Project Caving and Permanent Rigging

by Benjamin Schwartz, NSS #32206

Long-term cave exploration projects demand long-term rigging. For safety and low maintenance, rigging must resist water, mud, corrosive minerals, time, and caver traffic. This article looks at the requirements for permanent rigging, the limitations of widely available technologies, and some alternative hardware that I have identified and used extensively.


The cave has gone deep, but trips are infrequent due to flood hazards and caving schedules. The breakout occurred four years ago: a dig in a narrow canyon led to a second drop. Four more drops have been found, with long, wet, difficult crawls in-between. Each drop has been rigged at great expense in time and effort. On the last trip, a breathtaking lead climb resulted in a static rope hanging ready for further exploration. It's time for another trip. The cavers are ready. Is the rigging ready?

1936-Img0092_r1.jpg (15571 bytes) Anchors as an investment

The anchors at this drop in a West Virginia cave are under heavy spray for most of the year.

The lower anchor is a steel hanger made from angle-iron and a high-grade steel bolt. It is 20 years old and has been unsafe for probably 15 of those years.

The upper anchor is a stainless steel hanger on a 3/8-inch stainless steel stud. It was installed using a hammer drill that was in the cave for an aid climb. It is 10 years old, and will last for hundreds of years.

(J. Ganter photo)


Project caving often pushes the limits of both caves and cavers. Explorers must strike a balance between carrying too much or too little equipment. Not knowing what lies ahead forces us to carry rigging equipment, which we may or may not need, or risk having to turn around at a climb or drop. Weight and bulk are always concerns, and this affects what types of artificial anchors (bolts) can be set when natural anchors are not available.

Ideally, we would set long, single-piece anchors made of stainless steel. However, these types of anchors (studs) require a separate drill to create a deep hole. Self-drilling anchors have a built-in drill, but because of the required hardness they cannot be made of stainless steel. (For details see Artificial caving anchors for the present and future," May 1990 NSS News or

Few are willing to carry a gas or battery-powered hammer drill on push trips. Although it would be nice to have long, 10mm stainless steel studs and hangers quickly placed at every drop, this is often impractical in deep, wet, body-contact caves.

Instead, our equipment usually consists of a fairly lightweight and compact self-drive kit, with enough anchors, hangers, and aid gear to rig several drops or do a short climb. In the past, most of us have used Petzl’s 8mm self-drive anchors and hangers, combined with carabiners or steel quick-links. Petzl gear is easy to purchase, easy to use, lightweight, and relatively inexpensive. Carabiners and steel quick-links are also easy to acquire.

However, there are corrosion problems associated with leaving aluminum hangers, aluminum carabiners, steel cap screws, and steel quick-links hanging in wet and muddy caves for a multi-year project. If the project is seasonal, rigging can be removed, ropes can be removed or stashed in the cave, and everything can easily be inspected or replaced before the next season. This still takes quite a bit of time though. Note: Some cavers debate the safety of using 8mm self-drive anchors as primary rig points. I am not debating this point here; I use them. However, the reliability of any type of anchor depends upon its proper placement and continuous inspection. Only you are responsible for checking the rigging you clip into!

In long-term projects, the rigging on frequently traveled "trade routes" can quickly become three, five, or even 10 years old. Removing and replacing badly corroded rigging may be postponed "until the next trip" and is sometimes delayed for far longer than it should be. Almost nobody wants to take the time to maintain rigging on the way out after a long, hard trip.

Even if the cave is visited frequently, inspection is uncertain. Who can be sure that an aluminum hanger is truly in good shape? Aluminum can be very deceiving and difficult to check for weaknesses. After only one year in some very corrosive caves environments, hangers can exhibit deep surface pitting, gel deposits, invisible corrosion, and even calcite coatings. With all the things that can go wrong in vertical caving, the last thing anyone wants to be worrying about is whether the carabiner and hanger at the top of a 2-year-old aid climb is going to fail before someone gets to the top and checks it.

With these problems in mind, I began searching for something to replace aluminum both in comparable price and weight, with more durability. An excellent choice would be to use stainless steel. Starting at the rope and working towards the anchor, I looked for opportunities to replace aluminum or steel rigging components with stainless steel.


Here is a cost-effective way of reducing the amount of speculation and anxiety concerning aging rigging, while at the same time reducing some of the hazards of vertical caving.

I priced box quantities (20) of Long Oval Stainless Maillon Rapide 7mm quick-links from several speleo-vendors. These have a gate width of 9/16-inch which easily accommodates ropes commonly used in caving. The cost of these is less than all but the cheapest of locking ‘biners and they will last almost indefinitely with some basic care. In addition, they weigh less than the average ‘biner (42 grams compared to about 65 grams) and are much more space-efficient as far as both size and packability are concerned. As for strength, they are more than strong enough, with a stated working load limit of 580kg (safety factor of 5).

