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View Full Version : Spacing on concentric circles on 4 jaw chuck ?



TR
12-12-2010, 11:07 PM
Is there a system to the spacing of concentric circles on a 4 jaw chuck ? Are they are certain distant apart ? I can image a metric version with circles at 30, 40, 50, 60mm being useful.

chipmaker4130
12-12-2010, 11:40 PM
I'm pretty sure there is no standard. Those are just for convienience in 'guestimating' jaw position at the beginning of a setup.

oldtiffie
12-12-2010, 11:48 PM
Put a metric rule over them - for the rest of the non-USA world - but just in case, check with an imperial rule in case your have a "for the USA" model.

I am not aware that there is any hard and fast standard or rule for them.

They are pretty well only used as an optical guide for concentricity subject to more accurate centreing later - if needed. They are also handy to set four-jaw chuck jaws to as well.

The "Eye-ball, Mark 1, humans for the use of" is remarkably accurate and sensitive to concentricity and centreing.

The same rings are on face-plates for the same reasons.

Paul Alciatore
12-12-2010, 11:51 PM
And there is nothing stopping you from adding addional ones wherever you please, English, metric, or whatever.

MichaelP
12-13-2010, 12:15 AM
...just don't forget to remove the jaws when you do. :)

j king
12-13-2010, 08:27 AM
Im sure there is a rule...Just dont get caught and you should be ok. lol

rws
12-13-2010, 09:38 AM
I've marked my 4-jaw all the way around. Yes, a metric tape is easy to compute. What I did, was wrap the tape around and record the circumference. I wanted divisions in 3, 4, 5, 6 and 8. So I marked each position, then used a stamp and marked the locations where each occurred.

A simple mag base and a pointer lets you index very well. I use this mostly for making muzzle brakes. With the pointer indexing the rotation, and an indicator locating along the length, it works fantastic.

Carld
12-13-2010, 10:32 AM
The circles on the face of the 4 jaw are to help center up the work easier. If you know the diameter of the work you measure across the circles for the size you want and locate the jaws there as a starting point.

Stepside
12-13-2010, 11:47 AM
The distance between the grooves is not to important, the fact that they are there is important. On real heavy/big parts, use them to get the jaws close so you can get the part held quickly and then use other means to get the accuracy needed.
On smaller parts I 1) gestimate the spread of the jaws and set them "kinda sorta" equal. 2) rotate chuck so the jaw are horizontal and vertical and set your part on the bottom jaw. 3) using the part as a guide, set the two horizontal jaws close. 4) rotate the chuck 90 degrees and repeat the 3rd step. 5) bring all 4 jaws in barely tight. Use the sharp corner of the jaws and the groove to get them even. Get them even using your "eyeball ruler".
6) check and finish with your dial indicator.

I used this method 4 times yesterday on different diameter parts. The error on being centered varied from .005 to .020 before using the indicator. My chuck is close to new and the grooves and jaw corners are sharp.