Does the red knob cut off the electricity? If not then yes, fit an estop (one that latches off).

You will also need to ensure that the electricity can not be restored by the Estop being released. Then ensure that there is a 'key' start if the contactor is remote from the machine. This makes it so that 2No. positive actions are required to start the machine when safe to do so.

Thanks for the information Zimmy.

Is it really a 60's "Student", they were mostly newer than that, especially if it has the 2 coloured gear change selectors on a common shaft.
It "Must" have an E-Stop, which can be retrofitted.
If you can remove or open guards without the use of a tool and access parts of the drive mechanism then these "must" be either fixed or interlocked, depending on the frequency & duration of access.
If you do add any control devices, remember that the ACoP for PUWER98 advises compliance with BSEN60204-1, which is in my first hand experience unfamiliar territory to most "normal" electricians who are used to working to BS7671, along with it seems many others, that I have had the pleasure of following onto machinery that has been modified to comply with PUWER98, which it does in one aspect, but then does not in many more.
I could relate some REAL horror stories, but will not.
The guidance on frequency of access is given in a BS that I can't remember, though it may have been re-categorised as a PD now.
I will try to remember to check & post if I can.
The contactor control should NOT be remote to the machine as it is a discrete machine tool, thus should be "self-contained".


BTW, the red handle is merely a spindle clutch, the motor continues to run, well at least on ALL the Colchester Students that I have ever worked on, & this was the lathe of choice when I did my apprenticeship, so I learned to turn on one!
Oh & how to rebuild the headstock, & saddle as they had a hammering & the apprentices had to fix them too!!!