Hi Bob,  I was in the same position at one time.  Bought one at a
flea market without a 3-jaw chuck.  Since Meir-Emco no longer makes
parts for the old Unimat I thought I was out of luck.

About four years ago at the MBSI convention in Orlando, Florida, at the
mart, I found a rep for Sherline Products who said they made a 3-jaw
chuck for the old Unimat thread.  If I remember correctly it cost about
$90.00; they may still be able to supply it.

    Sherline Products
    170 Navajo St.
    San Marcos, CA  92069
    (619) 744-3674    Phone
    (619) 744-1574    Fax
    (800) 541-0735    Outside Calif.

The area code may have changed during the last four years.
Hope this helps.

Bill Schaefer
whs1@erols.com