Acceptable run out for lathe

JoeyInCali said:

Find a small round .0005" indicator ( Shars makes one ).
Glue a round wood piece at the bottom ( about 1/4 thick ).
Then glue 4 small earth magnets on the wood ( 12,3,6 and 9 o'clock ).
You can stick that easily on your parting tool .

Click to expand...

Got the Shars' dial and tried what you suggested but the weight was too much for the three magnets (didn't use earth ones) used. Because of the thingy with the drilled hole, was able too simply lock it down to the tool post with just one set screw.

Appears the RO is .003. Not building, just doing repairs. Read in a search how to tighten up the RO. Just wondering if it's worth doing or if what I have is acceptable for what I'm doing?

Thanks for your previous suggestion which led to a solution.

That is because that is a "travel indicator", you should be using a "test indicator"

And no insult intended, the quality of that instrument couldn't be worse.

That's the big version of the .0005" indicator with a flat base .

I do not know anything about the particular chuck you have, but I am seeing quite a few chucks these days are not very good right from the get go at being any good. They will zero out at a particular size, and every size either above or below, they can run out as much as 0.006 inches, or 0.15mm.
I also recommend that you look for a metric DTI, the divisions are about the same spacing, but each division is about 4/10000 of an inch instead of 0.001 inch. So a 0.003 inch reading will be about 0.07 + 1/2 division. Just makes life a lot easier as you get older eyes. The 0.005 marked indicators seem to have too many markings all crammed in and I find awkward to read compared to the metric indicators. I do have inch stuff to use for travel on either X or Z for the Taig type or the imperial lathe I have. But I now always use the Metric DTI's for indicating runout.
Neil

conetip said:

I do not know anything about the particular chuck you have, but I am seeing quite a few chucks these days are not very good right from the get go. They will zero out at a particular size, and every size either above or below, they can run out as much as 0.006 inches, or 0.15mm.

Click to expand...

This has never been a problem until the poorly made chinese chucks came to the market place. Sounds like they don't "Repeat".

We are all watching our budget but some things you just can't cut corners on. A chuck is one of those things.

On a budget? look for chucks made in Poland, Japan, Germany, France, England, and the U.S.
You want to change your life forever? buy an "adjustable" chuck. Or convert a quality chuck into an adjustable chuck.
Makers names to look for are, Buck, Forkardt, Cushman, Pratt Burnerd, Bison, and Skinner.
Buck and Forkardt merged if I remember right.
Other makers as well. So long as they were made in a country that produces well made tooling.
And so long as the chuck appears to be well cared for and not abused.
First thing take it apart, clean it, inspect it, oil it, and reassemble it.

conetip said:

I also recommend that you look for a metric DTI, the divisions are about the same spacing, but each division is about 4/10000 of an inch instead of 0.001 inch. So a 0.003 inch reading will be about 0.07 + 1/2 division. Just makes life a lot easier as you get older eyes. The 0.005 marked indicators seem to have too many markings all crammed in and I find awkward to read compared to the metric indicators. I do have inch stuff to use for travel on either X or Z for the Taig type or the imperial lathe I have. But I now always use the Metric DTI's for indicating runout.
Neil

Click to expand...

No need to go metric.
It's all is what you choose. Some metric test indicators have small dials and narrow divisions too.
Consider getting an Interapid 312B-1 in .0005"
(Or the Brown& Sharpe equivalent)
(Interapid, Brown & Sharpe, and Tesa have merged)
Nice big face, wide divisions, Jeweled, self reversing, Swiss made, etc.

The truth is working, with and using, quality instruments and work holding devices is a pleasure. You enjoy using them.
Compare that to the lost time and frustration of dealing with poorly made products.
It makes buying right the first time a bargain all round.

You need a different indicator to check the tolerance. They make wheels that will screw on the tip of indicator that will allow you to use that indicator. Your better off buying the correct indicator for getting accurate measurements. Using the wrong indicator is better than using none.
A 4 jaw independent Chuck is more accurate than a 3 jaw.

stick130 said:

You need a different indicator to check the tolerance. They make wheels that will screw on the tip of indicator that will allow you to use that indicator.

Click to expand...

A quality roller tip cost more than the indicator he bought.
http://www.starrett.com/metrology/product-detail/25W

Those tips are generally used on huge parts and when there is a need for a lot of travel.

stick130 said:

Your better off buying the correct indicator for getting accurate measurements. Using the wrong indicator is better than using none.

Click to expand...

A good test indicator and he's off and running.

stick130 said:

A 4 jaw independent Chuck is more accurate than a 3 jaw.

