I spent a long time thinking about how and where to fit the scales so that they didn't get in the way of any adjusting screws or lubrication points. Various mounting accessories were supplied but I only used the cover for the y-axis and the swivelling mount for the display - I found it easier to make new mounts for the scales rather than codge together the universal bits they supplied. It's protected with a substantial cover (made from 3mm thick aluminium angle) which protects the scale from swarf and from impact when sliding the tailstock up to the cross slide. For the x-axis (cross slide) I used a smaller section scale (KA500) which is mounted to the right hand side of the cross slide. I used a standard sized scale for the y-axis (length of lathe) which is mounted on the machined surface at the back of the lathe. The Display is a universal 2-axis one (SDS6-2V) which can be configured for a lathe or milling machine. (They were open to a little bit of haggling over price - they weren't quite the cheapest but they do offer a 3 year warranty.) Mine is a SINO and I got it from (usual disclaimer) at a good price. The functions on the caliper type displays tend to be very limited. The SINO display has many features which I've yet to explore including storing the offset settings for several tools. The resolution is usually 0.005mm which means that one increment is equal to 0.01mm on diameter. The glass scale ones usually have a better accuracy and resolution. I don't know if you intend to fit a glass scale type DRO or one of the much cheaper digital caliper type. I can't help directly with a Harrison M250 but I have fitted a DRO to a Boxford 1130 which is a similar sized machine.