Equipment and ToolingMachining

Microboring: when drilling just won’t cut it

If the editor doesn’t change the font size on me, the period at the end of this sentence measures about 0.02″ (0.5mm) across. It’s tough to drill something that small or smaller, but with a modern CNC Swiss-style machine and the right drill bit, it’s doable.

But what if your customer wants a couple-tenths tolerance on that hole or an ultrafine surface finish? Could you bore it?

You might if you could find a tool that small. The boring bar would have to be smaller than a 12-lb. fishing line, and even if bars that small were made, they would be hellishly expensive, right? Not really.

Dale Christopher, president of Scientific Cutting Tools, Simi Valley, Calif., noted that most of the small boring bars his company offers cost less than a pair of movie tickets and a bag of popcorn.

“A bar like a 1-8-5 (0.185″ minimum bore) is in the $23 range,” he said.

OK, but what if I need an ultrasmall bar, one that could cut the cataracts out of a bumblebee? Christopher consulted his catalog. “Our smallest goes down to 0.015″, with a maximum depth of 0.05″. That one’s $28.74. It goes up a little because of how small it is. They’re a bit harder to set up.”

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