Counter Bore Versus Counter Sunk

This one's really simple but a lot of people get it wrong. In addition, I believe there is one other type of bolt that gets used, but I've never seen it used before I've only heard of it being an option. This post is probably not going to be the most exciting one you've read, but if you're buying your own holds which are pretty darn expensive, you should know with bolts to use because if you don't you can crack and break your holds. There's lots of pictures, so scroll through and make sure you understand the difference.

Counter bore uses the big wrench (5/16") and counter sunk uses the "baby" wrench (7/32").

Big Wrench and Baby Wrench

Here is a picture of a bolt for counter bore with the appropriate wrench, which is really common.

Big Wrench and Bolt

Here is a picture of a bolt for counter sunk less commonly used, but is more likely to be found on smaller holds like foot chips because they can sometimes have a lower profile.

Baby Wrench and Bolt

Here are some examples of holds that will use counter bore:

Counter Bore Holds

Here are some examples of holds that use counter sunk:

Counter Sunk Holds

You'll notice that both sets of holds are small holds. This is to show that even small holds can use counter bore or counter sunk, so unless you know your holds well, always just check before you accidentally end up breaking your holds. Most of the bigger holds will use counter bore.

Additionally, larger holds might need set screws so that they don't spin. If you don't want to put extra holes in your wall though, you can also put foot chips near a hold to keep it from spinning, but it's not as common to do that at a professional gym.

More on Counterbore and countersunk here:
http://en.wikipedia.org/wiki/Counterbore
http://en.wikipedia.org/wiki/Countersink
http://www.boltdepot.com/Socket_products.aspx

Fun facts:
http://www.merriam-webster.com/dictionary/bolt-hole

Hope this helps clarify things and leads to less broken holds. After all, if a hold is going to break, it should be from doing something epic, right?

Thoughts, questions, etc? Anyone want to identify any other types of bolts that get used? Comment below.