if you can get away from the 1/4-20 screws I highly recommend it! I have 1/4-20 acme screws on my maxnc machine and I can tell you this, if one of your backlash nuts locks up the screw will bend easy! Also with the 20 tpi screws you in theory get more accuracy but sacrifice speed. The maxnc type of machines are soo poorly built that any accuracy you gain from the higher tpi screws is lost in the flex of the machine. Remember that accuracy is in the SUM of all components!