Best practices for bolt placement

by Jason Haas

Bolt quality standards
Drilling and installing a new mechanical bolt
Drilling and installing a new glue-in bolt
Hand drilling
Considerations for developing new routes

Bolt quality standards

The days of using plated steel bolts and hardware-store specials should be a thing of the past. Bolters and re-bolters alike should only be putting in the very best metal available into the rock. A modern bolt should have a life expectancy of 50 years and, currently, plated steel bolts just don’t. The new standard, in most cases, is stainless steel.

Interestingly, plated bolts have a higher torque rating than stainless bolts, which people sometimes interpret to mean that plated bolts are stronger and safer. But this is not completely accurate—especially after the bolt has been exposed to the elements for years.

Using plated steel is cheaper—initially—which can make them seem appealing. However, if the bolt needs to be replaced two, three, or even four times before a stainless counterpart, is it really cheaper in the long run? Also, who’s going to do the replacing? The first ascensionist is motivated to put up the new route, but they may be less motivated to update the hardware on that route. Think long term. Hopefully your children’s children won’t have to replace a bolt you place today.

So plated steel is definitely out, but is stainless always in? To determine the best type of bolt to use at a particular crag, it’s important to know what the environmental conditions are like at that area. The Union Internationale des Associations d’Alpiniisme (UIAA)—the global leader in setting safety standards for climbing gear—has created four categories, or zones, in which climbing areas, and therefore bolts, exist. Each category has special considerations for bolt placement.

It should be noted that the UIAA defines the recommended potential lifespan of a bolt to be 50 years. The UIAA uses that timespan because it is the same benchmark used in the construction industry for safety-critical fasteners by the European Organization for Technical Approvals (EOTA), which defines 50 years as the normal working life of construction products.

  • Class 1 includes high-corrosion zones. These are typically seaside cliffs, like those found in Thailand, Vietnam and Cayman Brac, where the chlorine from the ocean can cause rapid stress corrosion cracking (SCC). But it’s also possible to get SCC in some karst formations, which include limestone and dolomite formations, and therefore, it’s possible to have class 1 areas that are inland. In these high-corrosion zones, SCC can happen extremely quickly, sometimes within a single year, and so climbers need to use titanium grade 2 bolts and the higher end High Corrosion Resistant (HCR) materials.
  • Class 2 is a step below Class 1, and as a result, most of the HCR materials would work. In this zone, SCC may occur in a few bolts per every 1,000 that are 316- or 304-grade stainless steel in a five- to 10-year period. However, it is extremely unlikely that the majority of these bolts would safely last for 50 years, so titanium is best in this class of climbing area as well. An example of a Class 2 area in the U.S. are the crags in Hawaii.
  • Class 3 is defined as all other outdoor climbing areas. Bolts placed in these cliffs need reasonable corrosion resistance, but SCC is not really a concern. For these areas, stainless steel bolts are the standard. Again, that means plated steel bolts are not acceptable.
  • Class 4 is indoor areas, such as climbing gyms.

What kind of stainless steel bolt should I use?
Not all stainless steel bolts are created equal. The UIAA recommends using bolts manufactured out of 316-grade steel, which is not widely available in the U.S., where most bolts and hangers are made of slightly lower-strength 304-grade steel. Petzl is one of the only manufactures making both bolts and hangers of 316-grade steel. Still, 304-grade steel is pretty dang tough and U.S. climbers must find a balance between what is ideal and what is practical and use the best materials available to them. While the goal is to use the absolute best material available, 316-grade steel is not readily available in the U.S. Furthermore 304-grade steel is adequate for climbing routes in the U.S and should be considered the current standard here for stainless steel quality.

You can purchase both wedge bolts and sleeve bolts in stainless steel, but wedge bolts are not as strong as their equivalently sized sleeve bolt counterparts. Because of this, we recommend placing stainless steel five-piece Powers sleeve bolts when drilling in good rock. Those bolts should be a 1/2-inch in diameter unless you are hand drilling in an area where power drills are not allowed or not practical, like a wilderness or backcountry cliff. In that situation, a 3/8-inch stainless steel bolt can be used. In extreme soft-rock circumstances, a slightly larger diameter bolt (or glue-in) may also sometimes be called for.

Bolt length can vary. In bullet-hard granite, 2.75-inch-long bolts are the standard. In weaker rock, like sandstone or most volcanic rock, a longer length of 4.75 inches is better. However, in weaker rock, you may need to use something that has greater holding power than a sleeve bolt, like a glue-in.

