This edition of the Fastener Training Minute with Carmen Vertullo was originally published February 15, 2018 as “How to use a torque wrench correctly” during episode 125 of Fully Threaded Radio.
Hi everybody, this is Carmen Vertullo at the Carver FACT Center in San Diego, California and the Fastener Training Institute with your Fastener Training Minute.
We’ve been talking about torque wrenches these past couple of episodes, and we have dealt with some general things, some things about torque wrenches from high altitude point of view. Today, we’re going to kind of zoom in and look at one particular aspect of torque wrench use, and it identifies and helps prevent one of the main errors that torque wrench users make. And that is applying too much torque on the initial pull, and then when it comes time to do the final torque, they can’t overcome the torque that’s already on the nut or the the bolt head. I’m going to tell you how to prevent that and some ways that you can train people to do it, and we will do that when we come back in just a minute.
So welcome back, its Carmen Vertullo with the Fastener Training Minute and we are talking about torque wrench usage. One of the things that we must take into consideration when we use a torque wrench, is that there’s going to be a certain amount of friction or force or torque that must be overcome to get the nut or bolt head or screw head in motion. Now, if we start with the fully loosened condition, it just starts moving right away, but at some point chances are we’re going to stop before we reach the final torque. It’s very important that we don’t stop close to the final torque because it will take a certain amount of force to get that nut restarted. I’m going to call that the restart torque. To ensure that we don’t get too close to the final torque when we do our restart torque, it’s important that we apply maybe only about 50% of the final torque.
So if the torque requirement is 100 foot pounds, we’re going to maybe apply 50 foot pounds on the first go and then make sure that the last 50 pounds of force is applied with a torque wrench fully in motion when the wrench clicks or beeps or the needle gets to where it’s supposed to be. We want the torque wrench to be in motion. If for example like some specifications require that we would torque up to 75%, there’s a chance that when we go to apply that final torque the nut is not even going to move because the final torque won’t be enough to get it on moving from it’s already seated position. So we just want to be careful when we use torque wrenches, that at the end of the process the wrench is in motion when that click or that deep or that needle hits its point. This is part of torque wrench training. That’s what we’re going to talk about next time.
This has been Carmen Vertullo with the Fastener Training Minute talking about torque wrench usage. Thank you for listening.