Lap Joint Stub End Dimensions
A stub end butt welds to the pipe and provides the lapped face that a lap joint flange bolts against. Only the stub end touches the process. The backing flange stays loose behind the lap and never sees the fluid.
Why the pair exists.
Because the backing flange is not wetted, it can be a cheaper material than the pipe. On stainless or alloy systems that is the whole point: a stainless stub end with a carbon steel backing flange gives the corrosion resistance where it matters, at a fraction of the cost of a solid alloy flange.
Bolt holes that swing.
The loose backing flange rotates freely until the joint is made up, so bolt holes can be aligned on site without rotating the pipe. On large-diameter and awkward field fit-ups that alone can justify the joint, which is why lap joints are common on tank nozzles and equipment connections that come apart regularly.
113 sizes across 6 schedules · dimensions in inches, weights in pounds · ASME B16.9
Schedule STD
| Nom. Pipe Size | Outside Dia. (Max.) | Outside Dia. (Min.) | Wall & Lap Thickness | Lap Diameter | Fillet Radius | Overall Length (Long) | Pipe Schedule Number | Approx. Weight in Pounds |
|---|---|---|---|---|---|---|---|---|
| ½ | 0.896 | 0.809 | 0.109 | 1.38 | 0.12 | 3.00 | 40 | 0.30 |
| ¾ | 1.106 | 1.019 | 0.113 | 1.69 | 0.12 | 3.00 | 40 | 0.40 |
| 1 | 1.376 | 1.284 | 0.133 | 2.00 | 0.12 | 4.00 | 40 | 0.75 |
| 1¼ | 1.716 | 1.629 | 0.140 | 2.50 | 0.19 | 4.00 | 40 | 1.10 |
| 1½ | 1.965 | 1.869 | 0.145 | 2.88 | 0.25 | 4.00 | 40 | 1.25 |
| 2 | 2.456 | 2.344 | 0.154 | 3.62 | 0.31 | 6.00 | 40 | 2.25 |
| 2½ | 2.966 | 2.844 | 0.203 | 4.12 | 0.31 | 6.00 | 40 | 3.50 |
| 3 | 3.596 | 3.469 | 0.216 | 5.00 | 0.38 | 6.00 | 40 | 4.75 |
| 3½ | 4.096 | 3.969 | 0.226 | 5.50 | 0.38 | 6.00 | 40 | 6.00 |
| 4 | 4.593 | 4.469 | 0.237 | 6.19 | 0.44 | 6.00 | 40 | 7.25 |
| 5 | 5.683 | 5.532 | 0.258 | 7.31 | 0.44 | 8.00 | 40 | 12.00 |
| 6 | 6.743 | 6.594 | 0.280 | 8.50 | 0.50 | 8.00 | 40 | 16.00 |
| 8 | 8.743 | 8.594 | 0.322 | 10.62 | 0.50 | 8.00 | 40 | 23.00 |
| 10 | 10.913 | 10.719 | 0.365 | 12.75 | 0.50 | 10.00 | 40 | 36.00 |
| 12 | 12.913 | 12.719 | 0.375 | 15.00 | 0.50 | 10.00 | * | 47.00 |
| 14 | 14.170 | 13.969 | 0.375 | 16.25 | 0.50 | 12.00 | 30 | 35.40 |
| 16 | 16.180 | 15.969 | 0.375 | 18.50 | 0.50 | 12.00 | 30 | 44.80 |
| 18 | 18.190 | 17.969 | 0.375 | 21.00 | 0.50 | 12.00 | * | 57.20 |
| 20 | 20.240 | 19.969 | 0.375 | 23.00 | 0.50 | 12.00 | 20 | 71.00 |
| 24 | 24.240 | 23.969 | 0.375 | 27.25 | 0.50 | 12.00 | 20 | 102.00 |
Schedule XS
| Nom. Pipe Size | Outside Dia. (Max.) | Outside Dia. (Min.) | Wall & Lap Thickness | Lap Diameter | Fillet Radius | Overall Length (Long) | Pipe Schedule Number | Approx. Weight in Pounds |
|---|---|---|---|---|---|---|---|---|
| ½ | 0.896 | 0.809 | 0.147 | 1.38 | 0.12 | 3.00 | 80 | 0.38 |
