Threaded Insert Type Threaded Insert Type | Show |
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![]() | Key Locking |
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Key Locking | Helical |
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How to Install Key-Locking Inserts
More
Mil. Spec. Stainless Steel Key-Locking Inserts

These inserts are made to stringent military specifications. Drive the keys into the surrounding material for a more secure hold than thread-locking inserts. Use them to repair or change threads in soft metals such as aluminum. Inserts may be mildly magnetic. They’re comparable to Keensert® inserts. Installation requires a drill bit, a standard tap, an installation tool, and a hammer.
Inserts with a thin wall are often used in small holes or near the edge of a workpiece.
Choose inserts with a thick wall for greater strength than thin-wall inserts, or to fill a large hole.
For technical drawings and 3-D models, click on a part number.
Inserts | Installation Tools | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
Thread Size | For Tap Thread Size | Installed Lg. | Drill Bit Size | For Max. Hole Dia. | No. of Locking Keys | Specifications Met | Each | Each | ||
303 Stainless Steel with Thin Wall | ||||||||||
2-56 | 8-32 | 1/8" | 29 | 0.137" | 2 | MS51830-101 | 000000000 | 00000 | 000000000 | 000000 |
4-40 | 10-32 | 11/64" | 20 | 0.164" | 2 | MS51830-102 | 000000000 | 0000 | 000000000 | 00000 |
6-32 | 12-28 | 11/64" | 3/16" | 0.19" | 2 | MS51830-103 | 000000000 | 0000 | 000000000 | 00000 |
8-32 | 1/4"-28 | 7/32" | 15/64" | 0.231" | 2 | MS51830-104 | 000000000 | 0000 | 000000000 | 00000 |
10-24 | 5/16"-18 | 5/16" | I | 0.276" | 2 | MS51830-105 | 000000000 | 0000 | 000000000 | 00000 |
10-32 | 5/16"-18 | 5/16" | I | 0.276" | 2 | MS51830-201, NAS1394C3 | 000000000 | 0000 | 000000000 | 00000 |
1/4"-20 | 3/8"-16 | 3/8" | Q | 0.336" | 2 | MS51830-106 | 000000000 | 0000 | 000000000 | 00000 |
1/4"-28 | 3/8"-16 | 3/8" | Q | 0.336" | 2 | MS51830-202, NAS1394C4 | 000000000 | 0000 | 000000000 | 00000 |
5/16"-18 | 7/16"-14 | 7/16" | X | 0.401" | 4 | MS51830-107 | 000000000 | 0000 | 000000000 | 00000 |
5/16"-24 | 7/16"-14 | 7/16" | X | 0.401" | 4 | MS51830-203, NAS1394C5 | 000000000 | 0000 | 000000000 | 00000 |
3/8"-16 | 1/2"-13 | 1/2" | 29/64" | 0.457" | 4 | MS51830-108 | 000000000 | 0000 | 000000000 | 00000 |
3/8"-24 | 1/2"-13 | 1/2" | 29/64" | 0.457" | 4 | MS51830-204, NAS1394C6 | 000000000 | 0000 | 000000000 | 00000 |
7/16"-20 | 9/16"-12 | 9/16" | 33/64" | 0.521" | 4 | MS51830-205, NAS1394C7 | 000000000 | 0000 | 000000000 | 00000 |
