Reaming is not simply drilling with a smaller feed. A reamer is a finishing tool whose geometry, stock allowance, hole condition and feed per revolution all influence the final size and finish. This page uses RPM and feed-per-revolution calculations to create a clean starting framework while leaving the actual reamer cutting data to the specific tool.
Use spindle speed when you know the reamer diameter and selected cutting speed. Use feed per revolution to verify that the programmed feed matches the intended surface travel per spindle revolution. The page is useful for straight-flute, helical, machine and CNC reamers because the arithmetic is common even when the recommended cutting range differs by tool design.
Basic calculation first. Advanced check second.
Run the simple relationship first, then use the advanced version when the operation needs more variables or machine constraints. The calculators are intentionally stacked, not side by side.
Basic Reaming Speed & Feed Calculator
Run the core calculation for this machining workflow.
Spindle Speed Basic
Enter the values you know. The result is calculated in your browser.
Calculation only. Verify toolmaker data, material grade, engagement, machine limits, workholding and actual cutting conditions before production.
Advanced Reaming Speed & Feed Calculator
Add the relevant process or machine variables for a fuller calculation.
Feed Per Rev Advanced
Enter the values you know. The result is calculated in your browser.
Calculation only. Verify toolmaker data, material grade, engagement, machine limits, workholding and actual cutting conditions before production.
What this speed and feed calculator for reamers calculates
Record reamer diameter, cutting-speed recommendation, feed per revolution, material, reamer style and target hole size. Also note the hole’s starting diameter, stock allowance, straightness, coolant delivery and machine runout. Reaming quality depends on the entire holemaking chain, not only the reamer’s final pass.
Formulas and unit handling
RPM is calculated from cutting speed and reamer diameter using the same rotating-surface relationship used for drills. Feed rate is RPM × feed per revolution. This makes it easy to verify that a CNC program’s feed rate matches the reamer recommendation expressed in mm/rev or in/rev.
RPM = (1000 × Vc) ÷ (π × D) for metric reaming.Use the source unit shown in your tooling reference before converting.RPM = (12 × SFM) ÷ (π × D) for imperial reaming.Use the source unit shown in your tooling reference before converting.Feed rate = RPM × feed per revolution.Use the source unit shown in your tooling reference before converting.Feed/rev = feed rate ÷ RPM.Use the source unit shown in your tooling reference before converting.Step-by-step workflow
Technical context for this search
Reaming is a finishing operation, so the calculator needs to be read differently from a drilling calculator. The hole already exists, and the reamer removes a controlled amount of stock while trying to hold size and finish. Diameter, cutting speed and feed per revolution establish the arithmetic, but stock allowance, runout, alignment and entry condition often dominate the result.
The reamer diameter belongs in the spindle-speed formula. The pilot or drilled hole diameter is a different dimension and should not be substituted. Before running the first part, confirm the actual pre-hole size and intended reaming allowance from the tooling source. Too little stock can make the reamer rub instead of cut; too much can raise load, damage the edge and reduce size control.
Reaming also magnifies alignment errors. Runout, machine spindle condition, workpiece location and the quality of the pilot hole all influence whether the reamer cuts evenly. Coolant delivery and tool lubrication can affect surface finish and chip evacuation. These process variables should be checked alongside the calculated RPM and feed rather than treated as unrelated maintenance details.
For production records, store the reamer part number, finished-hole tolerance, pre-hole size, selected feed/rev, RPM, coolant condition and measured first-hole result. If the next batch shows oversize holes or poor finish, that record lets you distinguish wear, allowance, alignment and cutting-condition changes. The calculator remains the arithmetic reference while the measurement record provides the process feedback.
Calculation audit checklist
| Check | What to verify |
|---|---|
| Operation check | Confirm that the job is actually reaming before entering values. The calculator pair on this page was selected for the speed and feed calculator for reamers search intent, so switching to another operation may require a different feed convention. |
| Source check | Use the exact tooling or process reference behind speed and feed calculator for reamers. Record the tool or process identifier, material and source units before converting anything; the site calculates from supplied values rather than selecting proprietary cutting data. |
| Input check | Verify the primary inputs used by the spindle-speed and feed-per-rev calculators. A field can be numerically valid while still being the wrong variable for the operation, especially when moving between chip load, feed/rev, feed rate and surface speed. |
| Unit check | Keep metric and imperial values separated through the calculation. Recheck diameter, cutting speed and feed units on the Speed and Feed Calculator for Reamers page before accepting the result, and only round after the relationship has been verified. |
| Machine check | Compare the theoretical output with machine spindle, feed, travel and process limits. A calculated value is not a machine capability statement, and a controller limit can make the effective cutting condition different from the selected target. |
| Tool/setup check | Review tool condition, runout, overhang, workholding and coolant or lubrication where relevant to reaming. These variables are outside the arithmetic model but can dominate the actual cutting result. |
| First-cut check | Treat the first part or first hole as a validation event. Record chips, sound, load, finish and dimensional result alongside the calculated RPM/feed so later changes can be traced to evidence rather than memory. |
| Recordkeeping check | For repeat work, save the source reference, selected inputs, calculated values and final programmed values together. The Speed and Feed Calculator for Reamers calculation then becomes a reproducible setup record instead of a one-time online number. |
Worked example
For a 12 mm reamer at 30 m/min, RPM is approximately 796. At 0.20 mm/rev, feed is about 159 mm/min. The arithmetic checks the CNC values; it does not establish whether 30 m/min and 0.20 mm/rev are correct for the reamer and material.
Practical setup checks
Reaming depends heavily on stock allowance and alignment. Too little allowance may fail to clean the hole; too much can increase cutting force and damage finish. Runout can cause uneven cutting and oversize holes. Coolant delivery and entry alignment matter because the reamer is meant to finish an existing hole rather than create it from solid material.
Common mistakes
- Selecting reamer feed from a drilling chart.
- Ignoring stock allowance.
- Using the nominal hole diameter rather than the reamer diameter in the speed calculation.
- Failing to measure the first hole.
- Assuming a good reamer condition guarantees a good result in a poor pilot hole.
Troubleshooting the calculated condition
For oversize holes, inspect runout, pilot-hole condition, reamer wear and alignment. For poor finish, check feed, coolant and the condition of the tool. If the reamer is cutting unevenly, inspect stock allowance and machine alignment before changing only the spindle speed.
How to cross-check tool data
The reamer manufacturer’s cutting table should control the selected speed and feed range because geometry and material compatibility vary widely. Use this page to convert and audit those values before they go into the CNC program.
Frequently asked questions
Should a reamer use the same RPM as the drill?
Not necessarily. The reamer manufacturer’s cutting-speed range may differ from the drill, so calculate RPM from the reamer’s own data.
Is reamer feed normally per revolution?
Yes. Feed per revolution is a common way to specify reaming conditions, and the linear feed follows from RPM × feed/rev.
Why does reamer allowance matter?
The tool needs enough material to cut consistently, but excessive allowance increases cutting load and can hurt finish and size.
Can this calculator guarantee hole size?
No. Hole size also depends on stock allowance, reamer condition, runout, alignment, material and coolant.
This page calculates relationships from the values supplied by the user. It does not inspect the machine, tool condition, workholding or material state. Verify production cutting values against the exact tooling reference and the actual setup before running the cut.