[gbrose85]

In the process of designing a small, precision 3-axis mill for processing aluminum. While I can do FEA to evaluate most any design feature, it really is not a substitute for experience. I have seen a few 'rules of thumb' quoted, such as thread depth = 2.5 diameter of the screw, and imagine (and hope) you can share more.

In particular, consider a mill box-column with sides and cross-braces made from 1in x 4in C1018. Deflection calculation seems to depend mostly on Elasticity, which appears to be roughly the same for most steels. Static analysis indicates that worst case deflection should be about 20% of my target. Cannot find any data on dynamic response to differentiate C1018 from any other steel. Or data on dimensional stability over time. Is there some other basis for choosing a different grade of steel or is C1018 a reasonable choice for the intended purpose?

Should the ends of the cross-braces be designed to slot into the vertical sides and, if so, by how much? Maybe 0.1in (as shown)? Static analysis suggests that the worst case forces at the brace end will be 70lbs or less in all directions. So, seems like it would be a good idea -- help to establish and maintain alignment -- but quite uncertain what it will do when dynamically loaded, or whether the slots will cause the sides to warp over time.

Also, how many screws, and what diameter, should be used to connect through the side and into the end of each brace? Cap-head and lock washers or just flat-heads?

Recommendations?

Thanks in advance.