Just picking the title brought back memories of lazy days floating the Jacks Fork and Current rivers in a canoe. Those trips often included a visit to the famous Alley Mill. http://www.nps.gov/ozar/historyculture/alley-mill.htm
However what I actually had in mind was describing a jig to assist drifting a hole when there is no one available to assist. The actual case which prompted the construction of the jig was the need to drift a square 3/8” hole in 3/8” x 3/4” square bar four times.
I wanted to work at the vise with torch heat so I designed to that setting. The jig needed to hold the work piece securely, prevent long-axis bending as the local spot was heated, allow the drift to pass all the way through, and allow the swell to develop on the sides. Since the bar is clamped there is essentially no growth in length. The pieces were long and awkward so I drilled small pilot holes with a 3/16” bit.
This will work but, when I have the luxury of helpers, I prefer to work at the anvil with coal forge heat an have one assistant hold the bar and another position the drift while I use the sledge.
|The finished jig.|
|Drift jig front.|
|Drift jig back.|
|Workpiece with pilot hole.|
|C clamps on workpiece.|
|Jig clamped in the vise.|