Mandrel problem

[gomeral]

Hello, all -

First, to the moderators: If this belongs in the Shops/Jigs/Fixtures/Tools forum, please move it there...but I felt this might be a better forum with which to start.

For the rest of you (and the moderators, too), I have a problem with my mandrel(s) and I'm seriously trying to figure out what to do. Forgive the long background, but let me start at the beginning:

I have two mandrels. Both are Woodcraft, both are "A" type, and neither will turn straight on my lathe. I have a spare "A" shaft (unopened) and a Rockler "B" shaft that I just bought and discovered won't fit my tapers. (Doh!) I've been turning for a little while now (I know, a very SHORT while compared to some of you!), and I have been getting frustrated with OOR that I see as a lack of skill, but have been starting to think may be due to the tools, not the user. I complained last week about the out-of-round problem, I think maybe now I've got it figured out.

Yesterday I spent some time disassembling my lathe and mandrels and looking everything over, and although I don't have a run-out gauge, I can tell that the middle of the mandrel is bowed. Here's what I get - when I hold the mandrel in my hand, the shaft wobbles a little. If I try tightening it, it doesn't turn. But it does wiggle a little. So I put it in the lathe and try to line up the tailstock to see how it lines up - turns out that it's off at the tailstock by about one radius - that is, before the live center enters the cone at the end of the shaft, the edge of the shaft is just at the point of the live center. If I just move the tailstock in, the shaft centers on it, and I usually just move the TS in until it starts turning at the same speed as the shaft, then give about a 1/10th turn to stop the occasional squeaking. However, once the TS is centered in the cone, I notice that the middle of the mandrel appears bowed. I have almost NO pressure on the shaft, so I'm not sure how this happened, but...there it is. If I take the shaft out and roll it on the workbench, it doesn't appear to be bent, but when it's in the lathe, I can feel it wobbling. I even moved the tool rest up underneath it and adjusted the height until it was just barely at the "bottom" of the wobble, then turned on the lathe and heard "tick-tick-tick-tick-tick".

I'm certain this is causing my problems, but I can't figure out how it's doing it on BOTH of my mandrels (one I just bought about 10 days ago). I haven't opened the spare shaft yet, I just may do that.

Anyway, does this sound familiar to anyone? Do I need to send the mandrel back to WC? Is there a good way to check the alignment of the lathe? I use a Jet 1014VS mini lathe, if that helps. Any advice or suggestions would be greatly appreciated, I'm getting VERY frustrated!


Thanks,

daniel

 

[pssherman]

Danniel,
If the mandrels roll smoothly on a flat surface, then they are probably not the problem. Check to see if there is any dirt on the tapers or in the spindle. Check both the headstock and the tailstock. This would make them wiggle a little even though they seem to be seated in the spindle. If this doesn't remove all of the problem then check for allignment. Once the mandrel is firmly seated with no play bring the tailstock close to the end of the mandrel and turn the spindle by hand. Use the tip of the center in the tailstock to judge how much the end of the mandel moves. If it moves too much then you will need to find the source of this wobble. Any significant misallignment will cause the mandrel to bend when it is turning even if the shaft is perfectly straight when off the lathe. Hope this helps some. Others here probalby can offer more suggestions and tips.

 

[leehljp]

Are you using a 60° live center in the tail stock?

The mandrel is metal; as such, it requires a 60° live center tail stock, which is the standard for metal.

The stock live center on your Jet is meant for wood. What you described in the OOR and not fitting correctly is exactly like the live center problem. But sometimes the way things are described makes it difficult to be absolute sure.

 

[gomeral]

The stock live center on your Jet is meant for wood. What you described in the OOR and not fitting correctly is exactly like the live center problem. But sometimes the way things are described makes it difficult to be absolute sure.

Hank,

Yes, I use a 60º live center in my TS. Made the switch a couple of weeks ago, in part due to what I read here.


daniel

 

[jkeithrussell]

Other common causes of OOR are bad bushings, dull tools, too much pressure on the tools (whether sharp or not), and too much tension on the tailstock. I suppose it could also be a bad mandrel.

I've tried the C2C method as discussed in many threads here, but I don't like it. My OOR problems pretty much went away when I figured out how to sharpen my tools and how to apply the right amount of tension on the tailstock.

 

[mick]

afteryou get everything in place on your mandrel turn the lathe on and lay the edge of your skew on each bushing. especially the center oneif turning slimlines. If the mandrel is true the skew will just lay there. If it's out you'll get chatter. If you want to go a step farther, before you put anything on the mandrel run your taulstock upand lock it in place just as if you had everything on and ready to go. Lay youskew on edge at various places along the mandrel. If it's smooth at all points the mandrel is true. If it chatters in the middle it can be one of two things the mandrel is nent ....or there's too much pressure from the live center. If it chatters near the end, three things come to mind... the live center's tip is worn, the tailstock is out of line ...or the live centers bearings are worn. I had problems at the head stock end with my pens being OOR and after checking I found a bad bearing. So with a little checking you can usually locate what is off...or out.

 

[NewLondon88]

If I read your post correctly, it sounds to me like your headstock is out of
alignment. Depending on the make and model, there might be bolts holding
the headstock in place, which might allow you some adjustment. Or the
bearings in the headstock might need to be replaced.. they might be affecting
alignment.

