I've recently gone 2×9, and being hard up, I decided to make some aluminium washers instead of buying shorter chainring bolts. So far, I've just filed these into a roughly round shape and put the bike back together.

Is there any trick way of making them nice and round? Holesaw was my first thought, but we don't have any small enough. I've got a pillar drill, files, chisels etc. We do have a woodworking lathe, but it's buried behind all the stuff at the back of the shed, so I'd rather not go for that option.

Nut & bolt through the hole, put the bolt in a battery drill and run it along a file in a vice. faster the drill the rounder it'll be.

bodge solution: put a stack of them onto a bolt, tighten the nut, shove the head of the bolt in the chuck of the drill and spin it near a file.

engineer solution: file them carefully until they are round

high five, Konastoner

Can you not just file the chainring nuts like I have done when singlespeeding, although a dam sight better to spend the £5 – £10 as all these solutions are a hassle.

The stack idea works. I was going to say that with one on a bolt, the bolt head is probably bigger than I want the washer to be.

Aye, it is a hassle, but I've got a second hand bash ring on the way, and I'm a student – a lot more time than money!

as tails – file the chainring bolts down.

Test your mettle with a bench grinder and your finger tip strength 😉

Ahh, but if I file the chainring bolts down, then I'll be stuffed if I ever want to go back to 3×9. You have to plan ahead with these things 😆

Never thought of making them round on mine, just cut some off-cuts of bar and drilled holes in them, wouldn't even say they are square in shape, just filed back where necessary to fit the cranks.