Your 7610 could be >30 years old.
I doubt if it was assembled in the last 20 years.
If, without the collet & nut, you can grab the armature and wiggle it axially
(up/down), scrap the machine. A guess at the depth of cut is only the 1/2 of it.
You have a genuine foogazy that is a safety hazard.
With only a 1/4" collet, you could throw a cutter spontaneously.