One of APM Hexseal's earliest innovations was a self-sealing hexagonal nut, or Seelnut®.

Seelnuts® install just like conventional nuts, and are designed for use with ordinary screws, bolts and studs, making them a quick and easy sealing option for all sorts of applications, especially where there is a need to withstand high internal or external pressures.

Our Seelnuts are made from high quality rubber, molded into a specially shaped cavity in the nut itself. With threads molded directly into the rubber, these self-sealing nuts form a positive seal along the threaded section of the Seelnut, as well as with the contact surface, removing the need for gaskets, sealing compounds or extra surface preparation.

Anatomy of Seelnuts

The single-piece design makes for a more consistent and reliable seal, resulting in a significant savings of time and expense, and contributing to overall performance efficiency. Our specially designed sealing nuts feature low-carbon steel with zinc-chromate plating and weatherproof silicone rubber or specialized elastomers on the interior threads. Available with both imperial and metric measurement designations, our Seelnuts are manufactured in standard style and jam nut style in a wide range of sizes. 

Features

While silicone is standard, a variety of other elastomers are available upon request.   

These nuts were designed to work with conventional nuts and bolts, however, if you need an extra layer of sealing protection, you can use one of our Seelskrews® or Seelbolts®.

APM Hexseal’s Seelnuts are also reusable, meaning that they can be easily removed and reapplied, reestablishing the same reliable seal when torqued. In addition, Seelnuts can be supplied with self-locking pellets for applications with excessive vibration to ensure they won’t loosen unexpectedly. We also offer a variety of different elastomers to suit your application needs. 

Our Seelnuts are available in all standard thread sizes, up to and including M90. Our award winning Nutzilla design is available for use with large bolts up to M90 with the same exceptional quality as our standard Seelnut designs. Using our state-of-the-art metal-to-rubber bonding process, we establish fully-molded threads into a precision cavity within the nut. The molded rubber provides a positive seal along the nut threads and the contact surface. 

No matter what size you require, you can depend on APM Hexseal’s Seelnuts.

Benefits of Using Seelnuts

Seelnuts are designed to be particularly durable, with exceptional seal integrity, optimal reusability, and a shelf life of more than 25 years. With optional self-locking pellets and a variety of thread sizes, there is a Seelnut for every fastening need. By using APM Hexseal’s Seelnuts, you eliminate the need for gaskets, sealing compounds, or excess surface preparation, resulting in a significant saving of time.

Materials

Our Seelnuts are manufactured using low-carbon steel with zinc-chromate plating, for optimal durability and corrosion resistance. Each Seelnut features silicone rubber elastomer material for the thread surfaces, with other elastomer options available for specialized applications. 

Applications

Seelnuts are highly versatile and exceptionally effective, providing excellent return on investment over an extended service life. With a wide range of thread sizes and diameters, Seelnuts are incorporated into a variety of applications, including: 

  • Air conditioning equipment
  • Food and beverage processing systems
  • Hydraulic systems
  • Military and defense equipment
  • Drilling and energy generation
  • Industrial and construction

In short, APM Hexseal’s Seelnuts can benefit any application where leakage can compromise reliability and operational efficiency. 

Innovative Sealing Hardware by APM Hexseal

Whether you need small diameter Seelnuts for your HVAC system or durable M90 Nutzilla designs for industrial equipment, APM Hexseal has the perfect sealing solutions for your needs. We’re always happy to discuss our Seelnuts, Nutzilla, Seelskrews, and other cutting-edge sealing and fastening technology.

For more information, Ask the Experts at APM Hexseal today.

Ever Better.

IMPERIAL SEELNUTS® - Standard Nut Style

IMPERIAL SEELNUTS® - Standard Nut Style

Seelnuts
MATERIAL SPECIFICATIONS

For APM Hexseal® Standard Seelnuts®

Nut Material:
Low Carbon Steel with Zinc-Chromate Plating †
Threads:
Imperial— Class 2B ‡; Metric— Class 6H
Elastomer:
Silicone conforms to A-A-59588, Class 3A, GR60, Red ◊
Temperature Range:
-103° F to +400° F ( -75° C to +204° C)
Pressure Range:
Up to 20,000 psig internal and external (subject to clearance hole dimensions).
Resistant to:
Splash, salt spray, sunlight, ozone, weather, fungus, dust, and most acids and lubricating oils.
Shelf Life:
Excess of 25 years.
Thread SizeHeight of Sealing Rib (R)Distance Between Flats (C)Max. Head Height (D)
6-32 UNC-2B1/64"5/16"9/64"
8-32 UNC-2B1/64"3/8"5/32"
10-32 UNF-2B1/64"3/8"5/32"
10-24 UNC-2B1/64"3/8"5/32"
1/4-20 UNC-2B1/64"7/16"7/32"
1/4-28 UNF-2B1/64"7/16"7/32"
5/16-18 UNC-2B1/64"1/2"17/64"
5/16-24 UNF-2B1/64"1/2"17/64"
3/8-16 UNC-2B1/64"9/16"21/64"
3/8-24 UNF-2B1/64"9/16"21/64"
7/16-20 UNF-2B1/32"11/16"3/8"
1/2-13 UNC-2B1/32"3/4"27/64"
1/2-20 UNF-2B1/32"3/4"27/64"
5/8-18 UNF-2B1/32"15/16"35/64"
IMPERIAL SEELNUTS® - Jam Nut Style

