Pick the right drill bushing and size it for your fixture.
Inch sizes follow the ANSI B94.33 charts, and part numbers are shown as Carr Lane references; metric sizes follow DIN 179 / 173 practice. Standard sizes vary by maker, so confirm final part numbers and fits against your supplier's catalog before ordering or machining.
Pressed straight into the plate, sits flush. The cheapest and most common choice for low to medium runs with one tool per hole. Use when the plate is thick enough to take the drilling thrust and you want a flat top surface.
Same as headless but with a shoulder that stops it from pushing through the plate. Pick it for larger drills with heavy thrust, thin plates, or when you want a positive stop at a set height.
One SF bushing works both ways: it has a slip notch and a fixed notch for the lockscrew (the old separate S and F types are obsolete). Used as slip, it drops into a liner and lifts out with a twist. Use it when one hole needs several tools in sequence, such as drill then ream, or drill then counterbore. Swap bushings without unclamping the part.
The same SF bushing, turned so the lockscrew holds it down. It stays put for the life of the job. Use for high-volume work where the bushing will wear out: replace it without damaging the fixture plate.
A permanent press-fit sleeve that protects the plate bore and holds renewable bushings. Always used with slip or fixed renewable types.
| Setting | Rule |
|---|---|
| Bushing ID | Nominal tool size, ground slightly oversize (inch: about +.0001 to +.0006 depending on size; metric: F7 for drills, G6 for reamers) |
| Bushing length | 1.5 × tool diameter for standard work, 2 × for precision, rounded up to a standard length |
| Chip gap to part | 0.5 × D for cast iron and brass, 1 × D for steel, 1.5 × D for aluminum and stringy materials, 0.5 × D for reaming |
| Mounting hole | Reamed for a press fit (metric H7 hole with n6 bushing OD) |
| Plate thickness | Match the bushing length so the bushing is fully supported |
| Heavy thrust | Drills 1/2" (12 mm) and larger get a head bushing by default |
These are starting points for fixture design. Tight tolerance holes, long-reach drills, and angled entry surfaces may need a longer bushing, a smaller gap, or a special bushing.
