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Round Head Seal Screws with Under Head Seal offer a cost-effective alternative to the use of o-ring seal screws – widely used as a replacement for traditional gaskets which prevent the leakage of fluids and gases under pressure.
They host a highly durable green seal that is permanently attached to the underside of the head. This does not shrink or dry out over time for great reusability. During installation, the under head element compresses to fill space between the bearing surface and counter bore, creating a gasket-type seal.
These components are designed to prevent galvanic corrosion between dissimilar materials and provide excellent resistance to a wide range of chemicals and automotive fluids e.g. alcohol, gasoline, kerosene, oil, diesel fuel and hydraulic fluids.
Round Under Head Seal Screws feature a deep slot drive and are typically in accordance with ASME B18.6.3 – supplied with a much shorter lead time compared to o-ring seal screws.
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. Special seal colours can also be supplied.
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.
We supply an extensive range of Sealing Fasteners here at Fastenright.
| ASME B18.6.3 UNC / UNF Technical Data & Availability | |||||||||||||||
| Thread Diameter (d) |
2-56 UNC |
3-48 UNC |
4-40 UNC |
5-40 UNC |
6-32 UNC |
8-32 UNC |
10-24 UNC |
10-32 UNF |
1/4″-20 UNC |
1/4″-28 UNF |
5/16″-18 UNC |
3/8″-16 UNC |
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| dk (in.) | 0.146 – 0.162 | 0.169 – 0.187 | 0.193 – 0.211 | 0.217 – 0.236 | 0.240 – 0.260 | 0.287 – 0.309 | 0.334 – 0.359 | 0.334 – 0.359 | 0.443 – 0.472 | 0.443 – 0.472 | 0.557 – 0.590 | 0.670 – 0.708 | |||
| k (in.) | 0.059 – 0.069 | 0.067 – 0.078 | 0.075 – 0.086 | 0.083 – 0.095 | 0.091 – 0.103 | 0.107 – 0.120 | 0.123 – 0.137 | 0.123 – 0.137 | 0.160 – 0.175 | 0.160 – 0.175 | 0.190 – 0.216 | 0.237 – 0.256 | |||
| Available Lengths (L) |
2-56 UNC |
3-48 UNC |
4-40 UNC |
5-40 UNC |
6-32 UNC |
8-32 UNC |
10-24 UNC |
10-32 UNF |
1/4″-20 UNC |
1/4″-28 UNF |
5/16″-18 UNC |
3/8″-16 UNC |
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| 1″ | |
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| 3 1/2″ | |
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| 4″ | |
| = Available Size not listed? Please make an enquiry – we may be able to provide it. |
