Dale Company
Top U-Bolt Manufacturer Since 1959

FLEXLOC locknutThe FLEXLOC® locknut is the classic self-locking nut. Its one piece, all metal construction stands up under extreme temperatures, vibration, and shock. Because a FLEXLOC® locknut has no nylon insert, it consistently provides better tensile strength than the leading “two-element” locknuts and is ideal for elevated temperature environments.

The real secret of the FLEXLOC® design, however, is the slotted locking feature. As the bolt engages the locking feature, the slotted section expands, initiating the locking action. This expansion lifts the nut upward, causing the threads to bear against the lower surface of the bolt threads. Once fully engaged, each FLEXLOC® thread provides a load-carrying capacity resulting in a lower more uniform distribution of stress per thread. This locking feature and the FLEXLOC® locknut’s all-metal construction combine to create superior vibration resistance.

The FLEXLOC® full height locknut provides up to 19% more tensile strength than the leading nylon insert (two-element) locknut and as much as 26% more strength than a competitive all-metal locknut of equal size.

The FLEXLOC® thin height locknut provides virtually twice as much tensile strength as the leading nylon insert locknut.

The FLEXLOC® locknut has imitators but no equal. For durability, strength, and overall value, it is the premier industrial locknut. Below you will find a brief overview of the FLEXLOC® locknut product line offered by Unbrako through industrial distribution for use in industrial applications. Each is the product of advanced engineering, sophisticated manufacturing systems, and rigorous quality control standards. Download our Brochure.

Sizes & Specifications Chart

TYPES APPLICATIONS & FEATURES MATERIALS STANDARD SIZES
UNC UNF
Full Height Heavy-Duty Steel
One-piece, all-metal locknut. Full size, heavy-duty hex for maximum strength and wrenchability.
Steel Stainless Steel Brass Aluminum
1/4″-2 1/2
Full Height Light Hex
Full height, light hex for better wrench clearance and lighter weight. Both, for a broad range of industrial and commercial applications.
Steel Stainless Steel Brass Aluminum
2 – 1″ 2 – 2 1/2″
Thin Height Heavy-Duty Hex
Exceptional strength in low height nut because all threads are load-carrying. Combines ruggedness with space savings. Also available in light hex with 20% less weight and 30% less height for compact or “tight” assemblies.
Steel Stainless Steel Brass Aluminum
1/4″-1 1/2″
Thin Height Light Hex
Steel stainless Steel Brass Aluminum
#6 – 1″ 6 – 2″
Microsize
For miniature threaded joints in small assemblies. Uses triangular displacement of the threads for positive locking power and optimum strength to weight ratio. Controlled locking torques provide accurate preloading of bolts, stufs, and screws. Ideal for instruments, radar, and electronic equipment.
Steel Stainless Steel Brass Aluminum
#0 – #4 0 – #4

Available In-Stock Products

Name
30FN-1807 Plain / Oiled FLEXLOCå¨ Locknuts
30FN-2007 Plain / Oiled FLEXLOCå¨ Locknuts
30FN-2206 Plain / Oiled FLEXLOCå¨ Locknuts
30FN-2406 Plain / Oiled FLEXLOCå¨ Locknuts

All Available Products for Order

SPS FLEXLOC® NUT

HEAVY HEX–FULL HEIGHT
STEEL–PLAIN FINISH

PART NUMBER PRODUCT NUMBER SIZE
20FAC-420 124476 1/4
20FA-518 114402 5/16
20FA-616 111622 3/8
20FA-714 114022 7/16
20FA-813 106371 1/2
30FA-1011 119957 5/8
30FA-1210 118123 3/4
30FA-1409 117351 7/8
30FA-1608 117482 1

SPS FLEXLOC® NUT

HEAVY HEX–FULL HEIGHT
STEEL–CADMIUM PLATED

PART NUMBER PRODUCT NUMBER SIZE
21FAC-420 124486 1/4
21FA-518 117328 5/16
21FA-616 111688 3/8
21FA-714 114087 7/16
21FA-813 106435 1/2
31FA-1011 119990 5/8
31FA-1210 119580 3/4
31FA-1409 117385 7/8
31FA-1608 117515 1

SPS FLEXLOC® NUT

HEAVY HEX–FULL HEIGHT
CORROSION RESISTANT STEEL–PLAIN FINISH

PART NUMBER PRODUCT NUMBER SIZE
50FAC-420 123561 1/4
50FA-518 113620 5/16
50FA-616 115516 3/8
50FA-714 115104 7/16
50FA-813 117237 1/2
50FA-1011 116974 5/8
50FA-1210 118969 3/4
50FA-1409 119101 7/8
50FA-1608 113165 1

