5/16"-24 Helicoils | McMaster-Carr

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38 Products

Helical Threaded Inserts


Pronged	Prongless

Restore, reinforce, or create metal threads. The tough coils on these inserts expand once installed to anchor in a tapped hole. Also known as Heli-Coil inserts, they're often used in engine heads and machinery housings where strong connections are critical. Unlike threadlocking inserts, you can remove and reuse them without them losing their strength.

Installation requires a drill bit, a helical insert tap, and an installation tool. Easy-start installation tools compress the diameter of your insert so it fits easily into a tapped hole. These tools are the best choice for preventing misaligned or damaged threads—just make sure you have space to turn the crank.

Pronged—The prong attaches to an installation tool for precise control as you drive inserts in. Remove the prong with a punch or break-off tool before inserting a screw.

Prongless—Without a prong to break off and retrieve, these inserts save time and avoid leftover debris in holes.

18-8 Stainless Steel—The choice for wet and outdoor environments, these inserts resist rust and mild chemicals.

	Inserts								Through-Hole Taps		Closed-End Hole Taps		Installation Tools		Prong Break-Off Tools		Inserts with Installation Tools
	Thread Size	Installed Lg.	Drill Bit Size	For Max. Hole Dia.	Specs. Met	Pkg. Qty.		Pkg.		Each		Each		Each		Each	No. of Inserts Included		Each
Pronged







				18-8 Stainless Steel

				5/16"-24	0.312"	21/64"	0.328"	MS124657	10	000000000	00000	000000000	000000	000000000	000000	000000000	0000000	000000000	0000000	10	000000000	000000


				5/16"-24	0.469"	21/64"	0.328"	MS124697	10	000000000	0000	000000000	00000	000000000	00000	000000000	000000	000000000	000000	10	000000000	00000
				5/16"-24	0.625"	21/64"	0.328"	MS124737	10	000000000	0000	000000000	00000	000000000	00000	000000000	000000	000000000	000000	10	000000000	00000
				5/16"-24	0.781"	21/64"	0.328"	MS124777	5	000000000	0000	000000000	00000	000000000	00000	000000000	000000	000000000	000000	—	———	0


				Prongless







								18-8 Stainless Steel

								5/16"-24	0.312"	21/64"	0.328"	NAS1130-5F-10	10	000000000	0000	000000000	00000	000000000	00000	000000000	000000	———	0	—	———	0


								5/16"-24	0.468"	21/64"	0.328"	NAS1130-5F-15	10	000000000	0000	000000000	00000	000000000	00000	000000000	000000	———	0	—	———	0
								5/16"-24	0.624"	21/64"	0.328"	NAS1130-5F-20	10	000000000	0000	000000000	00000	000000000	00000	000000000	000000	———	0	—	———	0

Extraction Tools

Remove installed helical inserts.

For Pronged Helical Inserts—Place the tip into pronged inserts and lightly strike the tool’s head. Then, turn the tool counterclockwise with pressure to extract the insert.

For Prongless Helical Inserts—Remove prongless inserts without damaging threads or the surface of your material. These tools also back out or adjust inserts that are installed too deep.

		Each
For Pronged Helical Inserts



	10-24, 10-32, 12-24, 12-28, 1/4"-20, 1/4"-28, 1/4"-32, 1/4"-80, 5/16"-18, 5/16"-24, 5/16"-32, 3/8"-16, 3/8"-24, M5, M6, M7, M8, M10	000000000	000000


	For Prongless Helical Inserts



			5/16"-24	000000000	000000

Helical Threaded Insert Removal Tools

To remove installed helical inserts, place the tip of these tools into the insert and lightly strike the tool’s head. Then, turn the tool counterclockwise with pressure to extract the insert.

Narrow Profile—The tip of these tools has a narrower angle than standard removal tools to reduce the chance it will dig into your material’s surface when you strike the tool.

