Socket Cap Head Reduced Shank Captive Screws

Cap Head Reduced Shank Captive Screws are one of the most popular types of Captive Screw, and are designed with an unthreaded portion below the head – often referred to as the reduced shank.

The unthreaded portion is typically used to retain a Threaded Captive Washer. When used alongside Captive Screws, the washer compresses during assembly to lock over the reduced shank and prevent loosening.

This screw is an adaptation of DIN 912 / ISO 4762 with a plain portion leaving a reduced core diameter. Designed to self-retain post installation, which prevents the loss of screws.

These components are often used for safety equipment, as well as within the manufacturing and military industries. They are now required by EU law on some equipment such as safety guards.

Cap Head Reduced Shank Captive Screws are manufactured from A2 / 304 Stainless Steel and A4 / 316 Stainless Steel as standard, with the latter specialised for prolonged exposure to aquatic environments. Other materials are available to order, including Brass, Aluminium, Titanium, and many more.

Available now in thread diameters from M1.4 to M12 as standard, and lengths from 6mm to 300mm. We supply a huge range of Captive Screws here at Fastenright – with head styles and drive types to suit your application or assembly.

Non-standard sizes, materials and finishes are available to order as specials, including small volume manufacture, modifications and bespoke parts made to drawings. Minimum order quantities apply.

d1 and L1 dimensions can be to customer specification.

Metric Technical Data & Availability
Thread Diameter (d)	M1.4	M1.6	M2	M2.5	M3		M3.5	M4		M5		M6		M8		M10	M12
dk (mm)	2.6	3	3.8	4.5	5.5		6	7		8.5		10		13		16	18
d1 (mm)	0.95	1.12	1.4	1.8	2.2		2.6	3		3.8		4.5		6.2		8	9.5
d (mm)	1.4	1.6	2	2.5	3		3.5	4		5		6		8		10	12
S (mm)	1.3	1.5	1.5	2	2.5		2.5	3		4		5		6		8	10
L1 (mm)	2.8	3.2	4	5	4*	6	7	5*	8	6*	10	8*	12	10*	16	20	24
K (mm)	1.4	1.6	2	2.5	3		3.5	4		5		6		8		10	12
t (mm)	0.6	0.7	1.0	1.1	1.3		1.6	2		2.5		3		4		5	6
Available Lengths (L)	M1.4	M1.6	M2	M2.5	M3		M3.5	M4		M5		M6		M8		M10	M12

6mm

8mm

10mm

12mm

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16mm

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25mm

30mm

35mm

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45mm

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250mm

260mm

270mm

280mm

290mm

300mm

= Available
Parts with * host different thread lengths.
Size not listed? Please contact us – we may be able to provide it.

UNC / UNF Technical Data & Availability
Thread Diameter (d)	2-56 UNC	4-40 UNC	6-32 UNC	8-32 UNC	10-32 UNF	1/4″-20 UNC	1/4″-28 UNF	5/16”-18 UNC	3/8”-16 UNC
dk max. (in)	0.140	0.183	0.226	0.270	0.312	0.375	0.375	0.469	0.562
d1 (in)	0.061	0.078	0.095	0.120	0.130 0.156*	0.175	0.175	0.230	0.280
S (in)	5/64	3/32	7/64	9/64	5/32	3/16	3/16	1/4	5/16
L1 (in)	1/8	5/32	3/16	3/16 5/64*	1/4	1/4	1/4	3/8	3/8
K max. (in)	0.086	0.112	0.138	0.164	0.190	0.250	0.250	0.312	0.375
t min. (in)	0.038	0.051	0.064	0.077	0.090	0.120	0.120	0.151	0.182
Available Lengths (L)	2-56 UNC	4-40 UNC	6-32 UNC	8-32 UNC	10-32 UNF	1/4″-20 UNC	1/4″-28 UNF	5/16”-18 UNC	3/8”-16 UNC

1/4″
5/16″
3/8″	*	*
7/16″	*	*
1/2″
9/16″
5/8″
3/4″
7/8″
1″
1. 1/8″
1. 1/4″
1. 3/8″
1. 1/2″
1. 3/4″
2″