Jacobs Drill Chuck Runout--

[mksj]

Agree with Bob Korves on trying to use the any runout between the arbor and the chuck to cancel out each other (or consider a keyless chuck with an integrated arbor). I recently had a Jacobs 14N which I bought used, but was in very good condition. I was surprised that it had a TIR of 0.005". I took off some high points on the jaws, and then milled a wedge tool out of some 1/2" aluminum. Took some effort, but was able to separate the chuck and the arbor without any damage. Put the arbor in the lathe and used some very fine grit sandpaper to clean the mating surfaces, then put the arbor in a 4J independent chuck and zeroed the runout. I put some 1/2" precision rod in the Jacobs chuck and hand mounted it to the JT3 arbor. I then kept indexing the Jacobs chuck to the arbor until I got the lowest TIR from the precision ground rod, the TIR was now 0.0005". When I pressed them together and mounted in my mill, the TIR was~ 0.0008" with 1/4 and 1/2" rod. Although you can measure the drill chuck and arbor separately and estimate what might give the least TIR, that did not give the lowest TIR, most likely because of slight difference in taper and the interference fit. Only by indexing the two, and measuring them together at difference points, was I able to get the minimum TIR with both pieces joined.

As others have mentioned, using a short stiff center drill to locate the hole really helps in decreasing the drill from walking. Using shorter screw machine drills with 135 degree flutes helps, a lot also depends on the material and final size hole. I usually use an end mill to finish a larger hole after stepping the hole larger with standard drills. As of recently, I have had issues with end mill bits causing over sized holes in some materials, because they do not clear the chips as effectively as a good sharp twist drill. Good lubricant and clearing the chips is important. You may use a chuck reamer if you need a high degree of accuracy or slightly over or under size diameter. I find that an ER-32 collet holder to have the least run out in my mill, and after that, a keyless drill chuck with an integrated arbor. There are also factors of how well your mill is aligned and rigidity.

 

[Bob V]

Put the arbor in the lathe and used some very fine grit sandpaper to clean the mating surfaces, then put the arbor in a 4J independent chuck and zeroed the runout

First, thanks to everyone--I've learned a lot.

mksj -- how did you "put the arbor in the lathe" for sanding it?-- the arbor I have has tapers on both ends.
--again, how did you "put the arbor in a 4Jchuck and zero the runout"?
--sorry if these are obvious to you and not to me-- but at my stage-- just about everything is new-----

 

[Techie1961]

I don't actually know how to get the arbor out of the Jacobs chuck--so I can't check the arbor independent of the chuck.
How do I get the arbor out of the chuck?? the drill end of the chuck (with the jaws) is a blind hole--

If you want to remove the chuck (but I don't think you need to in this case) I have had luck with this technique.

If there is a shoulder on the arbor, you can use two pieces of aluminum that are the same thickness as the gap between the back face of the chuck and the shoulder on the arbor. Mount one piece of aluminum in a vise and place the chuck/arbor over it. Put another piece over the top and hit it with a hammer a few times. When the aluminum deforms, it will push the pieces apart with a sort of hydraulic action.

 

[mksj]

Hi Bob,
Alignment between the arbor and the drill chuck can be done in the lathe or in your mill. In either case, I manually turn the spindle to check the TIR. Be very gentle in clamping the arbor in a lathe, just lightly tighten the lathe chuck jaws as not damage the arbor. I used the lathe because I wanted to check the arbor and Jacobs chuck TIR separately and clean up some marks on the arbor. If using the mill just find the arbor to drill chuck position that gives the least TIR and then mark the two (see red marker I used). Probably lots of ways to do this.
Mark

Polishing up the arbor.


Setting up the arbor to ~0 TIR with the 4J, I actually check it at different points on the taper.


Checking the drill chuck TIR, the Jacobs chuck is hand tightened to the arbor. I keep indexing (turning) the Jacobs chuck relative to a fixed position on the arbor until I get the minimum TIR position. I was actually amazed that I could reduce the TIR of the Jacobs chuck to under 0.001" when both separately measured worse.

 

[Paul in OKC]

Couple of thoughts. Using a center drill will give you a pretty accurate placement for your hole. The run out may effect the final diameter at the top of the hole making it slightly larger. As said above, smaller drill bits will flex a bit. Drill chucks can be like 3 jaw lathe chucks. Use all three holes for the chuck wrench to tighten, and there may be a 'magic' hole or combination that puts things in line.

 

[Jason Annen]

Is it a brand new Jacobs? We got one at work and the runout was .016", and that's not a typo.

Jason

 

[Bob V]

mksj and everyone else- thanks!

Today I just turned one of the components of my mill/drillchuck stack 180 degrees, and the runout went from 12 thou to one thou!
Thanks for all the "tips and tricks".
JA did you guys return that chuck with .016 TIR?
Bob

 

[Jason Annen]

Replaced the Chuck with an older one found in a draw and sent the new one back to the crib.

It's probably sitting on a shelf somewhere now.

Jason

 

[brino]

Today I just turned one of the components of my mill/drillchuck stack 180 degrees, and the runout went from 12 thou to one thou!

That's quite a lot!
Is it reproducible or was there some debris in the tapers?
-brino

 

[Big Bore Builder]

There is merit in buying the ball bearing super chuck.

As other posters have said, drilling is not accurate.

And inexpensive arbors add to the run out.

One question in my mind is how was the run out of the old Van Norman mill determined. May not be much at the beginning of the quill opening, but back in the quill where the small end of the MT is could have a ding, dirt, chip, burr, or whatever.

AND! what is the real taper of the Van Noman the OP has? Is there another adapter in place? NO. 2 MT does not appear to be the original spindle taper, I am guessing a C to No 2 adapter is in use.

Old collets and adapters wear and suffer from abuse.

We need photos!

Spindle Tooling For Van Norman Milling Machines
Van Norman milling machines used a number of different spindle tapers. In addition to standard 30, 40, and 50 tapers, there are two proprietary Van Norman tapers. The #6and #12 mills, as well as some #16 mills, used the Van Norman "C" taper. This taper is more commonly known as "5V", which is the Hardinge designation. The other Van Norman taper is "2", which Hardinge calls "50V". It was used in some 22L mills, and possibly others. Collets and tooling made by Van Norman will be marked "C" or "2", while items made by Hardinge or others will probably be marked "5V" or "50V".



The next drawing shows a milling arbor for a 5C spindle. The main difference is the addition of key slots that engage the keys on the front of the spindle. This drawing is also based on a drawing I got from Orrin Iseminger, as well as measurements made on my own machine.
(UNDER CONSTRUCTION - Drawing not done yet)



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