1/2"-13 | 5/8"-11 | 5/8" | 37/64" | 0.583" | 4 | MS51830-110 | 000000000 | 00000 | 000000000 | 00000 |
1/2"-20 | 5/8"-11 | 5/8" | 37/64" | 0.583" | 4 | MS51830-206, NAS1394C8 | 000000000 | 0000 | 000000000 | 00000 |
303 Stainless Steel with Thick Wall | ||||||||||
10-24 | 3/8"-16 | 5/16" | Q | 0.336" | 2 | MS51831-101 | 000000000 | 0000 | 000000000 | 00000 |
10-32 | 3/8"-16 | 5/16" | Q | 0.336" | 2 | MS51831-201, NAS1395C3 | 000000000 | 0000 | 000000000 | 00000 |
10-32 | 7/16"-14 | 5/16" | X | 0.401" | 2 | MS51832-201 | 000000000 | 00000 | 000000000 | 00000 |
1/4"-20 | 7/16"-14 | 3/8" | X | 0.401" | 2 | MS51831-102 | 000000000 | 0000 | 000000000 | 00000 |
1/4"-20 | 1/2"-13 | 3/8" | 29/64" | 0.453" | 2 | MS51832-102 | 000000000 | 00000 | 000000000 | 000000 |
1/4"-28 | 7/16"-14 | 3/8" | X | 0.401" | 2 | MS51831-202, NAS1395C4 | 000000000 | 0000 | 000000000 | 00000 |
1/4"-28 | 1/2"-13 | 3/8" | 29/64" | 0.457" | 4 | MS51832-202 | 000000000 | 00000 | 000000000 | 00000 |
5/16"-18 | 1/2"-13 | 7/16" | 29/64" | 0.457" | 4 | MS51831-103 | 000000000 | 0000 | 000000000 | 00000 |
5/16"-18 | 9/16"-12 | 7/16" | 33/64" | 0.521" | 4 | MS51832-103 | 000000000 | 00000 | 000000000 | 00000 |
5/16"-24 | 1/2"-13 | 7/16" | 29/64" | 0.457" | 4 | MS51831-203, NAS1395C5 | 000000000 | 0000 | 000000000 | 00000 |
5/16"-24 | 9/16"-12 | 7/16" | 33/64" | 0.521" | 4 | MS51832-203 | 000000000 | 00000 | 000000000 | 00000 |
3/8"-16 | 9/16"-12 | 1/2" | 33/64" | 0.521" | 4 | MS51831-104 | 000000000 | 0000 | 000000000 | 00000 |
3/8"-16 | 5/8"-11 | 1/2" | 37/64" | 0.583" | 4 | MS51832-104 | 000000000 | 00000 | 000000000 | 00000 |
3/8"-24 | 9/16"-12 | 1/2" | 33/64" | 0.521" | 4 | MS51831-204, NAS1395C6 | 000000000 | 0000 | 000000000 | 00000 |
3/8"-24 | 5/8"-11 | 1/2" | 37/64" | 0.583" | 4 | MS51832-204 | 000000000 | 00000 | 000000000 | 00000 |
7/16"-14 | 9/16"-12 | 9/16" | 33/64" | 0.521" | 4 | MS51830-109 | 000000000 | 0000 | 000000000 | 00000 |
7/16"-14 | 5/8"-11 | 5/8" | 37/64" | 0.583" | 4 | MS51831-105 | 000000000 | 0000 | 000000000 | 00000 |
7/16"-14 | 11/16"-11 | 5/8" | 41/64" | 0.646" | 4 | MS51832-105 | 000000000 | 00000 | 000000000 | 00000 |
7/16"-20 | 5/8"-11 | 5/8" | 37/64" | 0.583" | 4 | MS51831-205, NAS1395C7 | 000000000 | 0000 | 000000000 | 00000 |
1/2"-13 | 11/16"-11 | 11/16" | 41/64" | 0.646" | 4 | MS51831-106 | 000000000 | 00000 | 000000000 | 00000 |
1/2"-13 | 13/16"-16 | 11/16" | 49/64" | 0.771" | 4 | MS51832-106 | 000000000 | 00000 | 000000000 | 00000 |
