Seelskrews & Seelbolts

In addition to fastening, our self-sealing screws and bolts offer a reliable and reusable seal, preventing (or containing!) contamination from dust, air, water, lubricants and other liquid or gaseous substances. They are also vibration resistant, making them a great choice for applications that encounter day-to-day jarring, or repetitive movement.

Should you need a more serious level of vibration resistance, our screws and bolts are available with additional locking features, such as self-locking pellets, strips and patches. Seelskrews® and Seelbolts® are available in many standard thread sizes and with various o-ring elastomer options. Some additional customizations include specialty thread-forming variations, tamper-resistant drives, thread captivation, as well as paint and finish options.

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

MATERIAL SPECIFICATIONS
For APM Hexseal® Standard Seelskrews® & Seelbolts®

Screw/Bolt Material: 18/8 Stainless Steel, passivated
Threads: Imperial— Class 2A ; Metric— Class 6g
O-Ring Elastomer: Silicone conforms to A-A-59588, Class 2, GR60 or GR70, Red
Temperature Range: -80° F to +425° F ( -62° C to +219° 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.

† Standard for stock screws and bolts.
‡ Alternative o-ring elastomers are available. Consult our O-Ring Elastomer Options table for details.

STANDARD PAN HEAD with CROSS RECESS DRIVE (PHILLIPS) – TYPE RFig.1


Thread SizeDrive SizeMin. Length
Available (L)
Max. Head
Diameter (C)
Max. Head
Height (D)
Recommended Clearance
Hole (Min. - Max.)
2-56 UNC-2A#11/4"0.181"0.062"0.091" - 0.950"
4-40 UNC-2A#11/4"0.238"0.080"0.125" - 0.129"
6-32 UNC-2A#21/4"0.294"0.097"0.147" - 0.152"
8-32 UNC-2A#21/4"0.347"0.115"0.173" - 0.179"
10-32 UNF-2A#23/8"0.403"0.133"0.199" - 0.204"
10-24 UNC-2A#23/8"0.403"0.133"0.199" - 0.204"
1/4-20 UNC-2A#33/8"0.517"0.175"0.265" - 0.269"
1/4-28 UNF-2A#33/8"0.517"0.175"0.265" - 0.269"

METRIC PAN HEAD with CROSS RECESS DRIVE (PHILLIPS) – TYPE RM Fig.1


Thread SizeDrive SizeMin. Length
Available (L)
Max. Head
Diameter (C)
Max. Head
Height (D)
Recommended Clearance
Hole (Min. - Max.)
M2 X 0.40 6g#14mm4.24mm1.60mm2.31mm - 2.41mm
M2.5 X 0.45 6g#14mm5.46mm2.10mm2.67mm - 2.84mm
M3 X 0.50 6g#24mm6.70mm2.40mm3.55mm - 3.65mm
M4 X 0.70 6g#24mm8.69mm3.05mm4.39mm - 4.54mm
M5 X 0.80 6g#26mm9.90mm3.70mm5.56mm - 5.66mm
M6 X 1 6g#36mm12.58mm4.60mm6.73mm - 6.83mm

STANDARD PAN HEAD with SLOTTED DRIVE – TYPE SFig.2


Thread SizeMin. Length
Available (L)
Max. Head
Diameter (C)
Max. Head
Height (D)
Recommended Clearance
Hole (Min. - Max.)
2-56 UNC-2A1/4"0.168"0.055"0.091" - 0.950"
4-40 UNC-2A1/4"0.220"0.069"0.125" - 0.129"
6-32 UNC-2A1/4"0.271"0.083"0.147" - 0.149"
8-32 UNC-2A1/4"0.323"0.097"0.173" - 0.177"
10-32 UNF-2A1/4"0.374"0.113"0.199" - 0.201"
10-24 UNC-2A1/4"0.374"0.113"0.199" - 0.201"
1/4-20 UNC-2A5/16"0.493"0.148"0.265" - 0.269"
1/4-20 UNC 2-A5/16"0.493"0.148"0.265" - 0.269"

METRIC PAN HEAD with SLOTTED DRIVE – TYPE SMFig.2


Thread SizeMin. Length
Available (L)
Max. Head
Diameter (C)
Max. Head
Height (D)
Recommended Clearance
Hole (Min. - Max.)
M2 x 0.40 6g4mm4.24mm1.37mm2.31mm - 2.41mm
M2.5 x 0.45 6g4mm5.56mm1.73mm2.67mm - 2.84mm
M3 x 0.50 6g4mm6.22mm1.90mm3.55mm - 3.65mm
M4 x 0.70 6g4mm8.17mm2.43mm4.39mm - 4.54mm
M5 x 0.80 6g6mm9.70mm3.05mm5.56mm - 5.66mm
M6 x 1 6g6mm12.49mm3.73mm6.73mm - 6.83mm
M8 x 1.25 6g6mm15.62mm4.52mm8.45mm - 8.55mm

STANDARD FLAT HEAD with CROSS RECESS DRIVE (PHILLIPS) – TYPE SFRFig.3


Thread SizeDrive SizeMin. Length
Available (L)
Max. Head
Diameter (C)
Recommended Clearance
Hole (Min. - Max.)
2-56 UNC-2A#11/4"0.172"0.091" - 0.950"
4-40 UNC-2A#11/4"0.225"0.125" - 0.129"
6-32 UNC-2A#21/4"0.279"0.147" - 0.152"
8-32 UNC-2A#21/4"0.332"0.173" - 0.179"
10-24 UNC-2A#25/16"0.385"0.199" - 0.204"
10-32 UNF-2A#25/16"0.385"0.199" - 0.204"
1/4-20 UNC-2A#33/8"0.507"0.265" - 0.269"

STANDARD HEXAGONAL HEAD BOLT – TYPE STFig.4


Thread SizeMin. Length
Available (L)
Distance Between
Flats (C)
Distance Between
Points (P) †
Max. Head
Height (D)
Recommended Clearance
Hole (Min. - Max.)
1/4-28 UNF-2A3/8"0.440"0.510"0.163"0.265" - 0.269"
1/4-20 UNC-2A3/8"0.440"0.510"0.163"0.265" - 0.269"
5/16-24 UNF-2A1/2"0.502"0.580"0.211"0.332" - 0.336"
5/16-18 UNC-2A3/8"0.502"0.580"0.211"0.332" - 0.336"
3/8-24 UNF-2A5/8"0.565"0.650"0.243"0.395" - 0.399"
3/8-16 UNC-2A1/2"0.565"0.650"0.243"0.395" - 0.399"
1/2-20 UNF-2A1/2"0.752"0.870"0.323"0.530" - 0.534"
1/2-13 UNC-2A3/4"0.752"0.870"0.323"0.530" - 0.534"
† The values provided for Distance Between Points are for reference only.

METRIC HEXAGONAL HEAD BOLT – TYPE STMFig.4


Thread SizeMin. Length
Available (L)
Distance Between
Flats (C)
Distance Between
Points (P) †
Max. Head
Height (D)
Recommended Clearance
Hole (Min. - Max.)
M6 X 1 6g8mm10mm11.28mm4.15mm6.73mm - 6.83mm
M8 X 1.25 6g12mm13mm14.69mm5.65mm8.45mm - 8.55mm
M10 X 1.5 6g12mm17mm19.25mm7.18mm10.53mm - 10.64mm
M12 X 1.75 6g20mm19mm21.50mm8.18mm12.79mm - 12.9mm
† The values provided for Distance Between Points are for reference only.
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