A 20mm z-bar does neck to about 13mm prior to failure. Z-bar however does stretch slightly before failure and the failure does exhibit some necking as shown in the below photo. Because of the high strength of steel used in the thru tie bar, if a bar does snap there will be no warning sign. These will generally slip and destroy the thread before the z-bar snaps, and this is because the z-bar nuts are a softer cast steel. The limiting element is typically the z-bar nuts. Generally, z-bar is the strongest element of the thru-tie system. It is however still used because it does provide a small factor of safety and it is rare the safety nut doesn’t work. While we do this regularly, because of the course speed thread on the bar, the second nut can become loose. A safety wing nut behind a wingnut will act as a lock nut – INCORRECT.We do however have machined 90mm z-bar joiners that can be welded. Wingnuts are cast/forged and cannot be welded. We recommend welding a 90mm joiner then inserting the z-bar into the joiner. There is however a weldable z-bar by Dwidag, but it is not of the same strength. It is highly discouraged even with a weld procedure. You cannot weld to z-bar unless there is a specific weld procedure, and it is welded by a competent person. It will snap if trying to deform it like reo unless heat treated. Z-bar accessories and reo accessories are the same – INCORRECT. General reinforcement is ½ the strength of z-bar at only 500MPa.
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