“The more you twist the head, the more the nut gets sucked up.”
The Bolting Bible
The Book of Mechanical 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 the Bolting 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.
So mechanical bolts aren’t rocket science. If you have the right size hole, and a quality bolt made of stainless, the basic idea is that you smash it in and tighten it. A wedge gets sucked into something that expands. You can have a rod with a flared end or wedged nut, and if the part that expands is big enough, it’s no longer a plain ol’ wedge bolt but magically transforms into a sleeve bolt. However, like everything, it’s what they don’t tell you that gets ya… so let's go over the little nuances of each type of bolt that will help you install a safe mechanical bolt.
Smash them in and tighten them. It’s not much harder than that, but here is some stuff you need to know. It is important to install the hanger onto the bolt BEFORE hammering it in. If you forget to put the hanger on, then you may not be able to pull it back out. If you can partially remove it like the Power-Bolt, then you risk debris getting into the threaded cone at the bottom. If you take the nut off of Fixe’s Triplex bolt, then the whole rod can fall into the hole and probably deep enough to where you can’t get it out because there would be no way to grab it. So, install the hanger of your liking to the bolt BEFORE hammering it into hole. Place the coned nut, that is at the bottom, so it is just touching the sleeve but don’t pre-expand the sleeve (see pic above).
Now it’s time to hammer it in (the hole is clean, right!?). If it goes in really really easy, you may have a hard time getting it to tighten because the entire bolt and all its parts are spinning in the hole. If it is a bitch to get in the hole, then your hole is too small and you risk breaking or compromising your bolt, and the harder it is to get in a removable, the harder it will be to get it out!
Then tighten it. All bolts have a specific torque pressure they require to achieve the ratings that the manufacturer claimed. Torque wrenches are not expensive but can suck to take on a long hike. If you don’t use one on the mountain, at least use it on some practice bolts at home in your backyard so you know what it should feel like. If 25 foot lbs of torque is required and you have no freaking clue what that feels like, use a small to medium wrench and pull until your face scrunches but not so hard that you grunt.
If you don’t tighten it enough, obviously the risk is that it could come out. When I tensioned bolts from 25 to 35 torque lbs, I was shocked how much umpf I had to give it. There is a limit, like everything, that if you really really tighten it that you compromise its integrity by breaking the bolt or stress cracking it. A fun experiment is to try to pull out your test bolts after hardly tightening it at all. It is amazing how well they hold. However it is important that they are properly tightened.
Hangers want to be a certain direction depending which way you pull them. You don’t want to randomly place your hanger and then, when tension is applied to it, forces it to spin to the correct orientation while under pressure.
If it doesn’t spin, then you are pulling on that hanger in a very unfavorable way. It can reduce the strength. Hangers break lower in our tension tests on BoltBusters than in shear. Put a carabiner on the hanger and pull on it in the direction it will be used. And on highline anchors, remember that the furthest outside bolts are going to be pulled diagonally towards the master point, and not necessarily the same direction as the highline.
Keep in mind that if your hole is too shallow, the bolt obviously won’t go in all the way, but that means the hanger will be spinning because it isn’t secured to the rock. That doesn’t mean it will blow out the hole if you use it, but it is considered sloppy and I don’t know if I would trust a bolt that I knew nothing about if the hanger is loosely spinning. If you really goofed, and it is sticking way out, then it could leverage the bolt, breaking it at a much lower force.
Sleeve bolts are better for softer rock because they have a larger surface area and can open the split sleeve wider than just a wedge bolt with a small clip at the end of it. The softer the rock, the deeper and bigger you will want your bolt. There is no downside to using a sleeve bolt in hard rock so it is a good idea to use them unless you want marine grade 316 stainless, which is hard to come by in a sleeve bolt.
The real difference is the size of the expansion clip at the base of the rod. There is no real reason to use wedge bolts over sleeve bolts other than it’s easier to find 316SS, as most sleeve bolts are 304SS. So if you have an area that is prone to corrosion and have hard rock (as it’s not a good idea to install wedge bolts in soft rock), then these might be the right choice. But if the area is high risk of corrosion, you might as well put in titanium glue in bolts to make sure that it lasts.
To install, start in the same way as the sleeve bolts by putting the hanger on the bolt before hammering. These too require a specific torque. Tighter isn’t always better. Be sure to line up your hanger with the direction you will pull it and wrench it down. The rod will stick up higher than the nut after you torque it so start with the nut as high as possible without hitting it with the hammer. Make sure the wedge is expanding immediately and not sliding up the hole as you tension the nut 20+ rotations, leaving very little bolt left in the rock. You can feel if it is getting tighter and expanding in the hole.
Are you an Innie or an Outie?