A new sustainable option: ClimbTech’s Legacy Bolt
The Legacy Bolt—ClimbTech’s new, stainless steel mechanical sleeve bolt—is designed to be easily removed so that future generations of climbers will be able to re-use the bolt hole without any significant effort. You simply loosen the hex head with a wrench and the whole unit pulls out of the bolt hole, leaving nothing inside. When the time comes, you could then drop in a new Legacy Bolt, tighten it down, and be done with it.

These bolts are pretty expensive (though they come with a hanger), but they would be more sustainable in theory than regular stainless steel five-piece Powers sleeve bolts because they require so little effort to remove. While five-pieces are fully removable, the removal takes effort and not all re-bolters may be willing to do the necessary work instead of just chopping and patching.

If you choose to use Legacy Bolts, there are a couple things to note. First, the proper torque for tightening the bolts is 20 foot-pounds, and if you over-tighten them, they are extremely difficult to get out. Also, the bolts are designed to be placed and removed, not placed and replaced. This distinction is very important because in other words, they’re not designed to be pulled out, checked for corrosion, and then put back in. If you pull one out, be prepared to replace it with a brand new bolt.

Drilling and installing a new mechanical bolt

The vast majority of all bolts being placed in the U.S. today fall under this category. We recommend using a 1/2-inch stainless steel Powers (formerly Rawl) five-piece sleeve bolt over wedge bolts because of their superior strength.

Not sure if this is the best bolt for your climbing area? Check out the section on “Bolt quality standards” described above.

Tools you’ll need:

  • Hammer drill
  • Drill bit and optional backup
  • Blow tube (often a piece of aquarium tubing), hand air pump, or can of compressed air
  • Tube brush
  • Hammer
  • A 9/16-inch ratchet wrench for 1/2-inch bolts
  • Stainless steel bolts

Step 1: Select a good placement. (If re-using the same hole, skip to Step 2.) If you cannot reuse the same hole and must drill a new one, there are a few things to keep in mind. First, the anchoring industry recommends that you space two holes at least 10 anchor diameters (roughly 5 inches for a ½-inch bolt) apart to prevent spalling and splitting of the base material. This spacing should be greater the softer the rock is. Bolts also should not be placed near edges and corners. At least one anchor has failed because the bolts were placed too close to the edge and the weight of the climber fractured off the chunk of rock the anchor was in.

When bolting in roofs and overhangs, look for lower-angled breaks where the outward pull on the bolt will be less severe. Also, make sure that there are no small protrusions that will prevent the bolt from going in flush or block the hanger from being easily clipped by a carabiner. Also check that a carabiner clipped to the hanger would not be torqued or cross-loaded by a rock feature like a knob or ledge.

Once you’ve pinpointed the location you want, lightly tap the rock with a hammer. You want it to sound solid. If it sounds hollow, like when you tap a flake, or if it makes a thud, like when you hit dirt, it’s not a good location for a bolt. Also, be aware of fracture lines, both before and after tapping the rock, as well as exfoliating rock.

Step 2: If re-using the same bolt hole, bore the hole deeper and wider. If drilling a new hole, drill the hole. Be sure to go a little deeper than the bolt itself. This will be helpful in disengaging the cone from the sleeve when the next person needs to replace the bolt. The diameter of the hole needs to match the diameter of the bolt you’ll be placing, which should be a 1/2 inch.

Step 3: Clean the hole. It is important that you remove the rock dust so that the bolt can engage the rock wall properly. Blow the rock dust out of the hole, preferably with a hand pump or a can of compressed air rather than just a piece of aquarium tubing. Insert the tube brush into the hole and give it a light scrubbing. In soft rock, brushing the hole with the tube brush can literally widen the hole, so be careful. Blow out the last bit of rock dust.

Step 4: Insert the 1/2-inch stainless steel sleeve bolt. If you drilled the hole correctly, the bolt will not just drop into place. In fact, the fit should be tight enough that you’ll have to tap the bolt in to get it started and then hammer it a bit harder to sink the bolt all the way in.

Step 5: Angle the hanger for the direction of pull. One trick is to clip a quickdraw

to the hanger and see where it wants to naturally hang. Do not orient your hangers sideways or at other odd angles; you want to maximize the designed strength of the hanger.

Step 6: Tighten the bolt, ideally using a torque wrench set to the manufacturer’s specifications. For a 1/2-inch stainless steel Powers five-piece sleeve bolt, that’s 25 foot-pounds of torque. While using a torque wrench is best practice, the reality is many climbers tighten bolts to “feel” with just a crescent wrench. If you plan to use a crescent wrench—and especially if you’re new to bolting—you need to figure out what the correct“feel” is. Practice tightening a bolt at home using a torque wrench and then see what that pressure/resistance feels like with just your crescent wrench.

