The mini-foodgeek has a small vise on his workbench that he uses to hold random scraps of wood so he can cut them into smaller random scraps. Most of what he's been cutting lately has been dowels, and the flat jaws that came with the vise didn't work very well for the task. Here's how to turn some scrap aluminum into a pair of vise jaws with a v-groove to hold round material.
You'll need access to a mill, some 3/8" thick material, and a 60 degree drill-mill. Being mill-less at home, I made it at techshop.
Step 1: Square Up the Material and Cut It to Size
Cut two pieces of aluminum roughly the size of the original vise jaws. Square the material on all four edges and machine it more or less to the size of the original jaws. Given that my kid's vise is from harbor freight and the bolt holes seem randomly drilled, I felt like it was a safe bet to just eyeball the measurement.
Step 2: Cut a Groove and Drill/counterbore the Bolt Holes
Measure the distance between the bolt holes in the vise jaw. Using a 60 degree endmill, spot drill both of the holes. Use a DRO to be sure the spacing is correct (1.75" in this case).
Cut a v-groove down the length of one jaw using the same endmill.
Remove the endmill and switch to a drill chuck. Drill through both holes and then counter-bore with a larger bit.
Step 3: Install the Jaws
Clean up the edges with a file, then bolt the jaws into the vise. Now the kid can go back to work randomly cutting things!