Living with a misaligned lathe

[Tiger]

I have read through a number of posts on this forum regarding the difficulty of aligning the headstock and the tailstock. I use a dead centre in the headstock and a live centre in the tailstock. With some paper shims under the tailstock I get pretty close to perfect alignment, yet I still get some out of round/eccentric results with my pen barrels. The diameter of the barrels are consistent just the centre is slightly off. Now I cleaned the morse tapers and that gave me a little more accuracy. The dial indicator shows less than a thousandth inch run-out with the dead centre in place, the tailstock is approx 1 to 1.5 thousandths out. I still get less than a perfect result with eccentricity but I'd like to ask whether I am expecting too much. The resulting eccentricity is small. If you run your finger from pen part to barrel you barely notice a difference, if you run your fingernail in a perpendicular direction across the pen part and the barrel you certainly notice the uneven transition. It is not easy to notice the transition but if you know it's there, you'll find it easily enough. Now we can rule out bad bushings as I turn without them and turn BTC, the eccentricity seems to always be at the tailstock end and the lathe is a Jet 10 x 14 Variable speed. These are wood lathes and not metal lathes, I understand that. I just want to know, the pen turners who accept that these lathes are not high precision bits of equipment, can you get perfectly seamless transitions between your pen parts and barrels or is it unachievable with this sort of equipment? Other option is I keep spending lots of time trying to get perfect alignment which I'm not sure is even going to guarantee the perfect consistent transition that I desire.

 

[RKB]

I like my Commander lathe that sits on my bench and love the enjoyment I get from trying to make those "perfect" pens.

 

[Wood Butcher]

A difference of .001 would not be an issue for me but then my favorite tool is a hand ax, just kidding. However, if the 2 eccentricities are opposed when rotating, that could be significant. May I suggest you contact Jet and see what they say?
WB

 

[Tiger]

A difference of .001 would not be an issue for me but then my favorite tool is a hand ax, just kidding. However, if the 2 eccentricities are opposed when rotating, that could be significant. May I suggest you contact Jet and see what they say?
WB

Probably not an option, I bought the lathe second-hand, just not sure whether my expectations are too high for what it is.

 

[1080Wayne]

Not familiar with the Jet , so don`t know it`s eccentricities , but if you feel the problem is at the tailstock end , you might try doing the finish turning of each end of the blank at the headstock end . I doubt if it will help , but nothing lost by trying .

I would consider headstock-tailstock alignment and runout as measured by the dial gauge as two separate problems . Cleaning of the Morse taper improved the latter . A trick that might help you adjust the alignment is to place a 10-20 thou piece of shimstock or roof flashing or whatever similar you have handy between the points as you bring them together . If the material stays perpendicular to the lathe axis , you don`t have a problem , but if it ends up nearly parallel you have a large problem .

You also might want to consider using something a bit more robust than paper for shims . The force with which you tighten the tailstock should be the same each time , for consistent results .

 

[Tiger]

Some good points there Wayne, thanks.

 

[Mortalis]

Now we can rule out bad bushings as I turn without them and turn BTC, the eccentricity seems to always be at the tailstock end and the lathe is a Jet 10 x 14 Variable speed.

Your issue is not alignment of the two centers. The issue is that you have is lobing. Even if the two morse tapers were out of alignment by 0.050" you would get taper but not out of concentricity if the blank is running true. A bad live center will cause the blank to lobe. Debris between the blank and the live center point taper will cause loving also, like a burr or chip or small piece of dried glue.

 

[Sawdust1825]

Mortalis is correct. Misalignment will not cause concentricity issues. I am not going to repeat what he has already stated but he is spot on in his assessment. Check your setup for the issues stated and you will find one or more of the at fault.

 

[Tiger]

Thanks Mortalis and Sawdust but the live centre seems to be running true. I've cleaned everything but i'll change the live centre and see what happens.

 

[Carl Fisher]

are you checking your live center run out under actual turning conditions with pressure applied to it?

If there is a bearing issue in the live center, applying pressure as you would when you tighten down your work piece or apply forward pressure of a chisel may cause a problem. I have one live center that is like that and I just use it for finishing work where it's not noticeable but causes OOR if I use it for turning.

 

[Charlie_W]

Just thought I would mention this. I see too many turners turning without locking the tailstock quill in place. I guess they figure it takes too much time and want to advance the quill with out unlocking/locking every time.
My Jet mini has what I consider way too much lateral play in the quill when it is not locked down. For this reason, I do my drilling on my Nova which has less play when the quill is free to advance.
For penturning, we are working to a fixed demenision and thousandts of an inch are critical are critical.

Hope this helps.

 

[lwalper]

I found a burr inside the headstock taper. Filed that out and many problems were solved.

 

[gt64155]

I have a Jet midi lathe and had some issues with out of round. My lathe is also sitting on a Jet stand. Someone in our wood turning club suggested that I lay a small magnetic bubble level across the bed at the head stock and at the far end of the bed. I discovered that the bed was slightly twisted, causing the out of alignment issues. It was simply a matter of adjusting the feet on the stand to fix the problem.

Bill

 

[Tiger]

are you checking your live center run out under actual turning conditions with pressure applied to it?

If there is a bearing issue in the live center, applying pressure as you would when you tighten down your work piece or apply forward pressure of a chisel may cause a problem. I have one live center that is like that and I just use it for finishing work where it's not noticeable but causes OOR if I use it for turning.

Good question, not checking under actual workload conditions, will check tonight.