Ideal for new or experienced woodturners, this self centring chuck has 4 jaws which expand and contract, controlled by 2 tommy bars.
When drilling is complete, the screw thread is loosened by turning the tommy bar in the opposite direction - releasing the bar.
The saws in need only a pin or ‘tommy bar’ to tighten the grips, as the screws have a round head with a hole in the middle.
One end of the spring is attached to the shaft by a ‘plug’ with two Allen head grub screws and a series of holes to fit tommy bars to adjust the tension.
I have the old-style Vicmarc with tommy bars, and never had a need for a spindle lock unless I'm trying to remove a stuck chuck or faceplate.
Just because there are two tommy bars does not mean you have to hold one in each hand.
The hose is a snug fit over the end of the oil-pump drive shaft and prevents the tommy bar coming out of the drive slot.
There are a couple of tricks that others showed me when working with the tommy bars at a class I took.