For a few weeks I have been working on a bolt together cnc router design. The thread for that is located here:

http://www.cnczone.com/forums/diy-cn...45116-cnc.html

My question relates to the thread count of the screws holding everything together. If I am looking at a 3/8 inch screw on Mcmaster Carr, I can get it in two flavors, 16 TPI and 24 TPI. I was planning to use the 24 TPI screws since I will be simply drilling and tapping steel tubes to hold a lot of the structure together. Using 24 TPI means that I get more threads inside the screw hole. That started me thinking though about the relationship between the structural integrity of an assembly fastened with 24 TPI screws vs an assembly fastened with 16 TPI screws. What are some of the design considerations that would lend itself to using a particular thread count?