New blade and bolt for Mountfield lawn mower bolt too short!

Mike, that would depend on your mower. Depends what engine it is and if it is metric or imperial. Most of the time a good hardware store will carry those bolts. Just take the one that is to short and have them measure it, and get you a longer bolt. Also, try your local farm implement dealer etc. Okay, just found some more info on the Mayfield mower. The bolt is a

Thread : 8mm

Length : 50mm

Part number 12735698/0

As for where to purchase it, that would really depend on your geographic location, but it appears a run-of-the-mill bolt and should not be to hard to purchase. Hope this helps, good luck.