Introduction
In precision machining, every micron matters. A drilled hole that drifts by even half a thousandth of an inch can put a finished part out of spec — and on a high-volume production line, that single deviation multiplies into scrap, rework, and lost time.
This is why engineers rely on jig bushing tolerance charts to specify the correct components for their fixtures. Tolerances aren’t a minor design detail. They are the foundation of repeatable, accurate drilling — and they are the reason an industry-wide standard exists.
That standard is ANSI B94.33.
This guide explains what ANSI B94.33 covers, how to read a jig bushing tolerance chart, and how engineers apply it in real CNC and fixture work.
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