Sorry, I misread your original post and assumed that you were connecting the M18 terminals directly to an M12 tool. Agree with the other posters that a higher current converter is probably needed.
I bought Mitutoyo 500-196-30 digital calipers from GlobalTestSupply and am convinced that they are real.
The bad reviews seem focused on poor after-sales support and not complaints about fraudulent products, which plague Amazon, For what it's worth, searching for "acme tools review" or "cpo...
I doubt it would get hot enough to trigger a thermal shutdown after a few seconds. There's probably an overvoltage sensor or an RPM limiter that's shutting things down. Assuming that's the case, you'll need to step down the voltage, using a device like rlitman shared.