The next thing was to find a stainless steel hanger. With all the climbing companies that make hangers, it seemed many of them must make an 8mm hanger just for this purpose. I soon found the opposite to be true after calling several companies and gear manufacturers. None of them made any 8mm equipment and they either referred me to Petzl aluminum gear, or suggested using an 8mm washer over a 10mm hanger. This was an unacceptable solution for me. I even looked into having someone custom stamp and bend a large quantity of 8mm hangers.

The only thing that comes close to matching my requirements is an SMC 5/16-inch hanger. (5/16 and 8mm are almost identical in size.) The problem is that they are fairly expensive ($3.50 ea.) and have a very small attachment hole. I needed something comparable in price that could easily accommodate two carabiners during use on aid climbs.

More searching on the Internet turned up a company in Spain called Fixe. They sell 8mm stainless hangers with a large attachment hole. I called the only U.S. distributor of Fixe products (Kevin Daniels & Associates) and got pricing for 150 hangers. In addition to the cost of the hangers, there were still costs for shipping, stainless cap screws, and the small capture/seal O-rings similar to the Petzl design that keeps the cap screw attached to the hanger until installation. With all this added to the cost, the price is only slightly higher than a Petzl hanger. ($2.32 compared to $2.25±) This price includes the cost of having to buy 200 each of both the cap screws and O-rings. (Package quantities on these were 100 each.)

Hanger_fixe1.gif (7961 bytes)
Fixe 038 stainless steel hanger (photo courtesy of Fixe)

The total weight is more than the Petzl aluminum hanger, (72 grams compared to 30 grams) but I feel the increased life span and peace of mind more than offset the few ounces added to an already heavy pack.


For a slightly higher cost, I now have a permanent hardware option that will last me a lifetime. Each part of the rigging hardware (except the anchor) can easily be re-used an almost unlimited number of times. Two weak links in a permanent or long-term rig point have essentially been eliminated.

The self-drive anchor is now the only non-stainless component. Fortunately, it is somewhat protected by being surrounded by rock and covered by the O-ring and hanger.

Some cavers fill the inside of the anchor with petroleum jelly from a small squeeze tube to help exclude water and reduce rusting.

The pricing of all these items was done for large quantities. At quantities of 10 or 20 each, the price would be somewhat higher (Note: see new information below for smaller quantities). As it currently stands, I can set an anchor and permanently rig it for around $9.00. (Whatever happened to caving as a cheap hobby?!) This is the same as, or less than, the cost of using a Petzl anchor, Petzl hanger, and a carabiner.

Thank you to John Ganter and Phil Lucas for making suggestions and providing constructive criticism

Which anchor? by John Ganter

All anchors have advantages and disadvantages. The 8mm anchors that Ben discusses are small -- not much bigger than a 1/4-inch anchor. By using them you are accepting risk of lowered strength and reliability. And since anchors usually become permanent cave " infrastructure," some future users may not be aware of this risk. But on the other hand they are easier than 10mm to drill, and the drivers are available.

Here is a comparison of anchor systems to help you decide on options:

  Advantages Disadvantages
Natural anchor(s) - Less damage to cave
- Often less time to rig
- Often stronger and less prone to deterioration
- May take extra skill to rig
- May take extra skill, time, effort to use by cavers
Stainless studs - Single body thus very strong
- Completely stainless, unlike self-drives
- Requires hand drill (1) or hammer drill to install
10mm self-drive
(or 3/8-inch)
- Much better safety margin than 8mm
- Will lose less strength with rusting
- Harder to drill than 8mm
- No driver or driver adapter available? (2)
8mm self-drive
(or 1/4-inch)
- Easier to drill than 10mm
- Driver readily available
- Low safety margin
- Smaller anchor will lose more strength with rusting

If you decide to go with the 8mm anchor, try to compensate for the disadvantages with the following practices. (See "Artificial Rigging Anchors for the Present and Future" for analysis.)

Installation and maintenance


Permanent rigging components illustrated by John Ganter, with Ben Schwartz

This section provides more details on the components discussed above.

The US sizes can be considered a "legacy" system. For example, in the 1980s I bought a large number of 3/8-inch self-drives that were being closed out by a hardware store. Art Petit made me a high-quality aluminum and stainless steel driver. So I plan to use these supplies until they are gone, and other cavers will do the same.

