Taig Lathe Runout

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benster

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I'm having trouble with runout on my Taig lathe. Starting out I'll center work in a 4 jaw chuck, usually to within .0005. I'll also use the tailstock. Workpieces around 2-4" long, about .5"-1" diameter. The problem is after roughing passes, and finishing passes of .001 I'll still end up with about a difference of .003-.005 in the end diameters. I've tried making my last pass or two a spring cut and I still end up with runout. Do I need to be using a follow rest? Should I just not expect more accuracy on a lathe this small? Would turning between centers help?
 
Benster,
Have you checked to make sure your tailstock is correctly lined up and not off center?

Peter J.
 
How old is your Taig? Perhaps the bed is worn hourglass shapped.

An easy check for that is seeing if the carriage is looser towards the chuck and tighter towards the end of the bed.

An out of line tail stock will skew the work off center with a chuck an amazing amount, good reason to turn betwen centers, another check.

Check the four jaws to see if the jaws gripping surface is 90 degrees to the face and not worn.

Just my experience with a Taig with over 1600 hours on it. In good shape and set correctly it should hold to less than .001 deviance along the travel.
 
Its only about a year old and I've lapped it a few times in that period. I'll try aligning my tailstock more accurately and see where that gets me.
 
Mine has seen some rough use as it was my first lathe, and suffered through my learning curve, but the runout is still less than .001.
 
Benster, you have called the topic heading runout, when you actually have a problem with taper on your work. Runout is something different altogether, I'm sure that your problem is with the tailstock alignment. One way to adjust the tailstock is to use a dial indicator and run it along your turned workpiece, it should read zero all the way along, then let's say that the tailstock end of the work is .004" bigger than the other end, adjust the tailstock so that the indicator reading is zero at the headstock end and +.002" at the tailstock end (half the difference). This will mean that you will be turning more off the larger end and hopefully be parallel all the way along.

Paul.
 
A 'Garden Gate' engineering rather than a precision suggestion is to put in a couple of centres and nip a 6" rule between them.

Let me know

Norman
 
Workpiece 3-4 inches long, 1/2 to 1 inch diameter , centered in a 4 jaw !
No way does this need a tailstock centre for turning such a piece , look elsewhere , try adjusting the carriage for a start.
 
I did try adjusting my tailstock and it was a little out "left to right" I adjusted it to about .0005. However, it's off by .001-.002 vertically, is there some way to shim the Taig tailstock? The way its built I can't think of a way. Also, I've tried adjusting the carriage gibs but they're just at the point where any tighter and it won't slide.
 
Please define what you mean by 'lapping several times'.
Again, let us know how you are getting such claimed 'inaccuracy- or accuracy'.
You are using arguably one of the cheapest and smallest of lathes yet by deduction , you are able to measure to half a thous which means that you possess or have access to inspection equipment capable of measuring in 'tenths'

I may be wrong but that is how it comes over to me.
 
The first time I got the inaccuracy I thought it was poorly adjusted gibs, so I took the lathe apart and used lapping compound to lap the gibs/carriage to the ways. When I adjusted the tailstock I used a test indicator with half thou resolution. My diameter measurements are with Mitutoyo Absolute calipers or micrometer. I center work in the 4 jaw with a dial indicator, then with the test indicator.

Just because I have a cheap/small lathe doesn't mean I don't have good auxiliary equipment or lack the knowledge to use them.
 
benster said:
Don't bother that kind of comment from him,:hDe:
I have a Taig and 2 others and even if it's small it's dead on accurate.
as for the up and down offset not often:wall::wall: some people
did mill the under side of the tail stock and added a small brass plate
with screws to adjust it. I have the riser kit on mine and had to mill it down
to adjust it.
Click to expand...
 
Apologies but I was merely trying to find out the problem and was going to attempt to answer it.
I'm playing with a little Unimat clone- a MJ189 . Amazing what can be done with a scraper and a trace of Engineers blue.

Norman
 
The tailstock height is not the critical dim.The front to back alignment is the important dim.It affects taper turning greatly but is the easiest one to adjust
If the heights are within 2 thou then I would suggest it is near enough,
the front to back should be adjusted as accurately as possible.
If possible,grip the job in a collet and use the tailstock centre.This usually gets within a thou for me
 
benster said:
The first time I got the inaccuracy I thought it was poorly adjusted gibs, so I took the lathe apart and used lapping compound to lap the gibs/carriage to the ways. When I adjusted the tailstock I used a test indicator with half thou resolution. My diameter measurements are with Mitutoyo Absolute calipers or micrometer. I center work in the 4 jaw with a dial indicator, then with the test indicator.

Just because I have a cheap/small lathe doesn't mean I don't have good auxiliary equipment or lack the knowledge to use them.
Click to expand...


I generally cringe when I see mention of ways, Gibbs and lapping compound. It is generally a bad idea to use lapping compound to correct fit up problems. I know this can lead to endless arguments but if you machine has fit up problems you really want to consider scrapping in the components. Lapping simply isn't a controlled way to correct fit up issues.
 
If the tailstock is high then simply tape some wet/dry paper to the bed
A few minutes stroking the tailstock over the WD should remove any high spots
and lower 2 thou easily
 
No one has mention if the bed may have a twist in it . Not likely but still possible on such a short bed ! Keep looking you will find the problem .
 
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