In Reply to: thread chasers 2 posted by dave#1 on January 27, 2016 at 07:45:04:
Thread chasers are good tools to have. A good set of regular taps on hand are a must as well, both INCH and METRIC sizes. Most, if not ALL spark plug threads are METRIC. One must be cautious to ensure they have the correct thread size and PITCH size or risk boogerin' up the mating part. Our N's have spark plugs have thread size at 14mm x 1.25mm pitch. Some think a 9/16-20 tap will work but that'll just wallow out the plug holes. For an OD thread, a good thread file will work too. Be careful.