Reprint from LINK, Summer 2020
A number of years ago I owned an old John Deere tractor that was clearly showing its age. As I tooled around my yard cutting the grass I noticed that the engine was laboring more and more and it was consistently blowing oily blue smoke from the exhaust. I knew it was time to either retire the tractor or rebuild the engine. Although I had never done it before, I decided I would try my hand at rebuilding the engine.
Reprint from Hardware & Fastener Components Magazine, Vol. 51
What are Tension Control Bolts?
Tension Control Bolts have a domed head, body, threads, and a splined tip known as the Pin Tail. (See Figure 1) Tension Control Bolts are part of the structural bolting family given by ASTM F3125. Like the other structural bolt variations, these come in two different types, regular and weathering steel and two different strength grades, 125,000 psi and 150,000 psi. The 125,000 psi version is considered Grade A325 and marked as A325TC or A325TC depending on whether it is Type 1 (regular steel) or Type 3 (weathering steel), respectively. The 150,000 psi version is considered Grade A490 and marked as A490TC or A490TC depending on whether it is Type 1 or Type 3, respectively.
Reprint from China Fastener World Magazine, Vol. 190
Heat treating fasteners is a complicated topic with many details to keep track of. The following are some questions and answers that should shed some light on basic concepts.
Reprint from Fastener World Magazine, Vol. 174
To understand why fasteners are manufactured to different strength levels, one must first understand how a fastener is intended to work. To work properly, a fastener must possesses some elasticity and stretch as it is tightened. For many this is counterintuitive because, for example, a large 1” diameter steel bolt hardly seems like an item that would stretch. However, stretch it must if it is going to function the way it was intended.
Figure 1 illustrates a demonstration that one can use to understand the behavior of a bolted joint. To conduct this demonstration, one places their thumb, index, and middle fingers together, wraps a wide rubber band twice around, and then opens their fingers against the resistance of the rubber band. In the second part of the demonstration a third wrap of the rubber band goes around the fingers and reopening the fingers is, once again, attempted. Individuals attempting this demonstration should notice that with the third wrap in-place the rubber band is much more highly stretched and it becomes significantly more difficult to open the fingers.