Ok, so bolts don’t have innies as much as flush hex heads. A hex head attached to the rod sucks up the nut at the bottom like a good cough will do to yours! The rod/shaft doesn’t get any higher the more you tighten it; all the magic happens in the hole. Only sleeve bolts have this design.
But then there are outies where the rod/shaft is being pulled out of the rock as you tighten the nut. This can be on some sleeve bolts, but it is on every wedge bolts. The nut should be installed when you hammer it in, but you don’t want to hit the nut because that means you are putting all the force on the threads and that can damage them. However, you don’t want the rod sticking way up when you are done, so you want to start the nut as high as you can get it, without actually hitting it. If the rod is sticking out far enough, it can hit the gate if your carabiner gets rotated and literally open it!
The hanger that the bolt is securing to the rock, is as important as the bolt itself. Many hangers are rated for 22kn to 25kn just like the carabiners climbers generally attach to them. However some hangers have broken past 50KN as seen in our BoltBuster tests. It is nice to have a hanger that is similar strength to the bolt it is attached to, otherwise you could be leaving some strength on the table since the weakest link will break. Hangers made from round stock can have rope threaded directly into them for highline anchors. The round stock generally has less of an impact as they don’t shine quite the same way as a flat hanger, so that can be a benefit to using them in climbing, but is not ideal for climbing anchors as they could wear down quickly if ropes are constantly running inside of them. Offset hangers are designed for anchors so your rings or quick links added to them allow the rope to go sideways and not get smashed against the rock. Additional hardware should be added to hangers for climbing lower off anchors.
● Fixe Hardware has a 316L SS hanger that meets all new EU Standards for $3.95. It has
an MBS of 25kn and broke at 30kn or higher in Bolt Busters. DON’T BE A CHEAP ASS AND
BUY THE PLATED STEEL HANGERS. THOSE ARE FOR INDOOR GYMS.
● Petzl has a 316SS hanger that is about $4 each and they are rated by Petzl for 25kn.
● CMI has a hanger for a ⅝” bolt and is powder coated steel that has been chromated first.
If used in shear they break as low as 7500lbs or 34kn instead of 10,000lbs they are rated
for. If pulled straight out, they hold 44kn or 10,000lbs. They are NOT made for climbing or
slack lining but instead made for Challenge Courses and Arborists. They are over sized, not
for giant bolts in soft rock, but for tree overgrowth.
● Bolt-Products has a hanger made from a 8mm 316SS (A4) welded rod
for a 12mm bolt at a price of €5.20. These allow a rope to be threaded
directly inside of them. For highliners, these are amazing. They work
great with Fixe’s Triplex Bolts or any 12mm bolt that you have. I have to
drill the hole slightly bigger if I want to use them on ½” bolts.
Team Tough is the US distributor for Bolt-Products.
● Bonier has a hanger without sharp edges so that a rope can be
threaded through, which is ideal as a highliner since we won’t have the
rope running over this surface wearing it out like a climbing anchor.
Comes in 304SS. See this EPISODE.
● Bonier also has an omnidirectional hanger for 12mm or ½” bolts,
though power bolts will NOT work with it because this gets set on a bolt
after it is installed. Certified for the construction world but possibly a
great highline hanger for lines pulling straight out of a wall.
● Chain links require many washers between the link and the rock to
raise it high enough so the second link doesn’t grind on the rock. This means all the
pressure is being put towards the top of the bolt instead of the base, significantly reducing
strength. Also, they should not be pulled in tension, so if you put your bolts in the middle of
a cliff face to be pulled directly outward, chain links should not be used. Keep in mind these
don’t work for sleeve bolts (because of the flush heads). If you use chain, wedge bolts are
the best bolt. They can have a rope threaded in them eliminating the need for quicklinks in
a highline rig or for a lower off at a climbing anchor. However, chain links you may see are
probably zinc plated because cost was the determining factor when installing them.
1st Chain Supply also offers ½” made from 316SS but it is 14.90 per foot with a 10 foot
minimum. This can be a good solution for those in countries without easy access to good
Believe it or not, bolting companies are not lining up to sponsor us; mostly because there is no money in such a niche industry. $1 per episode helps a ton and so does grabbing MERCH if something grabs your eye. Lots of designs and options.
Ugh, why is it doing that? (FAQs)
● Why is my sleeve bolt just spinning and not getting tighter?
○ The hole is probably too big, the entire bolt and all its parts are spinning inside. The
nut at the bottom of a sleeve bolt needs to stop spinning, so give friction to the nut by
pulling up against the sleeve while you tighten. This is done by pulling up/over on the
hanger. If it comes out too much, after you get some progress, hit it back down flush
against the hanger and rock and finish tightening it.
● Why is the wedge bolt rising as I tighten but not getting tighter?
