jet mini lathe ?

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fshenkin94

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I have a jet mini lathe. When I pull the tailstock up there is about 1/32" difference between the points onthe head and tail. Is there an adjustment that I can make to bring these in line? Is that enough to make the pen mandrel seem like it is bent? I have been having a problem with what I thought is the mandrel but when I check it it seems to be straight. I have even gotten a couple of new mandrels but keep running into the same problem.
 
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There is no adjustment per se; but there are a number of things that can be done to achieve better alignment. Most involve shimming various parts of the lathe; but we need to know a little more about the misalignment.

Is is up and down misalignment or left-right misalignment or a little of both. And be sure to indicate the relative direction of the misalignment. (Example: HS center is 1/32" above LS center.)

I'm not sure how much misalignment is too much with respect to turning pens; but, my gut feeling is 1/32" is probably about the outside limit of what is usable and that less would be preferred.
 
Fred: I haven't had a chance to look at this situation as closely as I would have liked. I did do a couple of drawings on my computer drafting program to see what the lathe geometry would look like and discovered that if the 1/32" offset that you are seeing is due to misalignment of the headstock, then at the TS end of the mandrel, the error would be more than 1/10". Since you say the mandrel and the point of your live center line up pretty well, I'm not sure what is going on. My gut feeling is that you don't have a major problem; but I need to think about this a little more.

My advice to you, for right now, would be to call JET and talk to one of their technical people and see what they have to say. You can get hold of them at
1-800-274-6846 or you can email them. They have quit listing an email address on their web site; but you might try the old address which I think was: customerservice@jettools.com

or you can try this: Jet Web Site Message Center
 
Originally posted by fshenkin94
<br />The headstock center is about 1/32" in front of the TS. THey are right on height wise.
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1/32" is a mile as far as accuracy is concerned. Before calling Jet, try shimming the feet of the lathe, it may not be setting perfectly square/flat on your bench. If reasonable measures do not correct the situation, call Jet.
 
I still differ on this alignment thing. As a machinist, I can be pretty anal about things like this, and understand the importance, at the same time a little miss-alignment on a wood lathe, though frustrating, is not that big a deal since size and accuracy are determined by tools used by hand, and sand paper[:D].
The tail stock may be able to be pulled or pushed to the front side or back side of the 'slot' to help, or twisted one way or the other to help. My only concern for missalignment like this would be for short mandrel turning as this would put more stress on the center. Over 6" or so it shouldn't be that big of a deal. As for the center aligning with the end of the mandrel, that can be subjective to the straightness of the mandrel. I have never had a mandrel run that true on the end to be able to rely on that as a measurement of alignment, but no issue with it when hooked up and turning. If you are drilling on the lathe, then there is a bit more issue, but again, try to wiggle or push your tail stock over and hold it while locking down nd see if that helps any.
 
My question is: What live center are you using? I had a major problem with wobble with the original Jet live center. I bought a LMS LS and the wobble went away.
 
Originally posted by Paul in OKC<br />..... The tail stock may be able to be pulled or pushed to the front side or back side of the 'slot' to help, or twisted one way or the other to help.....
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Paul: That was the first thing I thought about when making my post. Was thinking about suggesting shimming the TS if there was a little play. However, I checked my TS and there is almost no play, whatsoever. I can feel some wiggle in my tailstock; but when I put the centers together, that wiggle does not translate into an offset that I can see without using a 7x magnifier. It has to be less than 1/128" or 0.008".

An interesting result of looking at the points under magnification is that I discovered the point on my spur drive is not a very good point. It is not a perfect cone; but rather has a couple of flats on the side of the cone, Don't know if I damaged the point or it came that way from the factory. The look more like something that happened during the manufacturing process than something caused by me dropping the spur center; but who knows?? Anyway, with those flats there the actual point of the center is not exactly where it would be if the point were perfectly machined. When I turn the spindle, the point of the SC sort of orbits the point of the live center. They don't line up exactly; but are pretty close. All of this by way of suggesting that some/all of the "misalignment" could be due to a bad point rather than a true misalignment of the HS and the TS.

Originally posted by Paul in OKC<br />.....As for the center aligning with the end of the mandrel, that can be subjective to the straightness of the mandrel. I have never had a mandrel run that true on the end to be able to rely on that as a measurement of alignment, but no issue with it when hooked up and turning.....
Click to expand...

Assuming that Fred's statement about the mandrel being straight (or even close to straight) is true and that the mandrel meets more or less perfectly with TS center, I am still of the opinion the "problem" may not of too much concern, although I would still like to hear what JET has to say. As I pointed out earlier, if there is a real 1/32" misalignment at the centers, the end of a 6" mandrel would be off by about 3/32" which would be more than obvious to Fred.
 
Questions for Fred:

1. Are you using your spur center to check the alignment or do you have a dead center?

2. Do you feel or see much wiggle in your tailstock or is it pretty tight? Mine is pretty tight; but maybe you got one that was a little loose.

3. Is your lathe still under waranty?
 
Originally posted by Rifleman1776
<br />.....try shimming the feet of the lathe, it may not be setting perfectly square/flat on your bench. If reasonable measures do not correct the situation, call Jet.
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Frank, that is a good thought and you may very well be correct. It certainly wouldn't hurt to check that everything is flat and square. That being said, I don't think there is much likely hood that that is the problem. The lathe lathe frame is so stiff that twisting it enough to throw off the alignment would require significant force. As a test, I just put blocks under three of the feet on my lathe and left the fourth leg hanging totally unsupported. It did not change the alignment at all.

