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Old 12-21-2016, 10:44 PM
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Default 4 jaw chuck

Mounted the 4 jaw chuck, and went to school indicating a work piece. Watched a couple of videos before attempting the dance. Using two chuck keys machinist make it look like a no brainier.

Made a few feeble attempts to copy the moves, going around the chuck (laughing @ myself) in circles. Started to understand the concept, and developed my own routine using a single chuck key.

Came together nicely, I'll go back a few times just to indicate some different size and shape of bar. I like the 4 jaw and the goal is to use it most of the time.

A question, other than the expense & holding power of a 6 jaw chuck are there other advantages to know about?

Greg
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Old 12-21-2016, 10:48 PM
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I'm guessing that the advantages you mentioned are relative to the 6 jaw. I am sill considering getting a 6 jaw mostly for the low run out they provide.
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Last edited by milomilo; 12-22-2016 at 11:48 AM.
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Old 12-21-2016, 11:03 PM
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Four jaws are enough for me and I watched the same video and I still only use one key. The new three jaw I got is very close to true, run out is a thousandth or so I don't think they make a six jaw with independent jaws
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Old 12-22-2016, 08:52 AM
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I read some manufacture pages, was wondering the same about the 6 jaw, they are scroll only.

Other than holding hex, which a 3 jaw can do, they allow one to machine thin walled tubing.

Run out on a 3 jaw is it the chuck or the material, makes ya wonder, the reason?

When we mill the first operation is truing the raw material

Greg
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Old 12-22-2016, 10:54 AM
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For work starting from raw stock a three jaw is usually the best bet.
If the stock has a feature that makes the chucking problematic use a four jaw.
If you are chucking a machined part and need to return it to register before machining on it use a four jaw.
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Old 12-22-2016, 11:42 AM
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A new used four jaw using a one inch collet to mount. I don't know that I will ever use it but its ready to go.
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Old 12-22-2016, 03:18 PM
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Quote:
Originally Posted by pepi View Post
...Run out on a 3 jaw is it the chuck or the material, makes ya wonder, the reason?
A normal 3-jaw chuck will always have some runout--you have to have clearance to allow the scroll and jaws to move. The more money you spend the more accurate your chuck will be. A high precision CNC power chuck will provide superior accuracy and repeatability but it will also cost many times more than even a high quality manual chuck.

And, as far as 4-jaw chucks go, I have a couple and use them when necessary but in a jobbing shop like ours a decent 3-jaw is all we need for 95 per cent of the work we do. Like Terry says, if you're making a part that is turned on opposite ends and the two have to register perfectly--less than .0002"--then use a 4-jaw--that and holding odd-shaped parts is where they shine. On the other hand, for the vast majority of the work we do the .002"-.003" runout of a 3-jaw is more than tight enough. You never want to make a job more complicated--and therefore more time consuming--than it needs to be and in these situations a 3-jaw will always be faster than a 4-jaw...
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Old 12-22-2016, 03:30 PM
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The two key technique works fine. I made a pair of short ones for the chuck at school and was going to post a picture but can't find it either in my picture files or on the Photobucket site where I thought I had up-loaded it. So IF I can remember it when school starts again, I'll take the pic and post it. It really helps to have a knob on each of them and a bar to do the final tightening.
...lew...
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Old 12-22-2016, 06:51 PM
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Quote:
You never want to make a job more complicated--and therefore more time consuming--than it needs to be and in these situations a 3-jaw will always be faster than a 4-jaw...
That's why the first thing I asked somebody or looked at a print was this: what's the tolerance. I had a so called engine builder tell me he could hold tolerance down to a tenth (.0001) I had him make me a wheel spacer, gave him the dimensions and the part he produced of course was too far out to work by about 010" as I recall. When I asked him about it, he whipped out an electronic vernier caliper and proclaimed the part was "perfect". So I whipped out my certified and calibrated mikes and dial bore gauges and showed him that no, they weren't perfect and the axle wouldn't go though the part. Over the years I've found that the people that claim they can hold a tenth tolerance never seem to. At least on anything they've done for me. IF I machine a part that close, it was part luck really. Most of the time I tried to get within about 3 tenths on a cylinder, but honing it to size with a Sunnen hone that wears took some doing.
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Old 01-04-2017, 09:21 PM
Lew Hartswick Lew Hartswick is offline
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4 jaw two key use:
Finally school started again so I had the chance to photograph the keys I made some years ago. Any questions, I'll be happy to tryand answer.
...Lew...
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