Thin Parts..Thin Shims..Drill Chuck Runs True..Fixing stuff that is not quite right

[jjr2001]

I found some Jacobs chucks at fire sale prices on eBay. Bought a few and a couple of MT-2 arbors for them. They are designed for threaded arbors so that is not the best way to get a true running chuck but work ok for portable tools.

The challenge was to get the assembly of arbor to chuck to run true..Maybe not perfect but better than the .013" inch that I had when the parts were mated.

There was this video by Joe Pieczynski (one of my favorite machinists) on YouTube so I used what I learned there to make some .001, .002, .003 and .005 shims out of my sheets of shim stock. I ended up with two nice arbors with washers that can be used at a later date for some other project and a bunch of shims with 3/8" and 1/2" center holes and they were easy to make using Joe's method with a bit of modification. Joe used the tail stock to hold the bunch of pieces together on the lathe but I made the two small mandrels out of some bolts and nuts. Just cut out a bunch of square pieces of shim stock. Clamp them with two scrap squares of aluminum about 3/16 thick. Drill the bunch in the center for your arbor diameter. Make an arbor from a common shop bolt of the proper diameter. Clamp with nut and turn in the lathe until they have the outer diameter you need.

Joe Pieczynski

By adding shims and testing the runout with a 1/4" dowel pin in the chucks I was able to get them to run better than .002" run out. Not bad for some $12.00 chucks.

Chucks are still available here: Jacobs 5038C 33BA 5/8-16 Thread Mount 2-13mm Cap Plain Bearing Chuck

They also have 1/4" and 1/2" inch Jacobs chucks.

I bought the chuck keys from McMaster Carr.

[WildKata]

This is the trick I need to remove end play from the spindle that came with my Chinese CNC mill

[DIYer]

Thanks jjr2001! We've added your Chuck and Arbor Mating Shims to our Machining category,
as well as to your builder page: jjr2001's Homemade Tools. Your receipt:

Chuck and Arbor Mating Shims by jjr2001

tags: chuck, arbor

[JeffEck]

Thank you for sharing this. I really enjoyed that video! I might have to give this a try sometime.

[Paul Jones]

jjr2001,

I too enjoy the YouTube videos by Joe Pieczynski and he has also become one of my favorite machinists on YouTube. I like has explanations of the underlying mathematics or principles for why it works as well as it does in the machining techniques he demonstrates.

I now use the upside down threading tool technique Joe demonstrated with the lathe spindle running in reverse for most of my single point threading work on the lathe. This technique has been especially useful for single point chasing metric pitches where I keep the half nut engaged. ABOM 79 also demonstrated a way to re-catch the thread dial position when running the normal position but Joe's method is much easier when threading to a shoulder.

Regards,

Paul

[tmoore4748]

So, this will probably sound really dumb, but I gotta ask: are you removing end play/runout by preventing the threads from the arbor engaging at the bottom of the threaded hole in the chuck? Would the washers introuduce enough of a gap that, once tightened down, runout wouldn't happen because of the small gap introduced?

[jjr2001]

So, this will probably sound really dumb, but I gotta ask: are you removing end play/runout by preventing the threads from the arbor engaging at the bottom of the threaded hole in the chuck? Would the washers introuduce enough of a gap that, once tightened down, runout wouldn't happen because of the small gap introduced?

Hello Tim, well my theory is that the chuck jaws are not concentric with the threads in the back of the chuck. The arbor threads are not concentric with the arbor. (worst of both worlds). So depending on where the thread tightens about the 360 degree rotation of the chuck on the arbor you can "null out" some of the errors in both. The washers (shims) simply set this rotation about the 360 degrees of one revolution of the thread. Of course there is a limit to the lowest runout you can get with this method. I have found it useful on some chuck/arbor combinations.

Anyhow that is my theory!

Here is another method that I prefer:

http://www.homemadetools.net/forum/a...1478#post93906
Cheers, JR

[tmoore4748]

So, you effectively change the point at which it tightens down by "extending" the thread with washers/shims, and in the process may end up "aligning" the runout. That's actually pretty cool, never thought of it that way.

And I definitely like the adjustment method you've listed, think that it more than likely will be used when I finally get my Logan back together.

[jjr2001]

Very good, glad we helped you to find a solution.

Cheers, JR

[thehomeengineer]

Hi JR
I also bought some really cheap chucks (brand unknown) to overcome the run-out issue. I first machined the arbours required by screw cutting the thread until they were a nice tight fit on the chuck. At this point the shank diameter is over size. I set a ground dowel (6mm) in the collet chuck so I knew it was running true and then clamped the chuck to the dowel as you would chuck a drill, with the arbour facing the tailstock, centre drilled the arbour and supported with a revolving centre and turned the arbour true to the lathe axis. This worked well but I don’t think I would buy screw on chucks in the future but saying that if I could get the same deal when I bought these it is worth considering as it was a big saving. I only paid £3.00 per chuck and the seller chucked (excuses the pun) in another one free for buying 5 of them so ended up being £2.50 per/unit. Right place at the right time.
What I should also point out these were parallel shank arbours for my capsten attachment but cutting a morse taper, Int taper, or R8 etc can be cut using this method
Thank again for the post
The Home Engineer