Tightening a Bolt

Post by **overhung** » Mon Sep 15, 2003 2:04 pm

Saw a guy a couple of weeks ago with an adjustable wrench hanging from his harness. I asked him about it and he says that if he's on a route with a spinning hangar that he just tightens the nut before going on. Having limited bolting experience I asked him how tight does he tighten the bolt and he said, "as tight as humanly possible. I'm not sure that's a good idea. I tighten loose nuts with my fingers, but that's it. How tight should a bolt be?

Post by **Spragwa** » Mon Sep 15, 2003 2:06 pm

From what my friends Terry and Hugh have told me, tightening them as tight as humanly possible is a BAD idea. Apparently, you can break the bolt way back in the rock and not know it. That's why we're having the route maintenance clinic at Rocktoberfest. I can't tell you how tight to tighten it though because I just don't know.

Post by **the lurkist** » Mon Sep 15, 2003 3:45 pm

According to Tery Kindred, who in addition to putting up more routes in the Red than basically anyone else (including Porter?, I think so), and maintenancing more routes than everyone else put together, is also a certified aircraft mechanic. He know something about specs on metal, metal fatigue, etc.

He says that the number one "shade tree" mechanic mistake is over torquing, or aka over tightening, bolts. The shaft of a bolt is not meant to take a twisting force, but a shear force. The Camming mechanism in the back of the hole is meant to take a pull out force (this refers to mechanical bolts only, not not glue ins- these type rely on chemical bonding with the rock to resist pull out.)

When the over- enthusiasitic climber torques on a nut or bolt head using a 9 in or 12 in lever arm, this allows him or her to place a huge turquing force (measured in foot pounds). Remember waht Archimedes said " Give me a lever arm long enough and I can move the world".

This is especially damaging to threaded bolts where the threads stick out of the rock with a nut. Here, in this instance, the inner diameter between the threads (in the trough) doesn't have as much steel to absorb the torquing force. These bolts are typically of cheaper, softer steel, too.

I have not personally seen this in the Red, but that may be because most of the routes have gone up by people who know of these pitfalls. In the Morehead district (Cave Run area), there are whole cliffs with cheap bargain basement bolts all over torqued. Terry described easily twisting the heads off some of these bolts with very little effort, clearly much less force than a body weight fall would create. These bolts ae time bombs...

I am teaching a clinic in route maintenance at the Rocktober Fest. See thered.org for details.

Hugh

Post by **Joe Patton** » Mon Sep 15, 2003 4:09 pm

as tight as humanly possible might be an ok answer if the wrench was a very small one that you can't get much torque with. I have a 5 inch long adjustable wrench and as tight as I can pull with it isn't real tight compare to what you can do with a open end wrench.

Post by **Wes** » Mon Sep 15, 2003 4:17 pm

Even really strong SS bolts are only rated to around 100 lbs of torque, whici isn't all that hard to generate. They should be snug, but not over tightened. Over tightning is very bbad.

Wes

Post by **air canada** » Mon Sep 15, 2003 4:24 pm

Unless you know exactly what you're doing, you'd probably want to check out the clinic, or stick with finger tightening.
I was belaying P2U on Stay the Hand a few months ago, and while he's midway up the climb(3-4 bolt) the first bolt wiggles out and draw-bolt-hanger set up is down by my gri-gri, with half the bolt left in the hole. The shaft had snapped. Over torquing is a likely culprit.

Post by **Wes** » Mon Sep 15, 2003 4:28 pm

Yep. While Terry was re-bolting super dario this weekend, serveral of the old bolts snapped under not all that much torque. They were the older, stud type bolts. Now they are nice new 5-piece.

Wes

Post by **Johnny** » Mon Sep 15, 2003 4:56 pm

Rawl recommended 60 pounds of torque for tightening. By my best estimate, with a normal wrench of about 8-10" you are looking at about 60 lbs if you use a nice firm tightening using just arm strength. It's probably not much more than that torque you use to open a vaccuum sealed jar of applesauce.

Post by **the lurkist** » Mon Sep 15, 2003 8:47 pm

Speaking of vacuum seal and applesuace, I know something else that gets 10" of torque. Know what I mean... yuck,yuck..

Post by **the lurkist** » Mon Sep 15, 2003 8:49 pm

Sorry, after sending that I realized that might have sounded a bit immature and juvenile... yeah...