How are self drilling & self tapping scews manufactured?
How are self drilling & self tapping scews manufactured?
(OP)
I need to know how self drilling and self tapping screws are really manufactured. The heads on a batch of screws I ordered for site are breaking off and the sales guy is giving me the run-around. Could anyone provide a breif description of the process of manufacture? Or if there is a "net site" which is particularly good or a book, I would appreciate recieving the information.





RE: How are self drilling & self tapping scews manufactured?
RE: How are self drilling & self tapping scews manufactured?
the self tapping/self drilling screws and how hard
it the material that you are tapping into with
these? I would guess you are using these in
very hard material in relationship to the screws.
RE: How are self drilling & self tapping scews manufactured?
I can't prove it, but I think there's a lot of scrap/crap in much of the material that's on the market now, and that quality control at the mills is not nearly what it used to be. However, I don't necessarily blame the manufacturers. They provide exactly what the customer will pay for. As Pogo said: "We have met the enemy, and he is us."
RE: How are self drilling & self tapping scews manufactured?
I know that the workers always complain that the self-drilling screws will not drill into the flanges of hot-rolled sections. They overcome the problem by pre-drilling, which takes time. Perhaps if they were a little more patient with the self-drillers they would not have as many problems. The catalogue suggests "a 500 Watt drill running at at least 2500 rpm. Use maximum revs for drilling then slow down when the thread engages in order to set the screw properly. No need to push too hard. Let the screw do the drilling."
Are you able to watch the installation. It could be poor technique in installation, with the operator applying too much force.
Our hot-rolled sections have a nominal ultimate of 410 MPa, and yield of 320, but obviously this is a lower limit. For typical Australian production, the mean yield is 118% nominal, with a coefficient of variation of 10%. There is a portable hardness tested, that you can use to compare the surface hardness of the rolled steel with a standard.
Russell Keays