well. ive dismantled my cosworth rear axle and everything is fairly dirty/rusty. Ive used a wire brush on the parts and was going to hammerite them but theyre still very bumpy etc, the bumps are bits of metal that still seem very hard. What can i do to get them relitavely flat?? i was going to buy a sand blaster but wasnt sure this would work?? any suggestions?

you can sandblast, but you really don't want grit in the moving parts...

Electrolysis.... dig a trench in the garden and line with plastic sheet to make a bath.

Use an arc welder for the power and your off!

ive also got the disk covers (from inside of disks on std axle. should i use them on the kit car or just leave them off??

get an angle grinder with a metal wire brush attachment! that will get anything off!

Use electrolosys on the smaller parts will work a treat. Then Grinder with Brush for the main casing.

Really there is only one good way and that is the electrolysis method. Do a search on the forum for it and you’ll find everything you need to know. Largest thing I’ve done now was a lawnmower tractor that was totally cleaned of all rust (very thick rust at that) without even having to dismantle it and then washed and painted, all with it in one piece! Buy a cheap paddling pool for large items and a couple of basic battery chargers, so iron rod and baking soda is all you need. It’s a lot of fun too

I know what you mean about the lumpy rust stuff. For that I use a file. You will end up with pits though which you can't do much about other than spray and flatten but for an axle, that seems rather too much effort.