How To Sharpen Carbide Inserts

We produce quite a lot of commercial grade turned work here at The Woodshop (publishers of this blog), and over the years we have switched almost completely from traditional gouges and skews to carbide insert tools. Those same turning tool inserts can be found in a number of cabinet shop machines such as planers and jointers. In high volume shops, it makes sense to discard the inserts when they’re dull, but for shops such as ours where we make one-of-a-kind pieces and prototypes, it’s almost painful to throw them. The manufacturers obviously recommend disposal and re-purchase, but some of the inserts are quite expensive. We use a 600 grit/25 micron diamond sharpening stone to sharpen carbide inserts off the tool (credit-card sized stones are available from DMT and Trend). Just apply a little lube (Windex™ or even just water works well), and use a forefinger to move the wide, flat face of each insert around the stone for maybe ten seconds. Carbide edges are brittle, so don’t use too fine a stone or you’ll instantly lose your new cutting edge. If the inserts are gummed up, soak them in mineral spirits or something a little stronger such as lacquer thinner for an hour or two and wipe them clean before introducing them to the diamond stone. And if the screws are stuck and won’t release the cutter, Easy Wood Tools has a downloadable, short PDF with some suggestions about that.