if you would like to maximise those willing to help you stephenj I'd suggest supplying the clue and any letters you may already have in situ - not everyone has clues to every crossword on the go!
27a - certainly looks like chainsaw - can only come up with a very tenuous connection which is 'staying'= was in (backwards (crtptically) in the clue) for a cutter is obviously chain saw - am sure the boffs will solve it to your satisfaction later on today.
For the other one Bit Tie fits and a bittie is necktie (?control) for nerds (?boring) - very tenuous again but all I can come up with - sorry