Hi,,,, I got 2 Hitachi M 12V's,,, I was reading your post,,, and am kind of lost to what you were talking about ? This router has a 1/4 inch adaptor sleeve that you insert into the spindle so it will be reduced to hang onto a router bit with a 1/4 inch shank bit,, take out the adaptor sleeve and it will accept 1/2 inch shank bits,,,, If your router got shipped with the sleeve already in the spindle, I could see it may be stuck in there maybe,, but you should have been able to just insert a 1/4 inch bit in there and hopefully it would come out with the bit,,,
( one bit of advice I might add though,,, when using that 1/4 " adaptor sleeve,, make sure you have it installed ALL the way into the spindle,,, I used mine once when it was sticking out maybe 1/8" or so and it got crimped and now cannot be installed all the way into the spindle,, it works, but I wish I could get it all the way in though,,, I would feel better about that )
anyway,,,, I hope you got your problem solved,,,, it should not need any dissembley of the router to change the collet over to work with 1/4" from 1/2"
and by the way ,,,, nice to see you on this forum... lots of nice people here with answers and comments,,,
It seems like every where I go,,,,,,,,,,,,,,,,,,,,,,,,, there I am...