Replacement chuck for drill press


I've never checked the precision of my drill press (Delta 14", model 14-070). So I picked up a piece of drill rod at McMaster-Carr (convenient having a distribution center on the north end of the town I live). I chucked it and could tell visually that there was substantial runout. I pulled the chuck off and measured runout of the taper and got 0.002" TIR, which I think is pretty good. So, now I'm considering replacing the chuck. Trouble is, the instruction manual doesn't specify the size. I started off assuming this was a Morse taper, but I think I'm finding out it's a Jacobs taper. I measured the part on the drill press to have a minor diameter of 0.767" and a major diameter of 0.814". From what I can tell, this should line up with a Jacobs taper #3. Does that sound right? Grizzly sells a precision 5/8" x JT3 chuck for $40. Anywhere else to check for a replacement chuck?
todd
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The taper that is in the chuck is a Jacobs taper. The taper that is in the drill press spindle (if it has one; on some presses a male jacobs taper is machined on the end of the spindle) is a morse taper. I don't have access to the dimensions right now, but you are on the right track. You can look them up in a Machinery's Handbook or easily find them on the web. Look for the min dia, max dia, and lenght. There is generally enough of a difference bewtween the different sizes that it is easy enough to tell which you have. Also, the jacobs taper is often marked on the chuck itself.
If you don't mind some watching and waiting, I recommend trying for a genuine Jacobs chuck on ebay, or perhaps a Rohm or Albrecht or other quality unit. Not trying to disparage the Grizzly, they may be fine, but I've bought some very nice Jacobs chucks at very good prices on ebay. Just takes some patience and restraint to find one at a good price.
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Larry Wasserman Baltimore, Maryland
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HF sells Jacobs chucks at a very reasonable price. Bugs
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todd wrote:

Runout of even .002" on a jacobs isn't too good. How bad it is depends on the type of runout.
If the runout is the same at the top and bottom of the taper, and on the same side of the taper, then the taper is at least parallel to the axis of the spindle and the runout of the chuck or a cutter won't be any worse.
If it's not the same at the top and bottom of the taper, or if it changes direction, then the taper is not parallel to the spindle axis and the runout will get worse at the chuck and cutter.
If the Delta manuals don't specify the taper - which they should - see if it is marked on the chuck. It is not as likely to be a J3 as it is a J33 or one of the other tapers. The Jacobs #3 was typically used only for some of the heavier chucks.
What chuck you use is up to you. If the spindle taper is off, using a precision chuck may be overkill. I like the Albrecht keyless chucks, but they are pretty expensive. MSC carries a variety of decent replacement chucks.
John Martin
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todd wrote:

http://www.jacobschuck.com /
They'll have the spec's on the taper as well.
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Jack Novak
Buffalo, NY - USA
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Patience, and ebay, yielded an industrial strength Jacobs chuck (forget the exact model now) for about $30 (included shipping), in good condition.
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Regards,

JT
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