I'm 50 yr old hobbyist that has been dabbling in hand tools and power tools for 40 years. I'm not expert at anything, but know enough to be dangerous with just about any common power tool.
I own various things like a table saw, dual sliding compound mitre saw, drills, circular saw, reciprocating saw, sanders, etc, and am reasonably mechanically inclined - although not so artistically talented!
So anyways, when I opened up my new Bosch 1617 router and attempted to tighten a bit into the collet, I was a little perplexed... I have a brand new Bosch 85294M 1/4" shank roundover bit, and I can't get it to tighten in my new router. I also tried a Freud 1/4" shank forstner bit for the hell of it, because it was lying about, and it wouldn't tighten either.
So then I tried the Bosch 1/2" collet with a drill bit that has a 1/2" shank, and it wouldn't tighten either. So I think I have eliminated the collets and the bits from being the problem. Pretty sure that I've eliminated stupidity (at least, mine) from the equation also. This should be a no-brainer.
It seems (I speculate) that the collets are tightening down in the threads but the inside of the motor spindle is not tapered enough to provide compression for the collet leafs. If so, this would be extraordinarily bizarre - I have done a search on the web, and can find no indication of a manufacturing defect, and I'm hard pressed to believe that mine would be a "one-off" given modern manufacturing practices.
So... any ideas what is going on here? I'm stumped.