(-)Flat head machine screw(Coarse Stainless steel Unplated 1.6 X 4.0

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): M1.6
• Length under head (ℓ): 4.0
• Pitch (P): 0.35
• Head diameter (dk): Nominal 3.0, Tolerance 0, -0.4
• Head height (k): Nominal 1.0, Tolerance ±0.1
• Slot width (n): Reference 0.4
• Slot depth (t): Reference 0.55
• *M1.6 is available in stainless steel only.