(-)Flat head machine screw(Coarse Stainless steel Unplated 6 X 25 Pitch 1.0

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) M6
• Length under head (ℓ) 25.0
• Pitch (P) 1.0
• Head diameter (dk) Nominal 10.5 Tolerance 0,-0.7
• Head height (k) Nominal 3.9 Tolerance ±0.2
• Slot width (n) Reference 1.2
• Slot depth (t) Reference 2.1