"Some slip right on in, some you have to force, but either way it is just a sticky mess"
Glue in bolts are better in many ways but installation is trickier. They are stronger, last longer and are more convenient to use (not install) since many don’t require hangers. Water never gets inside the hole so if there was corrosion, it’s on the part you can see and inspect. However, the holes have to be really clean, the glue has to mix right AND fill up the whole hole… all without getting it everywhere. Also, the bolt isn’t adjustable later so it better be right. They can last a long long time and can be the best option, especially in soft or layered rock, so let’s go over what you need to know so you can do it like a pro.
Chapter 1 - Bolts Types
I suppose you could glue anything inside of a hole, but if you are installing glue in bolts, I assume you are thinking long term and want to do it right. It is NOT recommended to use mechanical bolts with moving parts like we described in the last section. The glue wouldn’t grab the right parts, like sitting on the sleeves and not the actual stud, and the mechanical parts get gummed up by the glue and aren’t free to do what they need to do. And any properly placed mechanical bolt is going to fit the hole so tightly, there wouldn’t be any room for the glue and therefore push it all out. There are bolts specifically designed for glue, so let’s go over those options.
U shape bolts
Also called staple bolts, these are almost never used in highlining as they require two holes and have twice the impact. And consider that the 2 legs rarely share the load so you don’t necessarily get 2x the strength. If one leg goes, so do you. AND… when holes are drilled that close together, it could weaken the rock. The benefit to these is that they do test stronger when being pulled straight out than the P shape bolts. These have the potential for one side to open the gate a carabiner if things are pulled around, probably the main reason these are not used on climbing crags, but rather via ferratas where the hardware is fixed. Please don’t buy any ol’ U shape bolt from the hardware store! If you must use them, please use Titan’s because they are very corrosion resistant and rated for 15kn with an MBS rating of 30kn but commonly break above 50kn.
Solid leg glue in bolts
Climbing-specific glue-in bolts generally have an eye at the top so they don’t require a hanger. These are nice because you can thread it with a static rope eliminating the need for quicklinks. The single rod, or solid leg bolt, has grooves or notches on the shaft for the glue to have something to grab. This is critical as epoxy glue doesn’t adhere to stainless steel very well, but stainless is critical for longevity. Solid legs are either welded or forged. Welds aren’t ideal, especially where SCC (stress corrosion cracking) is a concern, but they are not always consistent. In BoltBusters, we have found Fixe’s welded glue ins are consistent but the Crux Monster bolts have not been consistent... all super good enough, but still all over the chart.
“P” shape or Continuous Rod glue in bolts
Another option is a continuous rod that is like a U shape bolt, except it is “P” shaped, so it shares one hole like the everlasting titanium Titan Eterna bolts, the bomber Twisted Leg Bolts, and the popular wave bolt. Some of these bolts require a hammer which is unusual for a glue in. The wave bolt requires a lot of hammering as it fits tight like a compression bolt, and Titan’s Eterna and Bolt-Product’s Twisted leg bolts requires a little bit of hammering because the neck gets tight. The reason for this is so the bolts don’t fall out before the glue hardens when installed by climbers in vertical or overhanging rock.
The titanium bolts will last longer than you will because they are significantly more corrosion resistant than 316SS or even the fancy Duplex Steel, though those are also fine in normal conditions. We are fortunate to have them available as a glue in option, as titanium is still a bit too expensive to manufacture as a mechanical bolt. The 316SS Twisted Leg bolts are crazy strong at 79KN and have been very hard to break in Bolt Busters. The glue holds all these bolts well from either notches in the legs or the bent/twist pattern which snuggles that bolt in the security of all that gooey glue.
This is literally a ½” threaded rod glued into a hole. Just like everything, too much is bad. It is also important to use stainless steel (SS) and not cut the end that will be exposed to ensure you have really good threads for you to screw your nuts. Cutting exposed ends also risk leaving iron deposits embedded into your precious SS that can cause corrosion, but that is fine if it is embedded in the bottom of a hole surrounded by glue. Many cut the bottom of their rods at an angle so it helps prevent the risk of twisting the bolt in the cured glue (like if the nut seized on the threads and you were trying to remove it with a lot of pressure). “Why cut it at all?” you ask, so you can buy a 12” rod and cut it in half and have two rods.
Threaded rod gives the option of using hangers, removing hangers, or turning hangers so the same bolts can be used for multiple highlines.
You can also drill a hole in a hand sized rock, glue a nut in the hole and screw the rock onto the threaded rod to hide bolts in sensitive areas. The risk with threaded rod is that the threads can get damaged, especially if removing hangers is frequent and then you are left with a useless stubby sticking out of the rock. These don’t save you any money as you need to buy a SS nut, washer and hanger to match the metal you are using. These also have been used to glue death flakes to the cliff that you can’t seem to remove. Fully bury the threaded rod and throw a little sand over the exposed glue spot and you have a bomber-ish flake.
Chapter 2 - Glue In Bolt Buying Guide
Solid legs come in 8mm, 10mm, and 12mm. The large 12mm bolts have a thick rod which means better bend radius for ropes. Popular among highliners who use threaded rope for anchors. Size of bolt is size of hole required. Comes in 304SS and 316SS. Bolt buster break tests have these welds breaking all over the board but plenty strong enough and I recommend them.
