Cross recessed (+) old JIS flat head screw Stainless steel Unplated 3 X 16 Pitch 0.5

※For flat head screws, the total length including the head is the nominal length.

The head has a flat top surface with a conical bearing surface.
When expressing the nominal length, most other screws measure only the length of the shank, but for flat head machine screws, the length is measured from the top of the head, which may cause them to appear shorter than other screws of the same nominal length.

They are used when you do not want the head to protrude, or when you want it to sit flush with the surface of the parts being fastened.
However, it is necessary to pre-machine a countersink in the part to match the conical bearing surface of the head. If this countersinking is insufficient, the head will protrude above the surface. Countersinking is also referred to as "saramonmi" (countersink drilling).
Machine Screw Head Dimension Chart　How to Measure Flat Head Screws (Nejikuru Facebook)　Flat Head Screw Encyclopedia

• Cross recessed (+) old JIS flat head screw
• Nominal diameter (d): M3
• Length (ℓ): 16.0
• Pitch: 0.6
• Cross recess number: 2
• Head diameter (dk): Nominal 6, Tolerance 0,-0.5
• Head height (k): Nominal 1.75, Tolerance 0,-0.3
• Head chamfer (c): Approx. 0.25
• Cross recess (m): Reference 3.6
• Cross recess depth (q): Max 1.43, Min 0.91