[How do I?] Lathe Question - Probably common but for a noobie like me...

[ScrapMetal]

Did you mean to say "not to be used with an independant jaw chuck"? Works fine with my 6 jaw.

Picky, picky, picky. :biggrin: (But true)

I am sorry but i have not introduced myself as yet, but i just wanted to put my 2 cents in. if you are unsure about the ability of your chuck to hold the material why not support the end of it with a steady rest?

PS I have been a hobby machinest for about 8 years and I specilize in turning good metal into scrap.

Yep, that's a great point. If the work is out far enough to be a concern either a steady rest, center/tailstock, or both would be highly recommended.

-Ron

 

[clevinski]

To centre up the work, rather than a piece of wood or similar use a roller bearing on a stick (OK, on a piece of cold-rolled held in the toolpost!) - that way the bearing tells you when there's contact (by rotating) and when it's constant contact (it keeps rotating all the way around the work!) - if you wind it in until the bearing rotates smoothly, *then back out slowly* it'll leave the work nicely centred within a thou" or two, good enough for Government work

Dave H. (the other one)

Now THAT is one really great idea! Thanks, Dave H.!

Charlie

 

[clevinski]

I am sorry but i have not introduced myself as yet, but i just wanted to put my 2 cents in. if you are unsure about the ability of your chuck to hold the material why not support the end of it with a steady rest?

PS I have been a hobby machinest for about 8 years and I specilize in turning good metal into scrap.

Hi, Kd7fhg... (hmmm... sounds like a ham radio call sign?)...

I wasn't worried about the chuck holding the material, I was asking how to make sure that it was held in line with the chuck centerline if both ends had not yet been faced. Sorry if it wasn't clear.

A steady rest in general often strikes me as a good idea for a lot of applications...

Charlie

 

[clevinski]

I can't read all these posts. I turn on the lathe to a slow RPM,and present a non cutting surface to the rotating piece. Move the cross slide in until your bar runs true,AND DO NOT go past the point where the bar runs true.or you will soon tear the piece out of the chuck,possibly damaging it. Takes just a few seconds to do this. The piece will run at true as the bar is round(it may be a bit out of round from extruding,rolling,etc.,but the bar will run nice and true for all practical purposes.

Hi, George,

This approach seems to be the practical consensus, whether using wood, a "non cutting surface", or even a roller bearing. The more formal (?) approach seems to be by using a dial indicator. Amazing how many different solutions people come up with for the same problem! Many thanks for yours...

Charlie

 

[clevinski]

That is certainly a nice trick to remember for problem pieces. Generally simply kinda wiggling/rattling the piece as you slowly and lightly tighten the chuck will get stock about as straight as it is going to run. If it isn't straight enough rotate 120° and try again. Stock generally isn't perfect (unless you buy ground) and 3 jaw chucks aren't usually perfect so you can either have them compound the runout or partially cancel each other.

Copper shims aren't just for 4 jaws, or to prevent marking. Some chucks with a lot of error will run a good bit better with soft copper shims between the jaws and the stock. It gives that one high jaw something to deform a little and let the other 2 get where they belong. I use this when I need something at finished OD to run better than the .003" of my chuck but not needing it to run so true as to change to the 4 jaw. Not lazy just bad back and heavy chucks. Of course if the work isn't at finished OD it'll have 0 runout after finishing so no worries.

Steve

Steve,

Good advice on both points... thanks!

Charlie

 

[Kd7fhg]

Hi, Kd7fhg... (hmmm... sounds like a ham radio call sign?)...

I wasn't worried about the chuck holding the material, I was asking how to make sure that it was held in line with the chuck centerline if both ends had not yet been faced. Sorry if it wasn't clear.

A steady rest in general often strikes me as a good idea for a lot of applications...

Charlie

Yes it is a Ham call sign.
What I was getting at with the steady rest, it will actually do two things, 1 is to keep the stock from wobbling around and the other is keep it alligned with the center line of the chuck. I replaced the fingers on my stead rest with roller bearings which allows them to have full contact with the material held in the chuck, using this method I just have to grip the sides of the work and not worry about seating it aginst the face of the chuck. using a dial indiactor i true up the material closest to the chuck than true up the stock at the steady rest. Hope this made sence.

 

[clevinski]

Yes it is a Ham call sign.
What I was getting at with the steady rest, it will actually do two things, 1 is to keep the stock from wobbling around and the other is keep it alligned with the center line of the chuck. I replaced the fingers on my stead rest with roller bearings which allows them to have full contact with the material held in the chuck, using this method I just have to grip the sides of the work and not worry about seating it aginst the face of the chuck. using a dial indiactor i true up the material closest to the chuck than true up the stock at the steady rest. Hope this made sence.

Ah, now I get it! I wasn't thinking of using it for alignment, but understand what you meant now from your detailed description.

Many thanks...

Charlie (N2GHJ)

 

[Tony Wells]

They wouldn't, unless the lathe are a really, really tiny one.

 

[British Steel]

Now THAT is one really great idea! Thanks, Dave H.!

Charlie

You're welcome

It works on both axes too, if you need to true up referred to a face instead of a diameter, bring the bearing up towards the chuck from the tailstock end then back out - great when you need to drill or bore a hole square to a face or put an o-ring groove on mating parts. I've thought about making a cranked one so I could square up work in the drill press vice, but haven't the necessary tuits so far...

Dave H. (the other one)

 

[12bolts]

...as I needed it for an emergency angle grinder repair....

So, is it lucky you found the bearing happened to fit. Or perhaps you should'nt have stolen the bearing from the grinder in the 1st place!?:lmao:

Cheers Phil