Classification by Thread Type2 ME350= .Thread forming >similar to the standard form >often spaced further apart (larger pitch)for use in metal or plastic -allow the displaced material a place to go as the screw forces its way into a small pilot hole while forming the threads. Thread cutting >have a standard thread form >relieved with axial grooves and hardened provides a cutting edge to tap the part as the screw is inserted. 21
ME 350 21 Classification by Thread Type 2 •Thread forming ¾similar to the standard form ¾often spaced further apart (larger pitch) for use in metal or plastic ⁼ allow the displaced material a place to go as the screw forces its way into a small pilot hole while forming the threads. •Thread cutting ¾have a standard thread form ¾relieved with axial grooves and hardened ⁼ provides a cutting edge to tap the part as the screw is inserted
Classification by Thread Type2 ME350 .Self-drilling s screws >have a drill-bit shape at their tip to make the pilot hole. BT OR 25 BF G BP 0R23 B THREAD FOR刚ING THREAD OR SCREMS THREADS MACHINE AB SCREW CUTTING SPACED THREADS SCREWS THREAD SPIRAL DRIVE SCREW
ME 350 22 Classification by Thread Type 2 •Self-drilling screws ¾have a drill-bit shape at their tip to make the pilot hole
Classification by head style1,2 ME350= .Some standard head styles include >Straight-slot >Cross-slot (Phillips) L山客TE青 >Hexagonal LOTTED PHILLIP Hexagonal socket lengths 1/8"to 6" .Shape of head can be diameters #0 to 3/8" steel-stainiess-brass-bronze-monel-nylon-etc. Round BINDING >Flat (recessed) Pan (a)Round (b)Elliptical c）Countersunk (d)Phillips head head head head 23
ME 350 23 Classification by head style1,2 •Some standard head styles include ¾Straight-slot ¾Cross-slot (Phillips) ¾Hexagonal ¾Hexagonal socket •Shape of head can be ¾Round ¾Flat (recessed) ¾Pan
Classification by head style1,2 ME350- .Head styles that are used in combination with slots (straight,Phillips,etc)are used typically only on >Small machine or tapping screws Since the maximum torque obtainable with the slots is limited. .Hexagonal heads are used on larger bolts and when the torque is high. 24
ME 350 24 Classification by head style1,2 •Head styles that are used in combination with slots (straight, Phillips, etc) are used typically only on ¾Small machine or tapping screws ⁼ Since the maximum torque obtainable with the slots is limited. •Hexagonal heads are used on larger bolts and when the torque is high
Classification by head style1,2 ME350= For high torques,especially in machinery >Socket heads are used Because they are typically made of high-strength, hardened steel or stainless steel Commonly applied with special tools such as an Allen wrench(通用扳手)to apply more torque. 25
ME 350 25 Classification by head style1,2 •For high torques, especially in machinery ¾Socket heads are used ⁼ Because they are typically made of high-strength, hardened steel or stainless steel ⁼ Commonly applied with special tools such as an Allen wrench(通用扳手) to apply more torque