self tapping screws 3

[cesarjulio]

I want to know the procedure used to fabricate self tapping screws of less than 4mm in diameter and no more than 50 mm in length. A lathe will just bend the material.

 

[11echo]

You are not going to be able to lathe cut these threads! They are rolled on. Plus they are heat treated afterwards to be able to standup to "self tapping" requirement.

 

[CoryPad]

Process: cold form head and shank, roll form threads, bulk heat treat (either neutral through hardening or case carburizing), apply surface treatments

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[cogsman1]

You can do this very easy on a "SwissTurn Lathe" We do it for bone screws all the time and alot smaller than 4mm. We face then turn any nose radius and/or angle. Next we use the cross milling tools to form the self-tapping notches. Now we come back with the turn tool to remove burrs caused from the milling. Many times we need to go back with the milling tool for a deburr pass. Then we thread the part. Then cutoff/pickoff. Most of the Swiss machines have a sub spindle for pickoff.

 

[11echo]

cogsman ...These "bone threads" aren't these a "buttress type thread"??? Which are way different then the threads used on self tapping screws. The only way you can make ANY of these threads economically is with a CNC machine and you better have a run of a few 10K orders!

 

[mfgenggear]

The qty required will dictate the method of manufacturing.

CNC screw machines will have no problem manufacturing
a qty of 300-3000 pcs or more.

some 8 axis machines can machine complete
because of 2nd spindle, and live tooling.



thread rolling is much more economical than thread cutting
on the cnc, However the screw machine can cut threads fine.