Bicycle Mechanics - luggage rack mounting...dificulties

I picked up an Axium Journey from craigslist about a week ago and was mounting it to a bike I got recently. The hex bolts it comes with fit the eyelets fine, but don't seem to go into the mounting holes on the rack itself, at least for the mounts near the hub (the seatstay mounts seem fine.) It is puzzling because I am 80% certain he used the rack before, so maybe he was using a smaller bolt of his own.

So what I wonder is if I should just drill a 6mm hole through the 5mm one, tap the hole (pending on whether or not my dad has a metric tap and die set) or just forcing it through (I'm thinking this is the Option I least want to deal with). If I try to screw it in in just bores out the Aluminium (I have probably taken out about .5mm before I decided it wasn't going in.

By the way, Axiom's website doesn't have any information regarding it.

jrhii: Forcing things where they don't readily fit rarely has a good outcome. My preference would be to find a bolt which fits or failing that carefully drill and tap the hole. Keep in mind that once you remove metal you can't easily put it back.

the screws/bolts won't go there the holes? both of them? is there marks on it where he had it mounted? what kind of bike are you trying to put it on?

Most bicycle fender/rack eyelets are tapped for a 5x.8 metric screw. Likewise most racks are drilled for 5mm screws. If your frame uses 6mm fender eye screws, go ahead and drill the rack to the nearest close size above 6mm.

But double check that your frame is in fact tapped for a 6mm screw because that's fairly rare.

the outside diameter of the bolt is about 5.9mm, the inside about 5, the calipers I have measuring to .05mm. it fits the bike eyelets fine (bianchi strada). Both the rack and the bike have 5mm inside diameters, but the rack doesn't appear to be threaded...there are faint marks that are treaded form putting something in, but not deep and not treaded all the way around.

My guess is that the previous owner just used a smaller bolt that had a 5mm outside diameter or just above it, and perhaps used a nut on the other side.

I figure If I just drill a 5.9 or 6mm hole, it shouldn't be a problem because it will be sandwiched between the head and the bike eyelets.

Screws are measured by the major (outside) diameter so you apparently do have 6mm fender eyes. And obviously a 6mm screw won't fit into a 5mm hole, so get out the drill.

the rack is not susposed to be threaded!! atleast the bottom one at the dropout, the screw goes through it and and screws into the frame.

I am not familiar with that rack. are the upper holes threaded?

Yep, that seemed to be the best solution. 7/32 bit (god forbid we keep anything metric around, at least 5 sets of bits I found at they were all imperial) and I was able to just use the bolts to tap the little bit that was left, because I already worked out that they are easily harder than the Al rack. Thanks for the input.

Bianchi girl: No, but they are also bigger. (before I drilled the bottom still had paint on the inside, and so does the top, so they hadn't been bored out.

The frame should be a threaded hole, the rack should be a through hole. If both pieces had threads how could you tighten the one against the other?

Yeah, already thought of that, so i just stepped it up to like 15/64 or something that worked...now i need to go get some spacers or a smaller bolt so it doesn't interfere with the chain, but i had to go up to the hardware store anyways.