Bolts To Avoid
by Duane Raleigh
Externally threaded sleeve anchors
We really gave Taper Bolts a chance, setting dozens of them in their optimum substrate, hard rock. We tried to set the bolts by "feel," just as you would when climbing. Half the time we got it right and the 3/8inch Taper Bolts held up to 3000 pounds in a straight pull out. But we blew it with the other half and the bolts slid out of the hole at only 700 pounds. Worse yet, we couldn't tell the good placements from the bad until we ripped them all out.
The Wejit Anchor Bolt is another variety of torque bolt, bur fortunately most climbers have more sense than to use it. This anchor has two pushwires running down the shaft that culminate in a pair of tangs that splay out when you crank the bolt down. Tested in shear, the 3/8inch Wejit Anchor Bolt held around 2600 pounds in hard rock but broke or pulled out at an average of 1300 pounds in tensile.
Rickety and somewhat expensive at $2 each, there's no excuse for ever using a Dryvin. If you see a star icon on a nail head that's embedded in a sleeve, yank the sucker out and put in a real bolt.
Stud bolts can be strong in hard rock, but suffer from several maladies that make them unsuited to rock climbing. First, you have to drill the hole to an exact depth to make sure the expansion pin engages the stud. Second, the exposed threads on these bolts makes them subject to work fatigue. Third, you can't remove or countersink these anchors without destroying the rock around them. And last, you can't buy studs in stainless steel.
In medium rock these bolts pull out around 700 pounds. In hard rock the "bit" dulls easily and usually two or three are needed to finish the hole. But, in most cases, climbers only drill the bolt half-way before they become frustrated with the system and stop; leaving a hideously weak and botched bolt. Even when placed correctly the strongest self drilled bolt only holds 3000 pounds shear - which is not much considering the amount of effort required to drill the hole and the other superior bolts available.
Editors Note: Be aware this article was written for rockclimbers and all comments may not apply to the cave environment. Being sedimentary rock, limestone is generally soft. Make sure the bolt you choose is designed for the hardness of rock into which it is to be placed.
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