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Only because they can be adjusted. But an adjustable three jaw is way faster and good ones often repeat within .0005".
(which can be tuned much closer if needed)
And the three points of contact can be more stable. The jaws are drawn to the center of the chuck and oppose each other equally.
With a four jaw, an independent four jaw, it's four points of contact oppose each other. You lose the advantage of the "triangle".
The triangle is the principle that "V" blocks and St. Mary's fixtures are based on.
You pull out the independent four jaw when you have to grip a square or rectangular workpiece, or an odd shaped workpiece,
or a workpiece that is too large to manage in your three jaw.
(On average a machine that uses an 8" three jaw will have as a companion a 10" four jaw)

Four jaws are slow as the dickens, but can save your bacon when you are backed into a corner.
Especially when are dealing with an odd shaped workpiece.

A five sided workpiece?
2 jaw, no, 3 jaw, no, 4 jaw, no, 6 jaw, no, 8 jaw, no...........

What you have there is a real problem!


LOL

While it is important to tune you lathe to the best it can be.......... for pool cue work, most things will never need a chuck better than 1 or 2 thou runout..................

Kim

whammo57 said:

While it is important to tune you lathe to the best it can be.......... for pool cue work, most things will never need a chuck better than 1 or 2 thou runout..................

Kim

Click to expand...

While this sounds somewhat logical, I have to point out some pitfalls.

If you make your own collets, or other jigs or fixtures, the runout becomes very important.

If you machine the outside of a particular collet or jig, and then mount that machined diameter in your chuck on order to machine the insides, you will compound the runout and make a bad piece. It's always a good idea to machine both insides and outsides of critical parts in the same "chucking" so they will be concentric to each other.

In our shop, we have a normal Set Tru type chuck on our manual lathe, and don't worry about it too much. But, all of our end work on cues and shafts are done on machines with collet closers as opposed to normal chucks. We see .0004" or less as typical from the collets. We also machine threaded collet bushings that attach to the back of the collet. These are bored to accommodate the stock so it's supported in 2 places to make sure it's dead straight.


Royce

RBC said:

While this sounds somewhat logical, I have to point out some pitfalls.

If you make your own collets, or other jigs or fixtures, the runout becomes very important.

If you machine the outside of a particular collet or jig, and then mount that machined diameter in your chuck on order to machine the insides, you will compound the runout and make a bad piece. It's always a good idea to machine both insides and outsides of critical parts in the same "chucking" so they will be concentric to each other.

In our shop, we have a normal Set Tru type chuck on our manual lathe, and don't worry about it too much. But, all of our end work on cues and shafts are done on machines with collet closers as opposed to normal chucks. We see .0004" or less as typical from the collets. We also machine threaded collet bushings that attach to the back of the collet. These are bored to accommodate the stock so it's supported in 2 places to make sure it's dead straight.


Royce

Click to expand...

If you make your own collets, and you have .xxx" of runout, if you make them all the same OD, and mark them in conjunction with a mark on one of your jaws, won't you minimize runout?

To use RMS's example of something of something odd shaped, you find the center of the hole you want to bore, indicate that in the 4 jaw, and bore the hole, right? Isn't the hole still true?

Or is the runout creating an oval area of travel?

shakes said:

If you make your own collets, and you have .xxx" of runout, if you make them all the same OD, and mark them in conjunction with a mark on one of your jaws, won't you minimize runout?

To use RMS's example of something of something odd shaped, you find the center of the hole you want to bore, indicate that in the 4 jaw, and bore the hole, right? Isn't the hole still true?

Or is the runout creating an oval area of travel?

Click to expand...

Skins,

The bore will always be concentric with you spindle but if your piece's OD is not indicated and chucked true, your ID and OD will not be concentric to each other on a cue.

Rick

RBC said:

While this sounds somewhat logical, I have to point out some pitfalls.

If you make your own collets, or other jigs or fixtures, the runout becomes very important.

If you machine the outside of a particular collet or jig, and then mount that machined diameter in your chuck on order to machine the insides, you will compound the runout and make a bad piece. It's always a good idea to machine both insides and outsides of critical parts in the same "chucking" so they will be concentric to each other.

Royce

Click to expand...

Your method in bold makes Kim's .001" to .002" tolerances work out just fine when making collets and many other things. Since lower dollar chucks can only achieve those tolerances consistently we have figured out ways to make cues within those tolerances, like you did in your above method. We also tap or push the work piece to under .001" runout when needed.

scdiveteam said:

Skins,

The bore will always be concentric with you spindle but if your piece's OD is not indicated and chucked true, your ID and OD will not be concentric to each other on a cue.

Rick

Click to expand...

Easy solution is to machine a ROD in making collets .
Machine the EXPOSED part of the rod . Then bore the hole . That hole and the OD should be concentric. Unless your rod is really bad to start with.
Then part that off .
Leave a lip.
That collet will be good .
If your chuck is off, time to play with receipt paper when using that collet.