But we should use the best possible materials for the remainder of the anchor system: the cap screws and hangers. Sources of these items are listed in the 3/8-inch column.

Petzl-based 8mm Petzl-based 10mm 3/8-inch Illustration
Driver Petzl PERFO PRO P09 or PERFO SPE P08 - Raumer Stroker universal driver with 10mm insert. Available through Expé and Inner Mountain Outfitters, about $35?

- Adapter for Petzl 8mm driver has been discontinued (2). We are looking for a source.

Current US manufacturer unknown  (3) DriverP09.gif (6417 bytes)
Bolt (technically a "cap screw") Metric SS Hex Head Cap Screw, M8 X 16 mm long, 1.25 mm Pitch, Fully Threaded
- McMaster-Carr, Part #91287A151, $25/100
McMaster-Carr 3/8 x 16, 3/4-inch SS Hex Head Cap Screw, NC thread, Fully Threaded
- McMaster-Carr, Part #92240A622, $13/100
ssfullthread.gif (5074 bytes)
Rapid link 7mm Long Oval SS Quick-Links
- Inner Mountain Outfitters, $6
same as Petzl 8mm same as Petzl 8mm RapidLink.gif (1533 bytes)
Hanger Fixe 8mm SS Hanger
- Adventure Gear, $2.50 each

- K. Daniels, $1.75 at quantity 150 (4)

Kong-Bonaiti SS Hanger 894, 8mm

- Adventure Gear, $1.95 each
Petzl COEUR P34050 10mm hole
- Inner Mountain Outfitters, $2
Petzl COEUR P34050 10mm hole
- Inner Mountain Outfitters, $2

Metolius 3/8" SS hanger
- Metolius, $2.65 or dealer?
HangerCoeur.gif (3929 bytes)
O-ring Silicone O-ring, 1/4" ID, 3/8" OD
- McMaster-Carr, Part #9396K15, $10/100
same as Petzl 8mm same as Petzl 8mm
- Inner Mountain Outfitters, $1.25
Inner Mountain Outfitters has some Petzls Rawl seems to have discontinued these anchors, others? (3) AnchorAndWedge.jpg (6098 bytes)
Dimensions - Hole in rock is 12mm
- Diameter of cap screw is 8mm
- Socket size is 13mm
TBD - Hole in rock is 1/2-inch
- Diameter of cap screw is 3/8-inch
- Socket size is 1/2-inch
Images courtesy of Petzl and McMaster-Carr


SS = stainless steel. Not all stainless steels are rust resistant. You want 200/300 Series austenitic alloys. Most "18-8" (18% chromium and 8% nickel) steel is austenitic. This includes types 302, 303, 304, and 316. 316 is for marine uses and is probably not worth the extra cost for cave environments if other options are available. Avoid 4XX (400 series): these are ferritic or martensitic steels and they may rust. For an overview of series, see For compositions, see (Thanks to Bill Storage for SS information.)

(1) Hand drills are available for placing studs. These typically consist of a holder that accepts bits like those used in hammer drills (SDS shank). One model is the Pika Rock Drill, available from Adventure Gear. Drill_Pika.jpg (5975 bytes)
Pika Rock Drill (photo courtesy of Pika)

(2) Why has Petzl discontinued 10mm self-drive anchors? No one seems to know, but the theory is that Petzl believes that caving anchors should be either 8mm with aluminum hangers for short-term use or stainless studs set with a hammer drill for long-term use. The problem is that neither approach works for some deep, tight, wet cave projects.

(3) Self-drive anchors and hand drivers are mostly obsolete for construction because of hammer drills. From an engineering standpoint, it is much better to have drill and anchor separate. Stainless studs are far superior to self-drives in almost every way. So self-drives are relegated to rock climbing and caving, where Petzl is the international standard.

(4) Fixe hangars are available in quantity 150 for $1.75 each, plus shipping, directly from the importer: K. Daniels and Associates (see Sources).


Adventure Gear,, anchors at

Expé,, available through Inner Mountain Outfitters

Fixe,, anchors at

Inner Mountain Outfitters,

K. Daniels and Associates, 14891 Sabre Lane, Huntington Beach, CA 92647 Phone: (714) 751-5038 Fax: (714) 540-3845

Kong-Bonaiti,, anchors at

Metolius,, hangers at

McMaster-Carr Supply Co., nationwide offices, Chicago is (630) 833-0300,

Petzl,, anchors at

Pika Mountaineering,

Raumer, available through Expé


Thanks to Tommy Shifflett and Alex Sproul for suggestions and information.

Version 1.95, 12 November 1999. Version 1 was published in the NSS News, October 1999.


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