McMaster-Carr logo
    Filter by
    Pressure Class
    Industrial Info Snippet
    Connects To
    Pipe Material
    System of Measurement
    Fitting Type
    Flanged Connection Surface
    Number of Bolt Holes
    Thread Type
    Fitting Material
    Pipe Schedule
    Industrial Info Snippet
    For Use With
    For Flange Pipe Size
    Industrial Info Compare
    Gender
    For Fitting Schedule
    Industrial Info Snippet
    Flange Type
    U.S.–Mexico–Canada Agreement (USMCA) Qualifying
    DFARS Specialty Metals
    Export Control Classification Number (ECCN)
    Industrial Info Snippet
    Forward
    Enter e-mail addresses in the fields below
    Message
    Cancel
    Print
    How can we improve?
    Comments
    E-mail address (if you would like a response)
    54 Products
    About Pipe and Fittings
    industrial info icon

    Measure your pipe and fittings to identify their pipe size, thread size, schedule, and thread type. Then, find compatible components.

    Fitting Type

    Threading

    Low-Pressure Aluminum Unthreaded Pipe Flanges

    Also known as Pressure Class 125 flanges, these are for use in low-pressure applications. Bolt two same-size flanges together with a gasket (sold separately) to create an access point within a line. Flanges are aluminum, which is lightweight with good corrosion resistance.
    Flanges
    Image of Product. Front. Front orientation. Pipe and Fittings. Low-Pressure Aluminum Unthreaded Pipe Flanges, Flanges, Butt Weld, Flat Surface.
    Image of Product. Flat Surface on Back. Back orientation. Pipe and Fittings. Low-Pressure Aluminum Unthreaded Pipe Flanges, Flanges, Butt Weld, Flat Surface.

    Front

    Flat Surface

    on Back

    Butt-Weld Fitting Connection—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 Fitting Connection—Slip-on weld flanges have no internal stop; slide a pipe through the flange and weld on both sides.
    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.
    Each
    Butt Weld
    1/2
    		1/2
    		Flat3 1/2"1/2"5/8"42 3/8"125
    		356 Aluminum150 psi @ 72° F44705K543000000
    3/4
    		3/4
    		Flat3 7/8"1/2"5/8"42 3/4"125
    		356 Aluminum150 psi @ 72° F44705K54400000
    1
    		1
    		Flat4 1/4"1/2"5/8"43 1/8"125
    		356 Aluminum150 psi @ 72° F44705K54500000
    1 1/2
    		1 1/2
    		Flat5"1/2"5/8"43 7/8"125
    		356 Aluminum150 psi @ 72° F44705K547000000
    2
    		2
    		Flat6"5/8"3/4"44 3/4"125
    		356 Aluminum150 psi @ 72° F44705K548000000
    2 1/2
    		2 1/2
    		Flat7"5/8"3/4"45 1/2"125
    		356 Aluminum150 psi @ 72° F44705K549000000
    3
    		3
    		Flat7 1/2"5/8"3/4"46"125
    		356 Aluminum150 psi @ 72° F44705K551000000
    4
    		4
    		Flat9"5/8"3/4"87 1/2"125
    		356 Aluminum150 psi @ 72° F44705K552000000
    6
    		6
    		Flat11"3/4"7/8"89 1/2"125
    		356 Aluminum150 psi @ 72° F44705K553000000
     
    Slip-On Weld Female
    1/2
    		1/2
    		Flat3 1/2"1/2"5/8"42 3/8"125
    		356 Aluminum150 psi @ 72° F44705K3700000
    3/4
    		3/4
    		Flat3 7/8"1/2"5/8"42 3/4"125
    		356 Aluminum150 psi @ 72° F44705K3800000
    1
    		1
    		Flat4 1/4"1/2"5/8"43 1/8"125
    		356 Aluminum150 psi @ 72° F44705K36100000
    1 1/4
    		1 1/4
    		Flat4 5/8"1/2"5/8"43 1/2"125
    		356 Aluminum150 psi @ 72° F44705K36200000
    1 1/2
    		1 1/2
    		Flat5"1/2"5/8"43 7/8"125
    		356 Aluminum150 psi @ 72° F44705K36300000
    2
    		2
    		Flat6"5/8"3/4"44 3/4"125
    		356 Aluminum150 psi @ 72° F44705K36400000
    2 1/2
    		2 1/2
    		Flat7"5/8"3/4"45 1/2"125
    		356 Aluminum150 psi @ 72° F44705K36500000
    3
    		3
    		Flat7 1/2"5/8"3/4"46"125
    		356 Aluminum150 psi @ 72° F44705K36600000
    4
    		4
    		Flat9"5/8"3/4"87 1/2"125
    		356 Aluminum150 psi @ 72° F44705K367000000
    6
    		6
    		Flat11"3/4"7/8"89 1/2"125
    		356 Aluminum150 psi @ 72° F44705K542000000
    8
    		8
    		Flat13 1/2"3/4"7/8"811 3/4"125
    		356 Aluminum150 psi @ 72° F44705K772000000
     
