(-)Flat head machine screw(Coarse Stainless steel Unplated 5 X 20 Pitch 0.8

The head of a round machine screw is nearly hemispherical in shape, similar to today's truss head machine screw. The flat head machine screw has a low-profile cylindrical head. It was commonly manufactured in the past due to its simple production method.
Machine Screw Head Dimensions List　Encyclopedia of Round & Flat Head Machine Screws

• Slotted (-) flat head machine screw coarse pitch
• Nominal thread diameter (d) M5
• Length under head (ℓ) 20.0
• Pitch (P) 0.8
• Head diameter (dk) Nominal 9.0 Tolerance 0,-0.6
• Head height (k) Nominal 3.3 Tolerance ±0.15
• Slot width (n) Reference 1.2
• Slot depth (t) Reference 1.8