# New arbor for Jacobs drill chuck



## Ischgl99 (Sep 6, 2021)

I got a Jacobs 1B drill chuck (0-1/4") with my mill when I bought it, but didn't have a key that small to use it, so it sat on the shelf for years.  I finally got tired of using the bigger chuck and got around to getting a key and decided to replace the sloppy arbor the previous owner made with something that fit better.  

The first photo shows what was on there, a threaded stud with a straight section and an aluminum sleeve.  The sleeve threaded into the stud and was supposed to register on the smooth section of the stud, but the gap was so big, I couldn't imagine it did any good.  I never tested it, but probably should have to see how bad it was.


I decided to machine an arbor with the 5/16-24 threads and a 1/2" section to mount in the collet.  The back side of the drill chuck has a recess at about the major diameter of the threads, so I machined a register there, the thread groove, and the 5/16-24 threads.  If I was smart, I would have taken some photos while I was machining it, but didn't think of that until I was done.




The picture shows some sanding marks, but you can't really see it in person.  I installed this new arbor and checked the runout using a spotting drill that I assumed was fairly round and came up with 0.0027", better than I expected!  The back of the chuck was a bit rough and I probably should take a clean up cut on it, but I'm afraid I might screw something up and make the runout worse, so for now I am going to leave it.  Below is the final assembly.


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## MrWhoopee (Sep 6, 2021)

I had a similar chuck that I salvaged off an electric drill. I put a 3/8" shank on it and made a 1/2" OD sleeve for the shank. Makes a nice sensitive drill chuck.


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## Ischgl99 (Sep 7, 2021)

I was thinking of going with 3/8”, but used 1/2” since I assumed I would be using the drill after using the edge finder that is 1/2”.  Time will tell if a smaller shank and a sleeve would be better, but it’s easy enough to make another one if so.


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