(-)Flat head machine screw(Coarse Brass Unplated 5 X 8 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 diameter (d): M5
• Length under head (ℓ): 8.0
• 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