3 3/4" OD Flanges | McMaster-Carr

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23 Products

How to Identify and Measure Fittings

Pipe size is an industry designation, not the actual size. View information about how to measure threaded and unthreaded pipe and pipe fittings.

High-Pressure Stainless Steel Unthreaded Pipe Flanges

Use these heavy duty forged flanges for high-pressure applications. Bolt two flat-surface flanges or two raised-surface flanges of same size together with a gasket (sold separately) to create an access point in a pipe line.

304 stainless steel flanges offer very good corrosion resistance. 316 stainless steel flanges have excellent corrosion resistance.

Butt-weld flanges are also known as weld-neck flanges; the flange neck has a beveled end that, when flush to pipe, creates a trough for a strong weld. Slip-on weld flanges have no internal stop; slide a pipe through the flange and weld on both sides. Socket-connect flanges have an internal stop that supports the pipe when welding and prevents the pipe from sliding all the way through.

Cap flanges are also known as blind flanges.

For technical drawings and 3-D models, click on a part number.

Butt-Weld Flanges

Front

Raised Surface on Back

For Use With: Air, Hydraulic Fluid, Natural Gas, Oil, Steam, Water
Pressure Class: See table
Specifications Met:
Pressure Class 300: ASME B16.5, ASTM A182, MSS SP-25, MSS SP-6
Pressure Class 600: ASME B16.5, ASTM A182
Certification: Material Certificate with Traceable Lot Number and Test Report
Pipe Nipples and Pipe: Use Schedule 40 stainless steel
Fittings: Use Schedule 40 stainless steel

				Bolt Hole
Pipe Size	Dash Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure	Max. Steam Pressure		Each
304/304L Stainless Steel
Pressure Class 300
1/2	08	3 3/4"	1/2"	0.625"	4	2 5/8"	600 psi @ 72° F	300 psi @ 360° F	00000000	000000
316/316L Stainless Steel
Pressure Class 300
1/2	08	3 3/4"	1/2"	0.625"	4	2 5/8"	600 psi @ 72° F	300 psi @ 360° F	00000000	00000
Pressure Class 600
1/2	08	3 3/4"	1/2"	0.62"	4	2 5/8"	1,200 psi @ 72° F	840 psi @ 400° F	0000000	000000

Socket-Connect Flanges

Front

Raised Surface on Back

For Use With:
4 and 6 Pipe Sizes: Air, Hydraulic Fluid, Natural Gas, Oil, Water
All other sizes: Air, Hydraulic Fluid, Natural Gas, Oil, Steam, Water
Pressure Class: See table
Specifications Met: See table
Certification:: Material Certificate with Traceable Lot Number and Test Report
Pipe Nipples and Pipe: Use Schedule 40 stainless steel
Fittings: Use Schedule 40 stainless steel

						Bolt Hole
Pipe Size	Dash Size	Max. Pressure	Max. Steam Pressure	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Specifications Met		Each
304/304L Stainless Steel
Pressure Class 300
1/2	08	600 psi @ 72° F	300 psi @ 360° F	3 3/4"	1/2"	0.625"	4	2 5/8"	ASME B16.5, ASTM A182, MSS SP-25, MSS SP-6	00000000	000000
316/316L Stainless Steel
Pressure Class 300
1/2	08	600 psi @ 72° F	300 psi @ 360° F	3 3/4"	1/2"	0.625"	4	2 5/8"	ASME B16.5, ASTM A182, MSS SP-25, MSS SP-6	00000000	00000
Pressure Class 600
1/2	08	1,200 psi @ 72° F	840 psi @ 400° F	3 3/4"	1/2"	0.62"	4	2 5/8"	ASME B16.5, ASTM A182	0000000	000000

Slip-On Weld Flanges

Front

Raised Surface on Back

For Use With: Air, Hydraulic Fluid, Natural Gas, Oil, Steam, Water
Pressure Class: See table
Specifications Met:
Pressure Class 300: ASME B16.5, ASTM A182, MSS SP-25, MSS SP-6
Pressure Class 600: ASME B16.5, ASTM A182
Certification:: Material Certificate with Traceable Lot Number and Test Report
Pipe Nipples and Pipe: Use Schedule 40 stainless steel
Fittings: Use Schedule 40 stainless steel

