U-Bolts Definitions

(A) Thread Diamter Pitch

The diameter refers to the diameter of the bolt thread and does not also imply that the unthreaded part is the same diameter. Refer to our knowledgebase article on Cut-Thread versus Rolled-Thread for more information on this topic. The Thread Pitch indicates a distance between the threads which has different designations using the Imperial Standard (U.S. Standard) versus the Metric Standard. For more in-depth information, refer to our knowledgebase article on Imperial versus Metric Thread measurements. Imperial thread pitches are separated by a hyphen (a dash, “-“) such as ¼”-20 where ¼” is the diameter and “20” represents the number of threads counted in a 1” long thread. This designation may be confusing when fractional diameters with fractional diameters, i.e. 2¼”-4½ if presented 2-1/4”-4-1/2. Metric threads are usually separated by and “x” and may look diameter x pitch x length, i.e. M10 x 1.5 x 20mm . The internal nut threads will always be matched to the external bolt threads. If additional nuts are needed, the Imperial standard UNC-2B should be used except for Hot Dip Galvanized bolts which require Tapped-Oversize nuts due to excessive zinc buildup on the bolts.

(B) Inside Width

The inside width is measured between the threads and not measured between the unthreaded sections. Since U-Bolts are usually made from Rolled-Thread wire, the inside distance between the unthreaded legs will be somewhat wider but should not be considered if the fixture must pass the threads to be fastened in place.

(C) Distance Between Centers

An alternate method for measuring distance is between the U-Bolt centerlines. It is very important to subtract the entire thread diameter (2 halves) from the distance between centers. If this is not done, the U-Bolt will be too small.