| ¾ | 1.106 | 1.019 | 0.154 | 1.69 | 0.12 | 3.00 | 80 | 0.51 |
| 1 | 1.376 | 1.284 | 0.179 | 2.00 | 0.12 | 4.00 | 80 | 1.00 |
| 1¼ | 1.716 | 1.629 | 0.191 | 2.50 | 0.19 | 4.00 | 80 | 1.25 |
| 1½ | 1.965 | 1.869 | 0.200 | 2.88 | 0.25 | 4.00 | 80 | 1.75 |
| 2 | 2.456 | 2.344 | 0.218 | 3.62 | 0.31 | 6.00 | 80 | 3.00 |
| 2½ | 2.966 | 2.844 | 0.276 | 4.12 | 0.31 | 6.00 | 80 | 4.50 |
| 3 | 3.596 | 3.469 | 0.300 | 5.00 | 0.38 | 6.00 | 80 | 6.50 |
| 3½ | 4.096 | 3.969 | 0.318 | 5.50 | 0.38 | 6.00 | 80 | 7.75 |
| 4 | 4.593 | 4.469 | 0.337 | 6.19 | 0.44 | 6.00 | 80 | 9.50 |
| 5 | 5.683 | 5.532 | 0.375 | 7.31 | 0.44 | 8.00 | 80 | 17.00 |
| 6 | 6.743 | 6.594 | 0.432 | 8.50 | 0.50 | 8.00 | 80 | 23.00 |
| 8 | 8.743 | 8.594 | 0.500 | 10.62 | 0.50 | 8.00 | 80 | 32.00 |
| 10 | 10.913 | 10.719 | 0.500 | 12.75 | 0.50 | 10.00 | 60 | 53.00 |
| 12 | 12.913 | 12.719 | 0.500 | 15.00 | 0.50 | 10.00 | * | 62.00 |
| 14 | 14.170 | 13.969 | 0.500 | 16.25 | 0.50 | 12.00 | * | 89.00 |
| 16 | 16.180 | 15.969 | 0.500 | 18.50 | 0.50 | 12.00 | 40 | 96.00 |
| 18 | 18.190 | 17.969 | 0.500 | 21.00 | 0.50 | 12.00 | * | 112.00 |
| 20 | 20.240 | 19.969 | 0.500 | 23.00 | 0.50 | 12.00 | 30 | 125.00 |
| 24 | 24.240 | 23.969 | 0.500 | 27.25 | 0.50 | 12.00 | * | 151.00 |
Schedule 40
| Nom. Pipe Size | Outside Dia. (Max.) | Outside Dia. (Min.) | Wall & Lap Thickness | Lap Diameter | Fillet Radius | Overall Length (Long) | Pipe Schedule Number | Approx. Weight in Pounds |
|---|---|---|---|---|---|---|---|---|
| ½ | 0.896 | 0.809 | 0.109 | 1.38 | 0.12 | 3.00 | 40 | 0.30 |
| ¾ | 1.106 | 1.019 | 0.113 | 1.69 | 0.12 | 3.00 | 40 | 0.40 |
| 1 | 1.376 | 1.284 | 0.133 | 2.00 | 0.12 | 4.00 | 40 | 0.75 |
| 1¼ | 1.716 | 1.629 | 0.140 | 2.50 | 0.19 | 4.00 | 40 | 1.10 |
| 1½ | 1.965 | 1.869 | 0.145 | 2.88 | 0.25 | 4.00 | 40 | 1.25 |
| 2 | 2.456 | 2.344 | 0.154 | 3.62 | 0.31 | 6.00 | 40 | 2.25 |
| 2½ | 2.966 | 2.844 | 0.203 | 4.12 | 0.31 | 6.00 | 40 | 3.50 |
| 3 | 3.596 | 3.469 | 0.216 | 5.00 | 0.38 | 6.00 | 40 | 4.75 |
| 3½ | 4.096 | 3.969 | 0.226 | 5.50 | 0.38 | 6.00 | 40 | 6.00 |
| 4 | 4.593 | 4.469 | 0.237 | 6.19 | 0.44 | 6.00 | 40 | 7.25 |
| 5 | 5.683 | 5.532 | 0.258 | 7.31 | 0.44 | 8.00 | 40 | 12.00 |
| 6 | 6.743 | 6.594 | 0.280 | 8.50 | 0.50 | 8.00 | 40 | 16.00 |
| 8 | 8.743 | 8.594 | 0.322 | 10.62 | 0.50 | 8.00 | 40 | 23.00 |
| 10 | 10.913 | 10.719 | 0.365 | 12.75 | 0.50 | 10.00 | 40 | 36.00 |
| 12 | 12.913 | 12.719 | 0.406 | 15.00 | 0.50 | 10.00 | 40 | 52.00 |
| 14 | 14.170 | 13.969 | 0.438 | 16.25 | 0.50 | 12.00 | 40 | 73.00 |
| 16 | 16.180 | 15.969 | 0.500 | 18.50 | 0.50 | 12.00 | 40 | 97.00 |
| 18 | 18.190 | 17.969 | 0.562 | 21.00 | 0.50 | 12.00 | 40 | 126.00 |
| 20 | 20.240 | 19.969 | 0.594 | 23.00 | 0.50 | 12.00 | 40 | 147.00 |
| 24 | 24.240 | 23.969 | 0.688 | 27.25 | 0.50 | 12.00 | 40 | 205.00 |
Schedule 80
