3 1/2 Caps | McMaster-Carr

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23 Products

Tapered Caps

Don't worry about having the exact size you need on hand. These caps are shaped to fit a range of ODs—just keep pushing on until they're snug. Because they make less contact with the parts they cover, they’re easier to remove than straight caps. In a pinch, you can flip tapered caps over and use them as plugs.

Polyethylene—Convenient and economical, these flexible caps are one and done. Instead of cleaning and reusing, just toss and grab a new cap.

	For Pipe Size	Inside Ht.	Flexibility	Max. Temp., ° F	Color	Pkg. Qty.		Pkg.
Polyethylene



	3.71" to 3.84"	3 1/2	3/4"	Flexible	150	Red	25	4491K152	000000


	3.94" to 4.07"	3 1/2	3/4"	Flexible	150	Red	25	4491K127	00000

Metal Round Caps

Tougher than plastic and rubber caps for best protection from impact and wear. These caps cover pipe ends to prevent damage and keep out dust and debris during shipping and storage.

Steel—The strongest caps, but moisture can cause them to rust.

Aluminum—Use aluminum caps instead of steel to prevent corrosion from spreading to aluminum pipe and tubing.

18-8 Stainless Steel—Our most corrosion-resistant caps for parts exposed to moisture and the outdoors.

					Steel		Aluminum		18-8 Stainless Steel
For OD	For Pipe Size	Inside Ht.	Flexibility	Max. Temp.		Each		Each		Each
4"	3 1/2	1 1/2"	Rigid	Not Rated	9275K68	00000	9275K35	000000	9275K443	000000

Hollow Tapered Plugs

A hollow construction makes these plugs extra flexible, so they compress for easy installation and a snug fit. The tapered profile fits a range of hole diameters. If you flip the plug over, it can be used as a cap.

Polyethylene—Convenient and economical. Instead of cleaning and reusing, just toss and grab a new plug.

	For Pipe Size	Ht.	Max. Temp., ° F	Color	Flange Dia.	Pkg. Qty.		Pkg.
Polyethylene



	3.47" to 3.6"	3 1/2	3/4"	150	Red	3 7/8"	10	4491K94	00000


	3.79" to 3.92"	3 1/2	3/4"	150	Red	4 1/8"	25	4491K104	00000

Adhesive-Back Caps for Pipe Flanges

Stick these caps onto the raised face of flanges to prevent nicks and scratches during shipping and storage. They stay in place until you peel them off and leave no residue behind.

Polyethylene—These tough caps are hard and wear resistant to hold up against scrapes and gouges.

	Max. Temp., ° F	Color	Adhesive Material	Pkg. Qty.		Pkg.
Polyethylene







	For ANSI Flanges

	3 1/2	5 1/2"	Rigid	160	Black	Rubber	4	3445T19	000000

FM-Approved Low-Pressure Iron and Steel Unthreaded Pipe Flanges

FM-approved for fire protection applications, these flanges are cast iron, so they're brittle and can be quickly opened by hitting them with a sledge hammer. Bolt them together with a gasket (not included) to create an access point within a low-pressure pipe line. All are cap flanges, which are also known as blind flanges. Use them in noncorrosive environments.

Cast Blind Flanges


Front	Back

Cast flanges are also called MSS flanges.

					Bolt Hole
	Pipe Size	Flanged Connection Surface	Flange OD	For Bolt Dia.	Dia.	No. Of	Bolt Circle Dia.	Pressure Class	Material	Max. Pressure @ Temp.	Max. Steam Pressure @ Temp.	Certification		Each
Flanged



		3 1/2	Flat	8 1/2"	5/8"	3/4"	8	7"	125	Cast Iron	200 psi @ 72° F	165 psi @ 300° F	FM Approved	4824N16	0000000

ABS Threaded Cleanout Plugs

Recessed

Close off your drain cleanout pipe with these threaded plugs. Note: If you do not know your pipe size, measure the OD of your existing cleanout plug or the ID of your cleanout fitting and match to the value listed.

To prevent leaks in threaded connections, apply a sealant to the male threads. Threaded connections can be taken apart as needed for maintenance and repair. For metal threads, use PTFE tape. For plastic threads, apply a non-hardening, plastic-compatible sealant. Tape or sealants with PTFE are not recommended for plastic-to-plastic connections. When making a threaded connection be careful not to overtighten the threads. To prevent cracks and leaks, finger tighten the fitting, then wrench-tighten one to two turns.

				Recessed
Cleanout Plug OD/Fitting ID	For Pipe Size	Thread Type	Material		Each
3 31/32"	3 1/2	NPT	ABS	9359T25	00000

Plug Wrenches

		Each
Plug Wrench for Recessed Plugs	2400K1	000000

Brass and Bronze Threaded Cleanout Plugs

Raised

Recessed

				Recessed		Raised
Cleanout Plug OD/Fitting ID	For Pipe Size	Thread Type	Material		Each		Each
3 31/32"	3 1/2	NPT	Brass	2400K56	000000	2400K76	00000

Plug Wrenches

		Each
Plug Wrench for Recessed Plugs	2400K1	000000

Low-Pressure Galvanized Iron and Steel Threaded Pipe Fittings

The galvanized finish on these fittings provides fair corrosion resistance. Fittings are for use in low-pressure applications.

