Standard metric drill sizes and how to size holes
Standard drills come in fixed steps. Holes on those steps are drilled in one move; anything else costs extra.
| Diameter range | Standard step |
|---|---|
| up to 13 mm | 0.1 mm |
| 13–20 mm | 0.5 mm |
| above 20 mm | 1 mm (larger holes are often milled) |
Tap drills
Precision holes
For dowel pins and bearings, drill undersize and ream to size with a tolerance such as H7. Model the hole at its nominal size and write the fit on the drawing. See ISO fits.
Draw your own part
Drop a STEP file into DrawMyPart. It finds every body, asks you to confirm threads, fits and tolerances, and draws a sheet your manufacturer can build from.
Open the tool