○ The clip at the bottom is either spinning with it or the wedge at the bottom is lifting
the clip instead of expanding it. The clips commonly have 2 bumps on them to give
some friction along the rock and so it shouldn’t do this, but if that’s your problem then
try to pull up on hanger while tightening but if you try to hammer a wedge bolt back
down because it got to high/extracted, it only knocks the wedge out of the clip and you
are more or less starting all over. Hole size is pretty important here.
● Why is it snug and tightening but won’t get solid?
○ If you are sure the sleeve or clip is expanding and it is snug but not increasingly
getting tighter, then the rock is shit and it’s expanding the rock (I have had this happen
to me before in Iceland).
What are those plastic parts on the sleeve bolts?
Sometimes there are spacer sleeves or bushings or compression rings that are made out of plastic. These just separate the parts and it’s not holding any force but helps with installation. The powers spec sheet states, “The Power-Bolt is also designed to draw the fixture into full bearing against the base material through the action of its flexible compression ring. As the anchor is being tightened, the compression ring will crush if necessary to tightly secure the fixture against the face of the base material.” There is also a plastic star shape below the nut on some bolts and that helps with the loose nut syndrome, something we all try to avoid! Leave them on there, they help. Don’t worry, they aren’t the parts that hold the bolt in the rock.
● The wedge bolt is secure but the rod sticks up higher than the
hanger, is that ok?
○ It cosmetically looks bad and leaves any wandering climber
curious as to how much bolt is left in the rock. If you are absolutely
sure you have a sufficient amount of bolt left in the rock, and the
wedge and clip are NOT just below the surface, then it is going to hold.
If it sticks out too much it could hurt someone or be an unclipping
hazard as the gate would be opened if the carabiner rotated. I
recommend loosening the nut, hammering it in again and trying to get
it to seat deeper. Just having the tip in the hole isn’t going to satisfy everyone involved!
Real life shit
This video is of a bolt breaking during a highline whipper. Andy Lewis set up a highline for an Alex Mason’s Red Bull eclipse shot and had to use some existing shitty bolts. They were shitty zinc plated bolts that corroded enough to snap during approximately a 5kn whipper which was spread out over that 3 point anchor probably only putting a maximum of 3kn on that bolt.
As nice as it would be to write in this book, “Just use this 1 bolt”, there is no perfect bolt as each has pros and cons. We want you to know HOW to buy bolts and NOT tell you WHAT to buy. Consider the following when reviewing bolts you see online...
● Length is TOTAL bolt length for mechanical bolts. If you have a 4 ½” bolt, you may only
end up having 3.75” embedded in the rock when you are finished.
● Some bolts are certified with EN 959:2007 certification or CE/UIAA or some construction
certification. And some are not. Go with a reputable company in either case.
● Don’t buy zinc plated or plated steel or galvanized bolts.If you can’t afford stainless, don’t
install bolts. PLX stainless is awesome but fading out for the new standards of 316L SS.
● Read the spec sheets and know what the torque specs are (how tight that bolt is
supposed to be wrenched down).
● Be sure your hanger is made of the same metal as your bolt so you don’t get galvanic
These companies sell mechanical bolts that I would take a whipper on.
Fixe Hardware has great selection including Powers sleeve bolts but unfortunately they sell PS (plated steel) which technically can be used in the driest of deserts but it ought to be made more clear as they get installed in wetter areas all too often. They still have some PLX products but are phasing them out for 316L SS. All their products are bomber. Manufactured in Spain and distributed in the US.
ClimbTech sells Powers sleeve, wedge and removable anchors. Unfortunately they also sell PS Powers!?!? US Based.
Vertical Evolution has a single mechanical bolt option that comes in 8mm (too small), 10mm and 12mm… in 316SS or galvanized??? Most of the bolts on their sight are glue in bolts. Based in Italy.
Petzl sells quality bolts but they aren’t cheap. Sold everywhere.
The Power-Stud was a great 304SS wedge bolt that is about $3 each and is very accessible and comes with a SS washer and nut. In our Bolt Buster shear tests, they will snap at 60kn, higher than almost any hanger you can buy for it.
Confast’s “American 316SS Thunderstud Anchors” are a good price at $5ish each with washer and nut included.
What NOT to Buy
I am NOT convinced Keith Titanium makes bolts that are OK to use but my OCD won’t let me exclude it from this book if I’m attempting to make a complete guide to bolts. I tried buying some but they supposedly don’t sell these in the US and after researching the product this is what I found. Someone couldn’t screw on the nut when they bought it because the threads were poor quality.
The website claimed UIAA approved and the UIAA took action and it is no longer on their website. It is not certified to EN959 either. Tested by a third party said this is NOT a titanium alloy like the website states but is commercially pure and not an alloy. The nut and bolt threads appeared cut and not rolled (rolled is stronger and holds up to fatigue). The wedge piece is floppy so a large portion of the bolt gets pulled out of rock when tightening leaving a shallow embedment depth.
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