	Mfr.		Each
Standard Profile



	4-40, 4-48, 5-40, 6-32, 6-40, 8-32, 8-36, 10-24, 10-32, 12-24, 1/4"-20, 1/4"-28, 5/16"-18, 5/16"-24, 3/8"-16, 3/8"-24, 7/16"-14, 7/16"-20, 1/2"-13, 1/2"-20, M3, M3.5, M4, M5, M6, M7, M8, M9, M10, M12, M13, M14	—	000000000	000000


	6-32, 6-40, 8-32, 8-36, 10-24, 10-32, 12-24, 1/4"-20, 1/4"-28, 5/16"-18, 5/16"-24, 3/8"-16, 3/8"-24, 7/16"-14, 7/16"-20, 1/2"-13, 1/2"-20, 9/16"-12, 9/16"-18, 5/8"-11, 5/8"-18, 3/4"-10, 3/4"-16, 7/8"-9, 7/8"-14, 1"-8, 1"-12, 1"-14, M4, M5, M6, M7, M8, M9, M10, M12, M13, M14, M15, M16, M18, M20, M22, M24	—	000000000	00000


	Narrow Profile



			10-24, 10-32, 12-24, 12-28, 1/4"-20, 1/4"-28, 1/4"-32, 1/4"-80, 5/16"-18, 5/16"-24, 5/16"-32, 3/8"-16, 3/8"-24, M5, M6, M7, M8, M10	Heli-Coil	000000000	00000

Helical Threaded Insert Assortments with Installation Tools

Repair damaged threads or create new ones. These convenient assortments include helical inserts, an installation tool for each thread size, a drill bit, and a tap. The inserts are also known as Heli-Coil inserts.

Pronged—The prong attaches to an installation tool for precise control as you drive inserts in. Remove the prong with a punch or break-off tool before inserting a screw.

18-8 Stainless Steel—The choice for wet and outdoor environments, these inserts resist rust and mild chemicals.

	Drill Bit Size	For Max. Hole Dia.		Each
Pronged







	18-8 Stainless Steel

	36	5/16"-24 Thread × 0.312" Installed Lg. (12 Each) 5/16"-24 Thread × 0.469" Installed Lg. (12 Each) 5/16"-24 Thread × 5/8" Installed Lg. (12 Each) Drill Bit Installation Tool Prong Break-Off Tool Through-Hole Tap	Fine	21/64"	0.328"	000000000	000000


	60	1/2"-20 Thread × 3/4" Installed Lg. (6 Each) 1/4"-28 Thread × 3/8" Installed Lg. (12 Each) 3/8"-24 Thread × 0.562" Installed Lg. (12 Each) 5/16"-24 Thread × 0.469" Installed Lg. (12 Each) 7/16"-20 Thread × 0.656" Installed Lg. (6 Each) 10-32 Thread × 0.285" Installed Lg. (12 Each) Drill Bits Installation Tools Through-Hole Taps	Fine	13/64" 17/64" 21/64" 25/64" 29/64" 33/64"	0.203" 0.266" 0.328" 0.391" 0.453" 0.516"	000000000	000000

Helical Insert Taps

Match the size of helical inserts so they fit tightly when installed in the hole.

High-Speed Steel—These taps resist heat and wear to stay sharp.

Plug Chamfer—Our go-to chamfer type. With a longer taper than a bottoming chamfer, they are easier to turn but won't thread as close the bottom of a hole.

Bottoming Chamfer—Cut all the way to the bottom of blind holes with taps that have the shortest taper. Since these require the most force to turn, they’re often used to finish holes started by taper- or plug-chamfer taps.

						Drill Bit			Plug Chamfer		Bottoming Chamfer
	For Insert Size	Thread Lg.	Overall Lg.	For Insert Thread Type	No. of Flutes	Size	Decimal Size Equiv.	Shank Type		Each		Each
High-Speed Steel







				Uncoated

				5/16"-24	1 1/4"	2 15/16"	UNF	4	21/64"	0.3281"	Square	000000000	000000	000000000	000000

Easy-Start Helical Threaded Insert Installation Tools

These tools compress the diameter of your insert so it fits easily into a tapped hole. They’re the best choice for preventing misaligned or damaged threads—just make sure you have space to turn the crank. Screw or slide an insert onto your tool and drive it between a quarter-turn and half-turn below the surface. Also known as prewinders.

