Why U-Bolt body is thinner than thread part?


Why U-Bolt body is thinner than thread part?

    Hi, I hope you are doing well! Today, I would like talk about amazing thing of U-Bolts which used for locking round pipe, also Square U-Bolt which used for locking square pipe.

    As many of you may already know that body part of U-Bolt(The part without threads) is made to be thinner than thread diameter but why bolt, screw or other fasteners are often made with the same diameter for both thread and body part?


Thin legs (Body part) are very easy to make!

Actually, to make body part to be thin it needed completely different method unlike making same diameter as thread and body part.

To make a U-Bolts, there are 2 main processes, 1. Make a double-sided screw 2. Bend the screw

The process of making screw thread is the point, when we rolling the thread, I will become slightly bigger from its original diameter. So thinner body screw part is easier to make.

                Illustration as below shown the rolling process (Even it was a hex bolt but U-bolt also the same). Even with large diameter, it can make thread process very fast in mass production. In Japan, most of bending factory ought to have rolling machine, so even with small quantity of special size, they can produce fasteners quickly with competitive cost.

What is lower diameter of rolling?

    It is a diameter of the material before rolling. For example, to make M10 screw, we are going to use a round bar with outside diameter of 8.97 to 8.91. Then when it rolled, the part which pressed by dies will be squeeze and it will expand into M10 thread system (Outer diameter 9.96mm to 9.77mm). Please see rolling diameter table as below,

What if you need screw body to be the same, how to do?

    On the other hand, if you need screw body part to be the same as screw outer diameter, I will take more effort with it by using round bar with the same diameter as the screw outer diameter.

                Then how to make thread to be the same size as body part? It need at least 2 processes to make thread, first is to first toll thread part then lathe it to make it thinner, then roll it, or cut thread my machining. This complication made this way gain higher cost.


    U-bolts can be seen commonly in our daily life but there are some technical knowledge required to make the gain cost competitive and good quality. If you are planning to produce U-bolt, U-shaped bolts, or double-sided screw, and etc. Yon can make it at competitive cost with quicker delivery time if narrow body part is allowed.

Thank you for your time reading our article, I hope this will helpful for everyone who are in manufacturing unit.