I have been working with the metric system for more than 50 years building and modifying scale models. H-O trains....
The scale is 3.5mm to 1.0 foot. The end result is that I work as easily with the metric system as with imperial. Although imperial is what I grew up with, metric is somewhat easier. The important thing is to "get comfortable" with metric measurement. Most of my construction experience is with imperial. The machine work is maybe 30-70 metric.
A few years ago, I built an electric powered bicycle. The doner(?) was a late model Schwinn, made in China. So all the additions I made were done in metric. With few exceptions, such as I don't have metric keyway broaches. Had to finagle that. A three wheeler arrangement, it worked out well.
A few dimensions to get comforteble with:
25 mm is a fuzz less than an inch (25
.4mm=1 inch)
1 mm is 0.03937 inch (roughly 40 thou)
10 mm X 1.5 thread is so close to 3/8-16 TPI you need to measure cose to find the difference.
With little expenditure, you can tool up for metric. A good metric caliper or micrometer along with the conversion factors for imperial leadscrews will yeild good metric measurements. On the other hand, conversion to imperial is just a matter of converting all the measurements, to the above listed factors. The bicycle mentioned was done in metric to make everything one system, no half and half, no two sets of wrenches, et al. My model building is done to imperial, because I must interact with others that have no grasp (nor want) of metric. Go for it, Dude. By whatever system is easiest for
you.
Bill Hudson