    Reducing Flanges
    Image of ProductInUse. Slip-On Weld. Side1 orientation. Contains Annotated. Pipe and Fittings. Low-Pressure Aluminum Unthreaded Pipe Flanges, Reducing Flanges, Slip-On Weld Female, Flat Surface.
    Image of Product. Front. Front orientation. Pipe and Fittings. Low-Pressure Aluminum Unthreaded Pipe Flanges, Reducing Flanges, Slip-On Weld Female, Flat Surface.
    Image of Product. Flat Surface on Back. Back orientation. Pipe and Fittings. Low-Pressure Aluminum Unthreaded Pipe Flanges, Reducing Flanges, Slip-On Weld Female, Flat Surface.

    Slip-On Weld

    Front

    Flat Surface

    on Back

    Reducing flanges allow you to transition your system to a smaller pipe size; attach to a flange with a larger pipe size but with the same flange dimensions.
    Slip-on-Weld Fitting Connection—Slip-on weld flanges have no internal stop; slide a pipe through the flange and weld on both sides.
    Bolt
    Hole
    Pipe Size
    (A)
    For Flange
    Pipe Size (B)
    Flanged Connection
    Surface (B)
    Flange
    OD
    For Bolt
    Dia.
    Dia.
    No.
    Of
    Bolt Circle
    Dia.
    Pressure
    Class
    Material
    Max. Pressure
    @ Temp.
    Each
    Slip-On Weld Female
    3
    		4
    		Flat9"5/8"3/4"87 1/2"125
    		356 Aluminum150 psi @ 72° F44705K7680000000
    6
    		8
    		Flat13 1/2"3/4"7/8"811 3/4"125
    		356 Aluminum150 psi @ 72° F44705K771000000
     
    Blind Flanges
    Image of Product. Front. Front orientation. Pipe and Fittings. Low-Pressure Aluminum Unthreaded Pipe Flanges, Blind Flanges, Flanged, Flat.
    Image of Product. Flat Surface on Back. Back orientation. Pipe and Fittings. Low-Pressure Aluminum Unthreaded Pipe Flanges, Blind Flanges, Flanged, Flat.

    Front

    Flat Surface

    on Back

    Bolt
    Hole
    Pipe
    Size
    Flanged Connection
    Surface
    Flange
    OD
    For Bolt
    Dia.
    Dia.
    No.
    Of
    Bolt Circle
    Dia.
    Pressure
    Class
    Material
    Max. Pressure
    @ Temp.
    Each
    Flanged
    1/2
    		Flat3 1/2"1/2"5/8"42 3/8"125
    		356 Aluminum150 psi @ 72° F44705K531000000
    3/4
    		Flat3 7/8"1/2"5/8"42 3/4"125
    		356 Aluminum150 psi @ 72° F44705K53200000
    1
    		Flat4 1/4"1/2"5/8"43 1/8"125
    		356 Aluminum150 psi @ 72° F44705K53300000
    1 1/4
    		Flat4 5/8"1/2"5/8"43 1/2"125
    		356 Aluminum150 psi @ 72° F44705K53400000
    1 1/2
    		Flat5"1/2"5/8"43 7/8"125
    		356 Aluminum150 psi @ 72° F44705K53500000
    2
    		Flat6"5/8"3/4"44 3/4"125
    		356 Aluminum150 psi @ 72° F44705K53600000
    2 1/2
    		Flat7"5/8"3/4"45 1/2"125
    		356 Aluminum150 psi @ 72° F44705K53700000
    3
    		Flat7 1/2"5/8"3/4"46"125
    		356 Aluminum150 psi @ 72° F44705K538000000
    4
    		Flat9"5/8"3/4"87 1/2"125
    		356 Aluminum150 psi @ 72° F44705K539000000
    6
    		Flat11"3/4"7/8"89 1/2"125
    		356 Aluminum150 psi @ 72° F44705K541000000
    8
    		Flat13 1/2"3/4"7/8"811 3/4"125
    		356 Aluminum150 psi @ 72° F44705K399000000
     

    Low-Pressure Aluminum Threaded Pipe Flanges

    Also known as Pressure Class 125 flanges, these are for use in low-pressure applications. Bolt two same-size flanges together with a gasket (sold separately) to create an access point within a line. Flanges are aluminum, which is lightweight with good corrosion resistance.
    Flanges
    Image of Product. Front. Front orientation. Pipe and Fittings. Low-Pressure Aluminum Threaded Pipe Flanges, Flanges, Flanged Fitting Connection, Threaded Fitting Connection, Female, Flat Surface.
    Image of Product. Flat Surface on Back. Back orientation. Pipe and Fittings. Low-Pressure Aluminum Threaded Pipe Flanges, Flanges, Flanged Fitting Connection, Threaded Fitting Connection, Female, Flat Surface.

