Torque vs Clamp. Challenge the status quo my friends!
Torque is the best measure of strength! Isn't it? Or maybe not....as I like to say, Torque is cheap but Huck is forever!
I would like to share some life altering information with you. Over the years, design engineers across the globe have focused on a stable, consistently tight joint for long-term durability and vibration resistance in the heavy equipment and transport industry. At the same time, torque has long been the standard by which the tightness, and overall integrity of joints were measured (just a hint...this is not correct!). This conventional thinking is based upon the idea that if an individual or machine applies more power to a nut and bolt assembly in the form of torque, the tighter, more secure, and vibration resistant the joint. And as it turns out, like a lot of conventional thinking, the belief that higher torque resulted in a more secure and durable joint was wrong and we can prove it!
Torque- A brief explanation in technical terms
Torque, as it relates to fasteners, is the twisting force required to spin a nut along the thread of a bolt. The basic formula for this is
where T= Torque in Foot Pounds, D= Nominal Diameter in Inches, P= Desire Clamp Load or Tension in Pounds, and K= Coefficient of Friction. The problem with this equation is that K is extremely hard to predict or measure, since it can be impacted by a wide range of variables such as surface texture, oil, rust, debris, type of thread, material, and even humidity. Another element in the joining equation, tension, is the stretch or elongation of a bolt that provides the clamp on the joint. A further explanation would define tension as the load on the joint brought about by drawing the fastener components together. Critical to the joining process, tension, is for the most part unrelated to torque. Interesting eh? At best, torque is an indirect measurement of the tension applied to the bolt.
This method of measurement is fundamentally flawed in its basic formula as a result of the wide range of variables.
But alas, not all is ruined! Because there is another unit of measure with much greater accuracy available and we are going to share the secret with you to help you ensure your projects are engineered to the best and most accurate specifications!
Clamp – The Real Measure of Joint Integrity. And the crucial ingredient to secure vibration resistant fastening
Clamp, defined as the load on a joint brought about by the drawing together of the fastener components, is virtually unrelated to torque. Say what???? Ongoing studies of clamp using sophisticated Skidmore-Wilhelm pre-load test equipment have clearly established that even when torque between two or more nuts and bolts is absolutely the same, the clamp value of a standard nut/bolt combination can vary more than 30%...not exactly what you would call a precise measurement is it?
By comparison, a HuckBolt® lockbolt will vary 5% or less. This is an important point, given the fact that clamp is the critical element in joint integrity and durability. And with that, I leave you with food for thought. The status quo has been challenged for once and for all! I have faith you will ensure your next specs use clamp rather than torque as the measurement of joint strength! Happy engineering my dear friends.
Oh and PS, we have a wide range of HUCKBOLTS in stock in our Edmonton warehouse to help with your next prototype or project!