Replies

1. 
   JohnWW | Oct 23, 2006 06:58pm | #1

   The shallow taper in the back of the chuck is almost certainly a Jacobs taper which, though created by the maker of Jacob's chucks, is now used almost universally by all manufacturers. 

   The drill chuck that came off of your machine will probably have two sets of numbers engraved on it.  One set will give the drill bit capacity, something like 0-1/2" and the second number will give the chuck mounting size and type, typically on a drill press "JT2" meaning Jacobs taper size #2.  Any chuck with a JT2 designation will fit on the spindle of your press.  If you have a different taper size or a threaded spindle you just have to match whatever the old chuck was marked.

   If there was a small mounting screw accessed through the jaws of the chuck, it was just a safety screw to prevent the chuck from dropping off if the taper attachment came loose or it may have been added to compensate for a poorly machined spindle end that wasn't solidly attaching to the old chuck.  A new chuck may not have a hole in it for the safety screw but it isn't needed if the chuck is properly mounted of a well machined taper.

   John White, Shop Manager, Fine Woodworking Magazine

1. 
   KzooRichie | Oct 24, 2006 04:39am | #2

   John,<!----><!----><!---->

   Thank-you for your response.  It's pretty cool to have an editor answer my question. So if I'm understanding you it is not MT but a JT.  The chuck reads 1--16mmJT33.  So I just need to replace it w/ a #3 JT or is at a #33? It was on the taper quite soundly and a dial indicator found very little runout so I'm optimistic that the chuck is the only problem.

    

   Cheers

1. 
   JohnWW | Oct 24, 2006 05:15pm | #3

   You will want a #33 Jacobs taper on the back of your replacement chuck, it is a common size. 

   The machine tool industry has made an art form out of creating confusing code systems.  This is how the Jacobs system works if you are interested:

   Jacobs #1 through #5 tapers increase in size starting at 1/4" in diameter, at the widest part, for the #1 to almost 1 1/2" diameter for the #5.  Then they created a #6 which would fit in size between a #2 and a #3 and then there is a #33 which is just slightly bigger than a #6.  There is also a #2a which is slightly smaller than a #2.

   Hope this helps, John W. 

2. 
   BruceS | Oct 24, 2006 06:28pm | #4

   Just a little addendum to the good info JohnWW gave you.  If you do have the safety screw inside the chuck,  Be careful I have found both right and left handed threads on that little bugger, most of the time they were Left handed.  

   Just remembered something else I have done in the past.  And thats to add a dab of never seize to the safety screw before putting it back in.

   Work Safe,  Count to 10 when your done for the day !!

   Bruce S. 

    

   Edited 10/24/2006 2:39 pm ET by BruceS

1. 
   JohnWW | Oct 24, 2006 08:44pm | #5

   I had thought to remind him about this, but I got the impression that the chuck was already removed.  In addition to usually being left handed, the screws are often treated with thread lock compound, they can be a challenge to remove.

   John W.

1. 
   PADDYDAHAT | Oct 25, 2006 02:45am | #6

   JWW, you just hit a nerve as I remembered that a short tap, tap ,tap with an air wrench -real gentle-will be the best solution if it's tight, A machinist friend and I just removed a 6" pad from a Metabo ros, It was a bummer with hand tools and we have them all. Pat