SPS FLEXLOC® NUT

LIGHT HEX–FULL HEIGHT
STEEL–PLAIN FINISH

PART NUMBER PRODUCT NUMBER SIZE
20FA-256 120704 #2
20FA-440 113704 #4
20FA-632 114572 #6
20FA-832 105717 #8
20FA-1024 105795 #10
20FC-1032 109078 #10
20FA-420 109304 1/4
20FC-428 108726 1/4
20FAF-518 118634 5/16
20FC-524 117459 5/16
20FAF-616 115899 3/8
20FC-624 109641 3/8
20FAF-714 120467 7/16
20FC-720 106112 7/16
20FAF-813 120533 1/2
20FC-820 116788 1/2
30FAF-1011 120664 5/8
30FC-1018 120089 5/8
30FAF-1210 118754 3/4
30FC-1216 117286 3/4
30FAF-1409 120478 7/8
30FC-1414 117417 7/8
30FAF-1608 120544 1
30FC-1612 125896 1
30FC-1614 117547 1
30FC-1812 1-1/8
30FC-2012 1-1/4
30FC-2212 1-3/8
30FC-2412 1-1/2

SPS FLEXLOC® NUT

LIGHT HEX–FULL HEIGHT
STEEL–CADMIUM PLATED

PART NUMBER PRODUCT NUMBER SIZE
21FA-256 108930 #2
21FA-440 138001 #4
21FA-632 138004 #6
21FA-832 138007 #8
21FA-1024 138010 #10
21FC-1032 138012 #10
21FA-420 108591 1/4
21FC-428 138014 1/4
21FAF-518 138167 5/16
21FC-524 138016 5/16
21FAF-616 138168 3/8
21FC-624 138018 3/8
21FAF-714 138169 7/16
21FC-720 138021 7/16
21FAF-813 138170 1/2
21FC-820 138022 1/2
31FAF-1011 138171 5/8
31FC-1018 138026 5/8
31FAF-1210 138172 3/4
31FC-1216 138028 3/4
31FAF-1409 138173 7/8
31FC-1414 138030 7/8
31FAF-1608 138174 1
31FC-1612 138032 1
31FC-1614 138033 1
31FC-1812 1-1/8
31FC-2012 1-1/4
31FC-2212 1-3/8
31FC-2412 1-1/2

SPS FLEXLOC® NUT

LIGHT HEX–FULL HEIGHT
CORROSION RESISTANT STEEL–PLAIN FINISH

PART NUMBER PRODUCT NUMBER SIZE
50FA-256 126236 #2
50FA-440 106189 #4
50FA-632 106286 #6
50FA-832 106383 #8
50FA-1024 106480 #10
50FC-1032 106512 #10
50FA-420 113491 1/4
50FC-428 113556 1/4
50FAF-518 124176 5/16
50FC-524 106571 5/16
50FAF-616 124128 3/8
50FC-624 115581 3/8
50FC-720 115138 7/16
50FAF-813 123868 1/2
50FC-820 105834 1/2
50FC-918 105898 9/16
50FC-1018 117042 5/8
50FC-1216 119034 3/4
50FC-1414 119134 7/8
50FC-1612 611389 1
50FC-1614 113229 1

SPS FLEXLOC® NUT

HEAVY HEX–THIN HEIGHT
STEEL–PLAIN FINISH

PART NUMBER PRODUCT NUMBER SIZE
20FKC-420 125582 1/4
20FK-518 105047 5/16
20FK-616 102647 3/8
20FK-714 118496 7/16
20FK-813 118627 1/2
30FK-1011 102612 5/8
30FK-1210 102414 3/4
30FK-1409 110920 7/8
30FK-1608 111616 1
30FK-2007 119709 1-1/4
30FK-2406 106758 1-1/2

SPS FLEXLOC® NUT

HEAVY HEX–THIN HEIGHT
STEEL–CADMIUM PLATED

PART NUMBER PRODUCT NUMBER SIZE
21FKC-420 125737 1/4
21FK-518 110514 5/16
21FK-616 107329 3/8
21FK-714 118528 7/16
21FK-813 116307 1/2
31FK-1011 102645 5/8
31FK-1210 102481 3/4
31FK-1409 120769 7/8
31FK-1608 111649 1
31FK-2007 119742 1-1/4
31FK-2406 106790 1-1/2

SPS FLEXLOC® NUT

HEAVY HEX–THIN HEIGHT
CORROSION RESISTANT STEEL–PLAIN FINISH

PART NUMBER PRODUCT NUMBER SIZE
50FKC-420 125668 1/4
50FK-518 109565 5/16
50FK-616 103911 3/8
50FK-813 115263 1/2
50FK-1011 102368 5/8
50FK-1210 111451 3/4
50FK-1409 111549 7/8
50FK-1608 622952 1

