Flatten Wide Boards on a Narrow Jointer
Simple plywood spacer increases the capacity of your 6-in. or 8-in. jointer
Synopsis: In most home shops, there is a mismatch between the capacity of the jointer and planer–mostly because wide jointers are expensive. Working in a shop with a 12-in planer and a 6- to 8-in. jointer limits the width of boards you can mill to the smaller size. This technique can help. The secret is a wide, shallow rabbet cut on the jointer, and a spacer that is used on the planer. Follow these instructions, and you’ll be able to stretch a 6-in. jointer’s capacity to 9 in., and an 8-in. jointer’s capacity to 12 in.
From Fine Woodworking #204
As most woodworkers know, it takes both a jointer and a thickness planer to machine a board so both faces end up truly smooth, flat, and parallel to each other. The jointer gets one face flat and the thickness planer makes the other face parallel to the first.