External-Square-Drive Plugs

Threaded

Fitting

Connection, Male

	Construction	Pressure Class	Body Shape	Material	Max. Pressure @ Temp.	Max. Steam Pressure @ Temp.	Certification		Each
NPT Male



	3 1/2	Hollow	125	Square	Galvanized Iron	125 psi @ 72° F	125 psi @ 350° F	UL Listed	4638K936	000000

Low-Pressure Iron and Steel Threaded Pipe Flanges

Use these flanges for low-pressure applications in noncorrosive environments. Bolt two flanges of the same size together with a gasket (sold separately) to create an access point within a line.

Forged Flanges


Front	Raised Surface on Back

Forged flanges have better strength than cast flanges.

	Pipe Size					Bolt Hole
	(A)	(B)	Flanged Connection Surface (B)	Flange OD	For Bolt Dia.	Dia.	No. Of	Bolt Circle Dia.	Pressure Class	Material	Max. Pressure @ Temp.	Max. Steam Pressure @ Temp.		Each
NPT Female



		3 1/2	3 1/2	Raised	8 1/2"	5/8"	3/4"	8	7"	150	Steel	285 psi @ 72° F	230 psi @ 300° F	68095K444	0000000

Wing-Nut Expansion Plugs

Style A

Twist the wing nut on these plugs to expand the seal and close off pipe openings.

Style A—Style A aren’t recommended for pressure testing, so they’re often used as a dust cover.

Stainless Steel Plate—Plugs with a stainless steel plate have excellent corrosion resistance.

Maximum Air Back Pressure—Maximum air back pressure is the amount of pressure a plug can withstand without moving.

Maximum Water Back Pressure—Maximum water back pressure refers to the pressure resulting from the height of the water above the plug.

	For Pipe		Max. Back Pressure
	Size	ID	Air, psi	Water, ft. of head	Overall Ht.	Temp. Range, ° F	Seal Material		Each
Style A







				Stainless Steel Plate

				3 1/2	3.44" to 3.60"	5	12	2 15/16"	0 to 175	Neoprene	2613K73	000000

Low-Pressure Iron and Steel Threaded Pipe Fittings

Use these fittings for low-pressure applications in noncorrosive environments.

Square-Drive Plugs

Male

	Construction	Pressure Class	Material	Max. Pressure @ Temp.	Max. Steam Pressure @ Temp.		Each
NPT Male



	3 1/2	Hollow	125	Iron	175 psi @ 72° F	125 psi @ 350° F	44605K707	000000

External-Square-Drive Plugs

Male

	Construction	Pressure Class	Body Shape	Material	Max. Pressure @ Temp.	Max. Steam Pressure @ Temp.		Each
NPT Male



	3 1/2	Hollow	125	Square	Iron	175 psi @ 72° F	125 psi @ 350° F	44605K703	000000

Hex-Nut Expansion Plugs

Style B

Tighten the nut on these plugs to expand the seal and close off pipe openings.

Stainless Steel Plate—Plugs with a stainless steel plate have excellent corrosion resistance.

Maximum Air Back Pressure—Maximum air back pressure is the amount of pressure a plug can withstand without moving.

Maximum Water Back Pressure—Maximum water back pressure refers to the pressure resulting from the height of the water above the plug.

	For Pipe		Max. Back Pressure
	Size	ID	Air, psi	Water, ft. of head	Overall Ht.	Temp. Range, ° F	Seal Material		Each
Style B







				Stainless Steel Plate

				3 1/2	3.44" to 3.60"	5	12	3 1/16"	-40 to 250	Neoprene	2599K55	000000

T-Handle Expansion Plugs

Twist the easy-grip T-handle on these plugs to expand the seal and close off pipe openings.

Zinc-Plated Steel Plate—Plugs with a zinc-plated steel plate have fair corrosion resistance.

Stainless Steel Plate—Plugs with a stainless steel plate have excellent corrosion resistance.

Maximum Air Back Pressure—Maximum air back pressure is the amount of pressure a plug can withstand without moving.

Maximum Water Back Pressure—Maximum water back pressure refers to the pressure resulting from the height of the water above the plug.

For Pipe		Max. Back Pressure					Brass Handle		Stainless Steel Handle
Size	ID	Air, psi	Water, ft. of head	Overall Ht.	Temp. Range, ° F	Seal Material		Each		Each







			Zinc-Plated Steel Plate

			3 1/2	3.44" to 3.60"	5	12	3 15/16"	-40 to 250	Neoprene	2527K26	000000	———	0




					Stainless Steel Plate

					3 1/2	3.44" to 3.60"	5	12	3 15/16"	-40 to 250	Neoprene	———	0	2908K31	000000

Quick-Snap Expansion Plugs

Turn the cam handle to expand the seal, then snap the handle down to hold it in place and close off pipe openings.

Zinc-Plated Steel Plate—Plugs with a zinc-plated steel plate have fair corrosion resistance.

Stainless Steel Plate—Plugs with a stainless steel plate have excellent corrosion resistance.

Maximum Air Back Pressure—Maximum air back pressure is the amount of pressure a plug can withstand without moving.

Maximum Water Back Pressure—Maximum water back pressure refers to the pressure resulting from the height of the water above the plug.

For Pipe		Max. Back Pressure					Brass Handle		Stainless Steel Handle
Size	ID	Air, psi	Water, ft. of head	Overall Ht.	Temp. Range, ° F	Seal Material		Each		Each







			Zinc-Plated Steel Plate

			3 1/2	3.38" to 3.60"	5	12	2 5/16"	-40 to 250	Neoprene	2598K37	000000	———	0




					Stainless Steel Plate

					3 1/2	3.38" to 3.60"	5	12	2 5/16"	-40 to 250	Neoprene	———	0	9191T63	000000