SPS FLEXLOC® NUT

LIGHT HEX–THIN HEIGHT
STEEL–PLAIN FINISH

PART NUMBER PRODUCT NUMBER SIZE
20FK-632 120662 #6
20FK-832 105926 #8
20FK-1024 106087 #10
20FK-1032 117188 #10
20FK-420 104355 1/4
20FK-428 103790 1/4
20FKF-518 102393 5/16
20FK-524 116374 5/16
20FKF-616 117936 3/8
20FK-624 107393 3/8
20FK-720 118562 7/16
20FKF-813 118066 1/2
20FK-820 116405 1/2
30FK-918 115652 9/16
30FKF-1011 114067 5/8
30FK-1018 102679 5/8
30FKF-1210 117649 3/4
30FK-1216 110789 3/4
30FK-1414 111311 7/8
30FKF-1608 130555 1
30FK-1612 124241 1
30FK-1614 111682 1
30FK-1812 1-1/8
30FK-2012 1-1/4
30FK-2212 1-3/8
30FK-2412 1-1/2

SPS FLEXLOC® NUT

LIGHT HEX–THIN HEIGHT
STEEL–CADMIUM PLATED

PART NUMBER PRODUCT NUMBER SIZE
21FK-632 138039 #6
21FK-832 138042 #8
21FK-1024 138045 #10
21FK-1032 138046 #10
21FK-420 110480 1/4
21FK-428 138048 1/4
21FKF-518 111444 5/16
21FK-524 138050 5/16
21FKF-616 117968 3/8
21FK-624 138052 3/8
21FK-720 138054 7/16
21FKF-813 114035 1/2
21FK-820 110543 1/2
31FK-918 115685 9/16
31FKF-1011 114100 5/8
31FK-1018 102711 5/8
31FKF-1210 106125 3/4
31FK-1216 138176 3/4
31FK-1414 138057 7/8
31FKF-1608 124303 1
31FK-1614 138059 1
31FK-1612 138177 1
31FK-1812 138061 1-1/8
31FK-2012 138062 1-1/4
31FK-2212 106726 1-3/8
31FK-2412 113671 1-1/2

SPS FLEXLOC® NUT

LIGHT HEX–THIN HEIGHT
CORROSION RESISTANT STEEL–PLAIN FINISH

PART NUMBER PRODUCT NUMBER SIZE
50FK-632 114856 #6
50FK-832 102528 #8
50FK-1024 115371 #10
50FK-1032 115402 #10
50FK-420 103406 1/4
50FK-428 103471 1/4
50FKF-518 123898 5/16
50FK-524 114951 5/16
50FKF-616 123515 3/8
50FK-624 103273 3/8
50FK-720 103372 7/14
50FKF-813 124506 1/2
50FK-820 115295 1/2
50FK-918 102301 9/16
50FK-1018 102401 5/8
50FK-1216 111484 3/4

MICROSIZE LOCKNUTS

STEEL–PLAIN FINISH

PART NUMBER PRODUCT NUMBER SIZE
30FM-256 109239 #2
30FM-264 103867 #2
30FM-440 107442 #4

MICROSIZE LOCKNUTS

STEEL–CADMIUM PLATE

PART NUMBER PRODUCT NUMBER SIZE
32FM-256 105802 #2
32FM-264 107282 #2
32FM-440 118513 #4

MICROSIZE LOCKNUTS

CORROSION RESISTANT STEEL–PLAIN FINISH

PART NUMBER PRODUCT NUMBER SIZE
50FM-080 104949 #0
50FM-256 116248 #2
50FM-348 115626 #3
50FM-440 107363 #4

LARGE SIZE FLEXLOC® NUTS

FULL HEIGHT
STEEL–PLAIN FINISH

PART NUMBER PRODUCT NUMBER SIZE
30FN-1807 117614 1-1/8
30FN-2007 114986 1-1/4
30FN-2206 113117 1-3/8
30FN-2406 107657 1-1/2
30FN-2605 104360 1-5/8
30FN-2805 102220 1-3/4
30FN-3204 120531 2
30FO-1808 102067 1-1/8
30FO-2008 116274 1-1/4
30FO-2208 116306 1-3/8
30FO-2408 116339 1-1/2
30FO-2608 111040 1-5/8
30FO-2808 111073 1-3/4
30FO-3208 104725 2
30FO-3608 2.25

LARGE SIZE FLEXLOC® NUTS

FULL HEIGHT
STEEL–CADMIUM PLATED

PART NUMBER PRODUCT NUMBER SIZE
31FN-1807 109442 1-1/8
31FN-2007 115018 1-1/4
31FN-2206 111905 1-3/8
31FN-2406 107689 1-1/2
31FN-2605 114846 1-5/8
31FN-2805 104407 1-3/4
31FN-3204 120597 2