What screws for stabilizing jacks?

[kevinkatz]

I have new scissor jacks that I need to install on my tube frame. I can’t use a nut and bolt and need to either use a self drilling screw or tap a thread. Planning on using 5/16” screw if I tap. If I do self drilling a #12 or #14. In the self drilling I have used #12 fine thread for other applications in the past and other than the #2 Phillips stripping I have felt that they were strong. Not sure if they are heavy enough for this application. The #14 appear to be all course thread and I have had problems with those breaking in the past. So do you think tapping a thread or self drilling is stronger? If you were to use self drilling what screw would you use? Thanks.