setting bolt torque

[Chads93GT]

Like tightening any bolt, there is a recommended torque setting to fully engague the anchor. If I remember right from the bolts that I have bought, its around 20-25 ft/lbs torque. My question is, how do you guys guage this in cave? If i were at home building an engine on my engine stand, I would be building with a torque wrench. Bringing that into a cave isn't quite...........realistic. Granted, on the bolts that I have set, I have only used a small hand wrench to tighten them down and I know from experience that I can't get too much torque out of that.

Obviously over torquing the bolt could cause it to start pulling itself out of the wall, right?

I just wondered if you guys also sipmly guage how tight they are by tightening them down by hand.

I have a bolt climb to do in our project cave soon and since I will have all my weight on each single bolt as I progress up the wall, I was wondering other peoples techniques.

[Scott McCrea]

I just go by feel. You can try setting a couple bolts above ground with a torque wrench to almost the what you need then add the little bit with your cave wrench. Then measure it again with your torque wrench. But it also depends on the quality of the rock and placement. Ultimately, you need to simply get it tight, but not too tight... or too loose

[Mudduck]

My vertical experience is kept to the simple stuff so bolt setting is not my speciallty with respect to rock, however, aviation and engine building are. I would use the "torque angle" method". In relating this to engines think of rod caps or mains or even some head bolts. As I'm sure you know performance bolts are tightend to a "stretch" rather than a torque(rod bolts anyway). Since measuring stretch on a blind fasterner is not very practical(or possible in some apps) what is often used is a torque angle gauge between the wrench and fastener. The nut or bolt is tightened to a pre determined point of contact then tightened "X" number of degrees(rotationaly speaking) further, "X" being determined by the application, intended strength and required loading which is further based on tension or shear loads or both.This "X' has been calculated in a lab setting to produce the desired stretch and is duplicateable due to the known compression values of the materials involved. As you know rock density is not consistant(although the "type" area chosen to bolt should be of an assumed minimum strength to carry the applied load) that being said if you had a rock close by on the surface typical of what you'll be bolting you could simply drill the bolt hole, drive it in, run the nut to firm contact with your hand then torque the bolt to 25 ft lbs starting at say a 6 or 12 oclock position while observing the stopping point that torque is achieved. Duplicating this in the field should get you plus or minus 3 lbs everytime. If the bolt pulls through obviously its no good. Also if while approaching the "torque angle" you've predertermined, you feel the nut tighten to a point and is not getting any tighter and you have a fair amount of rotation left before reaching the "angle" you can assume the rock will not hold the torque and the fastener has failed. Think of it as your stripping the threads of a poor quality nut (or over torqueing one) as your tightening and the nut begins to strip you'll feel a peak in tension before you actually reach the desired tightness. If the peak occurs or continues to climb as you reach your angle of torque, you can assume the fastener is good. If you do this several times and actually over-torque to the point of overloading you'l rapidly get a feel for this. The main advantage of the torque angle method is it eliminates the variable of friction from the equation of desired tightness(cause by dirt, mud etc..). Right or wrong, overcomplicated or not this is how I'll do it when I get to a cave I need to bolt

[Chads93GT]

I guess I could always drill a test hole at the bottom of the dome, but then again, that would require a torque wrench in the cave. I put bolts on top of a 98' drop maybe 1/2 mile away, around the same depth underground, that is easily accessable. I could always test those and I did them by hand with no fear.

[Mudduck]

If you do decide to carry a torque wrench in a cave to do some test bolts, I believe Craftsman still sells the older style manual wrench with a pointer. They used to offer a 250 inch lb that was fairly compact and the pointer type would not be affected by dirt. Also the only calibration required is the pointer to be set at zero before starting. While that is only 20. something ft lbs that would get you pretty darn close. They also have a ft lb model that goes signifigantly higher if you wanted to torque to failure just for knowledge. If you try this please post the failure point(I'm curious).

[PeterFJohnson]

I have a bolt climb to do in our project cave soon and since I will have all my weight on each single bolt as I progress up the wall, I was wondering other peoples techniques.

In my humble experience, bounce testing your bolts should give you some idea if they will hold body weight. But if you take a lead fall the bolt will have to sustain a force far greater than body weight.

As for torque angles etc., I am all for standardization and consistency, but I am not sure the rock will cooperate...

[Chads93GT]

I have a bolt climb to do in our project cave soon and since I will have all my weight on each single bolt as I progress up the wall, I was wondering other peoples techniques.

In my humble experience, bounce testing your bolts should give you some idea if they will hold body weight. But if you take a lead fall the bolt will have to sustain a force far greater than body weight.

As for torque angles etc., I am all for standardization and consistency, but I am not sure the rock will cooperate...

