1/100" off - OK?

[InvisibleMan]

Sorry, folks. I'm sure this topic is well hashed if I only knew proper terminology to look for:clown:

I've got the 8.5X16 Little Machine Shop lathe, and on a standard sized pen blank, I get a gradual taper of about 1/100", or .3mm from one end of the blank to the other. Is that fairly normal for a relatively inexpensive Chinese machine? It bugs me a little, but doesn't cause any issues with my pens since the parts are fairly short.

Thanks.

 

[BSea]

That tells me the tailstock is out of alignment. You should have some alignment set screws on each side of your tail stock. If the taper is to the tailstock side, you should adjust the tailstock toward the front of the lathe. There is a good video on Youtube about adjusting the tailstock to take out the taper. I'll see if I can find it.

Ok, I found it: https://www.youtube.com/watch?v=1EZh8SUoA4o

 

[frank123]

Tailstock needs alignment, a dial indicator and a known perfectly straight rod (i.e. TGP rod) long enough to go max between the tailstock center and the chuck -or headstock center- helps but trial and error combined with time works as well. This is best done between centers since alignment can also be affected by the chuck mounting or headstock fitting (correctable, but not so easily).

You should be able to get any taper down to well under .001 over the between center length of the bed.

 

[Rockytime]

<SNIP>
I've got the 8.5X16 Little Machine Shop lathe, and on a standard sized pen blank, I get a gradual taper of about 1/100", or .3mm from one end of the blank to the other. Is that fairly normal for a relatively inexpensive Chinese machine? It bugs me a little, but doesn't cause any issues with my pens since the parts are fairly short.

Thanks.

If you are using your tailstock taper it is a lot off. Your tailstock should have an X Y or front to back adjustment. I am not sure I can explain how to determine if it is in line. I do it with tramming bar but it can be dome quite closely with a small steel rule. Run the tailstock with a dead center up to the headstock also fitted with a dead center. Move the tailstock toward the headstock until the two centers just touch each other. Then with a small steel rule place the rule between the centers holding it place this the two centers. When the rule is perpendicular to the ways the height adjustment is very close. Then tilt the rule horizontal to the ways and the rule should be at right angles to the ways. I know this will not make a lot of sense. Perhaps another machinist type can expand on this or have a better suggestion.

 

[InvisibleMan]

Thanks all! That was indeed the problem, and I was making progress until.....SNAP! The metal tab inside the tailstock broke right off. Hard to imagine as thick as it is. Obviously not great quality metal! Anyway, I took a photo and am sending it off to LMS. We'll see what they say.