7/16"-20 Helicoils | McMaster-Carr

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Military Specification

NASM21209

For Insert Thread Size

7/16"-20

For Use With

Helical Inserts

Screw-Locking Helical Inserts

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Yes

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EAR99

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23 Products

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



	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	—	90254A113	000000


	Narrow Profile



			7/16"-14, 7/16"-20, 1/2"-13, 1/2"-20, 1/2"-28, 9/16"-12, 9/16"-18, 5/8"-11, 5/8"-18, 5/8"-24, 3/4"-10, 3/4"-16, 3/4"-20, 7/8"-9, 7/8"-14, 7/8"-20, 1"-8, 1"-12, 1"-14, M12, M14, M16, M18, M20, M22, M24	Heli-Coil	90254A330	00000

Helical Threaded Inserts

Pronged

Restore, reinforce, or create threads in metal. 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.

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		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

				7/16"-20	0.438"	29/64"	0.453"	MS124659	10	91732A528	00000	91709A155	000000	91709A458	000000	90261A165	0000000	92955A203	0000000	10	98356A143	000000


				7/16"-20	0.656"	29/64"	0.453"	MS124699	10	91732A235	0000	91709A155	00000	91709A458	00000	90261A165	000000	92955A203	000000	10	91732A936	00000
				7/16"-20	0.875"	29/64"	0.453"	MS124739	5	91732A755	0000	91709A155	00000	91709A458	00000	90261A165	000000	92955A203	000000	—	———	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.

		Each
For Pronged Helical Inserts



	7/16"-14, 7/16"-20, 1/2"-13, 1/2"-20, 1/2"-28, 9/16"-12, 9/16"-18, 5/8"-11, 5/8"-18, 5/8"-24, 3/4"-10, 3/4"-16, 3/4"-20, 7/8"-9, 7/8"-14, 7/8"-20, 1"-8, 1"-12, 1"-14, M12, M14, M16, M18, M20, M22, M24	90254A330	000000

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

	18	7/16"-20 Thread × 0.438" Installed Lg. (6 Each) 7/16"-20 Thread × 0.656" Installed Lg. (6 Each) 7/16"-20 Thread × 7/8" Installed Lg. (6 Each) Drill Bit Installation Tool Prong Break-Off Tool Through-Hole Tap	Fine	29/64"	0.453"	91732A935	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"	90285A124	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

				7/16"-20	1 21/32"	3 3/8"	UNF	4	29/64"	0.4531"	Square	91709A155	000000	91709A458	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. The tough coils on these inserts expand once installed to anchor in a tapped hole.

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

	7/16"-20	0.438"	29/64"	0.453"	10	Drill Bit Installation Tool Through-Hole Tap	98356A143	000000


	7/16"-20	0.656"	29/64"	0.453"	10	Drill Bit Installation Tool Through-Hole Tap	91732A936	00000

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



	7/16"-20	—	Crank	Threaded	Helical Inserts, Screw-Locking Helical Inserts	1338N33	0000000


	7/16"-20	Heli-Coil	Crank	Threaded	Helical Inserts, Screw-Locking Helical Inserts	90261A165	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



	7/16"-20	Heli-Coil	Square	Threaded	Helical Inserts	93060A045	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 pumps and other machinery that shakes and rattles. 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		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

				7/16"-20	0.438"	29/64"	0.453"	MS21209F7-10, NASM21209	5	90296A221	00000	91709A155	000000	91709A458	000000	90261A165	0000000	92955A203	0000000


				7/16"-20	0.656"	29/64"	0.453"	MS21209F7-15, NASM21209	5	90296A222	0000	91709A155	00000	91709A458	00000	90261A165	000000	92955A203	000000
				7/16"-20	0.875"	29/64"	0.453"	MS21209F7-20, NASM21209	1	90296A223	0000	91709A155	00000	91709A458	00000	90261A165	000000	92955A203	000000

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



	7/16"-14, 7/16"-20, 7/16"-28	—	92955A321	0000000


	7/16"-20	Heli-Coil	92955A203	000000


	For Long Inserts



			7/16"-14, 7/16"-20	—	92955A421	000000

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



	7/16"-20	Square	Helical Inserts, Screw-Locking Helical Inserts	93060A085	000000

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



		7/16"-20	Helical Inserts, Screw-Locking Helical Inserts	91049A656	0000000	91049A743	000000