Threaded Insert Installation Tools with Depth Stop


Crank Handle	Threaded Drive

Ensure consistent installation across multiple inserts. Set your desired installation depth, and the stop will prevent you from driving your insert any further.

Threaded Drive Helical Insert Tool—These tools align each coil of your insert perfectly with the thread pitch of your tapped hole for easy installation.

	Mfr.	Handle Style	Helical Insert Tool Drive Type	For Use With		Each
Standard (UN) Thread



	5/16"-24	—	Crank	Threaded	Helical Inserts, Screw-Locking Helical Inserts	0000000	000000


	5/16"-24	Heli-Coil	Crank	Threaded	Helical Inserts, Screw-Locking Helical Inserts	000000000	000000

Other Threaded Insert Installation Tools

No Handle

Square Shank—These tools don’t have a handle. Attach them to a tap wrench to turn.

Threaded Drive Helical Insert Tool—These tools align each coil of your insert perfectly with the thread pitch of your tapped hole for easy installation.

	Mfr.	Shank Type	Helical Insert Tool Drive Type	For Use With		Each
Standard (UN) Thread



	5/16"-24	Heli-Coil	Square	Threaded	Helical Inserts	000000000	000000

Screw-Locking Helical Threaded Inserts

Pronged

The irregularly shaped threads tightly grip screws to prevent them from loosening or backing out under vibration. Use these inserts to create or repair threads in automobile parts and other machinery that shakes and rattles. Also known as Heli-Coil inserts.

Pronged—The prong attaches to an installation tool for precise control as you drive inserts in. Remove the prong with a punch or break-off tool before inserting a screw.

18-8 Stainless Steel—The choice for wet and outdoor environments, these inserts resist rust and mild chemicals.

	Inserts								Through-Hole Taps		Closed-End Hole Taps		Installation Tools		Prong Break-Off Tools
	Thread Size	Installed Lg.	Drill Bit Size	For Max. Hole Dia.	Specs. Met	Pkg. Qty.		Pkg.		Each		Each		Each		Each
Pronged







				18-8 Stainless Steel

				5/16"-24	0.312"	21/64"	0.328"	NASM21209, MS21209F5-10	10	000000000	00000	000000000	000000	000000000	000000	000000000	0000000	000000000	0000000


				5/16"-24	0.469"	21/64"	0.328"	NASM21209, MS21209F5-15	10	000000000	0000	000000000	00000	000000000	00000	000000000	000000	000000000	000000
				5/16"-24	0.625"	21/64"	0.328"	NASM21209, MS21209F5-20	1	000000000	0000	000000000	00000	000000000	00000	000000000	000000	000000000	000000
				5/16"-24	0.781"	21/64"	0.328"	NASM21209, MS21209F5-25	1	000000000	0000	000000000	00000	000000000	00000	000000000	000000	000000000	000000

Easy-Start Prongless Helical Threaded Insert Installation Tools

Install prongless (tangless) helical inserts more quickly and consistently than with standard tools. These tools compress your insert’s diameter and align each coil with the thread pitch, guiding it straight into a tapped hole. They’re the best choice for preventing misaligned or damaged threads. Just make sure you have space to turn the crank. Screw an insert onto these tools and drive them a quarter- to half-turn below the material’s surface. Also known as prewinders.

	Handle Style	For Use With		Each
Standard (UN) Thread



	5/16"-24	Crank	Helical Inserts, Screw-Locking Helical Inserts	000000000	0000000

Replacement Tips

Replacement tips (sold separately) come with one installation tip, two pins, and two springs. Tip for 10-32 internal thread size does not require springs and pins.