						Bolt Hole
Pipe Size	Dash Size	Max. Pressure	Max. Steam Pressure	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.		Each
304/304L Stainless Steel
Pressure Class 300
1/2	08	600 psi @ 72° F	300 psi @ 360° F	3 3/4"	1/2"	0.625"	4	2 5/8"	00000000	000000
316/316L Stainless Steel
Pressure Class 300
1/2	08	600 psi @ 72° F	300 psi @ 360° F	3 3/4"	1/2"	0.625"	4	2 5/8"	00000000	00000

Caps

Front

Raised Surface on Back

For Use With: Air, Hydraulic Fluid, Natural Gas, Oil, Steam, Water
Pressure Class: See table
Specifications Met:
Pressure Class 300: ASME B16.5, ASTM A182, MSS SP-25, MSS SP-6
Pressure Class 600: ASME B16.5, ASTM A182
Certification:: Material Certificate with Traceable Lot Number and Test Report
Pipe Nipples and Pipe: Use Schedule 40 stainless steel
Fittings: Use Schedule 40 stainless steel

						Bolt Hole
Pipe Size	Dash Size	Max. Pressure	Max. Steam Pressure	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.		Each
304/304L Stainless Steel
Pressure Class 300
1/2	08	600 psi @ 72° F	300 psi @ 360° F	3 3/4"	1/2"	0.625"	4	2 5/8"	00000000	000000
Pressure Class 600
1/2	08	1,200 psi @ 72° F	840 psi @ 400° F	3 3/4"	1/2"	0.62"	4	2 5/8"	0000000	00000
316/316L Stainless Steel
Pressure Class 300
1/2	08	600 psi @ 72° F	300 psi @ 360° F	3 3/4"	1/2"	0.625"	4	2 5/8"	00000000	00000
Pressure Class 600
1/2	08	1,200 psi @ 72° F	840 psi @ 400° F	3 3/4"	1/2"	0.62"	4	2 5/8"	0000000	00000

High-Pressure Stainless Steel Threaded Pipe Flanges

Front

Raised Surface on Back

For Use With: Air, Hydraulic Fluid, Natural Gas, Oil, Steam, Water
Pressure Class: See table
Specifications Met: ASTM A182, ASME B16.5
Pipe Nipples and Pipe: Use Schedule 80 stainless steel

Forged for high strength, these heavy duty flanges can handle high-pressure applications. They are also known as ANSI flanges. Bolt two same-size flanges together with a gasket (sold separately) to create an access point within a line.

304 stainless steel flanges provide very good corrosion resistance. 316 stainless steel flanges have excellent corrosion resistance.

For technical drawings and 3-D models, click on a part number.

				Bolt Hole
Pipe Size	Dash Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure	Max. Steam Pressure		Each
304/304L Stainless Steel
NPT
Pressure Class 300
1/2	08	3 3/4"	1/2"	0.62"	4	2 5/8"	600 psi @ 72° F	300 psi @ 300° F	0000000	000000
Pressure Class 600
1/2	08	3 3/4"	1/2"	0.62"	4	2 5/8"	1,200 psi @ 72° F	840 psi @ 400° F	0000000	00000
316/316L Stainless Steel
NPT
Pressure Class 300
1/2	08	3 3/4"	1/2"	0.62"	4	2 5/8"	600 psi @ 72° F	300 psi @ 300° F	0000000	00000
Pressure Class 600
1/2	08	3 3/4"	1/2"	0.62"	4	2 5/8"	1,200 psi @ 72° F	840 psi @ 400° F	0000000	000000

High-Pressure Steel Unthreaded Pipe Flanges

Forged for extra strength, these heavy duty flanges can withstand high-pressure applications. Bolt two flat-surface flanges or two raised-surface flanges of the same size together with a gasket (sold separately) to create an access point in a pipe line.

Butt-weld flanges are also known as weld-neck flanges; the flange neck has a beveled end that, when flush to pipe, creates a trough for a strong weld.

Slip-on weld flanges have no internal stop; slide a pipe through the flange and weld on both sides.

Socket-connect flanges have an internal stop that supports the pipe when welding and prevents the pipe from sliding all the way through.

Stub-end flanges are also known as lap-joint flanges; use them with a stub-end straight adapter (not included). The stub-end straight adapter slides into the flange and welds to pipe (not the flange). Since the flange isn’t welded to the pipe, it can be disconnected easily for frequent cleaning and inspecting.

Cap flanges are also known as blind flanges.

For technical drawings and 3-D models, click on a part number.

