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Wedge Bolts   

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Best Use: Bottom up or top down route setting or rebolting
Rock Type: Hard rock and sometimes medium rock if an appropriate bolt
Pros: Can place with one hand; bolt will tighten itself when loaded
Cons: Unsafe in soft and variable density rock; difficult or impossible to remove; come in many types that work to extremely varying degrees of safety

Available from a number of manufacturers, wedge bolts are a very common and reliable design. Some manufacturers are climbing-specific (e.g. Petzl, Fixe) and others offer a wider variety for construction and engineering purposes (e.g. Hilti, Power). Most wedge bolts used today for climbing purposes are 3/8” and 10mm diameters, but ½” and 12mm versions are also being used. They come in a variety of lengths, 2” to 5” being the most commonly used by climbers.

Rock Climbing Photo: Fixe wedge bolt

Fixe wedge bolt
Wedge bolts consist of a threaded bolt with a single or double conical end wrapped in a clip. Single and double expansion clip versions are available, allowing the installer to choose the best setup depending on the rock characteristics. A nut and washer attach the hanger to the threaded end. The bolt is hammered into a properly sized hole and as it is tightened the cone pulls forward causing the clip to grip the inside of the hole.

Wedge bolts are reliable and strong and, if made with stainless steel, will last several decades in all but the harshest environments. They are relatively easy to place one-handed, on lead, and they are unlikely to result in botched placements.

Wedge bolts do have some weaknesses, however. The expansion clip on a wedge bolt must be fixed in place by friction with the rock, meaning that the physical properties of the rock will affect their holding strength. Plus, the contact force is concentrated in a relatively small area inside the hole when compared to equivalently sized sleeve bolts. Soft or irregular rock can deform or otherwise fail to provide adequate friction, leading to a bolt that will not tighten to spec and that may fail at low axial loads. Wedge bolts are also quite difficult to remove.

Placement: To place a wedge bolt, drill a hole in the rock with a carbide tipped SDS-plus drill bit equal to the stated diameter of the bolt. It is important that the hole be drilled at least as deep as the bolt’s length so that the bolt can be hammered flush with the rock at a later date if necessary (e.g. replacement or relocation).

Drill the hole perpendicular to the rock surface in a flat area with solid rock (inspect visually and with light hammer taps). Then use an air pump, CO2 tire inflator or blow tube in conjunction with a brush to remove the rock dust from the entire hole. With the hanger on and the nut flush with (but not over) the end of the threads, place the end of the bolt in the hole and begin to hammer the bolt. Never hit the threads or nut with the hammer, as this can ruin the threads and result in a botched placement.

Hammer until the hanger is firm against the rock surface. Now, using a box, socket, or adjustable wrench, tighten down the nut. The stud will retract from the hole by a few millimeters as the cone engages the clip. A properly engaged bolt will offer increased resistance with each turn until tight. From here, apply proper torque per manufacturer’s specs using a torque wrench.

Removal: Completely corroded wedge bolts can sometimes be pulled straight out much like compression bolts using leverage and “funking”. However, more often than not this approach will just result in a broken stud or a blown out hole in the rock.

The only proven method (an advanced procedure) of removing properly engaged wedge bolts is via the use of a diamond core bit, which drills the rock from around the bolt and allows the clip to disengage. Afterward, an appropriately sized glue-in or larger diameter mechanical bolt can then be installed in the enlarged hole.

The diamond core bit should be sized such that the wedge bolt stud just fits inside. The core bit must also be long enough to reach from the surface of the rock to the flange/clip on the end of the bolt. The walls of the bit should be thin (e.g. 2mm), and it must be diamond tipped. An SDS-plus adapter may be needed in order to use the core bit with many battery operated hammer drills.

This procedure also requires a portable water based cooling device to be used while drilling. The water can be delivered via a water bottle or other bladder like device with a valve, tube, and small nozzle. It must just be capable of delivering a constant but small stream of water in a relatively hands free manner, using either gravity or squeeze pressure.

To core the bolt out, it is either stripped of its hanger and nut or broken off using leverage or a saw. Do not hammer the stud into the hole any further, as this will just increase the time and effort needed to extract the bolt. Now the drill is placed over the stud and, using the rotary function alone on a hammer drill (no hammering action), the core bit begins drilling the hole around the stud. The entire time that the drilling is taking place, water is slowly fed through the water cooling nozzle, directly onto the area of rock being drilled. Go slow and use a lot of water (stop to refill the bladder as needed) until the core bit makes contact with the clip. From here the wedge bolt should pull with some force from a leverage or funkness device.

Because the diamond core drill will leave a very smooth surface on the interior of the hole, once the bolt is out a carbide tipped bit should be used to slightly enlarge the hole and to scour the surface. This will give the epoxy a better surface to grip when the appropriately sized glue-in (or larger diameter bolt) is used.

Though intriguing, the core drilling method is time consuming, equipment intensive, and uses a lot of water. In reality, it is just not going to be practical for large or remote bolt replacement projects. Most wedge bolts will need to be chopped or broken using a breaker bar. After removing the hanger, carefully hammer the stud flush with the rock. Then use a punch of some sort to push the stud slightly below the surface of the rock. This will allow an epoxy patch to be placed over the stud. If the hole is not deep enough, cutting the stud may be necessary. Use an angle grinder (carefully!) or a hacksaw to cut the stud off as low as possible without scarring the rock. Then hammer the cut stud below the surface (if possible) and patch.

Patching is more of an art than a science, as the goal should be to completely camouflage the chopped bolt. Epoxy in either liquid or putty form can be used to cover the old stud. Then take rock dust and cover the surface of the epoxy patch. Small pebbles from the cliff base can often be placed over the epoxy filled hole (prior to curing) and gently smashed/broken in place with the hammer. This method helps force the rock dust into the epoxy, often times blending better with the surrounding rock than just powdering it with loose dust.

Next Topic » Compression Bolts

Comments on Wedge Bolts Add Comment
By Alex Kirkpatrick
May 4, 2014
After having some bolts that I placed come loose, I have started applying loc-tite to the threads before snugging down the bolt. I think there can be a tendency to over-torque a bolt to prevent it from loosening, but the loc-tite provides the confidence to leave the bolt at an appropriate torque without fear of loosening. I use blue (semi-permanent) loc-tite in case I need to move a bolt during the FA process, but red (more permanent) would work fine too. Loc-tite can get expensive from your local hardware store. I recommend buying a large bottle from somewhere like
By J. Albers
From: Colorado
Oct 29, 2014
Some of the info above is already out of date. Courtesy of the cleverness of Gregger Man, wedge anchors can now be replaced in a somewhat painless manner.

Below I have pasted a link to the MountainProject forum discussion that contains two videos .The first video shows how they score the bolt so that the wedge won't engage when you try to remove the stud. However, that video uses a relatively expensive tool to do the actual removal of the stud. To remove the stud without the expensive tool, Gregger et al. came up with a cheap homemade alternative; making this tool is described in detail in the second video.

The first video link showing the bolt removal is:

The second video shows how to build your own cheap stud removal device (its called a C-clamp puller):

Finally, here is the MP forum discussion link:

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