck. Seems like I did this several years ago; but I don't recall what sort of result I encountered??
 
pwhay said:
The only way to truly check alignment is at the real distance apart the head and tail stock would be with the mandrel in the head stock and the two blanks would be fitted in place, that is where the action takes place.

This info is common practice followed by metal lathe users since I was young and before and since I am now 75 in a couple of weeks I have no evidence to disprove my practice.
When I commenced wood turning I must say I have been dissallusioned with the manufacturers of wood lathes in that for the same price comparison metal lathes are far more accurate. I do see a trend with the upmarket pens to turn between bush to bush in which case a small metal lathe would take away errors and make pen making far more simple.

I wish you success with your lathe and happiness when turning pens.

Peter.
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Basically agree with you here, Peter. Just because the tips line up when close together doesn't mean they are in that alignment when backed up, but for wood turning..... If you could run an indicator the length of the mandrel with the tail stock in, that would give you the best indication of true alignment end to end.
 
schellfarms said:
the 3 mm was just a ball park estimate. i measured with & without tailstock in place using the dial indicator at several points along the length of the mandrel--results posted previously in this conversation
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Sorry, Sarah. I did not read the post with the measurements carefully enough. It did not register that some of the measurements were for a supported mandrel and others for the mandrel when unsupported.

Those measurements are very interesting and and may tell us quite a bit about your problem. There is one set of measurements that look like they may be in error. Don't want to get into details until I have had a chance to take some detailed measurements of my mandrels and then we can get down to the nitty-gritty.:wink:
 
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