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Hand-drilling an emergency anchor
Escape Systems
Hand drilling an emergency anchor
If you’re climbing a little-traveled big wall, or venturing into soft-rock climbing areas like Utah’s San Rafael Reef (see story on page 34), you may want to carry an emergency bolt kit—and know how to use it. Here’s the lowdown.
THE BOLT KIT (fig. 1)A basic bolt kit consists of a hammer, drill holder, drill bits, blow tube (a short length of 1/4-inch plastic tubing), nylon hole brush (try a test-tube brush), correctly sized wrench for your bolts, and slings and rings to rig your anchors. Carry everything but the hammer in a sturdy satchel that can be rigged for hauling or clipped to your harness. Climbing bolts should be stainless steel and 3/8-inch or 1/2-inch in diameter. For hand drilling in solid granite and other hard rock, a 2 1/2-inch bolt is appropriate. In theory, longer bolts are not much stronger than shorter bolts, but they sometimes reach through a soft outer layer to firmer stone. Rarely, bolts fail by “dinner-plating” off a chunk of surface rock, and a long bolt makes this less likely. Most significant, hand-drilled holes are inherently sloppy, especially in soft rock, and a deeper hole tends to be tighter where the bolt grips.Wedge-style bolts, such as the excellent Fixe line, are simpler to use and stronger than sleeve bolts of the same diameter, as long as the rock is hard enough for them to tighten. In soft rock, 1/2-inch-diameter Rawl 5-piece sleeve bolts are the anchor of choice. Even if you choose to use the faster-to-place 3/8-inch sleeve bolts for sandstone, all soft-rock bolts should be at least 3 1/2 inches long. Just as you would not lead on the cheap, spooled nylon cord from the next aisle over, never use generic hardware-store anchors for climbing.
Sometimes, in very soft rock, no mechanical bolt will tighten properly. Then, just as in the early days of desert climbing, angle pitons driven deeply into drilled holes become your weapon. “Drilled angle” anchors are directional; just like a nut, they have little direct pullout strength. This makes them dangerous when treated like conventional bolts, and because of this they have fallen out of favor. Nevertheless, a few angle pitons up to 3/4-inch, carried in addition to your standard bolts, can save the day in super-soft sandstone.
The bits in an emergency drill kit should be brand new and sharp. I carry a drill that accepts SDS bits, for ease of bit change-out; other systems use easy-to-lose set screws or jam-prone tapered shanks, and the bits are harder to find. Regardless of shank style, look for a rock bit with a pair of carbide “wings” at the tip, with the fluted portion of the bit slightly thinner, so the bit doesn’t bind—a serious problem when drilling in hard rock. The downside of a “wing-tip” bit is that it wobbles more easily, risking sloppy holes.
PLACING AN ANCHOR (fig. 2)Positioning the bolts. If you are starting a rappel anchor from scratch, look for a clean panel of rock where you can set two bolts level with each other and 8 to 12 inches apart. You’re seeking sound, smooth rock where the hanger can sit flat. Place anchors well above ledges (head-height or more) to ease pulling rappel ropes. If you’re adding a bolt to an old anchor, locate any new hole at least 8 inches away from existing bolts.
Choose the best stone. Doublecheck that you’ve chosen solid, monolithic rock by tapping with your hammer. Listen for dull or hollow sounds that betray spongy or honeycombed rock, or invisible plates. Don’t drill into a block or flake, and stay at least 8 inches away from fractures or sharp arêtes.
Drilling the hole. A hand drill is a rotating chisel. The threads do not cut; rather, the drill’s tip chips away at the bottom of the hole. So don’t waste a lot of effort twisting the bit. Instead, turn the chisel point just a few degrees after each strike. Strike firmly: more than a tap, but not as hard as if driving a framing nail. Use your blow tube to clean the hole periodically; then you can also rest your arm and check your progress.
A good bolt hole is perpendicular to the rock surface and has a uniform diameter from bottom to top. Take special care drilling the first inch. Don’t change the bit’s angle or let it wobble; this will flare the hole and may prevent the bolt from tightening properly when you place it.
Finish strong. Holding the drill straight feels easier as you go deeper, but don’t get lazy and rest the bit against the edge of the hole—you’ll ruin your good work. Drill the hole at least 1/4-inch deeper than the length of the bolt, then blow out the dust, brush the hole with a test-tube brush, and blow again. Grit on the walls of the hole is a common reason bolts don’t tighten.
If you’re new to this process, allow at least half an hour to drill a 3/8- by 2 1/2- inch bolt in Yosemite granite, or a 1/2- by 4-inch bolt in desert sandstone.
Placing the bolt. With a hanger prefitted on the bolt shaft, set the bolt in the hole. For normal sleeve and wedge-type expansion bolts, this should require firm tapping with the hammer. If it doesn’t, or you can pull the bolt back out with your fingers, the hole is too big and the bolt will not tighten properly. Re-drill the hole at a larger diameter if you’re carrying bigger bolts—or start over. If you have to start over, you can pound small rocks into your botched hole to partially conceal your sorry failure (or, better, patch it properly with epoxy and grit).
When the hanger is flush against the rock, tighten the bolt’s hex head until it feels very snug with a small wrench—typically three to four full turns. The bolt just needs to bite firmly; overtightening will not make it stronger. If the bolt starts to tighten but then begins to spin, you can sometimes increase the bite by clipping a sling to the hanger and pulling out as you tighten. If the bolt still spins in its hole as you turn the wrench, the placement is botched. Remove the hanger and pull or bury the stud. Never leave a botched “death” bolt that looks OK.
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The following anchor supplies should allow you to equip two separate twobolt anchor stations, with a little room for error.For granite, gneiss, or hard sandstones:
- (4) 3/8 x 2 1/2-inch stainless wedge bolts
- (1) 3/8 x 3 1/2-inch stainless wedge bolt
- (1) 1/2 x 2 1/2-inch stainless sleeve bolt
- (4) stainless hangers
For desert sandstone and other soft rock:
- (2) 3/8 x 3 1/2-inch stainless sleeve bolts
- (2) 1/2 x 4-inch stainless sleeve bolts
- (1) 1/2-inch angle piton
- (1) 5/8-inch angle piton
- (1) 3/4-inch angle piton
- (4) stainless hangers
For more information on everything about bolting, check the American Safe Climbing Association website: safeclimbing.org.
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