Chamfering a bolt hole might require an extended reach countersink cutter. Here’s how to quickly make an extension for the more common 1/4″ shank cutters. First, drill a 15/32″ x 1″ deep hole in the end of a 6″ length of 3/8″ – 1/2″ diameter shaft. Ream the hole with a 0.0005 undersized 1/4″ reamer. A worn 1/4″ valve guide reamer will suffice. Heat the drilled end of the shaft with a torch to expand the hole. Then push the countersink cutter into place and allow it to cool. Time to start chamfering.
Tom Nichols
Automotive Machine & Supply, Inc
Cleburne, TX