For Thread Size		Each
5/16"-24	000000000	000000

Helical Threaded Inserts with Installation Tools

Drill Bit, Installation Tool

and Through-Hole Tap

Quickly restore stripped threads—these inserts come with through-hole taps and installation tools.

Pronged—The prong attaches to an installation tool for precise control as you drive inserts in. Remove the prong with a punch or break-off tool before inserting a screw.

18-8 Stainless Steel—The choice for wet and outdoor environments, these inserts resist rust and mild chemicals.

	For Max. Hole Dia.	No. of Inserts Included	Includes		Each
Pronged







	18-8 Stainless Steel

	5/16"-24	0.312"	21/64"	0.328"	10	Drill Bit Installation Tool Through-Hole Tap	000000000	000000


	5/16"-24	0.469"	21/64"	0.328"	10	Drill Bit Installation Tool Through-Hole Tap	000000000	00000
	5/16"-24	0.625"	21/64"	0.328"	10	Drill Bit Installation Tool Through-Hole Tap	000000000	00000

Spring-Loaded Helical Threaded Insert Prong Break-Off Tools

Cleanly snap prongs off installed helical inserts with just one hand. Because they work faster than standard prong break-off tools, these are a good choice when you have many prongs to remove. Press your tool into an insert to trigger the spring-loaded punch and snap off the prong.

For Standard-Length Inserts—Use these tools for inserts that are 1 to 2 times as long as the diameter.

For Long Inserts—Use these tools for inserts that are 2 _1/2 to 3 times as long as the diameter.

	Mfr.		Each
For Standard-Length Inserts



	5/16"-18, 5/16"-24, 5/16"-32	—	000000000	0000000


	5/16"-24	Heli-Coil	000000000	000000


	For Long Inserts



			5/16"-18, 5/16"-24, M8	—	000000000	00000

Prongless Helical Threaded Insert Removal Tools

Remove prongless inserts without damaging threads or the surface of your material. These tools also back out or adjust inserts that are installed too deep.

Replacement Tips—Replacement tips (sold separately) come with one removal tip, two pins, and two springs.

	Removal Tools				Replacement Tips
	For Thread Size	For Use With		Each		Each
Standard (UN) Thread



		5/16"-24	Helical Inserts, Screw-Locking Helical Inserts	000000000	0000000	000000000	000000

Left-Hand-Thread Helical Threaded Inserts

Fix threads in parts that rotate counterclockwise. Pair these inserts with left-hand-thread screws and turn them to the left to tighten. Also known as Heli-Coil inserts.

Installation requires a drill bit, a helical insert tap, and an installation tool.

Pronged—The prong attaches to an installation tool for precise control as you drive inserts in. Remove the prong with a punch or break-off tool before inserting a screw.

18-8 Stainless Steel—The choice for wet and outdoor environments, these inserts resist rust and mild chemicals.

	Inserts							Through-Hole Taps		Installation Tools		Prong Break-Off Tools		Inserts with Installation Tools
	Thread Size	Installed Lg.	Drill Bit Size	For Max. Hole Dia.	Pkg. Qty.		Pkg.		Each		Each		Each	No. of Inserts Included		Each
Pronged







				18-8 Stainless Steel

				5/16"-24	0.469"	21/64"	0.328"	1	000000000	00000	000000000	000000	000000000	000000	000000000	0000000	10	000000000	000000

Extraction Tools

Remove installed helical inserts.

For Pronged Helical Inserts—Place the tip into pronged inserts and lightly strike the tool’s head. Then, turn the tool counterclockwise with pressure to extract the insert.

		Each
For Pronged Helical Inserts



	10-24, 10-32, 12-24, 12-28, 1/4"-20, 1/4"-28, 1/4"-32, 1/4"-80, 5/16"-18, 5/16"-24, 5/16"-32, 3/8"-16, 3/8"-24, M5, M6, M7, M8, M10	000000000	000000

Left-Hand Thread Helical Threaded Inserts with Installation Tools

Save time when repairing threads in parts that rotate counterclockwise—these inserts come with installation tools. Pair them with left-hand-thread screws, and turn them the left to tighten. Also known as Heli-Coil inserts.

