Hex socket head cap screw(Full thread(Coarse Steel Zinc plated(Silver) 20X80X80 Pitch 2.5

This is a bolt with a cylindrical head featuring a hexagonal socket.
A hex key (Allen wrench) is used for tightening. Although classified as a bolt, it is most commonly used without a nut.
It is also known as a cap screw or socket screw. Open-end spanners and wrenches used to tighten hex bolts require clearance space around the fastener, whereas a hex key requires no such surrounding space.
For this reason, hex socket head cap screws enable work in confined spaces and allow for more compact machine designs.
Their aesthetic appearance has also led to increasing use in decorative applications.

• Hex socket head cap screw Full thread Coarse pitch
• Nominal diameter (d) M20
• Length under head (ℓ) 80.0 Thread section 80.0
• Pitch (P) 2.5
• Head diameter (dk) Max (Nominal) (1) 30 Max (2) 30.33 Min 29.67
• Head height (k) Max (Nominal) 20 Min 19.48
• Under-head fillet (r) Min 0.8
• Hex socket width across flats (S) Nominal (Nominal) 17 Max 17.23 Min 17.05
• Hex socket depth (t) Min 10
• Head chamfer (v) Max 2.0
• (1)Maximum diameter without knurling
• (2)Maximum diameter with knurling