Bolting techniques

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This article explains the basics for bolting and the equipment and tools that you will want to get if you ever want to start bolting canyoneering/caving routes.

Bolt Wars

This article does not want to discuss if bolting is right or not. Bolting is like religion: some strongly believe in it, some strongly reject it. The Canyoneering community engaged a few years ago in the so called "Bolt wars" where individuals of both sides engaged in verbal attack onto each other. Even the National Park Service is confused on this topic: while bolting is forbidden in Death Valley National Park, rangers themselves have bolted canyons in Arches National Park to protect the rock from rope abrasion. In general, most of Utah/Arizona bolting is heavily criticized and bolts get routinely chopped off by locals that do not believe in bolting. This is because most of the canyons in these regions DO NOT HAVE RUNNING WATER and solving anchor technical problems represents most of the thrill for these descents. However, in the rest of the Canyoning/Canyoneering world where canyons have running water bolting is considered the safest, least intrusive and most aesthetically appealing solution for technical routes. In the Caving community everyone assumes that if someone placed a bolt it's because it was needed and nobody will ever chop out bolts placed by someone else just because they think they were unnecessary.


You SHOULD use a Rotatory Hammer drill in order to drill granite, dense basalt and other hard rocks. Without a hammer drill you may not even chip the rock. Recommended drills, each has pros and cons:

This is the lightest drill available on the market and is powered by a steady hand and lots of muscle
The rotary motion is provided by hand, repeating the motion of smashing the drill with a hammer and then turning the bit 45 degrees many times
It can take from 15 to 30 minutes to drill a 1" in limestone or soft volcanic and 30 to 45 minutes for 1" hole in granite or dense basalt
Given the time requirements, this drill is frequently used only to save emergency situations and almost solely with Spit bolts
The Milwaukee M12 12v rotary hammer drill is the most compact hammer drill available on the market.
This drill weights 3.5 lbs, is half the size of the Bosch drill and fits inside a small 5L dry bag.
The batteries are smaller than a child fist and weight 7.2 ounces but bigger batteries are also available.
It will drill a 3" hole in about 15 seconds, not as fast as the Bosch but still awesome.
On long approaches one can easily carry the drill, 5 batteries, all bolts, 200 feet rope, wetsuit and all technical gear in one single pack.
This drill can be operated with one single hand while hanging on tiptoes over a raging hydraulic
Recommended for small teams (2-4 people), constricted environments, moderate bolting with small size bolts
The Bosch 11536C 36v rotary hammer drill is the most powerful medium size drill available on the market.
It can spank a 6" hole in granite or volcanic rock in maybe 15 seconds, a real energy/time saver.
At 6.25lbs, this drill is almost twice as heavy as the Milwaukee. Each battery weights 2lbs.
On long approaches you will definitely want to split drill, batteries and bolts among different people.
This drill cannot be operated with one single hand or while hanging in precarious locations.
Recommended for medium size teams (4-6 people), lots of bolting with big size bolts

Tips for using a rotary hammer drill:

  • drills are not waterproof, double dry bag drills for water canyons
  • drill in short bursts and take breaks
  • possibly lubricate the tip with water now and then to cool it off
  • if using the Bosch drill on hard rock, drill with slower speeds and do NOT press too hard with the drill because it will actually cancel out the hammer action
  • if using the Milwaukee on hard rock, lean heavily on the drill in short bursts to help the (weak) hammer action and help the bit penetrate the rock
  • frequently remove the dust from the hole, half way drilling and especially right before hammering in the bolt
  • clean hole with a pipe brush in wet environment or blowing with a straw in dry environment
  • even when using a drill you still need a hammer to put in bolts

Drill Bits

You MUST use carbide tip bits to drill granite, dense basalt and other hard rocks. Without a carbide tip you will most likely melt the bit.

  • Petzl/Hilti: Hilti carbide bits and considered by many the best bits available on the market for drilling rock. They are expensive. Petzl resells Hilti bits.
  • Bosh Xtreme: they are extremely tough bits sold for drilling in reinforced concrete (with embedded steel bars), they can drill into anything and last a very long time.
  • Bosch SDS Bulldog bits: they are about $20 and as far as how long they last, it depends. They are pretty tough, 20-30 holes is a wild guess.

