Here's my thoughts... right, wrong, or otherwise... I would have to agree with the posts about accuracy; but add in repeatability. You can be a little bit off on each one, and still be okay, but the farther you get away from either goal, the worse. Take an aluminum cylinder head from a v-8 and the bolts that hold it to the block. You want them about 80-ft lbs each, and you get there gradually, 20, 40, 60, 80, one at a time. If your wrench doesn't know where 80 is, AND can't hit that mark consistently, then you'll end up with a warped head. Even if you only get it to 70, or hit 85, as long as you can be consistent, you can create the even clamping force on all parts of the head.
I remember watch one of the Saturday morning car shows on Speed (TruckU, I think) and they were talking about the same subject - but they were talking about thread lubrication, and what a difference it makes when torquing bolts - Since the initial torque needed to turn a bolt is just for breaking the tension between the threads of the bolt and the hole, any kind of material on the threads can alter the amount of force needed. They were showing different kinds of thread lubricants and threadlockers and how it threw off the readings. One specialized lubricant was for use in drag racing where they do a teardown and rebuild between passes. This is extra slippery so that they can hit their desired torque in one shot. if a regular engine builder tried using this, he would over-torque every time because of the "Lubricity" of it. I believe they broke a bolt on the show with the torque wrench to show this in action. Other threadlockers and anti-seize compounds will have different effects, but mostly all will result in lower friction than a 'dry torque', so they were mostly saying read the directions on the fluid. Some will say to torque 2-3 times, others just one initial torque will do the trick. - JO On Mar 29, 2011, at 8:12 AM, surfswab wrote: > In choosing a torque wrench, it might help to visualize what one > does. Its purpose is to "stretch" a bolt (yeah, they stretch an > infintesimal bit) to its optimum (not maximum) ability to hold parts > together. > > "Optimum" meaning the ideal tightness (ft/lbs) calculated by engineers > to hold particular parts together without risking either the bolt, or > the assembly it joins, failing. > > Put simply -- too tight, things break (the bolt can snap). Too loose, > things break (the assembly can come apart). > > So, the assembly you want to hold together should dictate the quality > and accuracy of the wrench you buy. > > Kurt's pricey one is accurate to +/- 1 percent. The Harbor Freight > cheapy claims +/- 4 percent. > > > > > -- > You received this message because you are subscribed to the Google Groups > "Nighthawk Motorcycle Lovers!" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/nighthawk_lovers?hl=en. > -- You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/nighthawk_lovers?hl=en.
