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  1. #1
    Join Date
    Apr 2009
    Location
    Kingswood
    Posts
    930

    Default NT30 Drill Chuck Arbor Shortened

    I recently purchased a NT30 arbor and drill chuck for my mill.
    When the chuck was offered up to the arbor, the stick-out was judged excessive.

    Decided to mount the arbor in the lathe Burnerd chuck, which required the manufacture of a new adapter, Burnerd taper to NT30.
    I already had a similar adapter, Burnerd taper to 5C collet, to act as a model.

    Then, with the NT30 arbor mounted in the Burnerd chuck, the MT3 drill chuck mounting spigot had to be reduced to allow the drill chuck to position further up the spigot.

    This meant setting the topslide over for 3 different tapers.

    Thought it wise to do some trial tapers to sort out the methodology.
    Much experimenting to develop micro adjustment method of the topslide angle, and the addition of a maximum sized scalloped outer ring on the topslide handle.
    And much use of bearing blue.

    End result was 40 micron TIR ( < 2 thou) with the modified arbor in the mill.
    Acceptable for a drill chuck, but would need improving for a milling cutter.

    In the parts photo,
    - top row L to R: 5C collet adapter, new NT30 adapter, NT30 arbor,
    - bottom L to R: trial Burnerd taper, trial NT30 taper, drill chuck.

    Keep well all,
    John.
    Attached Images Attached Images

  2. #2
    Join Date
    Dec 2013
    Age
    56
    Posts
    1,416

    Default

    Good to see you are enjoying yourself John.
    This is the reason I'm going with a 150mm head riser for my mill in the near future

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  3. #3
    Join Date
    Dec 2011
    Location
    Sydney
    Posts
    505

    Default

    Nice!
    You're lucky to have a Burnerd collet set.
    Cheers,
    Bill

  4. #4
    Join Date
    Apr 2009
    Location
    Kingswood
    Posts
    930

    Default

    I mounted the drill chuck to the spigot on the NT30 arbor with the time honoured clean and tap method.
    When run in the mill, with a Dia 13 drill in the chuck, the TIR on the drill shank was about 110 microns, judged excessive.

    So, made some wedges and removed the drill chuck body, and proceeded to try and improve the situation.
    Obviously, something different is required, and I had a bit of metal in hand to allow more machining.

    Held the arbor by the short parallel end in a Burnerd collet, with outer end unsupported.
    Fiddled with, and tapped with a brass knocker, until got both ends of the NT30 taper showed identical TIR of 20 microns, with the high at the same rotational point, so an orbital offset.
    Carefully, very, very carefully cleaned up the centre in the end with a new small centre drill supported by a push rod held in the toolpost and copious lubricant.
    The idea was to re-cut the centre to be compatible with the 20 micron orbital motion of the arbor body.

    Then supported the end with a hard centre and took a shaving cut on the spigot.
    Got a cut the full length primarily on one side - I hoped I was reducing the error !

    The arbor, when mounted in the mill, showed about 20 microns TIR.
    Not much of an improvement, but still an improvement.

    Mounted the drill chuck on the spigot, inserted a Dia 13 drill and checked TIR on the drill shank as 80 microns.
    Not brilliant, but judged acceptable.

    Inserted a Dia 1 mm drill and pecked at, then drilled into some aluminium.
    Not a problem.

    I have put this drill chuck and arbor into the tool drawer for use, but I am now intrigued to see if I can do better.
    It could be that 80 microns is as good as a no-name cheap keyless drill chuck is ever going to be.

    Keep well,
    John.

  5. #5
    Join Date
    Sep 2006
    Location
    Mallacoota,VIC,Australia
    Age
    53
    Posts
    1,010

    Default

    That does look like a lot of stick out. Good job on what you done. I bought one of these integrated drill chucks https://www.ebay.com.au/itm/163198318364 I'm really happy with and although I haven't actually measured the run out there is visibly no noticeable run out.
    All The Best steran50 Stewart

    The shortest way to do many things is to do only one thing at once.

  6. #6
    Join Date
    Dec 2013
    Age
    56
    Posts
    1,416

    Default

    Is there a way to mount your lathe compound slide in your mill to get it better, using a angle plate maybe?

    With my horizontal/vertical mill it's pretty easy to use the horizontal for things like this using the compound slide from the lathe to machine it on the machine it's intended for.


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  7. #7
    Join Date
    Apr 2009
    Location
    Kingswood
    Posts
    930

    Default

    steran50,
    Thanks for the link, I want one of those.

    Dave,
    My horizontal mill is still a "work-in-progress", so no opportunity for any smarts like that.
    A good friend has said that he has a spindle with a NT30 fitting that will be mine 'soon', perhaps that could be useful for this job.

    But I think I now have a good work procedure to adjust the topslide angle after a bearing blue test.

    I wind the topslide to the end of its rear travel, then in one turn, and clamp the carriage.
    Mount a DTI in a tool post holder positioned close to the topslide pivot and contacting the job, and one on the tailpost to contact the topslide body.
    Both DTIs set to go up scale about 1/4 turn of the dial.

    Decide how much adjustment you are going to apply, loosen and firm up the topslide bolts.
    Back the cross-slide away from the job so both DTIs in free air.
    Apply finger to left end of topslide to oppose the intended knock.
    Use a heavy brass knocker to apply adjustment to right hand end of the topslide.

    Advance the cross-slide so the toolpost DTI reads as before, and note the reading on the DTI at the end of the topslide.
    Repeat as necessary to get desired result.
    While observing the DTIs, tighten up the topslide bolts.

    Keep well,
    John.

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