The concern with tightening a bolt to feel is over-tightening, which can cause the bolt to snap off or, worse yet, cause a stress fracture without snapping the bolt, leaving a time bomb in the rock. A rule of thumb some developers use is to stop tightening when the plastic, paper-thin ring right underneath the bolt gets pressed out and becomes visible. This isn’t a scientific approach, but more of a reminder to be aware of over-tightening. It’s also possible to under-tighten the bolt and create an annoying spinner.

How to camouflage hangers
It’s a good idea to camouflage hangers to reduce their visible impact. You can buy them pre-coated from manufacturers, such as Metolius, or you can do it yourself. Both coatings tend to wear off with time, but the treatment done by a manufacturer will last a lot longer.

If you want to camouflage the hangers yourself, run them through the dishwasher first to remove any oil, which will allow the paint to sticker better. Use a flat spray paint primer from the hardware store and apply a coat or two to the hangers. Let them dry for about a day before use.

Considerations for bolting anchors
When placing a new anchor, make sure the bolts are adequately spaced. Bolts should be about eight inches apart in good rock, such as granite, and up to 18 inches apart in softer rock. Anchor bolts placed closer together than that could fracture the rock. If you use a wider spacing, be sure to add some chain to the anchor bolts to ease the angle of force applied by the rope. Also, placing bolts side by side might not be the best answer in every situation—sometimes a vertical arrangement is better. Stacking the bolts vertically could allow you to take advantage of better rock and avoid rock edges. Just be sure that the two bolts are equalized using chain and quick links.

Drilling and installing a new glue-in bolt

Glue-in bolts are currently the best bolts for use in soft rock, including most forms of sandstone and limestone, as well as some volcanic rock, such as the welded tuff of Smith Rock. The biggest advantage of glue-ins over mechanical bolts is their high pullout strength, which is due to the even distribution of the load over the entire embedded rod. In some cases, the pullout strength is higher than the strength of the rock itself.

Expansion bolts, on the other hand, rely on a relatively small surface area within the hole to absorb the entire force. Because of that, the compressive strength of soft rock is too low to handle the high working loads exerted by mechanical bolts. Glue-ins are also better protected from corrosion and the elements inside the hole as the epoxy prevents moisture from penetrating the bolt hole.

Tools you’ll need:

  • Hammer drill
  • Extra long drill bit
  • Blow tube (often a piece of aquarium tubing), hand air pump, or can of compressed air
  • Tube brush
  • Glue (epoxy) and nozzles
  • A caulk gun that will work with the glue you’re using. Hilti glue requires a Hilti glue gun, for example, while Powers glue can use a standard caulk gun. But the bottles come in different sizes so make sure the glue fits into the gun. Also, it’s good to buy a durable, burly caulk gun, not the cheapo version, as it will most likely break.
  • Rags or paper towels and a plastic bag to throw them in
  • Hammer
  • Glue-in bolts

Step 1: Select a good placement. (If re-using the same hole, skip to Step 2.) If you cannot reuse the same hole and must drill a new one, there are a few things to keep in mind. First, the anchoring industry recommends that you space two holes at least 10 anchor diameters (roughly 2.5 inches for a 1/2-inch bolt) apart to prevent spalling and splitting of the base material. This spacing should be greater the softer the rock is. Bolts also should not be placed near edges and corners. At least one anchor has failed because the bolts were placed too close to the edge and the weight of the climber fractured off the chunk of rock the anchor was in.

When bolting in roofs and overhangs, look for lower-angled breaks where the outward pull on the bolt will be less severe. Also, make sure that there are no small protrusions that will prevent the bolt from going in flush or block the hanger from being easily clipped by a carabiner. Also check that a carabiner clipped to the hanger would not be torqued or cross-loaded by a rock feature like a knob or ledge.

Once you’ve pinpointed the location you want, lightly tap the rock with a hammer. You want it to sound solid. If it sounds hollow, like when you tap a flake, or if it makes a thud, like when you hit dirt, it’s not a good location for a bolt. Also, be aware of fracture lines, both before and after tapping the rock, as well as exfoliating rock.

Step 2: If re-using the same bolt hole, bore the hole deeper and wider. If drilling a new hole, drill the hole. Be sure to go about a half-inch deeper than the bolt itself to allow glue to get into the back of the hole and fully encase the bolt. The diameter of the hole will depend on the type of glue-in you use; check with the manufacturer.

