Assembly - January 2009 - (Page 62) Screwdriving The fastener can be removed and reinstalled multiple times, or it can be replaced with a standard metric machine screw. The fine pitch of the threads maximizes engagement with the mating material, so engineers can use shorter fasteners and smaller bosses than with standard fasteners. Fastening in Plastic The central problem when fastening plastic is that, well, it’s plastic. It flexes and flows. “As soon as you remove the tool, the material starts to relax,” says Simpson. To counteract that, engineers need fasteners specifically for plastics, such as the Delta PT from Semblex. The flank geometry of the fastener reduces radial stress on the boss. The flank starts with a 30-degree angle that quickly backs off into a 20-degree angle. This permits unimpeded flow of the plastic during installation. The multi-angled thread profile and cored recess of the fastener maximize When driving screws into plastic, an accurate tool is critical. It’s particularly important to avoid overtightening the screws. Photo courtesy Chicago Pneumatic Advanced Vacuum Solutions www.coval-inc.com COVAL VACUUM TECHNOLOGY INC. 212-112 Powell Drive Raleigh, NC 27606 Phone : (919) 233-4855 62 ASSEMBLY / January 2009 www.assemblymag.com http://www.coval-inc.com http://www.coval-inc.com http://www.assemblymag.com
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.