Design & analysis expertise in mobile equipment & bolted joints
A recent thread on a Mustang forum involved a question about the number of threads required to safely secure cast aluminum wheels. The original poster said he had 6 1/4 lug nut turns on his rear wheel studs and 8 1/2 turns on the front wheels. Most of the responders opined that this was insufficient …
Typically, with a nut and bolt you rely on approximately 15% metal-to-metal contact in the threads. Therefore, 85% of the inter-thread space is open and can be filled and bonded by anaerobic thread locking materials. They also provide excellent sealing against most liquids. Thread lockers can also prevent or reduce galvanic corrosion between dissimilar metals, …
Engineers occasionally run across situations where bolted joints have “loosened” even when head and/or nut positions have been marked with scratches or paint. This is known as “non-rotational loosening”. Several things can cause that. First of all, the components within the grip of the fastener must be checked for yielding (embedment or creep), causing “joint …
(Changing topics this time, the following is my response to an inquiry by a Harley rider as to expected belt drive system life on his H-D motorcycle.) Before answering your question, I need to mention that the condition of the 32-tooth transmission output sprocket controls belt life to a much greater degree than the 70-tooth …
Rules-of-thumb for thread engagement typically advise: For a steel nut member: 1 – 1 ½ times the fastener diameter should be engaged and for aluminum nut members: 2 – 2 ½ times the fastener diameter should be engaged. But these guidelines frequently result in over-designed joints and sometimes these full-thread lengths just aren’t available in …
(and how does this affect the nut factor?) The terms “bolt“ and “capscrew” are commonly used interchangeably. But the variations between the two are fairly significant from a manufacturing perspective and assembly standpoints. What’s the difference? Why does it matter? A bolt is designed for insertion through holes in assembled parts to mate with a …
Since bolts and nuts stretch slightly under load, the distribution of stress on the threads is not uniform. Theoretically, the first thread takes a third of the load, the first three threads take three-quarters of the load, and the first six threads take nearly the whole load. The percentage of total load carried by engaged …
T = k*Fi*d is the “short form” calculation to determine required installation torque, where T is the target installation torque in in-lbs; Fi is the initial preload; and d is the nominal bolt diameter. Seems like a simple, turn-the-crank calculation at first. The bolt size, d, can be “guesstimated” for an initial design calculation. Initial …