Butt-Weld Flanges

Front

Raised Surface on Back

For Use With: Air, Hydraulic Fluid, Natural Gas, Oil, Steam, Water
Pressure Class: See table
Specifications Met: ASTM A105, ASME B16.5
Certification: Material Certificate with Traceable Lot Number and Test Report
Pipe Nipples and Pipe: Use Schedule 80 steel
Fittings: Use Class 3000 and Schedule 80 steel

					Bolt Hole
Pipe Size	Dash Size	Wall Thick.	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure	Max. Steam Pressure	Material		Each
Pressure Class 300
1/2	08	0.147"	3 3/4"	1/2"	5/8"	4	2 5/8"	600 psi @ 72° F	300 psi @ 300° F	Steel	00000000	000000

Slip-On Weld Flanges

Front

Raised Surface on Back

For Use With: Air, Hydraulic Fluid, Natural Gas, Oil, Steam, Water
Pressure Class: See table
Specifications Met: ASTM A105, ASME B16.5
Certification: Material Certificate with Traceable Lot Number and Test Report
Pipe Nipples and Pipe: Use Schedule 80 steel
Fittings: Use Class 3000 and Schedule 80 steel

				Bolt Hole
Pipe Size	Dash Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure	Max. Steam Pressure	Material		Each
Pressure Class 300
1/2	08	3 3/4"	1/2"	5/8"	4	2 5/8"	600 psi @ 72° F	300 psi @ 300° F	Steel	00000000	000000

Socket-Connect Flanges

Front

Raised Surface on Back

For Use With: Air, Hydraulic Fluid, Natural Gas, Oil, Steam, Water
Pressure Class: See table
Specifications Met: See table
Certification: Material Certificate with Traceable Lot Number and Test Report
Pipe Nipples and Pipe: Use Schedule 80 steel
Fittings: Use Class 3000 and Schedule 80 steel

				Bolt Hole
Pipe Size	Dash Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure	Max. Steam Pressure	Material	Specifications Met		Each
Pressure Class 300
1/2	08	3 3/4"	1/2"	5/8"	4	2 5/8"	600 psi @ 72° F	300 psi @ 300° F	Steel	ASME B16.5, ASTM A105	00000000	000000

Stub-End Flanges

Stub-End Flange (Front)

Flat Surface on Back

For Use With: Air, Hydraulic Fluid, Natural Gas, Oil, Steam, Water
Pressure Class: See table
Specifications Met: ASTM A105, ASME B16.5
Certification: Material Certificate with Traceable Lot Number and Test Report
Pipe Nipples and Pipe: Use Schedule 80 steel
Fittings: Use Class 3000 and Schedule 80 steel

Flanges
				Bolt Hole								Straight Adapters
Pipe Size	Dash Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure	Max. Steam Pressure	Material		Each		Each
Pressure Class 300
1/2	08	3 3/4"	1/2"	5/8"	4	2 5/8"	600 psi @ 72° F	300 psi @ 300° F	Steel	00000000	000000	00000000	000000

Caps

Front

Raised Surface on Back

For Use With: Air, Hydraulic Fluid, Natural Gas, Oil, Steam, Water
Pressure Class: See table
Specifications Met: ASTM A105, ASME B16.5
Certification: Material Certificate with Traceable Lot Number and Test Report
Pipe Nipples and Pipe: Use Schedule 80 steel
Fittings: Use Class 3000 and Schedule 80 steel

				Bolt Hole
Pipe Size	Dash Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure	Max. Steam Pressure	Material		Each
Pressure Class 300
1/2	08	3 3/4"	1/2"	5/8"	4	2 5/8"	600 psi @ 72° F	300 psi @ 300° F	Steel	00000000	000000

Medium-Pressure Steel Threaded Pipe Flanges

Front

Raised Surface on Back

For Use With: Air, Natural Gas, Oil, Steam, Water
Pressure Class: See table
Specifications Met: ASTM A105, ASME B16.5
Pipe Nipples and Pipe: Use Schedule 80 steel
Fittings: Use Class 300 or Schedule 80 iron and steel

With better strength than our low-pressure steel flanges, these are for use in medium-pressure applications. Bolt two same-size flanges together with a gasket (sold separately) to create an access point within a line. Flanges are also known as Pressure Class 300 or Pressure Class 600 flanges. Use in noncorrosive environments.

For technical drawings and 3-D models, click on a part number.

			Bolt Hole
Pipe Size	Flange OD	For Bolt Dia.	Dia.	No. of	Bolt Circle Dia.	Max. Pressure	Max. Steam Pressure	Material		Each
NPT
Pressure Class 300
1/2	3 3/4"	1/2"	5/8"	4	2 5/8"	600 psi @ 72° F	300 psi @ 300° F	Steel	00000000	000000