IMPERIAL SEELNUTS® - Jam Nut Style

Seelnuts
MATERIAL SPECIFICATIONS

For APM Hexseal® Standard Seelnuts®

Nut Material:
Low Carbon Steel with Zinc-Chromate Plating †
Threads:
Imperial— Class 2B ‡; Metric— Class 6H
Elastomer:
Silicone conforms to A-A-59588, Class 3A, GR60, Red ◊
Temperature Range:
-103° F to +400° F ( -75° C to +204° C)
Pressure Range:
Up to 20,000 psig internal and external (subject to clearance hole dimensions).
Resistant to:
Splash, salt spray, sunlight, ozone, weather, fungus, dust, and most acids and lubricating oils.
Shelf Life:
Excess of 25 years.
Thread SizeHeight of Sealing Rib (R)Distance Between Flats (C)Max. Head Height (D)
6-32 UNC-2B1/64"1/2"7/32"
8-32 UNC-2B1/64"1/2"7/32"
10-32 UNF-2B1/64"1/2"7/32"
10-24 UNC-2B1/64"1/2"7/32"
1/4-20 UNC-2B1/64"5/8"7/32"
1/4-28 UNF-2B1/64"5/8"7/32"
5/16-18 UNC-2B1/64"5/8"7/32"
5/16-24 UNF-2B †1/64"5/8"7/32"
3/8-16 UNC-2B1/64"5/8"7/32"
3/8-24 UNF-2B1/64"5/8"7/32"
1/2-13 UNC-2B1/32"3/4"7/32"
1/2-20 UNF-2B1/32"3/4"7/32"

† The Jam Nut material used for this thread size is Low Carbon Steel with Zinc-Chromate plating.

METRIC* SEELNUTS® - Standard Nut Style

METRIC* SEELNUTS® - Standard Nut Style

Seelnuts
MATERIAL SPECIFICATIONS

For APM Hexseal® Standard Seelnuts®

Nut Material:
Low Carbon Steel with Zinc-Chromate Plating †
Threads:
Imperial— Class 2B ‡; Metric— Class 6H
Elastomer:
Silicone conforms to A-A-59588, Class 3A, GR60, Red ◊
Temperature Range:
-103° F to +400° F ( -75° C to +204° C)
Pressure Range:
Up to 20,000 psig internal and external (subject to clearance hole dimensions).
Resistant to:
Splash, salt spray, sunlight, ozone, weather, fungus, dust, and most acids and lubricating oils.
Shelf Life:
Excess of 25 years.
Thread SizeHeight of Sealing Rib (R)Distance Between Flats (C)Max. Head Height (D)
M3 x 0.50.2mm5.5mm2.2mm
M4 x 0.70.3mm7.0mm3.0mm
M5 x 0.80.4mm8.0mm3.8mm
M6 x 10.5mm10.0mm4.8mm
M8 x 1.250.6mm13.0mm6.3mm
M10 x 1.50.6mm17.0mm7.8mm
M12 x 1.750.8mm19.0mm9.3mm
M14 x 20.1mm22.0mm10.8mm

* APM Hexseal’s standard material for metric nuts is Stainless-Steel.