Step 3: Clean the hole. It is even more important that the hole is clean for glue-ins than for mechanical bolts. You want the glue to bond to the bolt but also the rock—but there is a limit. The more polished the rock, the harder it is for glue to bond to it. Blow the rock dust out of the hole. Insert the tube brush into the hole and give it a light scrubbing, then blow the rock dust out again.

Step 4: Put the tube of glue (epoxy) into a standard caulk gun, thread on a nozzle,

and squirt glue into the hole. Start in the back of the hole and slowly pull the gun out as you continue to fill the hole with glue. It will be hard to tell how much glue you’ve placed in the hole, but more is better than less, as you won’t be able to add any glue after the fact. Some glue inevitably will get pressed out of the hole when you insert the bolt. That’s OK, just wipe up the excessive glue with a rag.

Step 5: Insert the bolt. Push the bolt into the hole as far as you can with your fingers. Some glue-ins require tapping in with a hammer. Be sure to use a stainless steel hammer, or Climb Tech’s placement device—non-stainless hammers on stainless glue-ins can actually cause a small amount of metal transfer that can cause some superficial surface corrosion. Tap the glue-in the rest of the way in with a hammer. Try to keep the orientation of the eye as perpendicular to the ground as possible. When the bolt is all the way into the hole, tap the side of the eye if the orientation still needs to be corrected.

Step 6: Wipe up any excess glue that has squirted out of the hole. If there is no excess glue, you didn’t place enough glue in the hole. You’re not looking for a lot of glue to come out, that’s just a waste, but some ensures that you used enough. If none came out, consider taking the bolt out. You have to do it immediately or the glue will harden, and it requires a funkness device. Insert more glue and put the bolt back in. The amount of time you have to do this before the glue hardens depends on the temperature: The warmer it is, the less time you have.

Note: Glue is messy; bring lots of rags or paper towels and a few plastic grocery bags to put them in. Glue dries quickly and you’ll also go through a lot of nozzles if you’re not careful. Many developers who are bolting a whole route with glue will keep their glue in a cooler until they’re ready to use it. The glue can dry inside a nozzle so quickly that you may not have time to drill a hole, place the bolt, lower down and then do it again. The best way to make the most of your nozzles is to fully prep the route before you try to glue any of the holes. If all the holes are pre-drilled, all you have to do is fill the hole with glue and insert the bolt. This tends to allow you to use one nozzle for most of a route so long as it’s not too hot outside.

Lastly, dry times for glue-ins depend on the glue you’re using; read up on the manufacturer’s literature. Some glue is good to go in a few hours while others may take up to two days. The important thing here is you let people know if the route is not safe to get on yet.

Hand drilling

In some respects, hand drilling is a lost art, one that was quickly discarded with the advent of the power hammer drill. However, it is illegal to use power tools in certain parts of the country, particularly in wilderness areas. Because of that, if you want to place (or replace) a bolt, the only option is hand drilling.

The technique for doing so takes a bit more practice than drilling with a power drill. Be sure to practice on a small rock before trying to do the real thing or you risk boring too wide and too sloppy of a hole.

Hand drilling is the only instance when 3/8-inch bolts are acceptable to place. It is perhaps even more imperative that they are stainless steel as hand drilling is difficult and people are probably not going to be lining up for the opportunity to replace your bolt in 10 to 15 years when corrosion begins to set in. Please note some people hand drill wider diameter bolts than 3/8 inches, and that’s great. For example, volunteers in the Red River Gorge have gone the extra mile and hand drilled ½ inch bolts to replace anchors on routes in the Clifty Wilderness. Also, the guide torque for stainless steel 3/8-inch five-piece Powers sleeve bolts is only 12 foot-pounds.

Tools you’ll need:

  • Hand drill
  • 3/8-inch SDS masonry bit
  • 1/2-inch crescent wrench
  • Blow tube
  • Tube brush
  • Hammer
  • 3/8-inch bolts

Step 1: Drill the hole. If drilling a new hole, start off slow to get a good, clean, straight pilot hole. If you’re re-using the same hole you removed a 1/4-incher from, the pilot hole has already been set up. Either way, begin gently. Place the drill perpendicular to the rock, which is not necessarily the same thing as parallel to the ground. If you’re bolting a slab for instance, the angle needs to be beyond horizontal.

Tap the end of the drill with the hammer. Chips of rock will fly around during this process so be sure to wear safety glasses. After you hit the drill, rotate it about 1/8 to 1/4 of a turn and then take another whack. Quick, light strikes are better than slow, heavy blows as the bit will be less likely to bind. Also, when you hit the drill, let it bounce back a little bit with each strike.

