Found the owner's manual at
It says:
The
Spindle Taper of
JT-33 must refer to the "business end" of the arbor (the end that the chuck mounts to) and not the upper end that mounts the arbor to the machine.
In other words, the JT-33 chuck (female) taper fits onto the exposed JT-33 spindle (male) taper. Duh. What they DON'T say is which Morse Taper is on the upper end of the spindle arbor. My guess would be MT2, but I suppose an MT3 taper is also possible. For more on this general topic, see this informative page:
Now ... check out this search results page that shows "all things JT3" from the Grizzly catalog:
Notice that they offer replacement arbors (that will fit your JT3 chuck) with 3 different Morse Tapers: MT2, MT3 and MT4. All you need to know now is the actual Morse Taper on the upper end of the arbor.
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Oops! Hold the phone! I went a little further in the W1668 owner's manual, and found the following parts info (on pages 30 and 31):
I'm still willing to bet on the upper arbor taper being MT2, but I don't like the "extra" bit that I'm seeing in the diagram:
It could just be an extra piece that's screwed into the arbor, but it could also be a custom arbor, designed specially for the cool oscillating action. I say this because of the following info on page 13:
That raises a whole new issue. Suppose you go the easier route and just buy a new (keyless, JT33) chuck to replace the stock one. Would "generic" chucks like those sold by Grizzly be compatible with the capscrew mounting/tightening arrangement described in the manual?
Hmmm ... time to punt. Maybe give Shop Fox a call?