I have a 5/16" corkscrew drill bit that I want to use for building a trials obstacle. Is this going to be too much play for using 1/4" bolts? I doubt a 1/16" will make a difference and create a loose connection, but if I am jumping on it, will it loosen up? I bought the 5/16" drill bit a while ago thinking that the 1/4" drill bit would create a hole too tight for a 1/4" bolt. That may have been in error. Should have asked first.
I am going to take one of those greenish wood cylindrical fence posts you can buy at home depot and attach it lengthwise on top of a 2 x 6 and then practice riding on a skinny. They are about 7 feet long. The post is perhaps about 3" in diameter with a tapered point at one end that I will cut off. I plan to drill a hole near each end and one in the middle. Run bolts through it in those spots. I will also use some small blocks of wood as chalks on either side to help with stability. Then, finally, add some 26" 2x4s as stablizers perpindicular at each end.
As Tom Blackwood will attest you don’t need bolts at all. Just make ramps out of flexy 2x4’s running up to a cross piece resting on flimsy sawhorses. Sure, you have to set it back up every once in awhile but you don’t waste all that time bolting stuff together.
I worked in a metal workshop for a vacation job, and when I had to bolt something to something I always had to use the next size up. So, if I had to bolt something with an M4, I used an 4.5mm drillbit. I’m not sure how this translates to inches, but just use something that comes close. Basically, if you just screw in the bolts nice 'n tight, nothing’s going to be moving about.