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Jacobs Chuck Runout Expectations

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omni_dilletante

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#1
I am looking for a good drill chuck for my mill. I have purchased several on eBay but am less than impressed with the runout.

What should my expectations be?

Here is the runout on three of the chucks I have collected.

34B.runout_zpssqamu27d.jpg
11N.runout_zpsedryonk0.jpg
16N.runout_zpshuazx1yx.jpg

When I put the Z drill blank into a collet I get less than 0.0005" runout near the collet and at the end of the blank. So I believe the drill blank is not bent nor is there an alignment problem with the lathe.

I am pretty happy with the 34B. I got is for less than $25 on eBay. But I thought the ball bearing N series of chucks was supposed to be much better. (And I certainly paid much more for them.)

The arbor the 16N is mounted on is one I just turned on the lathe. I know it is not bent or abused.

None of these chucks seem abused, the jaws and body do not show any marks.

What should I expect from a good quality drill chuck?
 

mksj

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#2
The usual spec. for a drill chuck when new is a TIR of around 0.004" for the better ones, and much worse for the cheaper imports. Even the very expensive ones might get you 0.001" at best, and likely not repeatable for different size round stock. A used chuck, I would expect to be much worse unless one is rebuilt and the seller guarantees the TIR. There have also been significant issues with the newer Jacobs chucks now made in China, you might get lucky, but for the most part the TIRs are much worse based on what others have posted.

I mount my arbor in my lathe an zero it in my 4J chuck, and then index the chuck to find the position with the least TIR. I was able to get my Jacobs chuck 14N down to a 0.001" TIR from 0.004". I am not a big fan of keyless chucks on my mill, because I sometimes need to reverse a drill or tap, and this doesn't work with most keyless chucks. That being said, they tend to be a bit better with regards to the TIR, usually just under 0.001". The ones I have used and can recommend would be the Z-Live, QMT, Glacern, and probably Shar's. Have not used the Shar's keyless drill chuck, but other items such as collet holders have been better than spec. Collet system is the only way to go if you need a repeatable TIR below 0.001", much improved rigidity and usually less axial run-out as one gets further away from the chuck.

Jacobs 14N runout.jpg

I would also look at a new Llambrich chucks with in a keyed or keyless type, I have been impressed with their quality and reviews, and probably will get one in the future. They come in a lot of different models and guarantee their TIR. http://llambrich.com/industrial/pdf/Llambrich_Catalogo_Industrial_En.pdf
 

kd4gij

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#3
Here is what I did. I made a new arbor .020 over size then chuck a 1/2" x2" dowel pin in a collet chucked the drill chuck to it.And using the tailstock live center. then turned the arbor to size. Run out is less than .001 now.
 

chips&more

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#5
Sorry but your calibration method will introduce errors (especially solid angle errors) from the mounting collet and the spindle it’s in. May not be much…but. I would set the tail of the chuck in a “V” block and turn the chuck with your hand and make your findings that way. There are if’s to this method also. Like the condition of the mounting shank for example.

Or, turn a billet down then mount the chuck business end on that turning and indicate the tail/mounting shank for uncertainties.

I total understand your frustration. It took me awhile to find a decent chuck. But I have had it now for decades and it is just as good as the first day I got it. It’s a Jacobs ½” key chuck. I don’t like the keyless. I hope you find a chuck that you can be happy with. Then hang on to it and don’t loan it out…Good Luck, Dave.
 
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Fldvr

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#6
Wow, thanks for the thread and more importantly thanks for the well illustrated pictures!
 

Wreck™Wreck

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#7
Repeat after me, "it's just a drill chuck".

Drill holes with it, if you require more accuracy put the drill in a collett or tool holder, it is as easy as that.
 

4gsr

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#8
Can you post pictures of the inside gripping surfaces of the jaws on the 11 N and 16N chuck? I'm sure your jaws have lots of wear. If so, you can buy jaw sets, provided you can find them for the older chucks. They getting hard to find now days without paying a premium price for them. There are several threads out there on rebuilding Jacobs drill chucks.
 

randyjaco

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#9
Repeat after me, "it's just a drill chuck".

Drill holes with it, if you require more accuracy put the drill in a collett or tool holder, it is as easy as that.
Plus 1 on that. When one considers the amount of flex in a standard jobbers bit. You can probably drill a straight hole with a chuck that's . 025" out. Very few drill presses could be considered a precision machine .

It's all about getting the bit started in the right place.



Randy
 
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