DIN 921 Slotted Screw with Large Flat Cylinder Head

Standard DIN 921 covers clamping screws with a large-diameter flat cylinder head. The head has a slot for tightening and loosening with a flat-blade screwdriver. Head diameter ranges from 8 to 25 mm, head thickness is no more than 2 mm. The head rises only slightly above the surface, giving the connection good decorative qualities.

The shank has a full metric thread with diameter from M3 to M8. The overall length of the product is from 4 to 30 mm.

Manufacturing and application features

Clamping screws made to DIN 921 are used in instrument engineering and other industrial fields. They are designed for quick-release connection of thin-walled parts: the increased head diameter reduces pressure on the material and prevents its deformation. The screws are used for joining the thin walls of instrument housings, in the assembly of electronic equipment, in mechanical engineering, machine-tool building, aircraft assembly and other purposes.

A power tool with a flat bit or a regular screwdriver is used to drive the fastener. The screw’s design ensures tight clamping of the joined surfaces, while the head prevents cracking of the material.

Steel with standard property class 5.8 is used for manufacturing; it may have a galvanic zinc or nickel coating for corrosion protection. Stainless steel grades A1-A5 are also used, and the fastener can also be made of brass and other non-ferrous alloys.

Dimensions of DIN 921 screws with large flat cylinder head (stainless steel A2) in mm:

dk	8	12	16	20
k	1.8	2.4	2.7	3.1
n	0.8	1	1.2	1.6
t min	0.9	1.2	1.3	1.5
l	d
	M3	M4	M5	M6
4
5
6
8
10
12
14
16
20
25

Dimensions of DIN 921 screws with large cylinder head in mm

d	M3	M4	M5	M6	M8	M10
a	1	1.4	1.6	2	2.5	3
dk	8	12	16	20	25	30
k	1.8	2.4	2.7	3.1	3.8	4.6
n	0.8	1	1.2	1.6	2	2.5
t	1.15	1.5	1.6	1.9	2.4	2.8

Designations:

d - nominal thread diameter

a - height of head underside, max.

dk - diameter of cylinder head

k - head height

n - slot width

t - slot depth, max.