Tips for choosing a bit:

  • Make sure to get SDS bit, as most rotary hammers only accept SDS. Manual drills usually also accept SDS.
  • Make sure they are long enough but not too long, they should be at least 4" deep but no longer than 7"
  • Make sure they are the right size for the bolts you plan to place, metric or imperial units are different and will not fit each other
  • Standard sizes: 1/2" & 3/8" imperial, 12mm & 10mm metric

Bolts & Hangers

You SHOULD always use stainless steel bolts and hangers. "Plated" or "Anodized" steel is NOT the same as "Stainless" steel. Steel bolts will rust over time, even in dry canyons. Rain and air humidity will sip in the hole and inevitably rust the part of the bolt inside the rock. The bolt may look good from the outside but one day may break without warning with disastrous consequences. Stainless steel will never rust, the bolt may start spinning some day but will never suddenly break.

  • Single Bolt Stations: It's common to use "single bolt stations" for first descents in order to economize gear (you don't want to run out of bolts half way down the descent) and also because given the uncertainty of the route bolt placement may likely be improved on a second trip. However be aware bolts cannot be easily inspected and can fail without any warning, especially when ascending the rope. So ALWAYS back up any single bolt station for the first 2 or 3 people using them and convert them into a "double bolt station" on a future trip.
  • Dual Bolt Stations: this is two bolts placed at least 10 inches apart and joined with a load sharing system made out of webbing or chain. This is the recommended setup for popular canyoneering routes or for caving routes that require ascending the rope.
  • Spit: A spit bolt requires a shallow hole (30mm 1"1/4) and are the preferred setup when using a manual drill. It takes between 30 to 45 minutes to drill a hole manually, they are not very strong and should ALWAYS be backed up.
  • Expansion bolts: Expansion/Wedge bolts require deep holes (3" to 6") and a mechanic rotary drill. These are stronger and safer anchors than Spits, with double expansion bolts being safer than single expansion bolts.
  • Standard brands: Fixe and Powers are the high quality standard for rock anchors, but most stainless steel bolts rated for climbing will also work well. Petzl resells Fixe and Spit bolts.
  • Standard sizes: 1/2" & 3/8" imperial, 12mm & 10mm metric. Minimum length should be 3", with 4" or longer recommended for weak rock.

Tips for placing bolts:

  • Before drilling, locate a proper place for the bolts that fits with the rappel line and has reasonable flat surface around it
  • Hammer the rock all around the prospect location and notice different sounds and vibrations that mark where rock is stronger - If there's a Hollow sound: Find a better location
  • Make sure there is big enough flat area for the hanger to seat flat against the rock when aligned with the direction of pull
  • Drill holes perpendicular to the rock surface, preferably with a direction of pull aligned 90 degrees with the hole
  • Spits: DO NOT drill above the length of the bolt (1"1/4). Expansion Bolts: you MUST drill above the length of the bolt
  • Put on hangers AFTER hammering the bolts in, and make sure to tighten expansion bolts well
  • A 6" adjustable wrench can be useful to fit multiple size bolts and also the screw links (maillon rapide)
  • Petzl tam tam hammer incorporates a Ø13mm hex socket on the end but only works for 10mm spits, it does not work for expansion bolts.


Standard practice is generally to join two bolts together with webbing an an anchor ring on the end and then thread rope through the anchor ring. When placing webbing on standard bolt hangers, one may wish to consider webbing on bolt hangers.

A WEBBINGLESS anchor is preferred for locations subject to occasional massive floods, this will avoid the webbing to catch on floating debris that may destroy the bolts. Rope may be threaded directly through bolts with large, rounded heads such as the Petzl Collinox or the Wave Bolt. Standard bolt installations can be converted to webbingless anchors by adding very large maillon rapides to the bolt hangers. If large rapides are not available, two maillon rapides linked to each other (minimalistic chain) may be used instead, this will give the rope and block 360 degree of movement and facilitate the pull down.