Is There An Easier Way For Initial Set-up of 4 Jaw Chuck?

S

ShagDog

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I have not yet been able to find an easier way for initial set-up of a 4 jaw independent chuck. I use the concentric lines on the chuck; but, I have difficulty getting to where my dial indicator doesn't go more than full circle, when the part is first put in, unless I get lucky. I have no problems getting the 4 jaw into final alignment within a tenth or less, at least according to my indicator.

Is there a better way for initial set-up that you are using, and would not mind sharing?
 
I find just putting a tool or something near the part for initial setup really helpful. Much easier to "eyeball" than an indicator flying around!

Rings
Eyeball against something (usually whatever is in the toolpost)
Indicator

I reckon I can get within a few thou without an indicator, then it's easy with one getting those last few dialed out. That's the method I've developed get through exactly what you're describing.

I've often thought of building a toolpost mounted fixture with a slider on the end, on which is mounted a bearing which can be run against the work. The other end of the slider designed so you can place the tip of a finger over the hole it slides in, arranging it so the slider is nominally flush, allowing safely "feeling" the runout as the chuck is turned by hand. Call it a "haptic indicator", if you will. You can detect truly tiny movements with fingertips. Would also be great for those whose sight is maybe not as good as it once was.
 
First off, if you're chucking round stock and it doesn't have to be dead nuts, switch to your 3-jaw chuck. Less crazy-making.

Otherwise, spot drill (just a peck) at the center of your desired rotation and use a live center in the tailstock to support the part against the 4-jaw chuck.

Manually align the desired major and minor axes gripping points of the part with the 4 jaws, then move the jaws to support the part. This gets you pretty close.

Retract the tailstock and have TWO chuck keys so you can move the part laterally with a pushme-pullyou and still maintain a grip on the part.

Alternate X and Y adjustment by rotating the part until you are dialed in.

JWID, YMMV

Stu
 
At times I have centered the jaws on the tailstock quill/ram (whatever you call it), backed out the tailstock and then moved each jaw the same number of turns in or out to fit the work. I have also used a square to mark the center of the work. Then with a dead center in the tailstock adjusted the jaws until the work was centered like gr8legs described above. This is the method that I use most of the time.
 
As John said, it just takes practice. The trick is not to snug up any one jaw too tight until you are getting very close, to allow for slight adjustments
The more you do it the faster you'll get
 
When using a 4 jaw independent chuck. Start by using the lines on the jaws and chuck body to set each jaw at the same place, setting the opening with a rule to about the right size for the part.

Insert the raw material to be turned, I use brass shims between the jaws and work piece which helps with the adjustments and reduces damage from the jaws.

Then set up your dial indicator and work one set of jaws at a time. Get the one set close then do the other.
I do my initial dialing in close to the chuck, then move the dial indicator out to the end of the piece without the tail stock and bump the piece with a lead hammer to put the piece concentric.

Note: When adjusting the jaws, try first to tighten the one jaw and if that does not put you where you need to be then loosen, the opposite jaw and then back to the one that you have to tighten. As you get close you may only need to tighten a jaw for minimal movement.

Once you complete that move back to the chuck and double check your readings and make any adjustments.
I then double check again on the outboard point and if any significant adjustment is necessary, move back again to the chuck.

Repeat until concentric.

I hope this helps.
 
Look on the Littlemachineshop *how to* section, they have an Xlnt initial 4jaw set up.
 
I use a method my dad taught me and without trouble I can get parts within .01" TIR, square, rectangular or hex, even torch cut parts that are egg shaped.
 
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