I wonder if you put the mandrel up to the tailstock first, and then BACK it
into the headstock .. will you still get a wobble?

 

[gomeral]

I wonder if you put the mandrel up to the tailstock first, and then BACK it into the headstock .. will you still get a wobble?

This sounds intriguing. I'm trying to picture what you mean, perhaps I can ask for a further explanation or a PM...? Sorry for being slow, but if what I'm picturing is what you mean, I'm not sure how it will help... :redface:


daniel

 

[cowchaser]

Put in a dead center and pull your tailstock up to it and see if the live and dead center match tip to tip. If not it's something out on the lathe most likely. Take your mandrel and roll it across a mirror or something similar that is smooth and flat. If your mandrel starts to veer off instead of rolling straight it's most like the mandrel is bent.

You can try and adjust it back or buy a new one. I actually keep a few on hand. Never know what will happen and don't want to sit waiting on a new one. I bought mine from a member here, but can't seem to remember who it was.

 

[TurnedAround]

Hi,
If your headstock and tailstock match up like mentioned above check the mandrel collet. You said you had spare "shafts" so I'm assuming that they are either the threaded type or the collet type. If one of the fingers in the collet is damaged that would cause the shaft to wobble. If you have ever put a drill bit in a collet and caught it between two fingers instead of in the middle of all three fingers then you know what I'm talking about. Just a thought.

Ed

 

[Dave_M]

Hey Daniel,
Don't know if you've seen this yet, but it's a good place to start. ( http://www.woodturner-russ.com/Pen12b.html ) Russ has some great info on his site.

I used to fight with OOR problems until I bought a collet chuck that screws on to the HS. I tried the standard morse taper and the adjustable mandrels and both seemed to give me OOR issues. Since switching to the collet chuck, it's just a matter of getting the TS and the mandrel's thumb screw tightened properly and I'm turning true. Not that I'm trying to convince you to spend more money, but the collet chuck made a significant difference with eliminating my OOR problems. When I went to the collet chuck, I had to buy new mandrels because I tweaked the old ones trying to get them to turn straight.

Also keeping the tools very sharp so that you use a light touch to start shaving those blanks. Especially with those A mandrels. Those things seem to bend easily. I hope some of that info helps.

Dave

 

[NewLondon88]

This sounds intriguing. I'm trying to picture what you mean, perhaps I can ask for a further explanation or a PM...? Sorry for being slow, but if what I'm picturing is what you mean, I'm not sure how it will help... :redface:
daniel

You mentioned that the mandrel seems to be off by one radius when you
bring up the tailstock
If you put the mandrel up to the tailstock (instead of in the headstock) and
turn the handle so that you back the morse taper into the headstock
(rather than turning the tailstock into the end of the mandrel) you will line
it up manually.
If you do this (not tight) and then turn the motor/headstock by hand, you
will be able to see if it still wobbles. If it does, the mandrel is bent. It not,
then the headstock may be out of alignment.

The headstock and tailstock can match up point to point while still being
out of alignment. The theory is that if they meet point to point, they are
in line. (usually true, but not necessarily) But if either end is out of
alignment, they could meet in a vee instead of in a line.

Sorry, the more I try to explain it the worse job I seem to be doing.
It's really more simple than it looks by what I wrote

 

[gomeral]

Sorry, the more I try to explain it the worse job I seem to be doing. It's really more simple than it looks by what I wrote

Actually, this clarifies a lot. I'll see if I can inspect tonight when I get home. I've been taking a brief hiatus since Saturday and have been working on cleaning up the shop and making a bandsaw xc sled, it'll be nice to touch the lathe again.

I need to make a xc sled for the TS, too, and I have to say - it's a challenge to make a sled when you need a sled to cut the wood you're going to use for the sled...


Many thanks,

daniel

 

[me2cyclops]

to check tailstock alignment place center to center with the tailstock extended to max and retracted as far as you can without ejecting live center if the alignment is the same then tailstock is parallel to the bed (check vertical as well as fore/aft alignment when doing this tailstock may be parallel but tilted up or down)
also do you have a swivel or fixed headstock?

 

[jimbob91577]

Elaborating on what some have already said, put your spur center in your headstock and with the lathe off, bring your tailstock up so that the points of the spur center and live center just about meet. If they are not lined up, your headstock is out of alignment.

If they do line up, try putting a chuck on the lathe, turn a long cone and repeat this process with the tip of the cone, this way you are out a few inches from the headstock. If your tips do not line up, your headstock is out of alignment.

To fix, if you can adjust the bolts that fix the headstock to the bed of the lathe, start there. If the headstock point is low, you can try shimming by slipping a piece of sand paper between the bed and the headstock, if the tailstock is low, you can try the same thing with the tailstock. I had to do this when turning baseball bats on my fullsize Grizzly lathe and I was only out of alignment by about 3/32" at 28" from the head - the bats when turned down would begin to chatter. I shimmed my headstock and the problem went away.

Just my $.02

 

[jimofsanston]

lose

I found that i had a loose bolt holding my shaft at the belt which allowed it to move a litttle causing an out of roundness wauble. make sure all is tight.