Luckily we have a 30' extension ladder 2.5 miles into the cave, and about a 35 minute easy walk down the main river trunk to the dome in question. I plan on taking the ladder up as high was we can and setting a bolt at the floor to tie the bottom of the ladder down with (the "floor" has a meandering channel cutting it in half thats 20 feet deep) so i dont want the ladder to slip down it in. Anyway that will bring us withing 8 or 10 feet of the bottom of the canyon passage in which will give us access to the passage. Anyway I only need to set 3 or 4 bolts in the wall to safely get where we want to go and the first 2 I can drill while still on the ladder. If there is another climb further up this canyon (the ceiling of the dome is 98 feet over head and tree roots hang down 60' from the ceiling) we can haul the ladder up further from here since we have it.

Thanks for the tips.

[Extremeophile]

I've heard that if you use a short handled wrench (about the width of your hand) that it's difficult to over-torque, but I haven't verified this with a torque wrench.

[Chads93GT]

yeah i dont think i could overtorque a 3/8" bolt (10mm) with a short wrench either so im not really worried about it, hehe.

[chh]

Chad, it sounds like you turn a wrench fairly often, so I'd think you'd be ok to guess it. And really, if you're carrying a 6 or 8" wrench with you, you'll tighten it down fairly snuggly, but you won't have to hang on it to get 25 ft/lbs.
It also sounds like you won't be setting that many bolts because of your "head start", but when setting your first one from a height, you obviously want to make sure that the first 2 are bomber. Look around at the rock quality especially well here. Just because you're standing on the top of the ladder doesn't mean that's necessarily the best place to put your protection. If the rock/placement quality is better a little further down, start there. On longer climbs you may encounter differences in rock quality and you may need an assortment of bolt sizes. You also may want an assortment if you're climbing more than a few placements to save time and energy. Use your longer, stronger bolts only every few placements and use shallower bolts, spits, pitons, natural gear, etc. for the intermediate placements. Using spits inbetween todays more "standard" bolt sizes brings about a change in hardware compatibility, and you'll have to make the call there as to whether or not you want to deal with this. If you have a power drill I'd avoid this, but using shallower bolts of the same diameter in between longer bolts will save the battery and you'll get more placements out of it without having to change out bits or get the hammer out.
Good luck!
-caleb

[Chads93GT]

One of our guys just aquired a ton of pitons. If there is anywhere to put them on this wall, i would be suprised. I don't think there are any cracks and its all solid. I have 3 3/8" bolts that I use for rigging drops. I assume something like a 2" or 2.5" bolt would be ok for every other bolt? I realize the top of the ladder may or may not be the best spot to start at, but I will make that call when I get up there I guess. I still have some more bolts to buy and fixe anchor plates to buy before we start this. It will be my first bolt climb, but it will be rather short and I am personally not worried about it. The risk vs reward in this situation may add on quite a bit of footage to our cave, and if this leads to a giant stair step up to the ceiling channel, 150' above the stream, then I think its worth it.

I do turn wrenches often. Built a few cars in my day and I have snapped several bolts in half due to overtorquing. But when you are torquing down a 20 pound clutch bolt with a 2.5' long torque wrench and you accidentally set it to 40#................you tend to break stuff. I dont have that fear in a cave with a 6" wrench by far. Thanks for the advice. I really appreciate it.

[chh]

I assume something like a 2" or 2.5" bolt would be ok for every other bolt?

I would think that if the rock quality was good, that would be more than sufficient.

[Chads93GT]

Well.........as far as the quality goes..........it sure does look hard!

[jharman2]

I've heard that if you use a short handled wrench (about the width of your hand) that it's difficult to over-torque, but I haven't verified this with a torque wrench.

Exactly! Confast recommends a torque of 25-30 ft-lbs for a 3/8" wedge anchor.

http://www.confast.com/products/technic ... nchor.aspx

Assuming you have a 6" lever arm, you need to apply 50-60lbs of force to the bolt to reach that torque. You should have a pretty good idea of when you are pulling around 60lbs. Think of picking up a 60lb dumbell with one hand. It's not a trivial load.

[hunter]

Typical wisdom is to pull as hard as you can (one handed) with a short wrench without doing a huge amount of extra bracing. This usually works out to be about the right torque. Easy to test on the surface.

On worry about failing:
-If you over torque a wedge type bolt sufficiently it will usually break at the narrow point just behind the head (not pull out). This is a good way of removing most of the bolt if you need to.
-It is VERY important to get the bolt set by tightening it hard. I have personally had one bolt pull out when it wasn't tightened enough and know of a couple of others. This is frequently, but not always, related to leaving a lot of dust in the hole.
-Once a bolt is set it doesn't seem to matter so much that the nut remains perfectly tight. A very large number of bolts on rock climbs end up as "spinners" where the hanger spins around the stud but they still catch falls fine.
-If the rock is "bad" (usually too soft) the bolt will never set and as you tighten the nut it will continue to pull out. The softer the rock the more turns it typically takes for the bolt to set.