4-40 Adapters | McMaster-Carr

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478 Products

Thread Adapters

Inch-to-Inch Male-Female Hex Thread Adapters

Change thread sizes or types, such as fine to coarse threads, on parts without changing gender.

Inch-to-Metric Male-Female Hex Thread Adapters

Change inch threads to metric with these adapters, or swap metric threads for inch. An external hex lets you tighten or loosen them with a wrench.

Inch-to-Inch Male Hex Thread Adapters

Need to join two female-threaded parts, such as coupling nuts, with dissimilar inch thread sizes? Attach them to these adapters and tighten the exterior hex nut for a secure connection.

Inch-to-Metric Male Hex Thread Adapters

One side inch, one side metric, and a hex in the middle—these handy fasteners connect two female-threaded parts, such as coupling nuts, adapting from inch threads to metric. Tighten with a standard wrench.

Inch-to-Inch Female Hex Thread Adapters

Connect two differently sized male-threaded parts, such as threaded rods, and tighten with a standard wrench.

Inch-to-Metric Female Hex Thread Adapters

Adapt threaded rods from inch to metric. These adapters connect two male-threaded fasteners, so you can change the gender of a mating part or increase or decrease its thread size. The hex-shaped body fits into the head of a standard wrench.

Left-Hand to Right-Hand
Female Hex Thread Adapters

Often called sleeve nuts, these thread adapters fasten parts with right-hand threads to parts with left-hand threads.

Threaded Inserts for Metal

18-8 Stainless Steel Easy-to-Install
Thread-Locking Inserts

Made of 18-8 stainless steel, these inserts have better corrosion resistance than black-phosphate steel.

Black-Phosphate Steel Easy-to-Install
Thread-Locking Inserts

A black-phosphate finish provides mild corrosion resistance.

316 Stainless Steel Easy-to-Install
Thread-Locking Inserts

These inserts are the most corrosion-resistant thread-locking inserts we offer.

Mil. Spec. Stainless Steel Key-Locking Inserts

These inserts are made to stringent military specifications.

Mil. Spec. Alloy Steel Key-Locking Inserts

The strongest key-locking inserts we offer, these inserts are made to stringent military specifications.

High-Strength A286 Stainless
Steel Key-Locking Inserts

The strongest and most corrosion-resistant stainless steel key-locking inserts we offer. Made of A286 stainless steel, these inserts stand up to salt water, harsh chemicals, and even high temperatures.

Aligning Key-Locking Inserts

Install threads that align with off-center parts. These inserts have floating threads that account for misalignment, allowing you to insert screws at a slight angle as you fasten two parts together.

Closed-End Key-Locking Inserts

Protect threads from debris and leaks—these inserts have a closed end as a barrier.

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.

Threaded Standoffs

Male-Female Threaded Hex Standoffs

Position components in assemblies, as well as separate or connect parts with these standoffs.

NAS Male-Female Threaded Hex Standoffs

These standoffs are made to NAS specifications.

Male Threaded Standoffs

Hinged Male-Female Threaded Round Standoffs

Weld Nuts

Stainless Steel Narrow-Base Weld Nuts

Slim at the base, these weld nuts fit in channels and other spaces too tight for round-base weld nuts. Weld them to stainless steel surfaces to add strong, permanent threads that resist corroding from chemicals.

Steel Round-Base Weld Nuts

A smooth base provides more contact with the mating surface than weld nuts with projections.

Stainless Steel Round-Base Weld Nuts

Weld these nuts to stainless steel surfaces.

Stainless Steel Low-Profile Round-Base
Weld Nuts with Projections

Add corrosion-resistant threads to stainless steel sheets, even in spaces with low clearance.

Steel Low-Profile Round-Base
Weld Nuts with Projections

These steel nuts have a short collar to fit in low-clearance areas.

Adhesive-Mount Nuts

Stainless Steel Narrow-Base Adhesive-Ready Nuts

Add corrosion-resistant threads to channels, corners, and other tight spaces without drilling a hole. Glue these nuts on to thin surfaces and materials too hard and brittle to drill, such as acrylic and carbon fiber.

Stainless Steel Adhesive-Ready Nuts

Add strong threads to material that’s too difficult to drill or too thin to grip a threaded insert. Made of 316 stainless steel, they resist corrosion from salt water and harsh chemicals.

Steel Narrow-Base Adhesive-Ready Nuts

Fit these nuts into channels, corners, and other tight spaces to add strong threads without drilling a hole. They’re ideal for material that’s too thin or too hard and brittle to drill, such as acrylic and carbon fiber.

Stainless Steel Closed-End Adhesive-Ready Nuts

Adhere or mold these nuts onto a surface without gunking up the threads—the closed end blocks out adhesive, resin, and debris. Made of 316 stainless steel, they resist corrosion from salt water and harsh chemicals.