Jacobs Chuck Key Size?

M

mecompco

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I have a Jacobs No.3 chuck (1/2", I believe, with MT)--anyone have advice on what size/model of key it takes? Thanks!

Regards,
Michael
 
The Jacobs No.3 uses a #3 chuck key, same as the 14n Jacobs. See my thread on Jacobs Drill chuck repair info. The taper is Jt3.
 
Thanks for the quick response! After a quick bit of Googling, I have learned that JT and MT are not the same. Am I correct that this chuck won't fit my Atlas?
 
JT is the taper on the chuck. You would use an arbor that mates with the JT size on the chuck with the MT size you need.
 
Thanks, Will. After more Googling, I am a bit confused--is it possible there is a MT arbor already on my chuck? The arbors I see for sale have a little stub on one end (that I assume goes into the chuck) and a long MT on the other end. Of course, I've not yet actually tried it on the lathe. :)
 
mecompco said:
Thanks, Will. After more Googling, I am a bit confused--is it possible there is a MT arbor already on my chuck? The arbors I see for sale have a little stub on one end (that I assume goes into the chuck) and a long MT on the other end. Of course, I've not yet actually tried it on the lathe. :)
Click to expand...
Possibly, could you post a pic of it? Drill chuck arbors are generally available in MT & straight shanks as well as R8 & other direct spindle mounts. The arbors can be removed unless it's an integrated shank drill chuck. Most if not all Jacobs keyed chucks do not have integrated shanks.
 
Upon examination and measuring (and actually putting it in the lathe), my chuck seems to have a more-or-less (I'm thinking "more") permanently installed MT 2 arbor. Here's a pic:

948F14C4-0436-4400-8176-7A6A1E6C6A10.jpg

Thanks everyone for helping me figure this out. Oh, and I have a chuck key on the way.
 
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