I've been lurking here for awhile and I've been slowly building up the courage to tackle building my own machine. A twist of fate allowed me to get my hands on a small (13"x20" cutting area) cnc machine for a couple of months. I grabbed some part files from a web design and started cutting them on this machine. I've done a lot of refactoring and creative jig work to get the parts so I could cut them in the small envelope I've got available, but (so far) I've been able to cut all the pieces for my machine (except for a few small parts that I should finish up shortly and will easily fit in the cutting envelope).
Since I'm getting close to having the structure done (I've been test fitting everything as I go). I need to start considering lead screws and electronics. I've already decided I'm going to buy the motors and electronics as a kit, so that just leaves the lead screws (and sundry connection bits and pieces).
I'm looking at getting ACME screws from McMaster-Carr. I've seen 1/2-10 single start, 2 start, and 5 start discussed on the forums fairly regularly. My understanding is that the more starts the "smoother" the motion will be and the more linear distance per turn. For example 1/2-10 1 start will take 10 turns to go 1 inch, but 1/2-10 5 start will only take 2 turns to go an inch. Obviously precision is going to be affected as well since each rotational step for a given stepper is a finite size, fewer turns per inch also mean the smallest step it is possible to take is going to be larger on multistart screws.
Looking around it looks like I can get 1/2-8 8 for a price I'm willing to pay. Dumpster has AB Nuts for this too. Is there any reason this size lead screw isn't used more often? Don't want to drop the bucks for screws and nuts just to find out there is a really good reason why no one uses that size.
Thanks in advance for any insight.