Once you’ve drilled a hole that’s deep enough to hold the drill itself, loosen your grip on the drill so it rebounds slightly with each hit. This bouncing speeds up the drilling process by ejecting dust from the hole. A common problem is the “double tap,” when you swing the hammer and hit the drill, and then the bounce-back quickly hits the hammer once more. Be careful not to let it bounce too much, or you can get a wide, conical hole.

Every now and then—after 50 whacks or so—it’s good to stop drilling and blow the hole out to remove rock dust that may bind your drill. If the bit does bind, stop hammering. Try and gently wiggle the drill until it loosens. If the bit binds frequently, use lighter, quicker taps rather than slow, heavy blows. If you’re already doing that, then the bit is probably dull and needs replacing. Worn bits can compromise the hole by under sizing it, making it difficult to get the bolt into the hole.

Step 2: Clean the hole. Blow out the dust, scrub the hole with the tube brush, and blow it out one last time.

Step 3: Insert the stainless steel sleeve bolt. If you drilled the hole correctly, the bolt will not just drop into place. In fact, you should have to tap the bolt in to get it started, then hammer it a bit harder to sink it all the way in.

Step 4: Angle the hanger for the direction of pull. One trick is to clip a quickdraw

to the hanger and see where it wants to naturally hang. Do not orient your hangers sideways or at other odd angles; you want to maximize the designed strength of the hanger.

Step 5: Tighten the bolt. If you’re hand drilling, you’re probably in a wilderness area, which means you’re probably a long way from the car and trying to go as light as possible. While using a torque wrench is best practice, the reality is, you’re probably going to use a smaller, lighter crescent wrench and tighten to “feel.” If you plan to use a crescent wrench—and especially if you’re new to bolting—you need to figure out what the correct “feel” is. Practice tightening a bolt at home using a torque wrench and then see what that pressure/resistance feels like with just your crescent wrench.

The concern with tightening a bolt to feel is over-tightening, which can cause the bolt to snap off or, worse yet, cause a stress fracture without snapping the bolt, leaving a time bomb in the rock. A rule of thumb some developers use is to stop tightening when the plastic, paper-thin ring right underneath the gets pressed out and becomes visible. This isn’t a scientific approach, but more of a reminder to be aware of over-tightening. It’s also possible to under-tighten the bolt and create an annoying spinner.

Considerations for developing new routes

While the focus of this guide is re-bolting and maintaining established routes, it’s important to mention some considerations for people who are considering bolting new lines.

First, please don’t take that opportunity lightly. Chances are, others have at least seen your line, so be sure it’s worthy of bolting before sinking in some hardware—you can’t undrill holes. To do that, consult the guidebook and talk to local first ascentionists. Then set up a top anchor using trad gear or by slinging trees or other natural features and rappel the route, removing any loose rock along the way. Toprope the route several times and encourage your friends to do the same.

If it is a worthy line, pay special attention to potential clipping locations. Mark the spots with a dab of chalk and make sure it is reachable for all climbers—tall and short alike. If you’re not planning to bolt the route on the same day, you can also use lumber crayons, which last longer than chalk for marking and wipe off easily.

Clipping locations should be near solid holds and relatively comfortable climbing positions. Generally speaking, bolts are easier to clip if they are off to one side or the other from the climber’s body. At the same time, it is ideal to have the line of bolts be relatively straight to mitigate rope drag. The future bolt location should be in a basketball-sized area of smooth, solid rock. Avoid pocketed, hollow, or fragile rock. Do not place bolts next to edges or corners, as they are not as strong.

Your first bolt should be as high off the ground as is safe for the leader to climb without protection because you want as much rope out as possible to minimize the force of a fall on that bolt. However, the second bolt should be somewhat close to the first to minimize impact to the first bolt and also prevent a ground fall. From the third bolt on, the spacing should be whatever is appropriate for the terrain, but generally it’s a good idea shoot for around 8 to 10 feet between bolts.

Be cognizant of ledges and other obstacles the leader could hit during a fall. Bolts that can be clipped from ledges should be placed as high above the ledge as is practical, and the next bolt should be close enough to prevent the leader landing on the ledge in a later fall.

Before you install the bolts, be sure to camouflage the hangers, either by buying pre-treated hangers or by spray-painting them yourself with a flat primer. Do not spraypaint hangers already installed in the rock – you’ll just end up spray painting the rock itself. The paint will eventually chip off but the goal is to reduce your visual impact. Lastly, don’t put junk hardware in the rock—you should be using stainless steel bolts matched with stainless steel hangers. The only exception is where titanium glue-ins are needed. We encourage you to get a mentor, be safe and consult the community; they’ll appreciate it and you’ll enjoy your new routes more if others enjoy them as well.