1/2"-20 | 11/16"-11 | 11/16" | 41/64" | 0.646" | 4 | MS51831-206, NAS1395C8 | 000000000 | 00000 | 000000000 | 00000 |
1/2"-20 | 13/16"-16 | 11/16" | 49/64" | 0.771" | 4 | MS51832-206 | 000000000 | 00000 | 000000000 | 00000 |
9/16"-12 | 7/8"-14 | 13/16" | 53/64" | 0.833" | 4 | MS51832-107 | 000000000 | 00000 | 000000000 | 00000 |
9/16"-18 | 13/16"-16 | 13/16" | 49/64" | 0.771" | 4 | MS51831-207, NAS1395C9 | 000000000 | 00000 | 000000000 | 00000 |
9/16"-18 | 7/8"-14 | 13/16" | 53/64" | 0.833" | 4 | MS51832-207 | 000000000 | 00000 | 000000000 | 00000 |
5/8"-11 | 7/8"-14 | 7/8" | 53/64" | 0.833" | 4 | MS51831-108 | 000000000 | 00000 | 000000000 | 00000 |
5/8"-11 | 1"-12 | 7/8" | 15/16" | 0.942" | 4 | MS51832-108 | 000000000 | 00000 | 000000000 | 00000 |
5/8"-18 | 7/8"-14 | 7/8" | 53/64" | 0.833" | 4 | MS51831-208, NAS1395C10 | 000000000 | 00000 | 000000000 | 00000 |
5/8"-18 | 1"-12 | 7/8" | 15/16" | 0.942" | 4 | MS51832-208 | 000000000 | 00000 | 000000000 | 00000 |
3/4"-10 | 1 1/8"-12 | 1 1/8" | 1 1/16" | 1.067" | 4 | MS51831-109 | 000000000 | 00000 | 000000000 | 000000 |
3/4"-10 | 1 1/4"-12 | 1 1/8" | 1 3/16" | 1.192" | 4 | MS51832-109 | 000000000 | 00000 | 000000000 | 00000 |
3/4"-16 | 1 1/8"-12 | 1 1/8" | 1 1/16" | 1.067" | 4 | MS51831-209 | 000000000 | 00000 | 000000000 | 000000 |
7/8"-9 | 1 1/4"-12 | 1 1/4" | 1 3/16" | 1.192" | 4 | MS51831-110 | 000000000 | 00000 | 000000000 | 000000 |
7/8"-9 | 1 3/8"-12 | 1 1/4" | 1 5/16" | 1.317" | 4 | MS51832-110 | 000000000 | 00000 | 000000000 | 00000 |
7/8"-14 | 1 1/4"-12 | 1 1/4" | 1 3/16" | 1.192" | 4 | MS51831-210 | 000000000 | 00000 | 000000000 | 000000 |
1"-8 | 1 3/8"-12 | 1 3/8" | 1 5/16" | 1.317" | 4 | MS51831-111 | 000000000 | 00000 | 000000000 | 000000 |
1"-8 | 1 1/2"-12 | 1 3/8" | 1 7/16" | 1.442" | 4 | MS51832-111 | 000000000 | 00000 | 000000000 | 00000 |
Mil. Spec. Alloy Steel Key-Locking Inserts

The strongest key-locking inserts we offer, these inserts are made to stringent military specifications. Drive the keys into the surrounding material for a more secure hold than thread-locking inserts. Use them to repair or change threads in soft metals such as aluminum. Inserts may be mildly magnetic. They’re comparable to Keensert® inserts. Installation requires a drill bit, a standard tap, an installation tool, and a hammer.
Inserts with a thin wall are often used in small holes or near the edge of a workpiece.
Choose inserts with a thick wall for greater strength than thin-wall inserts, or to fill a large hole.
For technical drawings and 3-D models, click on a part number.
