The Home Machinist!

All--

I was having trouble aligning a work piece in my four jaw today. I decided to put an indicator on the chuck to see if it was doing something crazy. Here is a video. Tell me what you think.

I mounted the four jaw in all six D1-5 positions and recorded the run out both at spindle edge of the chuck and just behind the cam lock studs. The spindle edge of the chuck showed something between 0.000" and 0.001". Just behind the cam lock studs, I measured between 0.000" and 0.002". I don't know if that is good, bad, or about right.

Will you tell me if I measured correctly and whether the measurement means anything to work piece alignment?

Thanks.

--Bill

_________________
You are what you write.

It really should not be an issue as the jaws are independent and you would adjust them to eliminate any runout of the part being held. Unless it's an odd shaped part.

_________________
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

I'm a little confused by this one, too. I have probably indicated the outside of a chuck at one time or another, but I am not proud of it.

_________________
I like to think that I can see the negative in anything.

As stated, as long as it's not off to the point of being a balance issue, the only thing that matters is that the jaw face (gripping face) are parallel to the axis of the spindle.

_________________
Russ
Master Floor Sweeper

BadDog--

I bet I've read how to make the jaw gripping faces parallel to the axis of the spindle . . . when it didn't seem as important to me as it does now.

How is it done?

--Bill

_________________
You are what you write.

That was in the thread a while back where Richard W was describing the use of 1/16" thick soft copper as jaw pads which allows you to indicate the part true close to the chuck and then move the indicator farther out and tap the part to run true there as well. The soft copper allows the part slight movement to align it's axis with the spindle axis. Harold and Russ were in there as well with the same process as it's standard four jaw procedure.

Dunno which thread that was though

_________________
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

Usually by purchasing a quality chuck...

You first need to check that the jaw face is the problem. You can check it in a variety of ways (details of techniques and relative merits could be a long discussion in itself), but once you (think you) determine that you have a problem with the jaws, you can preload the jaws and use a "tool post grinder" (commercial or home brew) to touch up the jaws. However, even then you also have to make sure that the chuck remounts consistently, and that the jaws remain relatively consistent when tightened. Just to make it more complex to determine the answers, a 4 jaw tends to have a bit of "nudge" so that you can often get the piece running coaxial even when it does not start out that way.

_________________
Russ
Master Floor Sweeper

Glenn and Russ--

Glenn, I remember that thread. I'll see if I can find it.

Russ, yeah, I bet a quality chuck would make a big difference.

--Bill

_________________
You are what you write.

Russ and All--

I'm cruising e-bay looking for non-Chinese 4-jaw independent chucks. I have an 8", but a 6" would do everything I need to do. Do you have brand recommendations?

--Bill

_________________
You are what you write.

You might want to check your's first. Many folks get by quite nice on import chucks, they are not all created equal, and your's may be just fine for your needs.

As for good names in 4 jaws, all the usual suspects. Buck (and permutations), Pratt Burnerd (and permutations), Bison, and Rohm are recent/current names of the top of my head. Then there are the old standbys in Skinnard (or something like that?) and Cushman. Plus re-badges, and doubtless many I don't know of...

On my Rockwell I had an 8" Pratt Bernerd that was very finely made. I now have a 12" Buck and a 15" Rohm (thing must be 150 lbs), both well made.

_________________
Russ
Master Floor Sweeper

Russ--

I will definitely check and check and recheck mine. However, by just seeing the names of quality chucks and looking at them on e-bay, I have already learned a bit.

Thanks.

--Bill

_________________
You are what you write.

The problem is, quality chucks have a finite life, yet they continue to serve the purpose for which they were made---to hold parts. With a three jaw, the problem is circumvented by using soft jaws. With a four jaw, the problem is circumvented by applying the techniques one learns in the process of becoming a machinist, which would include holding the part such that it can be manipulated to achieve the desired orientation. If that was not the case, it would be uncommon for parts to be held properly, for chucks do not retain their original precision, and may or may not have that capability as the jaws are moved either in or out. Slides wear, and are known to spring---so error is an every changing condition. Bottom line---do not rely on the chuck, but on one's skills and talent, instead.

Harold

_________________
Wise people talk because they have something to say. Fools talk because they have to say something.