List of bolt types

by Jason Haas

Because route developers have at times used a wide variety of “hardware store specials” to equip routes, this list may not cover every type of bolt you come across on a climb, but it probably describes the vast majority of bolts out there.

Sleeve Bolts

Sleeve bolts can easily be identified by their hex bolt head. The standard bolt is made by Powers (formerly Rawl) and is commonly called a “five-piece” because of the five pieces that comprise the bolt itself: the bolt, a large washer, the sleeve, the blue plastic bushing, and a threaded cone. The longer versions have two sleeves, but are still called five-pieces.

When you tighten the hex head of the bolt, the cone pulls into the sleeve, causing the sleeve to expand and exert pressure on the walls of the hole. These bolts have more surface contact inside the hole than a wedge bolt, making it stronger in both pullout and shear strength. Sleeve bolts, however, have a lower pullout strength than glue-ins, though they are still plenty strong for medium to hard rock.

Wedge Bolts

Wedge bolts can be identified by their threaded shaft and nut. Wedge bolts also have a small clip on the tip of the bolt inside the hole that expands and grips the rock. They typically come in 3/8-inch and 1/2-inch diameters and can be plated or stainless steel. Non-stainless steel wedge bolts, particularly “Red Heads,” can be found at the hardware store for as little as a buck. Unfortunately, they’re not that strong.

Wedge bolts are weaker than sleeve bolts in both pullout and shear strength, and they also have a more limited expansion range than sleeve bolts, making them more prone to placement error. For example, you can over-tighten these bolts and unknowingly pull the clip off the expansion cone, thus reducing the bolt’s strength to virtually nothing. This is why we recommend sleeve bolts over wedge bolts even though some developers still use wedge bolts (often because they are cheaper to buy).

Glue-in bolts

When properly placed, glue-ins are the strongest, longest-lasting bolts available and they should be the go-to bolts for use in soft rock and in areas where stress corrosion cracking (SCC) is a serious concern. However, if the bolt hole is under- or oversized, if not enough glue was put in the hole or if the hole was not cleaned thoroughly or correctly, they can be rather weak.

Even glue-ins that are placed correctly have some drawbacks. Mainly, they are not removable; once they’re in, they’re in. But according to Powers, glue-ins have the potential to last exponentially longer than other bolts, which could make concerns over replacement essentially moot. Another drawback is that it takes time for the glue to dry before you can safely weight the bolts.

Compression bolts

Often referred to as button heads—because the end of the bolt looks like a smooth button—the majority of these bolts were made by Rawl and range in length from 1.25 to 2 inches long and are usually only 1/4 inch in diameter. Compression bolts have a split shaft that is slightly larger than the diameter of the hole. As the bolts are hammered in, the sides are compressed to create a force fit.

The 1/4-inch Rawls also came in a threaded-head version, which often featured a six-sided or square nut. Compression bolts also came in 3/16-inch diameters—essentially a mini-1/4-incher that could barely support the weight of a climber—and, later, 5/16-inch diameter. While only a small change, these differences in diameter have a huge impact on bolt strength.

Sheath bolts

There two common types. The Star Dryvin, commonly called a star drive, can be easily identified by the star stamped on its head. These bolts are essentially steel nails hammered into two halves of a soft, malleable, lead sheath inside the hole. The sheath expands as the nail is driven into it.

The other common variety is a taper bolt. These tend to have an Allen key or hex head with no threaded stud sticking through. The bolt is screwed into the bottom cone (kind of like, but not as good as, a sleeve bolt). Taper bolts can be confused with some types of self-drill bolts that look similar on the surface.

Self-drill Bolts (Aka Drop-ins)

One way to recognize these types of bolts is by their large machine-bolt heads, often in the form of an Allen key or hex-sided head. With self-drill bolts, the bolt itself acts as the drill bit. Because the “bit” dulls quickly, these kinds of bolts are difficult to place, and they are frequently left sticking out of the rock because of a botched placement job.

When placing a self-drill bolt, the hole is drilled and the cone is inserted, followed by a sleeve with internal threads. The sleeve and cone are then set in place with a blow from a hammer, which forces the cone against the back of the hole and subsequently forces the sleeve onto the cone. As with sleeve bolts, the cone forces the sleeve open, exerting force against the inside of the hole. Once the sleeve is set, a machine bolt is screwed in and holds the hanger in place.

The most common version, placed during the ‘80s and early ‘90s, was the Petzl Cheville Autoforeuse paired with an aluminum Vrillee hanger.

Torque Bolts

These obscure bolts were once popular around Tuolumne, but are rare elsewhere. They have a hex head that looks similar to a five-piece bolt from the outside. However, torque bolts have a solid shaft that’s threaded on the tip. A small, lead cone that is screwed onto the tip expands when you tighten the bolt.

They require a torque wrench to be set to a very precise setting in order for the bolts to work, which is why many of them are were not placed correctly and why they should not be considered safe.

Petzl Long Life Bolts

This 1/2-inch diameter, 2-inch long stainless steel bolt has a steel pin set in the shaft. Driving the pin into the bolt expands the shaft in the hole. They are easy to place and are actually very strong in bullet hard granite. Because they’re stainless steel—and so is the hanger they come with—they are strong and will last a long time. However, these bolts are not safe in medium to soft rock.

Zamac Nailins

Zamacs are similar to Petzl Long Lifes in design, but are smaller and made of inferior metal. They were intended for hanging rain gutters on cinder blocks, but they have also moonlighted as protection bolts on free climbs, especially in Yosemite.

Machine bolt rivets

These hardly exist outside of aid routes, such as those found on El Capitan, and can actually be quite strong for that purpose. But they rely heavily on a precise fit and the mashing of the threads as they are driven in. They usually are a standard 5/16-inch coarse-threaded machine bolt pounded into a 1/4-inch or 9/32-inch hole. Surprisingly, they can hold over 2,000 pounds. Not surprisingly, they can also fall out in your hands.

Aluminum dowel

Like a machine bolt, these are reserved for aid routes, mostly in Yosemite. They are simply a piece of aluminum rod stock hammered into a shallow hole and were commonly placed on Yosemite aid routes during the early ‘70s, especially those put up by Warren Harding.