Inserts | Installation Tools | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
Thread Size | For Tap Thread Size | Installed Lg. | Drill Bit Size | For Max. Hole Dia. | No. of Locking Keys | Specifications Met | Each | Each | ||
Cadmium-Plated Alloy Steel with Thin Wall | ||||||||||
4-40 | 10-32 | 0.17" | 5/32" | 5/32" | 2 | MS51830-A102 | 000000000 | 000000 | 000000000 | 000000 |
6-32 | 12-28 | 0.17" | 3/16" | 3/16" | 2 | MS51830-A103 | 000000000 | 00000 | 000000000 | 00000 |
8-32 | 1/4"-28 | 0.22" | 15/64" | 15/64" | 2 | MS51830-A104 | 000000000 | 00000 | 000000000 | 00000 |
Cadmium-Plated Alloy Steel with Thick Wall | ||||||||||
10-32 | 3/8"-16 | 5/16" | 21/64" | 21/64" | 2 | MS51831-A201, NAS13953 | 000000000 | 00000 | 000000000 | 00000 |
1/4"-20 | 7/16"-14 | 3/8" | 25/64" | 25/64" | 2 | MS51831-A102 | 000000000 | 00000 | 000000000 | 00000 |
5/16"-18 | 1/2"-13 | 0.437" | 29/64" | 29/64" | 4 | MS51831-A103 | 000000000 | 00000 | 000000000 | 00000 |
3/8"-16 | 9/16"-12 | 1/2" | 33/64" | 33/64" | 4 | MS51831-A104 | 000000000 | 00000 | 000000000 | 00000 |
Screw-Locking Key-Locking Inserts


Forming the strongest hold of any of our threaded inserts, these inserts have a distorted internal thread to lock screws into place and keys that drive into surrounding material to prevent slipping and rotating. This creates a mechanical lock, which is stronger than the chemical lock from adhesive on thread-locking inserts. Because they’re made of a solid piece of metal, these inserts are also stronger than helical inserts, which are made of coiled wire. They're often used in molds, tools and dies, and suspension systems in vehicles to create completely new threads, add strong threads in soft metal, or replace existing threads that are damaged or need to be resized.
A dry-film lubricant makes it easy to install them and screw fasteners in. To install, use a tap to create the threads in your material and an installation tool to drive the keys into the material. All are made to tight tolerances with strictly controlled materials. Many inch sizes also meet military or aerospace standards for dimensions and material.
These inserts resist corrosion in wet environments. Cadmium-plated steel inserts are stronger than stainless steel inserts.
Inserts with thin walls are best for small holes or near the edge of a workpiece. They’re often used in electronics that require small fasteners. Inserts with thick walls are most commonly used; they’re stronger than thin-wall inserts and are used in larger holes.
For technical drawings and 3-D models, click on a part number.
Inserts | Installation Tools | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
Thread Size | For Tap Thread Size | Installed Lg. | Drill Bit Size | For Max. Hole Dia. | No. of Locking Keys | Specifications Met | Each | Each | ||
