A U-bolt takes four answers: its bend shape, its thread size, the inside width, and the leg length. Easy enough — except for one twist in how round-bend U-bolts are named that sends most wrong orders out the door. Let’s clear that up first.
A round-bend U-bolt is sized to the nominal pipe it wraps — and nominal pipe size isn’t the actual measurement. A “2-inch” pipe is really 2.375″ across the outside. So if you measure 2-3/8″ inside your U-bolt and ask for a “2-3/8″ U-bolt,” you’ll get the wrong one. Tell us the pipe size it goes around (or what it’s clamping), and the trap disappears.
A U-shaped curve. For round pipe and tube. Sized by the pipe it fits.
Two right angles. For square tube, angle iron, and timbers. Sized by inside width & height.
A flat bottom with rounded corners. A middle ground for larger pipe and special fits.
Inside width — the gap between the two legs, measured on the inside. For a round bend this is the inside diameter; for a square bend it’s the inside width of the opening.
Leg length — measured from the inside of the bend to the end of the leg. This sets how deep it reaches and how much thread you have to work with.
Thread size — the diameter and pitch of the threaded ends (for example ½–13). Measure it like any bolt, or see how to measure a fastener.
If you’re wrapping standard pipe, give us the pipe size — not the outside diameter you measured. Here’s how the two line up for common sizes:
| Nominal pipe size | Actual outside diameter |
|---|---|
| 1/2″ | 0.840″ |
| 3/4″ | 1.050″ |
| 1″ | 1.315″ |
| 1-1/4″ | 1.660″ |
| 1-1/2″ | 1.900″ |
| 2″ | 2.375″ |
| 2-1/2″ | 2.875″ |
| 3″ | 3.500″ |
| 4″ | 4.500″ |
Standard pipe (NPS) outside diameters. Notice none of them match their name — that’s the whole trap. If you measured an OD that’s close to one of these, that’s your pipe size.
Bring the U-bolt, or whatever it’s clamping, to either counter. We’ll match the bend, size, and thread in a minute — and steer you clear of the pipe-size trap. Or call and we’ll walk through the four answers with you.
