“Some slip right on in, some you have to force, but either way it is just a sticky mess”
The Bolting Bible
The Book Of Glue In Bolts
Welcome to our free course as our way of contributing to the bolting community. It's nice to understand what you are clipping and trusting with your life, even if you never plan on installing or removing bolts. Also, if someone is going to spend their time and money to bolt something, I assume, they probably want to do it as good as possible. Hopefully theBolting Bible gives you the tools you need to do a great job. Get it?
Our courses are A-Z content in blog format, glued together with an over arching blog we call a text book. A blog format is easy to read, easy to update, and easy to translate. Be sure to begin at the TEXTBOOK and at the end of each episode we'll point you to the next.
Glue-in Bolts
These bolts have no way of staying in the rock except the chemical bond created by a mixture of chemicals we simply call glue. We'll get to the glue part in the next chapter and installing them in the chapter after that, but for just a basic of metal there are things worth knowing.
Glue-ins can come as a single shaft with a welded eye on top or a continue rod. U-shape (or staples) are a rarely used glue in, requiring 2 holes (one for each leg) which is more impact on an area and rare to see as they are prone to unclipping carabiners. Glue always comes in two parts and is very important to mix it right as most glue in failures is a result of improper mixing. But if mixed right and the hole is dust free, it can offer some of the strongest anchors available.
Mechanical bolts are just pushing on a fraction of the sides of a hole but glue-ins grab 100% of the hole and that is especially important in softer rock or layered rock. The glue gets into the pores of the rock and makes for a bomber anchor compared to a wedge. It also keeps water out of the hole preventing corrosion where you can’t see it. They are much more technical to install and can cost more (if using hilti epoxy) than a mechanical bolt, but they will last a lifetime therefore leaving less of a long term impact.
Do not use glue with mechanical bolts. You don’t get the best of both worlds, you get the worst. The glue will only sit on the outer sleeve and not attach to the actual rod that holds the hanger down. The glue could prevent the anchors from expanding. If the hole is big enough for glue, the wedge won’t wedge. If the hole is the right size for the hole, there is no room for the glue. The glue can also clog the threads. It’s not like a mechanical bolt is going to fall out of the hole easily if you use glue, but that is not how they are designed. Don’t try to get fancy!
Glue in bolts are a great option for most placements but installation is trickier. They are stronger, last longer and are more convenient to use (not install) since many don’t require hangers. It is thought that the adhesive can help seal the bolt preventing corrosion inside the hole but if you just use 316l stainless (or titanium near the ocean) then that isn't very valid. Longevity and minimal maintenance requirements makes them a great 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.
Bolt Types
You could just bolt anything inside of a hole, but if you are reading this, we 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. You get the worst of both options. 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 / Staples
Also called staple bolts, these are almost never used in highlining and rarely used in climbing, 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. It also requires more effort to line up the two holes. The benefit to these is that they can test stronger when being pulled straight out than the P shape bolts. These have the potential for one side to open the gate on 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 or (another climbing specific bolt) 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 designed to sit outside the rock so they don’t need 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 (or at all), but stainless is critical for longevity. Solid legs are either welded or forged. Welds aren’t ideal, they are a potential weak point for strength as well as corrosion resistance.
In BoltBusters we have found Fixe’s welded glue ins fail at consistent values but the Crux Monster, while all super good enough, are all over the chart. You can see some home made ones done in this VIDEO. We don’t recommend you make them!! It is important to have some
thing that is thoroughly tested and standardized is important but the process is neat.
“P” shape or Continuous Rod glue in bolts
Another option is a continuous rod that is like a U shape bolt, excep