Having lensboards precision-bored with a machinist's lathe may be the next best thing to buying lensboards pre-bored by the manufacturer. Metal boards (aluminum or mild sheet steel) can be easily drilled with reasonable accuracy, however, with a good hole saw in a drill press. Similarly, a good Forstner bit of the right size works well for wooden lensboards. Careful sanding or filing of the hole may be necessary for a proper fit.

Forstner bits in sizes up to 2" are fairly common at better woodworking supply stores. Woodshed Tools, Inc. also carries sizes up to 3".