WINTER 2025

12THE DISTRIBUTOR’S

12THE DISTRIBUTOR’S LINKLarry Borowski PresidentGREENSLADE & COMPANY INC.2234 Wenneca Avenue, Fort Worth, TX 76102TEL 817-870-8888 FAX 817-870-9199EMAIL sales1@greensladeandcompany.com WEB www.greensladeandcompany.comDUCTILITY TESTINGBrittle tapping screws can beproblematic for end users. Brittle isdescribing the heat treat/materialcondition as unyielding, and has norelationship to Hydrogen Embrittlement.Imagine using your nut driver to installa cover onto a casting, and as soonas you seat the screw, the head snapsoff. Now you have to figure out how toget that screw out when it is broken offflush with the surface of the casting.Luckily, industry experts developed tests years agothrough various consensus standards that give usguidance on how to test tapping screws before such aproblem occurs. Ductility testing is listed as one of theperformance tests in most tapping screw standards fromASME to DIN.Ductility can be generically defined as a solidmaterial’s ability to deform under tensile stress. Whenseating a screw head onto an uneven surface, the headwill have a tendency to conform to that surface. As thehead to shank junction deviates from perpendicular,one side of the shank is under compression, while theother side is in tension. It is the side in tension that willcrack and cause separation if the material is not ductileenough or is found to be too brittle.It is interesting to note that while many of thestandards utilize the same language, some standardsembellish more details than others. For instance ASMEB18.6.3 states that Head separation shall be cause forrejection. One might wonder if “head separation” means asignificant crack or complete separation from the shank.TECHNICAL ARTICLEDIN 7500 goes on to better qualify the requirement bystating “The test shall be regarded as satisfactory evenif a crack appears in the first thread, provided the headdoes not snap off.” As in all requirements of standards,it would be helpful to the users of those standards if thesame language was always used. What we should takeaway is that separation means complete separation orbreaking into two pieces.So How Do We Test For DuctilityOn Tapping Screws?[1] Determine what specification the tapping screwmust conform to, as well as what kind of tapping screwit is. This will provide you with the angle of head toshank deformation that must be achieved. Most tappingscrew types are required to have the heads bent to a 10degree angle with the shank. Most Thread Rolling screwsrequire a 7 degree angle, and most Self Drilling screwsrequire a 5 degree angle. There are also requirementsof 6 degree, and even up to 30 degrees stated in somestandards.CONTINUED ON PAGE 92