IMPERIAL SEELNUTS® - Standard Nut Style

IMPERIAL SEELNUTS® - Standard Nut Style

Seelnuts
MATERIAL SPECIFICATIONS

For APM Hexseal® Standard Seelnuts®

Nut Material:
Low Carbon Steel with Zinc-Chromate Plating †
Threads:
Imperial— Class 2B ‡; Metric— Class 6H
Elastomer:
Silicone conforms to A-A-59588, Class 3A, GR60, Red ◊
Temperature Range:
-103° F to +400° F ( -75° C to +204° C)
Pressure Range:
Up to 20,000 psig internal and external (subject to clearance hole dimensions).
Resistant to:
Splash, salt spray, sunlight, ozone, weather, fungus, dust, and most acids and lubricating oils.
Shelf Life:
Excess of 25 years.
Thread SizeHeight of Sealing Rib (R)Distance Between Flats (C)Max. Head Height (D)
6-32 UNC-2B1/64"5/16"9/64"
8-32 UNC-2B1/64"3/8"5/32"
10-32 UNF-2B1/64"3/8"5/32"
10-24 UNC-2B1/64"3/8"5/32"
1/4-20 UNC-2B1/64"7/16"7/32"
1/4-28 UNF-2B1/64"7/16"7/32"
5/16-18 UNC-2B1/64"1/2"17/64"
5/16-24 UNF-2B1/64"1/2"17/64"
3/8-16 UNC-2B1/64"9/16"21/64"
3/8-24 UNF-2B1/64"9/16"21/64"
7/16-20 UNF-2B1/32"11/16"3/8"
1/2-13 UNC-2B1/32"3/4"27/64"
1/2-20 UNF-2B1/32"3/4"27/64"
5/8-18 UNF-2B1/32"15/16"35/64"
IMPERIAL SEELNUTS® - Jam Nut Style

IMPERIAL SEELNUTS® - Jam Nut Style

Seelnuts
MATERIAL SPECIFICATIONS

For APM Hexseal® Standard Seelnuts®

Nut Material:
Low Carbon Steel with Zinc-Chromate Plating †
Threads:
Imperial— Class 2B ‡; Metric— Class 6H
Elastomer:
Silicone conforms to A-A-59588, Class 3A, GR60, Red ◊
Temperature Range:
-103° F to +400° F ( -75° C to +204° C)
Pressure Range:
Up to 20,000 psig internal and external (subject to clearance hole dimensions).
Resistant to:
Splash, salt spray, sunlight, ozone, weather, fungus, dust, and most acids and lubricating oils.
Shelf Life:
Excess of 25 years.
Thread SizeHeight of Sealing Rib (R)Distance Between Flats (C)Max. Head Height (D)
6-32 UNC-2B1/64"1/2"7/32"
8-32 UNC-2B1/64"1/2"7/32"
10-32 UNF-2B1/64"1/2"7/32"
10-24 UNC-2B1/64"1/2"7/32"
1/4-20 UNC-2B1/64"5/8"7/32"
1/4-28 UNF-2B1/64"5/8"7/32"
5/16-18 UNC-2B1/64"5/8"7/32"
5/16-24 UNF-2B †1/64"5/8"7/32"
3/8-16 UNC-2B1/64"5/8"7/32"
3/8-24 UNF-2B1/64"5/8"7/32"
1/2-13 UNC-2B1/32"3/4"7/32"
1/2-20 UNF-2B1/32"3/4"7/32"

† The Jam Nut material used for this thread size is Low Carbon Steel with Zinc-Chromate plating.

METRIC* SEELNUTS® - Standard Nut Style

METRIC* SEELNUTS® - Standard Nut Style

Seelnuts
MATERIAL SPECIFICATIONS

For APM Hexseal® Standard Seelnuts®

Nut Material:
Low Carbon Steel with Zinc-Chromate Plating †
Threads:
Imperial— Class 2B ‡; Metric— Class 6H
Elastomer:
Silicone conforms to A-A-59588, Class 3A, GR60, Red ◊
Temperature Range:
-103° F to +400° F ( -75° C to +204° C)
Pressure Range:
Up to 20,000 psig internal and external (subject to clearance hole dimensions).
Resistant to:
Splash, salt spray, sunlight, ozone, weather, fungus, dust, and most acids and lubricating oils.
Shelf Life:
Excess of 25 years.
Thread SizeHeight of Sealing Rib (R)Distance Between Flats (C)Max. Head Height (D)
M3 x 0.50.2mm5.5mm2.2mm
M4 x 0.70.3mm7.0mm3.0mm
M5 x 0.80.4mm8.0mm3.8mm
M6 x 10.5mm10.0mm4.8mm
M8 x 1.250.6mm13.0mm6.3mm
M10 x 1.50.6mm17.0mm7.8mm
M12 x 1.750.8mm19.0mm9.3mm
M14 x 20.1mm22.0mm10.8mm

* APM Hexseal’s standard material for metric nuts is Stainless-Steel.

APM Hexseal’s Seelnuts are also reusable, meaning that they can be easily removed and reapplied, reestablishing the same reliable seal when torqued.

Our Seelnuts are available in all standard thread sizes as well as a variety of different elastomers to suit your application needs. Seelnuts can also be supplied with self-locking pellets for applications where excessive vibration is an issue.

APM Hexseal Seelnuts Infographic

For information on maximum torque values for Seelnuts® please see our table of Torque Values for Self-Sealing Hardware.