Ok, a lot of yoyoer have been hubstacking their YYF yoyos, and quite a few of them have ruined the yoyo or PGM posts in the process. I'm writing this guide to tell everyone how to "properly" hubstack a YYF yoyo that exposes the axle, meaning this won't work with something like the Supernova. A list of items you will need is
-2 PGM posts
-The axle from the yoyo or from the PGM
-A fully threaded M4-0.7 bolt, at least 30mm in length
-A 5/64 size allen wrench
Start by forcing the axle through the side of the yoyo with the allen wrench, there will be Jerk in the axle for the wrench. Screw the axle through the threaded hole and unscrew it multiple times, until you can screw the axle through with just your fingers.
*The next two steps are optional, but I prefer to do this so the bolt doesn't look so much like it was taken off the PGM
Take both the posts and sand down the step on the bolt. The picture compares the unsanded one to the sanded one.
Then after each post is sanded down, put the post on a drill and basically round the hex part. I used the inner diameter of a C Bearing to know when to stop.
Now that the optional steps are over with, here's when the fully threaded bolt is useful. This is how the post is installed into the yoyo. First, screw the fully threaded bolt into the PGM post. Like in the picture.
Then, cut the rest of the fully threaded bolt using a hack saw, leaving only about 3mm of the actual axle poking out of the post. After it's cut, file down a bit of the axle so the top isn't as rough and can be screwed into the yoyo.
After, cover the post with duct tape or masking tape, this will keep the drill from damaging the post. Then, clamp the post into the drill and slowly screw the axle sticking out into the from the IRG, or the cup of the yoyo. Make sure the post is in tight enough that you are unable to unscrew the post with your fingers.
If it was done right, this is how the post should look like.
After both posts are installed, the original 12mm axle for the yoyo will be too long. Take the rest of the fully threaded bolt and cut a new axle that will fit. After the mod is done, you will have a hubstacked whatever!