Pronged—The prong attaches to an installation tool for precise control as you drive inserts in. Remove the prong with a punch or break-off tool before inserting a screw.

18-8 Stainless Steel—The choice for wet and outdoor environments, these inserts resist rust and mild chemicals.

	For Max. Hole Dia.	No. of Inserts Included	Includes		Each
Pronged







	18-8 Stainless Steel

	5/16"-24	0.469"	21/64"	0.328"	6	Installation Tool Through-Hole Tap	000000000	000000

Helical Threaded Insert Installation and Prong Break-Off Tools

L-Handle

Install helical inserts and break off prongs with one tool and a hammer strike. These tools have a slot that grips your insert’s prong for turning both left- and right-hand threads. Slide an insert onto these tools and drive them a quarter-turn to half-turn below the material’s surface. Then, strike the end of the tool with a hammer to break off the prong. These tools work with pronged helical inserts.

	Handle Style		Each
Standard (UN) Thread



	5/16"-24	L-Handle	000000000	000000

Left-Hand Thread Helical Insert Taps

Size holes for installing helical inserts that anchor left-hand bolts and rods. Helical inserts reinforce the connection between holes and fasteners that secure counter-clockwise rotating parts. Left-hand threads keep components such as flywheels and propellers from loosening and spinning off.

High-Speed Steel—These taps resist heat and wear to stay sharp.

Plug Chamfer—Our go-to chamfer type. With a longer taper than a bottoming chamfer, they are easier to turn but won't thread as close the bottom of a hole.

						Drill Bit			Plug Chamfer
	For Insert Size	Thread Lg.	Overall Lg.	For Insert Thread Type	No. of Flutes	Size	Decimal Size Equiv.	Shank Type		Each
High-Speed Steel







				Uncoated

				5/16"-24	1 1/4"	2 15/16"	UNF	4	21/64"	0.3281"	Square	000000000	000000

Go/No-Go Helical Insert Threaded Plug Gauges with Handle

Check that holes tapped for helical threads are within tolerance. You’ll sometimes hear these threads referred to as Screw Thread Insert (STI) threads. To speed up tests, these gauges have a go gauge on one end and a no-go gauge on the other. The double-ended taperlock handle makes them quick to thread and unthread. It also lets you swap in new plug gauges (not included) in place of worn ones.

The go gauge checks the minimum internal thread size, and the no-go gauge checks the maximum. A part is within tolerance if it’s easy to thread the go gauge but difficult to thread the no-go gauge more than two turns.

Plug Gauges with Accuracy Certificate Traceable to NIST—Gauges with an accuracy certificate traceable to NIST include verification from the manufacturer that their thread sizes are within tolerance. The certificate is also known as a certificate of compliance or a short-form certification.

Plug Gauges with Calibration Certificate Traceable to NIST—Gauges with a calibration certificate traceable to NIST were calibrated in a lab. The certificate, sometimes called a test report or long-form certificate, details the tested measurements.

								Plug Gauges with Accuracy Certificate Traceable to NIST		Plug Gauges with Calibration Certificate Traceable to NIST
	Thread Size	Thread Type	Pitch Dia. Tolerance	Hardness	Material	Features	For Thread Fit		Each		Each
Class X Gauge



		5/16"-24	UNF	-0.0003" to 0.0003"	Rockwell C70	Chrome-Plated Tool Steel	Double-Ended Taperlock Handle	Unified Standard Class 2B	0000000	0000000	0000000	0000000

Helical Threaded Insert Installation Tools

No Handle

Install your pronged helical inserts into tapped holes. Screw an insert onto these tools and drive them a quarter to half-turn below the material’s surface.

Square Shank—These tools don’t have a handle. Attach them to a tap wrench to turn.

	Shank Type	For Use With		Each
Standard (UN) Thread



	5/16"-24	Square	Helical Inserts, Screw-Locking Helical Inserts	000000000	000000