Brakes - Why won't you fit

There's been a thread on this before, but my issue is a little more complex. I have forks which leave very little clearance between the drilling and the bottom of the bearing race. The caliper can be spaced out easily enough, but it's the nut on the back that is the real bugger. If I use old-style non-recessed brakes, then the nut will not tighten down as it binds against the bearing race, however if I drill it out to accommodate recessed-type fitting, there is going to be precious little room to accommodate the flange of the allen nut, and I don't want to go drilling the fork to discover that later.

Do you reckon that I can safely file a couple of mm from the bottom of the aluminium cup which holds the bearing race? The headset is a 1" Tange job (falcon?) which looks like a campag copy.

Any ideas please!

Could you not add instead a thick spacer that would be itself filed to accomodate the bearing race instead of filing the bearing race? That would save you filing more important parts =)

Do you reckon I should drill out for the recess, then add a filed washer if need be?

I was thinking to only add a washer between the nut and the fork, but I'm not sure your bolt is going to be long enough to do that. If it's long enough, the only file the washer.
Otherwise, you may have only the option to have a special washer to accomodate the recessed nut, but that may not look so good :/

In all honesty, if it works, I'll be happy. The brakes I'd like to use are designed for recessed fitting, but I might try with some older weinmann ones first.

In that case, I'd go for a recessed type nut with a filed washer.
There is also a nice idea from Sheldon right here: http://sheldonbrown.com/calipers.html#mounting

option 3 for front mounting: Use the short recessed nut, but don't put it through the back of the fork. Instead, push it up into the inside of the steerer from the bottom. You can reach a 5 mm Allen wrench in through the hole in the back of the fork, and poke the short caliper bolt in from the front. You may need to shorten the recessed nut slightly to get it to fit inside your steerer.

Seems a cool idea!! Not sure it'd fit your steed.

I've done that before and although it seems like a good fix, the caliper can rotate forward under braking. I'm wondering whether I should drill the back to 8mm for the recessed fitting, then pad out with filed washers either side until the bugger fits. On the back, at the bridge (since there is no way for access to the back only), I'm guessing the whole thing can be drilled out to 8mm (including the rear curved washer) and recess fitted that way? Anybody done this?

Er, don't bother with all that washer/recess/puppy killing. Just get a clamp-on keirin brake. ALL problems are then solved.

Next!

Aren't clamp-ons flexy and fugly?

Mine wasn't. All black on an all back frame. Easiest way to solve your issue though. Unless you start looking fork alternatives.