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  1. #1
    Join Date
    Aug 2019
    Location
    Revesby - Sydney Australia
    Age
    56
    Posts
    1,183

    Default Repairing a keyless chuck? ... or, how my chuck lost its balls!

    1) A few months ago, toolmaker neighbour gave me an old keyless chuck.
    "VALIDUS" brand. It had no arbor.


    2) Found an old broken chuck with a workable MT3->JT6 arbor.
    Spent some pleasant time on the Hercus, machining the chuck off the arbor:
    IMG_1733.jpg



    3) Inserted arbor A into chuck C, and started using it.

    After tightening on a few different drills (#4 centre, 3/16", 5/16", 1/2"), it was obvious something was wrong. It felt like it was full of gravel.


    4) Sprayed a solvent (degreaser) in, blew it out with an air gun, repeated a few times, dribbled some oil in the back, tested again. Not much better. If I push the sleeve toward the arbor, it turns smoothly most of the way, until the last bit of tightening. If I pull the hood away from the arbor, it grinds all the way.


    5) Today, try to work out how to disassemble this thing. Unlike keyed chucks, where the sleeve taps toward the jaws and past the front of the chuck, this style of keyless chuck is small at the back and the front of the chuck. Eventually found a YouTube video that showed the knurled half of the sleeve just unthreading off the back part.


    6) Try to grab back part in a lathe chuck, and turn front off with Stilsons around scrap Aluminium. It slips in lathe chuck. Try to grab knurled half in lathe chuck. It slips.


    7) Knurled half in large bench vice, Stilsons on back half. Success:
    IMG_1923.jpg

    The jaws look OK, but spinning back part of chuck is full of rusty paste.


    If you look closely, you can see ball bearings with facets on them:
    IMG_1924.jpg
    I'm guessing that the grease dried up, and coolant sat in the back of the chuck for a long time.

    Long enough for some of the ball bearings to rust in place, and be ground away by the surfaces.




    8) Am soaking most of the parts in Kero overnight. Will try to carefully clean the bearing containing part tomorrow, and see if I can just get some BBs of an appropriate size to get this working again.




    P.S. Here is a helpful diagram:
    drill_chuck_keyless_diagram.jpg
    that I only found tonight, after I had already stripped the chuck

  2. #2
    Join Date
    Oct 2011
    Location
    Norwood-ish, Adelaide
    Age
    59
    Posts
    6,541

    Default

    Quote Originally Posted by nigelpearson View Post
    ...Today, try to work out how to disassemble this thing. Unlike keyed chucks, where the sleeve taps toward the jaws and past the front of the chuck, this style of keyless chuck is small at the back and the front of the chuck. Eventually found a YouTube video that showed the knurled half of the sleeve just unthreading off the back part.
    I hope it was this one https://www.youtube.com/watch?v=oUVxstNNwyY

    Michael

  3. #3
    Join Date
    Dec 2014
    Location
    melbourne
    Posts
    72

    Default

    Some trivia.
    The thread on the spindle that pushes the jaws forwards should be kept dry. If it does get any lube it won't self lock properly.

    Robert

  4. #4
    Join Date
    Aug 2019
    Location
    Revesby - Sydney Australia
    Age
    56
    Posts
    1,183

    Default

    Quote Originally Posted by Michael G View Post
    I hope it was this one https://www.youtube.com/watch?v=oUVxstNNwyY

    Sadly, no . Google found me this one: https://youtu.be/k2tj80vbIvo?t=240

  5. #5
    Join Date
    Mar 2011
    Location
    Southern Flinders Ranges
    Posts
    1,536

    Default

    Thanks for posting, I’m inspired to have a crack at removing the 1/2” drill that’s stuck in an older style Dewalt battery drill with a Rohm chuck on it.

  6. #6
    Join Date
    Aug 2019
    Location
    Revesby - Sydney Australia
    Age
    56
    Posts
    1,183

    Default My chuck is happier, now I found it some new balls!

    A) After cleaning parts, found the real cause of the grinding. Not just rust.

    Look at the edge of the body (on the right). Many broken angled chunks, instead of a nice flat flange or reverse radius:
    IMG_1927.jpg

    Almost seems like it was over-hardened, and someone used the chuck as a hammer which shattered that edge.

    Notice also the jaw guide (left). It is Aluminium. I will not be spending any money, or much time, repairing this chuck!



    B) Repair that smashed edge. MT3 arbor, so the Hercus spindle is the perfect candidate:
    IMG_1928.jpg
    Carbide didn't touch it. Hard as Hades. Contemplated setting up the little high speed toolpost grinder, but...



    C) Yesterday, some cheap "ceramic" and CBN inserts arrived from AliExpress.
    I try the TNMG160404-3T-CBN:
    IMG_1933.jpg

    Decide to machine the minimum off, because there isn't a lot of extra material there. It is too hard to create a little cup for the balls to roll in, so decide on a chamfer (which will force the balls into the outer corner), instead of a flat flange:
    IMG_1929.jpg

    Machined finish is beautiful. Best cutting I have ever done on the Hercus. Sounded like it was just rubbing, but shavings were dust, or little blue spirals, depending on how much I pushed it. Looked closely at the insert corner afterwards, and I couldn't tell which of the six corners did the cutting. I love this thing - best $13 I have ever spent!



    D) Clean up the rust and debris from the shell (sleeve that the balls run in):
    IMG_1930.jpg
    It is nasty in there, particularly in the very corner, but I can't be bothered centring it in the chuck to machine it out properly. The Emery cloth seems to have smoothed most of the area where the balls will touch.



    E) Now for the balls. Clean up a few old ones to measure:
    IMG_1931.jpg
    Bottom one here is actually a hemisphere, and the flat back is pitted.

    IMG_1932.jpg
    About 2.7 or 2.8mm. I'm guessing they started at 3mm?



    F) Look in the cup of salvaged BBs. Smallest are 4.something:
    IMG_1934.jpg
    Clearance between body and shell is about 3.6, so they won't fit. Ponder ordering some from somewhere - a local power steering refurb place might have some, but then found this...



    G) A linear bearing salvaged from a thrown out radial arm saw:
    IMG_1935.jpg

    Pry out the retaining sleeve, chop out an edge of one race track, and grab one ball:
    IMG_1936.jpg
    which will work OK!



    H) Ball extraction. A hook of wire got some of them, then a 3mm drill shoved down the tunnel to poke the others out:
    IMG_1938.jpg



    I) Cleaned them in degreaser, picked the least rusty, and a dab of grease on the finger to hold them in place. Then, screw the parts together:
    IMG_1940.jpg

    Note the gap. There is a pair of notches on the front of the shell that lock into the jaw guide. The way I assembled it, with the jaws held in the hood, means that this is hidden down in there, and needs a bit of fiddling around to get it engaged correctly.



    J) Lastly, force the two outer halves together:
    IMG_1941.jpg

    and create a bit of crush on the ball bearings:
    IMG_1942.jpg


    Winding the shell and hood is mostly smooth, although a little rattely if I spin it fast, and some slight grinding noise (probably from some rust on these recycled old bearing balls)


    So, after only 3 or 4 hours cleaning and labour,
    I have got the jaw adjuster on this free chuck spinning freely

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