Fully threaded bolt

This post was last edited by ylb913 on 2016-1-9 09:42. Two related statements have been seen: 1. The manufacturing process for fully threaded parts involves extrusion; the middle part of double-ended threads is not machined, resulting in relatively lower strength. These days, threads are all formed by extrusion; a full thread undergoes a single forging process as a whole, whereas the unprocessed portion in the middle of a double-end thread has lower strength. That’s the difference. 2. For fully threaded bolts, the cross-sectional area is the same throughout the bolt, unlike double-headed bolts where there is a significant stress concentration. ——Under the same material conditions, what is the difference between full-thread bolts and double-headed bolts when in use? The manufacturing process for fully threaded fasteners involves extrusion; the middle portion of the threads on stainless steel double-headed bolts is not machined, resulting in relatively lower strength. Fully threaded studs have relatively better flexibility and can withstand higher pressures. First, when version 2009 was introduced for HGT20592～20635 in the 1997 version, the pressure range for equal-length double studs was reduced; then, SHT3404-2013 completely eliminated equal-length double studs... In other words, there is a trend toward discarding equal-length double studs. Under the same material conditions, full-threaded bolts are superior, as the cross-sectional area of the entire bolt is consistent, unlike double-headed bolts which experience significant stress concentration. Full-threaded bolts can replace double-headed bolts, but double-headed bolts cannot replace full-threaded bolts!

For the 320-kilogram pipe flange connections on my end, alloy steel full-threaded connections are also used.

I remember there being a saying that if the thread at one end of the stud is damaged and the nut cannot be screwed in or out, it can be screwed in or out from the other end. Another reason is that when the flanges being connected are relatively thin, it ensures that the flanges are fully compressed after the nuts are tightened. And if the middle section of the stud has no threads and its length exceeds the total thickness of the flange, it is not possible to compress the flange.