Page 1 of 3 123 LastLast
Results 1 to 10 of 27

Thread: Half Dead Centers

  1. #1
    Join Date
    Aug 2009
    Posts
    5,183

    Default Half Dead Centers

    I got a different #3 Morse taper half dead center today. This one looks real nice, fit's nice in the TS taper but when I retracted the quill to pop the taper out the quill stopped before the taper popped. Aw crap !!!!
    Well, after taking a closer look and pulling some measurements I found that the small end of the taper is about .050 larger in dia. than any of my other #3 tapers are.
    It needs to seat about an 1/8" further in to pop when the quill is retracted. I'm sure there are a few fixes out there, super glue a 1/8" thick disc to the end of it?? blob of weld ?? Grind the taper??

    JL................

  2. #2
    Join Date
    Oct 2006
    Location
    Ivins, Ut
    Posts
    1,136

    Default

    Most often when that happens the OAL of the taper is short on the small end, (the big end seats at the normal position). My fix would be to build up the back end with weld or weld a 1/2" tang on there.

  3. #3
    Join Date
    Dec 2006
    Location
    Rugby, Warwickshire, England
    Posts
    800

    Default

    Blob of weld or drill/tap/insert sound like less greif than re-grinding the taper.

  4. #4
    Join Date
    Apr 2010
    Location
    Tropical Milwaukee, Wisconsin
    Posts
    387

    Default

    Probably stating the obvious, but many times there is a threaded hole back there for a set screw/bolt to live, so that they can be adjusted for ejection...

    I will also point out that one of the beautiful things about half centers is that it is a simple affair to place an adjustable wrench on them ( using the flat ) and gently twisting, which results in their release. I do this fairly commonly on a certain gear hob that has a hydraulically driven tail that incorporates a spring loaded seating position. This results in loading the darn thing incredibly snugly, so the above is by far the easiest method to employ removing the centers.
    Last edited by Zahnrad Kopf; 02-12-2018 at 07:25 PM.

  5. #5
    Join Date
    Sep 2008
    Location
    WI/IL border
    Posts
    1,996

  6. #6
    Join Date
    Aug 2009
    Posts
    5,183

    Default

    Here is a picture of the half dead next to one of my regular centers. The both look the same as far as length etc.



    Here is a picture showing how much of the end of my regular center protrudes from the end of an adapter bushing. The end of the taper protrudes about .146 from the end of the adapter.



    Here is a picture of the half dead center in the adapter. The end of the taper protrudes about .028 when seated.



    Best I can measure at the end of the taper..... the regular center measures .792 and the half measure about .801. Does that sound about right for all you math guys??
    .009 difference on the taper dia. equal about .118 difference in where it seats.

    JL.............

  7. #7
    Join Date
    Sep 2010
    Location
    Wheaton, Illinois
    Posts
    324

    Default

    Put a short plug of round brass inside the quill. Not to long so the longer taper will still seat. Small enough so it can be removes easily by taking the quill out and tipping it.
    Last edited by Juergenwt; 02-12-2018 at 08:26 PM.

  8. #8
    Join Date
    Dec 2015
    Location
    Chilliwack, BC, Canada
    Posts
    3,510

    Default

    Quote Originally Posted by Juergenwt View Post
    Put a short plug of round brass inside the quill. Not to long so the longer taper will still seat. Small enough so it can be removes easily by taking the quill out and tipping it.
    A lot of quills don't just come out that easily. An easier way would be to use a little slug of steel and then fetch it out with a magnet on the end of wand.


    But since we're talking about a difference of .146 -.028=.118" I'd make up a little slug of any old metal and just epoxy or use some other sort of glue. Or if you can drill and thread the end screw in a long set screw or a short round headed screw where the head is same or thicker than the difference. Depends on how hard the metal of the taper is.

  9. #9
    Join Date
    Aug 2009
    Posts
    5,183

    Default

    Quote Originally Posted by Juergenwt View Post
    Put a short plug of round brass inside the quill. Not to long so the longer taper will still seat. Small enough so it can be removes easily by taking the quill out and tipping it.
    No I can't do that because then any taper with a tang such as drill chuck arbor won't seat.

    JL....

  10. #10
    Join Date
    Nov 2008
    Location
    SF East Bay.
    Posts
    5,379

    Default

    My solution was simple and does not require any permanent changes. Each of these delrin spacers has a rare earth magnet pressed into a recess.

    Two different MT mounts, both too short. Two spacers that snick into place, giving exactly the right length.

    Measure twice. Cut once. Weld. Repeat.
    ( Welding solves many problems.)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •