A while ago I purchased a Thread Dial Indicator for the ML4. The saddle doesn't come ready drilled so it hgas been a process of checking the location then going through the fitting process.
TDI, bracket and fittings were purchased on eBay
This is where the bracket fits and to mark, drill and tap the holes I dismantled the saddle top from the apron.
Make sure the bracket doesn't rub the dovetail on the way
Mounted the saddle top on the pillar drill clamped up to a piece of angle iron which is the best I can do to ensure it is drilled vertically. Centre punch marks just about visible.
Tapping 4 BA. It was a blind hole which I started with a second cut tap and finished with a plug. WD40 as lubricant as so far it is all I have apart from clean engine oil in the oil can
Saddle top secured back on the apron and TDI fitted. Jobs a goodun
In dismantling the saddle I found that the 1/4/x 1/2 whit slot headed machine screws that fix it to the apron are a bit the worse for wear so I have some hex socket cap headed replacements on order.