303 Stainless Steel with Thin Wall | ||||||||||
2-56 | 8-32 | 1/8" | 20 ga. | 0.134" | 2 | MS51830-101L | 000000000 | 00000 | 000000000 | 000000 |
4-40 | 10-32 | 11/64" | 4.1 mm | 0.161" | 2 | MS51830-102L | 000000000 | 0000 | 000000000 | 00000 |
6-32 | 12-28 | 11/64" | 3/16" | 0.187" | 2 | MS51830-103L | 000000000 | 0000 | 000000000 | 00000 |
8-32 | 1/4"-28 | 7/32" | 1 ga. | 0.228" | 2 | MS51830-104L | 000000000 | 0000 | 000000000 | 00000 |
10-24 | 5/16"-18 | 5/16" | I | 0.272" | 2 | MS51830-105L | 000000000 | 0000 | 000000000 | 00000 |
10-32 | 5/16"-18 | 5/16" | I | 0.272" | 2 | MS51830-201L, NAS1394C3L | 000000000 | 0000 | 000000000 | 00000 |
1/4"-20 | 3/8"-16 | 3/8" | Q | 0.332" | 2 | MS51830-106L | 000000000 | 0000 | 000000000 | 00000 |
1/4"-28 | 3/8"-16 | 3/8" | Q | 0.332" | 2 | MS51830-202L, NAS1394C4L | 000000000 | 0000 | 000000000 | 00000 |
5/16"-18 | 7/16"-14 | 7/16" | X | 0.397" | 4 | MS51830-107L | 000000000 | 0000 | 000000000 | 00000 |
5/16"-24 | 7/16"-14 | 7/16" | X | 0.397" | 4 | MS51830-203L, NAS1394C5L | 000000000 | 0000 | 000000000 | 00000 |
3/8"-16 | 1/2"-13 | 1/2" | 29/64" | 29/64" | 4 | MS51830-108L | 000000000 | 0000 | 000000000 | 00000 |
3/8"-24 | 1/2"-13 | 1/2" | 29/64" | 29/64" | 4 | MS51830-204L, NAS1394C6L | 000000000 | 0000 | 000000000 | 00000 |
7/16"-14 | 9/16"-12 | 9/16" | 33/64" | 33/64" | 4 | MS51830-109L | 000000000 | 00000 | 000000000 | 00000 |
7/16"-20 | 9/16"-12 | 9/16" | 33/64" | 33/64" | 4 | MS51830-205L, NAS1394C7L | 000000000 | 00000 | 000000000 | 00000 |
1/2"-13 | 5/8"-11 | 5/8" | 37/64" | 37/64" | 4 | MS51830-110L | 000000000 | 00000 | 000000000 | 00000 |
1/2"-20 | 5/8"-11 | 5/8" | 37/64" | 37/64" | 4 | MS51830-206L, NAS1394C8L | 000000000 | 00000 | 000000000 | 00000 |
303 Stainless Steel with Thick Wall | ||||||||||
10-24 | 3/8"-16 | 5/16" | Q | 0.332" | 2 | MS51831-101L | 000000000 | 0000 | 000000000 | 00000 |
1/4"-20 | 7/16"-14 | 3/8" | X | 0.397" | 2 | MS51831-102L | 000000000 | 0000 | 000000000 | 00000 |
5/16"-18 | 1/2"-13 | 7/16" | 29/64" | 29/64" | 4 | MS51831-103L | 000000000 | 0000 | 000000000 | 00000 |
3/8"-16 | 9/16"-12 | 1/2" | 33/64" | 33/64" | 4 | MS51831-104L | 000000000 | 0000 | 000000000 | 00000 |
7/16"-14 | 5/8"-11 | 5/8" | 37/64" | 37/64" | 4 | MS51831-105L | 000000000 | 00000 | 000000000 | 00000 |
1/2"-13 | 11/16"-11 | 11/16" | 16.5 mm | 0.641" | 4 | MS51831-106L | 000000000 | 00000 | 000000000 | 00000 |
5/8"-11 | 7/8"-14 | 7/8" | 53/64" | 53/64" | 4 | MS51831-108L | 000000000 | 00000 | 000000000 | 00000 |
3/4"-10 | 1 1/8"-12 | 1 1/4" | 1 1/16" | 1 1/16" | 4 | MS51831-109L | 000000000 | 00000 | 000000000 | 000000 |
7/8"-9 | 1 1/4"-12 | 1 3/8" | 1 3/16" | 1 3/16" | 4 | MS51831-110L | 000000000 | 00000 | 000000000 | 000000 |
7/8"-14 | 1 1/4"-12 | 1 3/8" | 1 3/16" | 1 3/16" | 4 | MS51831-210L | 000000000 | 00000 | 000000000 | 000000 |