    Front

    Flat Surface

    on Back

    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.
    Each
    NPT Female
    1/2
    		1/2
    		Flat3 1/2"1/2"5/8"42 3/8"125
    		356 Aluminum150 psi @ 72° F44705K228000000
    3/4
    		3/4
    		Flat3 7/8"1/2"5/8"42 3/4"125
    		356 Aluminum150 psi @ 72° F44705K22900000
    1
    		1
    		Flat4 1/4"1/2"5/8"43 1/8"125
    		356 Aluminum150 psi @ 72° F44705K23100000
    1 1/4
    		1 1/4
    		Flat4 5/8"1/2"5/8"43 1/2"125
    		356 Aluminum150 psi @ 72° F44705K23200000
    1 1/2
    		1 1/2
    		Flat5"1/2"5/8"43 7/8"125
    		356 Aluminum150 psi @ 72° F44705K23300000
    2
    		2
    		Flat6"5/8"3/4"44 3/4"125
    		356 Aluminum150 psi @ 72° F44705K23400000
    2 1/2
    		2 1/2
    		Flat7"5/8"3/4"45 1/2"125
    		356 Aluminum150 psi @ 72° F44705K23500000
    3
    		3
    		Flat7 1/2"5/8"3/4"46"125
    		356 Aluminum150 psi @ 72° F44705K23600000
    4
    		4
    		Flat9"5/8"3/4"87 1/2"125
    		356 Aluminum150 psi @ 72° F44705K238000000
    6
    		6
    		Flat11"3/4"7/8"89 1/2"125
    		356 Aluminum150 psi @ 72° F44705K437000000
    8
    		8
    		Flat13 1/2"3/4"7/8"811 3/4"125
    		356 Aluminum150 psi @ 72° F44705K745000000
     
    Reducing Flanges
    Image of Product. Front. Front orientation. Pipe and Fittings. Low-Pressure Aluminum Threaded Pipe Flanges, Reducing Flanges, Flanged Fitting Connection, Threaded Fitting Connection, Female, Flat Surface.
    Image of Product. Flat Surface on Back. Back orientation. Pipe and Fittings. Low-Pressure Aluminum Threaded Pipe Flanges, Reducing Flanges, Flanged Fitting Connection, Threaded Fitting Connection, Female, Flat Surface.

    Front

    Flat Surface

    on Back

    Reducing flanges allow you to transition your system to a smaller pipe size; attach to a flange with a larger pipe size but with the same flange dimensions.
    Bolt
    Hole
    Pipe Size
    (A)
    For Flange
    Pipe Size (B)
    Flanged Connection
    Surface (B)
    Flange
    OD
    For Bolt
    Dia.
    Dia.
    No.
    Of
    Bolt Circle
    Dia.
    Pressure
    Class
    Material
    Max. Pressure
    @ Temp.
    Each
    NPT Female
    1/2
    		3/4
    		Flat3 7/8"1/2"5/8"42 3/4"125
    		356 Aluminum150 psi @ 72° F44705K712000000
    3/4
    		1
    		Flat4 1/4"1/2"5/8"43 1/8"125
    		356 Aluminum150 psi @ 72° F44705K71500000
    1
    		1 1/4
    		Flat4 5/8"1/2"5/8"43 1/2"125
    		356 Aluminum150 psi @ 72° F44705K71800000
    1 1/4
    		1 1/2
    		Flat5"1/2"5/8"43 7/8"125
    		356 Aluminum150 psi @ 72° F44705K72100000
    1 1/2
    		2
    		Flat6"5/8"3/4"44 3/4"125
    		356 Aluminum150 psi @ 72° F44705K72400000
    2
    		2 1/2
    		Flat7"5/8"3/4"45 1/2"125
    		356 Aluminum150 psi @ 72° F44705K72700000
    2
    		3
    		Flat7 1/2"5/8"3/4"46"125
    		356 Aluminum150 psi @ 72° F44705K733000000
    3
    		4
    		Flat9"5/8"3/4"87 1/2"125
    		356 Aluminum150 psi @ 72° F44705K736000000
    4
    		6
    		Flat11"3/4"7/8"89 1/2"125
    		356 Aluminum150 psi @ 72° F44705K739000000
    6
    		8
    		Flat13 1/2"3/4"7/8"811 3/4"125
    		356 Aluminum150 psi @ 72° F44705K742000000
     
    back to top