[COLOR= rgb(51, 51, 51)]Hi Everyone,[/COLOR] [COLOR= rgb(51, 51, 51)]I am new to road riding and have just got myself a 1978 Coventry Eagle [/COLOR]on eBay[COLOR= rgb(51, 51, 51)].[/COLOR] [COLOR= rgb(51, 51, 51)]I am pleased with the bike (admittedly I have nothing to compare it with) but after a few weeks riding, the left crank fell off.[/COLOR] [COLOR= rgb(51, 51, 51)]The nut came off somewhere on my commute and therefore I fitted a new one. My 14mm socket does not fit on the crank nut well so I am unable to tighten it enough to stop the whole crank arm wobbling.[/COLOR] [COLOR= rgb(51, 51, 51)]Do I need a different tool to tighten it fully? Or do I need a new crank arm?[/COLOR] [COLOR= rgb(51, 51, 51)]For reference, it is this type of nut/crank setup[/COLOR] [COLOR= rgb(51, 51, 51)]Any help is appreciated![/COLOR]