If the lathe were bolted down to a heavy table or stand that was not flat, I could conceive of enough force being generated to torque the frame of the lathe; but you would probably have to bolt it down so tightly that you would crush the soft bumpers on the legs.....not something I think most folks are likely to do. Bigger lathes with longer beds might be susceptible to torquing of the frame; but I'm not convinced that a short lathe like the Mini would suffer.
 
Originally posted by fshenkin94
<br />I have a jet mini lathe. When I pull the tailstock up there is about 1/32" difference between the points on the head and tail. Is there an adjustment that I can make to bring these in line? Is that enough to make the pen mandrel seem like it is bent? <b> I have been having a problem with what I thought is the mandrel but when I check it it seems to be straight.</b> I have even gotten a couple of new mandrels but keep running into the same problem.
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What kind of problems are you having? Lots of problems with turning good pens are totally unrelated to a bent mandrel. Are you using a 60° live center? Many folks have turning problems that clear right up with the use of such a center.

As to the alignment thing, you might want to check the following. Remove both centers and run a small piece of fine steel wool or a paper towel on the end of a pencil or dowel into each Morse taper. Use a few drops of kerosene, WD-40 or other solvent to remove any excess grease and lube. Pay attention to whether the steel wool or whatever tends to catch or run relatively smooth.....if it catches, there may be a burr in the taper that needs to removed. Clean off the tapers on your centers as well and make sure they are smooth and without burrs.

Other thing you should do is remove the tailstock from the lathe and carefully clean the surfaces that ride on the ways. (clean off the ways, too.) If there is any dirt or a burr on these surfaces, it will tilt the TS a little and could cause a misalignment of the centers.

I can't stand seeing situations like this and not have an answer so I got on the horn with the JET folks this afternoon. The guy I talked to said he had seen only one tailstock replaced under warranty in the past several years so if the TS is defective, it is a very rare occurrence. I asked about the JET tolerances for the aligning of centers. He wasn't sure; but thought it was about 0.008" which is right at 1/128". If we can't figure out something with your lathe, Fred, you may need to get some warranty relief.
 
Originally posted by Randy_
<br />
Originally posted by Rifleman1776
<br />.....try shimming the feet of the lathe, it may not be setting perfectly square/flat on your bench. If reasonable measures do not correct the situation, call Jet.
Click to expand...

Frank, that is a good thought and you may very well be correct. It certainly wouldn't hurt to check that everything is flat and square. That being said, I don't think there is much likely hood that that is the problem. The lathe lathe frame is so stiff that twisting it enough to throw off the alignment would require significant force. As a test, I just put blocks under three of the feet on my lathe and left the fourth leg hanging totally unsupported. It did not change the alignment at all.

If the lathe were bolted down to a heavy table or stand that was not flat, I could conceive of enough force being generated to torque the frame of the lathe; but you would probably have to bolt it down so tightly that you would crush the soft bumpers on the legs.....not something I think most folks are likely to do. Bigger lathes with longer beds might be susceptible to torquing of the frame; but I'm not convinced that a short lathe like the Mini would suffer.
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Randy, cast iron will change with time if forces are applied. I agree the small, short bed on the Jet mini might be difficult to mess with. But, depending on how it is setting or mounted, it could happen. I just offered the notion as one possibility.
 
I have been away for awhile and jsut got back and saw all the new postings about my issue. I will work on your suggestions this evening. I did buy a new mandrel and am still having a wobble issue when turning pens. I do have a 60 live center.

Thanks - Fred
 
Originally posted by fshenkin94
<br />.....am still having a wobble issue when turning pens.....{/quote]

What exactly do you mean by that? We really need a more detailed description of what sort of problem you are seeing before we can offer any meaningful advice.
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My Jet mini was off a little from headstock to tail stock horizontally. I loosened the headstock bolts and just tapped with machinest hammer, not hard, just a tap and it was a miracle, perfect alignment headstock to tail stock.
 
By "wobble" I meant that there is almost like a bow in the mandrel. I tried a new mandrel and am sure that I am not making the TS too tight on it. When I turn a pen the farther out toward the tailstock the more out of round issue I have. Hope that helps explain.
 
Curious to know, in regards to the wobble, and actually when you said that the HS point is approx 1/32" in front of the TS, does this offset stay in front when you rotate the HS by hand or does the offset move along with the rotation (bottom, back, top, front again)?
 
Hey Fred, I had a similar problem with my Jet mini, and found two more with the same issue at the Woodcraft store when I returned it and traded to a Rikon. On mine, the Morse taper was not drilled correctly, causing longer tapered attachments to wobble out.

I was able to look in the end of the morse taper and see the off-center drilling when turning the headstock wheel by hand.

Here's the thread detailing my particular issue, not sure if it's helpful, though! :)

http://www.penturners.org/forum/topic.asp?TOPIC_ID=30707

Good luck, it's no fun to have to monkey with tools. [B)]

Karl
 
I just chaecked my lathe. I can't tell if the mt is in alignment but the wheel on the outside of the headstock has a definite wobble. I assume that if that is woblling the whole thing is out of alignment. I had newm bearings put in about a year ago, so they should still be good. I don't use the thing that much.
 
The wobbling hand wheel probably doesn't mean anything. Most likely, it needs to be screwed onto the spindle a little tighter or the set screws need to be snugged up a bit.
 
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