It was not a trick question
cellardoor,
I’ve just had my fork drilled. I got my local frame builder to do it. Cost me a few bucks.
He had a good look at the fork and in his opinion it was OK to drill (and be used with a brake), so he did it.
No big deal and it was cheaper than a new fork.
Good luck…
Thanks for the replies.
The consensus seems to be either ‘depends on the fork’ or ‘drilling is sacrilege’ so I’ll have Shifter Bikes take a look and trust the man of experience.
In less there is frame builders in Melbourne someone would like to recommend. I live quite close to Hillman cycles. Is Gordon Hills work recommended?
I live close to Hillman as well and will not recommend that shop to anyone. There is a reason why their shop has shrunk to a quarter of what it used to be. Go to Dan. You’ll get better service there.
I used to own a nice track frame that was drilled by the previous owner. The wheel to crown clearance was so tight that it was tough to find a brake with the shortest reach possible to engage the rim. Fitting the brake in the first place wasn’t feasible as the distance from the hole to the bottom headset cup was so small that the body of the brake jammed against it and could not be bolted up properly.
Bottom line, the previous owner wrecked a perfectly good fork. If you’re going to do it, double and triple check that it’s going to work.
Des
You can calculate the second moment of area for an oval and a circular cross section fork blade quite easily, this will give you the section stiffness and difference in deflection. All you need is the radius/major-minor axes and the wall thickness.
That said, I have a round bladed fork meant for brakes (1940s) and I’m not worried about folding the fork in two. (I’d be more concerned about a small furry animal getting caught in the spokes and destroying the fork, and my face). I also have a track fork built with road blades and crown.
Also, is there enough reach between the hole location and the rim? i.e. are the clearances so tight that you’d have to use a super low reach brake?
edit: DAMNIT DES! Beaten like a red headed…
Wouldn’t the forward and backward stresses of a bumpy road be much greater than those from braking hard?
I’ll postulate while I sit offshore waiting for a chopper to take me home. 35-40kt winds and 45kt+ gusts today, it’s a bit rough out here, time for another espresso 
I would imagine that the fore/aft stresses experienced by a bumpy road would be orders of magnitude lower than those from braking.
The bending moment induced by the caliper brakes acting at the fork crown has to be far higher than that experienced at the crown race when riding on a bumpy road when you consider that the bumps don’t affect your speed significantly, i.e. not a large force opposing forward motion compared to braking. Continued riding on rough roads with a frame not designed for it would likely fail from fatigue crack growth.
There’s some analysis of the forces on brake bolts here:
http://pardo.net/bike/pic/fail-007/000.html
And here’s what can happen with sustained hard braking, a heavy rider and a frame where buckling instability is the failure mode:
http://pardo.net/bike/pic/fail-001/FAIL-017.html
Bike & Squirrel:
http://picasaweb.google.com/dbiked/BrotherSBikeCrash?authkey=iOs1rM3MJzo
if the frame and fork were that ‘nice’ you wouldnt be riding it on the street anyway.
just drill it and be done with it.
Here’s another bike and squirrel pic:
A case for not using low spoke count wheels.
Des
Clearances look ok to me.
It was the possibility of damaging the fork that promoted my question.
I probably will get it drilled. In less Dan advices against it on an engineering level.
Or I could get one of those bolt on disk brake mounts, that would really blow the wind up the skirts of the track bike purist 
I think you’re probably better off with low spoke count wheels (especially Spinergy Squirrel Slicers), as there’s a higher chance the bugger will get through. Improbable as it sounds I’ve read equal numbers of reports of fork breakage and the squirrel making it all the way through.
Then again, 4x 40H would be pretty hard to get through at all… what’s the optimum squirrel gap spoke count and lacing pattern?
16 spoke radial with flat blades. Squirrel stir-fry anyone?
check these out
they look strong
Very nice, but god, completely overkill don’t you think?
At the end of the day, if you need a front and rear brake for your training bike, just go out and buy a ROAD FRAME. Much easier than using this convoluted braking system.
i guess the japanese riders want everyone who sees them out on a training ride to know that they race keiran. panties probably fly off as they go past or something.
anyway, it’s such a cool piece of machinery, although the rear brake is a little overengineered i would think.
I giggle every time I read the first paragraph on that page.