Every season the humidity in our shop
changes -- and the wood in our shop changes with it. One of the first places we
notice this is when pushing a shop-built jig across the table saw. Many of our
jigs -- like our sliding cut-off table -- have wooden runners on the bottom that
slide in the miter gauge slot.
The problem is that for accuracy, we've made these runners fit fairly tight. But
when the wood swells or shrinks with changes in humidity, the fit becomes too
tight or too loose in the slot.
PLASTIC RUNNERS. Recently, we've been replacing the wood runners with strips of
1/4" Plexiglas. You'll find Plexiglas at a local plastic distributor or hobby
shop. (Look under "Plastics" in the Yellow Pages.) Plexiglas can be
cut on a table saw and sanded like wood (we use 400-grit wet-dry sandpaper for
final sanding). Then simply countersink and screw the strip to the bottom of the
jig.
Another good plastic for runners is UHMW (ultra high molecular weight) plastic.
It's a lightweight, dense white plastic that's very slick.
And finally there's phenolic (the stuff we make our router table inserts out of).
Both of these last two can be worked with regular woodworking tools, and are available
under "Plastics" in the Yellow Pages in most cities.
OTHER OPTIONS. There are other options. One is Masonite or hardboard. It's stable,
and can be easily worked with woodworking tools. Though it doesn't stand up to
abrasion as well as Plexiglas, it's a good alternative to solid stock.
We've also had good luck with medium density fiberboard. MDF is also strong, stable,
and easy to work with woodworking tools. We've been using scraps left over from
other projects. It's too expensive to go by a sheet just for this purpose.
Go to Tip #4 |
