Cap Head Seal Screws with Under Head Seal

Cap Head Seal Screws with Under Head Seal are designed to prevent the leakage of fluids and gases under pressure, offering an alternative to the use of traditional gaskets.

Featuring a highly durable under head seal, this reusable sealing solution prevents galvanic corrosion between dissimilar materials, while offering excellent resistance to a wide range of automotive fluids and chemicals – including alcohol, gasoline, kerosene, oil, diesel fuel and hydraulic fluids.

The green seal is permanently fused to the bearing surface of fastener and does not shrink or dry out over time. During installation, it compresses to fill the space between the bearing surface of the head and the counter bore. Special coloured seals are available on request.

Cap Head Seal Screws with Under Head Seal are more cost-effective compared to standard o-ring seal screws and can be supplied with a much shorter lead time. They are available with either a Socket drive, typically to DIN 912 standard / ISO 4762 / ASME B18.3, or a 6 Lobe TX drive, typically to ISO 14579.

The seal can be applied to all of our standard materials, including Steel and Stainless Steel, with non-standard materials and finishes available on request.

Available at Fastenright in thread sizes M1.4 to M30. UNC / UNF threads are also available.

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.

Our full range of Sealing Fasteners can be found here.

M10 to M30

M1.4 to M8 Technical Data & Availability
Thread Diameter (d)	M1.4	M1.6	M2	M2.5	M3	M3.5	M4	M5	M6	M8
dk max. (mm)	2.6	3	3.8	4.5	5.5	6	7	8.5	10	13
k max. (mm)	1.4	1.6	2	2.5	3	3.5	4	5	6	8
b (mm)	14	15	16	17	18	20	20	22	24	28
Available Lengths (L)	M1.4	M1.6	M2	M2.5	M3	M3.5	M4	M5	M6	M8

2mm
3mm
4mm
5mm
6mm
8mm
10mm
12mm
14mm
16mm
18mm
20mm
22mm
25mm
30mm
35mm
40mm
45mm
50mm
55mm
60mm
65mm
70mm
75mm
80mm
85mm
90mm
95mm
100mm
110mm
120mm
130mm
140mm
150mm
160mm
170mm
180mm
190mm
200mm
210mm
220mm
230mm
240mm
250mm
260mm
270mm
280mm
290mm
300mm

= A2 / 304 Stainless Steel //

= A4 / 316 Stainless Steel
Size not listed? Please make an enquiry – we may be able to provide it.

No.0 to No.12

M10 to M30 Technical Data & Availability
Thread Diameter (d)	M10	M12	M14	M16	M18	M20	M22	M24	M27	M30
dk max. (mm)	16	18	21	24	27	30	33	36	40	45
k max. (mm)	10	12	14	16	18	20	22	24	27	30
b (mm)	32	36	40	44	48	52	56	60	66	72
Available Lengths (L)	M10	M12	M14	M16	M18	M20	M22	M24	M27	M30

12mm
14mm
16mm
18mm
20mm
22mm
25mm
30mm
35mm
40mm
45mm
50mm
55mm
60mm
65mm
70mm
75mm
80mm
85mm
90mm
95mm
100mm
110mm
120mm
130mm
140mm
150mm
160mm
170mm
180mm
190mm
200mm
210mm
220mm
230mm
240mm
250mm
260mm
270mm
280mm
290mm
300mm

= A2 / 304 Stainless Steel //

= A4 / 316 Stainless Steel
Size not listed? Please make an enquiry – we may be able to provide it.

1/4″ to 1″

ASME B18.3 UNC / UNF Technical Data & Availability
Thread Diam. (d)	0-80 UNF	1-64 UNC	1-72 UNF	2-56 UNC	2-64 UNF	3-48 UNC	3-56 UNF	4-40 UNC	4-48 UNF	5-40 UNC	6-32 UNC	6-40 UNF	8-32 UNC	8-36 UNF	10-24 UNC	10-32 UNF	12-24 UNC
dk max (in)	0.096	0.118	0.118	0.140	0.140	0.161	0.161	0.183	0.183	0.205	0.226	0.226	0.270	0.270	0.312	0.312	0.343
k max (in)	0.060	0.073	0.073	0.086	0.086	0.099	0.099	0.112	0.112	0.125	0.138	0.138	0.164	0.164	0.190	0.190	0.216
b max (in)	0.99	0.99	0.99	0.99	0.99	0.99	0.99	0.99	0.99	1	1.05	1.05	1.19	1.19	1.27	1.27	1.27
Avail. Lengths (L)	0-80 UNF	1-64 UNC	1-72 UNF	2-56 UNC	2-64 UNF	3-48 UNC	3-56 UNF	4-40 UNC	4-48 UNF	5-40 UNC	6-32 UNC	6-40 UNF	8-32 UNC	8-36 UNF	10-24 UNC	10-32 UNC	12-24 UNC

3/32″

1/8″

5/32″

3/16″

7/32″

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″

2 1/4″

2 1/2″

2 3/4″

3″

3 1/4″

3 1/2″

3 3/4″

4″

5″

6″

8″

= A2 / 304 Stainless Steel //

= A4 / 316 Stainless Steel
Size not listed? Please make an enquiry – we may be able to provide it.

ASME B18.3 UNC / UNF Technical Data & Availability
Thread Diam. (d)	1/4-20 UNC	1/4-28 UNF	5/16-18 UNC	5/16-24 UNF	3/8-16 UNC	3/8-24 UNF	7/16-14 UNC	7/16-20 UNF	1/2-13 UNC	1/2-20 UNF	5/8-11 UNC	5/8-18 UNC	3/4-10 UNC	3/4-16 UNF	7/8-9 UNC	1″-8 UNC
dk max (in)	0.375	0.375	0.469	0.469	0.562	0.562	0.656	0.656	0.75	0.75	0.938	0.938	1.125	1.125	1.312	1.5
k max (in)	0.25	0.25	0.312	0.312	0.375	0.375	0.438	0.438	0.5	0.5	0.625	0.625	0.75	0.75	0.875	1
b max (in)	1.5	1.5	1.71	1.71	1.94	1.94	2.17	2.17	2.38	2.38	2.82	2.82	3.25	3.25	3.69	1
Avail. Lengths (L)	1/4-20 UNC	1/4-28 UNF	5/16-18 UNC	5/16-24 UNF	3/8-16 UNC	3/8-24 UNF	7/16-14 UNC	7/16-20 UNF	1/2-13 UNC	1/2-20 UNF	5/8-11 UNC	5/8-18 UNC	3/4-10 UNC	3/4-16 UNF	7/8-9 UNC	1″-8 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″

2 1/4″

2 1/2″

2 3/4″

3″

3 1/4″

3 1/2″

3 3/4″

4″

4 1/2″

5″

5 1/2″

6″

7″

8″

9″

10″

11″

12″

= A2 / 304 Stainless Steel //

= A4 / 316 Stainless Steel
Size not listed? Please make an enquiry – we may be able to provide it.

Please make full use of our Fastener rotation by left-clicking and dragging to rotate, and using the mouse wheel to zoom in or out.
For display only, visuals may differ.

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Cap Head Seal Screws with Under Head Seal

Please make full use of our Fastener rotation by left-clicking and dragging to rotate, and using the mouse wheel to zoom in or out. For display only, visuals may differ.

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Please make full use of our Fastener rotation by left-clicking and dragging to rotate, and using the mouse wheel to zoom in or out.
For display only, visuals may differ.