I'm building a thickness sander which at this point I wish was complete. ( https://www.instructables.com/id/Thickness-Sander/)
Every time I do another part of the project, I realize how little I know about metal working. I've never removed links in a chain to alter the tension of the chain before, so this was another opportunity to learn something new. Oh Boy!!
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Step 1: Get the Length / Find the Master Link / Grind the Chain / Put It Back Together
All chains have a "master link" that is designed to be able to be taken apart. If you look at the first red circle, towards the left, you will see that this clip that is open.
The way that you get the master link off, is to pry it off laterally with a needle nose pliers as I am doing here.
DO NOT LOSE THE CLIP, OR THE MASTER LINK, OR THE POSTS! You will need them later to put the chain back together.
After you remove the clip, you can remove the master link from the posts and set it aside. The posts will just easily come apart from the chain.
Once you have the chain apart, you can then shorten the chain by grinding open the back a link. Watch the youtube video for an example http://youtu.be/pnyz7Ao_MNw
Once you have ground the pins down, you can take a punch and hit the posts. and the chain will be able to be separated.
Putting the chain back together is easy. The issue is what to do if the length of the chain that you need is not a whole link, but only a half a link? The solution is to use a "half link" ;-)
If you look at the third photo, you will see that there is a tiny cotter pin that comes with the half link. Full links have two posts -- half links have a post and a hole like the one in this photo. Install the cotter pin, and bend it back, This is the "half link". The remaining hole connect to the other end of the chain, and is reassembled in the exact opposite manner than you took the chain apart.
Step 2: Test the Chain for the Correct Tension / Length
Once the chain is back together and you think that you have the right length, you need to test the tension.
In this video, you can see that the tension is not correct and the chain needs to be made a little bit shorter.
Testing chain length and tension: http://youtu.be/c227LtJk8cI
It is a trial and error process to get it right. It's always a good idea to have a half link around and some extra master links as well too!
After a great deal of going through a learning process, I made my chain at TechShop!