So, in building my frame saws, I'm using bolts for the mounting pins and I need them to fit very snugly so that the blade doesn't turn in use.
I bought 8mm bolts to use for this. And they're too loose in holes drilled with an 8mm bit. I found a 7.5mm bit, but they're too tight (ie, don't go in at all / might split the wood if I really drove them in)
Now, I can order a 7.8mm bit or 7.9mm bit, and I'll try those out for convenience. But I feel that is the lazy way of solving the problem, and not a solution that will work for everyone if I were to give anyone advice on how to build one themselves. I prefer not to rely on buying super specialized tools all the time.
So, let's say that you have drill bits in the following sizes: 6mm (1/4), 8mm (5/16), etc, and you want to get a very snug fit around an 8mm (5/16) bolt that that is too loose for your drill bit. How would you increase the size of that 6mm hole by 1.8mm or so? A rattail file is going to take a while to do the job, I think, and is prone to introducing error and inaccuracies. It could work, but I was wondering if there are better solutions.