(-)Raised countersunk head screw(Coarse Brass Nickel(Silver) 3.5 X 10

The top surface of the countersunk head has a rounded shape. A flat countersunk head can be installed flush with the mating surface, but when something slides across the surface, it may catch on the slot groove or cross recess depression. An oval countersunk head cannot be made flush, but it prevents snagging on the slot or cross recess. Because the slot groove or cross recess depression can be made deeper than the countersunk portion, it allows for a more secure engagement with a screwdriver.
Although it protrudes more than a flat countersunk head, the protrusion can be kept lower than that of a pan head. It is used when you do not want too much protrusion, but also do not want a flush finish. Since it resembles a countersunk head with a decorative touch, it is perfectly acceptable to choose it based on design or aesthetic preference.
Machine Screw Head Dimension Reference Oval Countersunk Head Screw Encyclopedia 。

• Slotted (-) raised countersunk head screw coarse pitch
• Nominal diameter (d) M3.5
• Length (ℓ) 10.0
• Pitch 0.60
• Head diameter (dk) Nominal 7.0
• Head height (f+k) Nominal 2.80
• Slot groove width (n) Nominal 3.14
• Groove depth (t) Nominal 1.20