Twisted leg series is a continuous rod twisted to give the glue a shape to hold onto and allow more glue in the crevices. The 6mm rod (12mm or ½” hole) has a very similar feel to a wave bolt. The 8mm rod requires a 16mm or ⅝” hole and is very very hard to break in bolt busters. These also come in 304SS and 316SS. There is also a large eye 8mm version.
The USA distributor is Team Tough but has a limited selection. If you contact them, they can get anything you need.
General thoughts: Jim Titt makes great bolts. His website was probably made in the 90s and rarely updated but a lot of the bolting bible came from the information found on his website. They are based out of Germany. Jim is very active in the bolting community.
Martin Roberts is an expert on Titanium and made the first certified climbing specific bolts. The continuous rod has no welds and is ideal for corrosive environments like near the ocean. They are more expensive than stainless naturally but not if you consider these could last 200 years. They did great in our Bolt Buster tests. He also sells Titanium U bolts and other titanium quicklinks/rings for anchors. Titan is based out of the UK and Rap Bolting is their US distributor. Martin has been very helpful in this Bolting Bible project.
These win the popular award, are plenty strong enough but I’m not that fond of them. They require a special tool to hammer in and spin as you hammer them so you have to hit them sideways after they are in the hole nice and tight. The tool isn’t just to keep a carbon steel hammer from leaving iron deposits on your stainless bolt, but it puts the pressure of your smacking on the bottom of the eye which is stronger than hammering the top in. We have bent these installing them during our Bolt Buster tests. Drill your hole bigger than they recommend and they might be a good option. I don’t recommend running a rope through them as the bend radius isn’t very large, reducing the strength in your rope. They broke all of our soft shackles before the rope broke! Some people think the tight fit means they are bomber and the glue is just added strength. We pulled them out with no glue at 1.5kn to 2kn in tension (straight out) and in shear was 19kn to 27kn to pull it out. Pretty impressive but make sure the glue is doing the work since we can get 40kn-ish with Ac100 glue and have yet to successfully break them with epoxy.
Fixe manufactures a ton of options out of Spain and sells in the US. All their high quality products seem to be made with the PLX/Duplex/HCR steel rather than 316SS. They had a glue in with no name that we keep calling “bell shaped” with an MBS of 35kn that gave us great results in Bolt Busters (45kn to 63kn in tension). It has a weld but is buried under the glue when we notch it. Bend radius of the metal is awesome for highline anchor ropes to be threaded through. As of writing this, they only have the 10mm bolt that goes in a 12mm hole. They used to have a super duper long one but I don’t think they sell it anymore. In fact, they don’t sell any long glue in bolts which really crappy rocks need to have.
Their newest latest and greatest glue in is their Hely PLX glue in with a wizard’s cane shape for the glue to grab and are forged instead of welded. These only require a 10mm hole but can also have a rope threaded through them. The eye snapped off of the shaft in Bolt Busters right at MBS of 28kn. These seem like great bolts but I hope they keep making the other ones!
The company had a recall on their PLX products (see metal section) but fixed the issues. They do make great bolts, one of the few retailers than sells Powers sleeve bolts, and has our favorite PLX hangers. They do sell Plated Steel products without specifying they are for interior use only. They also run out of stock often and have inconsistencies on their website. Overall I like what they make including their glue ins.
These things will break your bank. Their suggested glue cartridges are the worse glue you can use with the most expensive bolts… ironic. They are rated for oddly low numbers but I think they are being very conservative. At least you get 316SS but for these prices of $16 and $27 each, but it should be Duplex Titanium for that price (that’s a metal joke!)
Bat’inox is their big boy at 14mm requiring a 16mm hole
Collinox is their tiny guy at 10mm requiring a 12mm hole.
Here is a terrible break test video at 31.7kn (with ampule capsule). It came out of the glue. I think we will test these in epoxy for some real fun!
316SS, ½” rod for a 14mm hole ideally (5/8” works too but uses more glue) and cut to 5” - Costs $8.10 for 10” which you can cut in half and the SS nut and washer are $1 each on the same site. So $6 plus a $3.35 hanger from Fixe because SS needs to be compatible.
***Don’t buy home depot unrated rods. Buy rated threaded rods that are the correct length, or double length and no longer, so you can keep the factory finished end exposed and put the cut end in the hole with the glue. The cutting wheel will embed particles into the metal that can form rust otherwise.
Based in Italy, Vertical Evolution carries 3 different glue in designs named “arrows”, “glue in arrows” and “glue in rings”. You have to ask them for a price list and wait a couple days for it… not your average website where you can just order something and checkout. They have a lot of via ferrata products and variations of the bolts on this page for different anchor setups. All prices below are from the retail price list they emailed me without VAT or shipping.
“Arrows” are the continuous P shape rods that come in 10mm, 12mm and 14mm sizes. It says stainless but all their other products says 316L but the price sheet I gave specifically says 316L for these. The SS version ranges from €7.90 to €15.20 retail.
“Glue in Arrow” are welded versions of petzls solid leg bolts and come in 316SS 8mm, 10mm and 12mm. The 8mm and 10mm are available in a bent version and I’m not sure why? These range from €4.60 - €8.40
“Glue in Ring” is their solid leg P shape bolt but is welded backwards to Bolt-Product’s weld so I’m very curious to test these in Bolt Busters. Comes in 8mm, 10mm, and 12mm and range from €3.60-€6.50