1"-8 | 1 3/8"-12 | 1 1/2" | 1 5/16" | 1 5/16" | 4 | MS51831-111L | 000000000 | 00000 | 000000000 | 000000 |
Cadmium-Plated Steel with Thin Wall | ||||||||||
2-56 | 8-32 | 1/8" | 20 ga. | 0.134" | 2 | MS51830-A101L | 000000000 | 0000 | 000000000 | 00000 |
4-40 | 10-32 | 11/64" | 4.1 mm | 0.161" | 2 | MS51830-A102L | 000000000 | 0000 | 000000000 | 00000 |
6-32 | 12-28 | 11/64" | 3/16" | 0.187" | 2 | MS51830-A103L | 000000000 | 0000 | 000000000 | 00000 |
8-32 | 1/4"-28 | 7/32" | 1 ga. | 0.228" | 2 | MS51830-A104L | 000000000 | 0000 | 000000000 | 00000 |
10-32 | 5/16"-18 | 5/16" | I | 0.272" | 2 | MS51830-A201L, NAS1394-3L | 000000000 | 0000 | 000000000 | 00000 |
1/4"-20 | 3/8"-16 | 3/8" | Q | 0.332" | 2 | MS51830-A106L | 000000000 | 0000 | 000000000 | 00000 |
1/4"-28 | 3/8"-16 | 3/8" | Q | 0.332" | 2 | MS51830-A202L, NAS1394-4L | 000000000 | 0000 | 000000000 | 00000 |
1/4"-28 | 7/16"-14 | 3/8" | X | 0.397" | 2 | MS51831-A202L, NAS1395-4L | 000000000 | 00000 | 000000000 | 00000 |
3/8"-16 | 1/2"-13 | 1/2" | 29/64" | 29/64" | 4 | MS51830-A108L | 000000000 | 0000 | 000000000 | 00000 |
3/8"-24 | 1/2"-13 | 1/2" | 29/64" | 29/64" | 4 | MS51830-A204L, NAS1394-6L | 000000000 | 0000 | 000000000 | 00000 |
1/2"-13 | 5/8"-11 | 5/8" | 37/64" | 37/64" | 4 | MS51830-A110L | 000000000 | 00000 | 000000000 | 00000 |
1/2"-20 | 5/8"-11 | 5/8" | 37/64" | 37/64" | 4 | MS51830-A206L, NAS1394-8L | 000000000 | 00000 | 000000000 | 00000 |
Cadmium-Plated Steel with Thick Wall | ||||||||||
10-24 | 3/8"-16 | 5/16" | Q | 0.332" | 2 | MS51831-A101L | 000000000 | 00000 | 000000000 | 00000 |
10-32 | 3/8"-16 | 5/16" | Q | 0.332" | 2 | MS51831-A201L, NAS1395-3L | 000000000 | 00000 | 000000000 | 00000 |
1/4"-20 | 7/16"-14 | 3/8" | X | 0.397" | 2 | MS51831-A102L | 000000000 | 00000 | 000000000 | 00000 |
5/16"-18 | 1/2"-13 | 7/16" | 29/64" | 29/64" | 4 | MS51831-A103L | 000000000 | 00000 | 000000000 | 00000 |
5/16"-24 | 1/2"-13 | 7/16" | 29/64" | 29/64" | 4 | MS51831-A203L | 000000000 | 00000 | 000000000 | 00000 |
3/8"-16 | 9/16"-12 | 1/2" | 33/64" | 33/64" | 4 | MS51831-A104L | 000000000 | 00000 | 000000000 | 00000 |
3/8"-24 | 9/16"-12 | 1/2" | 33/64" | 33/64" | 4 | MS51831-A204L | 000000000 | 00000 | 000000000 | 00000 |
7/16"-14 | 5/8"-11 | 5/8" | 37/64" | 37/64" | 4 | MS51831-A105L | 000000000 | 00000 | 000000000 | 00000 |
7/16"-20 | 5/8"-11 | 5/8" | 37/64" | 37/64" | 4 | MS51831-A205L | 000000000 | 00000 | 000000000 | 00000 |
1/2"-13 | 11/16"-11 | 11/16" | 16.5 mm | 0.641" | 4 | MS51831-A106L | 000000000 | 00000 | 000000000 | 00000 |
1/2"-20 | 11/16"-11 | 11/16" | 16.5 mm | 0.641" | 4 | MS51831-A206L | 000000000 | 00000 | 000000000 | 00000 |
3/4"-10 | 1 1/8"-12 | 1 1/4" | 1 1/16" | 1 1/16" | 4 | MS51831-A109L | 000000000 | 00000 | 000000000 | 000000 |