| Nom. Pipe Size | Outside Dia. (Max.) | Outside Dia. (Min.) | Wall & Lap Thickness | Lap Diameter | Fillet Radius | Overall Length (Long) | Pipe Schedule Number | Approx. Weight in Pounds |
|---|---|---|---|---|---|---|---|---|
| ½ | 0.896 | 0.809 | 0.147 | 1.38 | 0.12 | 3.00 | 80 | 0.38 |
| ¾ | 1.106 | 1.019 | 0.154 | 1.69 | 0.12 | 3.00 | 80 | 0.51 |
| 1 | 1.376 | 1.284 | 0.179 | 2.00 | 0.12 | 4.00 | 80 | 1.00 |
| 1¼ | 1.716 | 1.629 | 0.191 | 2.50 | 0.19 | 4.00 | 80 | 1.25 |
| 1½ | 1.965 | 1.869 | 0.200 | 2.88 | 0.25 | 4.00 | 80 | 1.75 |
| 2 | 2.456 | 2.344 | 0.218 | 3.62 | 0.31 | 6.00 | 80 | 3.00 |
| 2½ | 2.966 | 2.844 | 0.276 | 4.12 | 0.31 | 6.00 | 80 | 4.50 |
| 3 | 3.596 | 3.469 | 0.300 | 5.00 | 0.38 | 6.00 | 80 | 6.50 |
| 3½ | 4.096 | 3.969 | 0.318 | 5.50 | 0.38 | 6.00 | 80 | 7.75 |
| 4 | 4.593 | 4.469 | 0.337 | 6.19 | 0.44 | 6.00 | 80 | 9.50 |
| 5 | 5.683 | 5.532 | 0.375 | 7.31 | 0.44 | 8.00 | 80 | 17.00 |
| 6 | 6.743 | 6.594 | 0.432 | 8.50 | 0.50 | 8.00 | 80 | 23.00 |
| 8 | 8.743 | 8.594 | 0.500 | 10.62 | 0.50 | 8.00 | 80 | 32.00 |
| 10 | 10.913 | 10.719 | 0.594 | 12.75 | 0.50 | 10.00 | 80 | 63.00 |
| 12 | 12.913 | 12.719 | 0.688 | 15.00 | 0.50 | 10.00 | 80 | 87.00 |
| 14 | 14.170 | 13.969 | 0.750 | 16.25 | 0.50 | 12.00 | 80 | 123.00 |
| 16 | 16.180 | 15.969 | 0.844 | 18.50 | 0.50 | 12.00 | 80 | 161.00 |
| 18 | 18.190 | 17.969 | 0.938 | 21.00 | 0.50 | 12.00 | 80 | 205.00 |
| 20 | 20.240 | 19.969 | 1.031 | 23.00 | 0.50 | 12.00 | 80 | 251.00 |
| 24 | 24.240 | 23.969 | 1.219 | 27.25 | 0.50 | 12.00 | 80 | 359.00 |
Schedule 160
| Nom. Pipe Size | Outside Dia. (Max.) | Outside Dia. (Min.) | Wall & Lap Thickness | Lap Diameter | Fillet Radius | Overall Length (Long) | Pipe Schedule Number | Approx. Weight in Pounds |
|---|---|---|---|---|---|---|---|---|
| ½ | 0.896 | 0.809 | 0.188 | 1.38 | 0.12 | 3.00 | 160 | 0.75 |
| ¾ | 1.106 | 1.019 | 0.219 | 1.69 | 0.12 | 3.00 | 160 | 0.95 |
| 1 | 1.376 | 1.284 | 0.250 | 2.00 | 0.12 | 4.00 | 160 | 1.13 |
| 1¼ | 1.716 | 1.629 | 0.250 | 2.50 | 0.19 | 4.00 | 160 | 1.51 |
| 1½ | 1.965 | 1.869 | 0.281 | 2.88 | 0.25 | 4.00 | 160 | 2.02 |
| 2 | 2.456 | 2.344 | 0.344 | 3.62 | 0.31 | 6.00 | 160 | 4.51 |
| 2½ | 2.966 | 2.844 | 0.375 | 4.12 | 0.31 | 6.00 | 160 | 6.02 |
| 3 | 3.596 | 3.469 | 0.438 | 5.00 | 0.38 | 6.00 | 160 | 8.80 |
| 4 | 4.593 | 4.469 | 0.531 | 6.19 | 0.44 | 6.00 | 160 | 14.10 |
| 5 | 5.683 | 5.532 | 0.625 | 7.31 | 0.44 | 8.00 | 160 | 26.40 |
| 6 | 6.743 | 6.594 | 0.719 | 8.50 | 0.50 | 8.00 | 160 | 36.40 |
| 8 | 8.743 | 8.594 | 0.906 | 10.62 | 0.50 | 8.00 | 160 | 60.00 |
| 10 | 10.913 | 10.719 | 1.125 | 12.75 | 0.50 | 10.00 | 160 | 113.00 |
| 12 | 12.913 | 12.719 | 1.312 | 15.00 | 0.50 | 10.00 | 160 | 160.00 |
| 14 | 14.170 | 13.969 | 1.406 | 16.25 | 0.50 | 12.00 | 160 | 190.00 |
| 16 | 16.180 | 15.969 | 1.594 | 18.50 | 0.50 | 12.00 | 160 | 245.00 |
| 18 | 18.190 | 17.969 | 1.781 | 21.00 | 0.50 | 12.00 | 160 | 309.00 |
