Четыре этапа развития самореза

1.Thefirstphase-ordinaryselftappingscrew
Itisthedirectproductofearlysheetmetalscrews.Soitalsoknownasthe Г.Г. Quot; sheetmetalscrew Г.Г. Quot; .Itismainlyusedinthesheetmetalchanneltoconnectheatingandventilationsystem.Whenputitintothepreformedhole, makethemetalmaterialsshiftwhichareclosetotheholes, andatthesametimepushthemetalmaterialintothespacebetweenthescrewandthread.Asaresult, itformstheinternalthreadconnectingwithscrews.Thisistheearlist, themostbasicandthemostwidelyusedtappingscrew.
2.Thesecondphase-theselfcuttingtappingscrew
Becausetheordinaryselftappingscrewcanformthethreadonlyontherelativelythinandgoodtoughnesssheetmetalmaterial, itcannotbeappliedtothick, жесткий, brittlematerialandmaterialwiththepoordeformationability.Thus, anewtypeofcommontappingscrews, Theselfcuttingtappingscrewwasborn.
3.Thethirdphase-theselfthreadingtappingscrew
Intheearly1950s, engineeringandtechnicalpersonneloffastenersdevelopedanewgenerationoftappingscrew - theselfthreadingtappingscrew.Thiskindofscrewhasthreadedrod (includingthread) androdend.
4.Thefourthphase-theselfdrillingtappingscrew
Theabovethreephasesofselftappingscrewhaveonethingincommoninuse: itisnecessarytoworkoutprefabricatedholeinadvancennthefittings.Thisisalsotheircommonweaknesses.So, intheearly1960s, engineersofspecialcustomscrewhavedevelopedtheselfdrillingtappingscrew.Thisisakindoftappingscrewwiththeshapeofdrillattheend.