A reamer enlarges and finishes an existing hole to a precise diameter and a smooth surface — something a drill bit alone can’t reliably do. This reamer technical data page covers reamer types, how much stock to leave for reaming, recommended speeds and feeds, and tips for accurate, chatter-free results.
Types of Reamers
| Reamer type | Best used for |
|---|---|
| Hand reamer | Straight or slightly tapered lead; turned by hand for light finishing and fitting. Best for occasional, low-volume work. |
| Chucking (machine) reamer | Held in a drill press, lathe or mill for production reaming. Rose and fluted styles for through and blind holes. |
| Taper reamer | Produces or finishes tapered holes (e.g. for taper pins and morse tapers). |
| Adjustable reamer | Blades expand to hit a precise, custom diameter — ideal for odd or worn sizes. |
| Shell reamer | Replaceable head on an arbor for larger diameters, saving tool cost. |
How Much Stock to Leave for Reaming
Reamers are finishing tools, so the drilled hole should be just under the final size. Leave roughly the amounts below on the diameter (i.e. drill this much smaller than the reamer). Use the lower end of each range for harder materials and precision fits, the higher end for soft materials and roughing reamers.
| Reamer / hole diameter | Suggested allowance |
|---|---|
| Up to 1/8″ (3 mm) | 0.003″ – 0.006″ |
| 1/8″ – 1/4″ (3-6 mm) | 0.006″ – 0.010″ |
| 1/4″ – 1/2″ (6-13 mm) | 0.010″ – 0.015″ |
| 1/2″ – 1″ (13-25 mm) | 0.015″ – 0.020″ |
| Over 1″ (25 mm) | 0.020″ – 0.030″ |
Reaming Speeds & Feeds
Run reamers at roughly one-half to two-thirds the RPM you’d use for a drill of the same size, but with a higher feed rate — feeding too slowly glazes the hole and dulls the reamer. Always feed the reamer into the cut and withdraw it while still turning forward (never reverse a reamer).
| Material | Speed (SFM) | Feed |
|---|---|---|
| Aluminium & brass | 130-200 | High |
| Cast iron | 50-80 | Medium-high |
| Mild steel | 50-65 | Medium |
| Alloy / tool steel | 30-45 | Medium |
| Stainless steel | 25-40 | Low-medium |
Tips for Accurate Reaming
- Rigid setup: Keep the reamer aligned with the hole — misalignment causes oversize, bell-mouthed holes.
- Never run in reverse: Reversing chips the cutting edges. Always withdraw while turning forward.
- Consistent feed: Feed steadily; hesitation leaves rings and chatter marks.
- Use cutting fluid: Lubrication improves finish and prevents built-up edge, especially in steel and stainless.
- Match reamer to job: Use a chucking reamer for machine work and a hand reamer only for light hand fitting.