| 20 | 20.240 | 19.969 | 1.969 | 23.00 | 0.50 | 12.00 | 160 | 379.00 |
| 24 | 24.240 | 23.969 | 2.344 | 27.25 | 0.50 | 12.00 | 160 | 542.00 |
Schedule XXS
| Nom. Pipe Size | Outside Dia. (Max.) | Outside Dia. (Min.) | Wall & Lap Thickness | Lap Diameter | Fillet Radius | Overall Length (Long) | Pipe Schedule Number | Approx. Weight in Pounds |
|---|---|---|---|---|---|---|---|---|
| ½ | 0.896 | 0.809 | 0.294 | 1.38 | 0.12 | 3.00 | * | 1.75 |
| ¾ | 1.106 | 1.019 | 0.308 | 1.69 | 0.12 | 3.00 | * | 2.50 |
| 1 | 1.376 | 1.284 | 0.358 | 2.00 | 0.12 | 4.00 | * | 4.00 |
| 1¼ | 1.716 | 1.629 | 0.382 | 2.50 | 0.19 | 4.00 | * | 6.25 |
| 1½ | 1.965 | 1.869 | 0.400 | 2.88 | 0.25 | 4.00 | * | 6.50 |
| 2 | 2.456 | 2.344 | 0.436 | 3.62 | 0.31 | 6.00 | * | 9.00 |
| 2½ | 2.966 | 2.844 | 0.552 | 4.12 | 0.31 | 6.00 | * | 14.00 |
| 3 | 3.596 | 3.469 | 0.600 | 5.00 | 0.38 | 6.00 | * | 18.50 |
| 4 | 4.593 | 4.469 | 0.674 | 6.19 | 0.44 | 6.00 | * | 27.50 |
| 5 | 5.683 | 5.532 | 0.750 | 7.31 | 0.44 | 8.00 | * | 39.00 |
| 6 | 6.743 | 6.594 | 0.864 | 8.50 | 0.50 | 8.00 | * | 54.00 |
| 8 | 8.743 | 8.594 | 0.875 | 10.62 | 0.50 | 8.00 | * | 73.00 |
| 10 | 10.913 | 10.719 | 1.000 | 12.75 | 0.50 | 10.00 | 140 | 116.00 |
| 12 | 12.913 | 12.719 | 1.000 | 15.00 | 0.50 | 10.00 | 120 | 167.00 |
Materials We Supply
Lap Joint Stub End to ASME B16.9 in the grades below. Tell us the service and we will confirm the right one.
| Material | Specification | Typical Service |
|---|---|---|
| Carbon Steel | ASTM A234 WPB / WPC | General process, steam, oil and gas gathering and utility lines |
| Low-Temp Carbon Steel | ASTM A420 WPL6 | Cold service to −50°F; LNG and northern pipeline work |
| Chrome-Moly Alloy | ASTM A234 WP11 / WP22 / WP91 | Elevated temperature; refinery heaters, power plant steam |
| Stainless Steel | ASTM A403 WP304/304L, WP316/316L | Corrosive service, chemical, food and beverage, water treatment |
| Duplex & Super Duplex | ASTM A815 UNS S31803 / S32750 | Chloride and seawater service, offshore, desalination |
Common Questions
What is a lap joint stub end?
A short butt weld fitting with a lapped face. It welds to the pipe and provides the sealing face, while a separate lap joint backing flange slides over it and carries the bolting. Only the stub end contacts the process fluid.
Why use a stub end and backing flange instead of a weld neck flange?
Cost and alignment. The backing flange never touches the fluid, so it can be carbon steel behind a stainless or alloy stub end. It also rotates freely, so bolt holes line up on site without turning the pipe.
What is the difference between long and short pattern stub ends?
Overall length. The tables above list the standard pattern with its overall length J. Confirm which pattern your flange and spool arrangement assumes before ordering, since the two are not interchangeable in a fixed spool.
