Machinist's Tools — Shop-Floor Precision Calculators

Speeds, Feeds & Grinding

Speeds & Feeds

Select your operation, material, and tooling to get recommended RPM and feed rates.

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Setup

Operation, material & tooling

Operation

Tool Material

Workpiece Material

Diameter (inch)

Number of Flutes

Cut Type

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Results

Recommended ranges

Select parameters and click Calculate

Layout & Angles

Bolt Circle Layout

Find the X/Y coordinates of equally-spaced holes on a bolt circle.

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Inputs

BCD, count & center

Inch Metric (mm)

BCD (in)

No. of Holes

Start Angle (°)

Center X (in)

Center Y (in)

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Hole Coordinates

X/Y positions from center

Enter values and click Calculate.

Layout & Angles

Bolt Circle Diameter

Find the diameter of an existing bolt circle by measuring between holes.

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Method 1 — Adjacent Hole Chord

Measure center-to-center of two neighboring holes

Chord Length (c-to-c)

Number of Holes

Bolt Circle Diameter—

Radius—

Spacing Angle—

Formula: BCD = chord ÷ sin(180° ÷ n) · Units must match (in or mm).

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Method 2 — Across Holes (Even Count)

Measure center-to-center across opposite holes

Across Distance (c-to-c)

Number of Holes (even)

Bolt Circle Diameter—

Chord (adj. holes)—

For even hole count, BCD equals center-to-center distance of diametrically opposite holes.

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Edge-to-Edge Method

Measure hole-to-hole including hole diameters

Edge-to-Edge (adj.)

Hole Diameter

Number of Holes

Center-to-Center Chord—

Bolt Circle Diameter—

Layout & Angles

Sine Bar & Sine Vise

Find the required gauge block stack height to set a precise angle.

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Setup

Bar length & desired angle

Sine Bar / Vise Length

Custom Length (if above)

Angle — Degrees

Minutes (0–59)

Seconds (0–59)

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Results

Gauge block stack height

Enter angle and click Calculate

Reverse Calculation

Know the stack height? Find the angle.

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Height → Angle

Find angle from known block height

Bar Length

Stack Height

Angle (decimal degrees)—

Angle (Deg Min Sec)—

Threading & Tapping

Tap, Drill & Die

Find tap drills, closest standard drill sizes, and die threading guidance.

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Thread Selection

UN inch or metric

Thread Standard

Thread Size

Or enter manually:

Major Dia. (in or mm)

TPI

Engagement %

Inch (TPI) Metric (pitch mm)

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Results

Drill sizes & thread data

Select a thread size and click Calculate

Turning & Fits

Knurling

Find the ideal workpiece diameter for your knurl pitch. The knurl tracks cleanly when the workpiece circumference is an exact multiple of the knurl pitch.

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Knurl Setup

Pitch and target diameter

Inch (TPI) Metric (pitch mm)

Common Knurl Pitches

Knurl Pitch (TPI)

Target Diameter (in)

Show ± Options

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Ideal Diameter Table

Closest diameters for clean tracking

Enter knurl pitch and target diameter, then click Calculate.

Threading & Tapping

Threading / Change Gears

Find single or compound change gear combinations to cut any thread on your lathe.

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Lathe Setup

Lead screw, desired thread & gear set

Leadscrew TPI

Desired Thread

Desired TPI

Tolerance

Available Gear Set (comma-separated teeth)

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Gear Combinations

Simple and compound trains

Configure lathe setup and click Find Gear Combinations.

Gear train notes: Simple train: Driver → [idler(s)] → Driven, ratio = Driver÷Driven. Compound train: (A×C)÷(B×D) where A drives B on one stud, C drives D on the spindle/leadscrew. The 127-tooth gear is the key to cutting exact metric threads on an 8 TPI leadscrew (127÷5 = 25.4mm).

Threading & Tapping

Thread Wire (3-Wire) Measurement

Find best wire size and measurement-over-wires to verify pitch diameter on 60° UN threads.

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Thread Data

Major diameter & TPI (60° UN threads)

Major Diameter (in)

Threads per Inch (TPI)

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Results

Best wire size & measurement over wires

Enter thread data and click Calculate

Uses the standard 60° UN thread 3-wire formula: best wire = 0.57735 × pitch; M = E + 3W − 1.5155 × pitch. Always cross-check against Machinery's Handbook for final inspection.

Threading & Tapping

NPT Pipe Thread Reference

Standard NPT (National Pipe Taper) sizes, TPI, and recommended tap drill sizes.

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NPT Size Lookup

Select a size for drill & thread data

NPT Size

Taper

NPT tap drill sizes are approximate (~75–80% thread engagement) and vary slightly by tap manufacturer — confirm with your tap's data sheet for pressure-critical applications.

Speeds, Feeds & Grinding

Ball Nose Effective Diameter & SFM

A ball end mill's actual cutting diameter shrinks as depth of cut decreases — find the real RPM needed to hit your target surface speed.

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Cutter & Engagement

Tool diameter & axial depth of cut

Ball Mill Diameter (in)

Axial Depth of Cut (in)

Target SFM

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Results

Effective diameter & corrected RPM

Enter values and click Calculate

Effective diameter De = 2√(ADOC × (D − ADOC)) for ADOC ≤ radius. RPM is calculated to hit your target SFM at that effective diameter, not the full tool diameter.

Speeds, Feeds & Grinding

Grinding Wheel Max RPM / Surface Speed

Cross-check your spindle RPM against the wheel's rated maximum — always use the values printed on the wheel.

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Wheel Rating & Intended Speed

From the wheel's label / blotter

Wheel Diameter (in)

Wheel's Rated Max RPM

Your Intended Spindle RPM

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Results

Surface speed & safety check

Enter values and click Check Speed

Safety: Never exceed the maximum operating speed printed on the wheel or its blotter. This tool only checks your numbers against what you enter — it does not know your wheel's actual rating.

Layout & Angles

Compound Angle Calculator

Combine two perpendicular component angles into a single resultant angle and rotation setting.

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Component Angles

Angles measured in two perpendicular planes

Angle A (°)

Angle B (°)

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Results

Resultant angle & rotation

Enter both component angles and click Calculate

Resultant angle = atan(√(tan²A + tan²B)). Rotation is measured from the Angle-A axis. Verify your fixture's rotation convention before cutting.

Layout & Angles

Taper Calculator

Find taper rate, included angle, or an unknown diameter from any three known taper values.

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Taper from Dimensions

Large dia, small dia & length → rate & angle

Large Diameter

Small Diameter

Length

Taper per Foot—

Taper per Inch—

Included Angle—

Angle per Side (half-angle)—

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Find Small Diameter

From large dia, length & taper/ft

Large Diameter

Length

Taper per Foot

Small Diameter—

Included Angle—

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Common Standard Tapers (Reference)

Nominal values — verify against exact manufacturer spec

Taper	Taper per Foot	Included Angle
Morse #0	0.6246"	2°59′
Morse #1	0.5986"	2°52′
Morse #2	0.5994"	2°52′
Morse #3	0.6024"	2°53′
Morse #4	0.6233"	2°58′
Morse #5	0.6315"	3°00′
Morse #6	0.6257"	2°59′
Jarno (all sizes)	0.6000"	2°52′
R8 Collet	0.5982"	2°51′
NPT Pipe Thread	0.7500" (1:16)	3°35′

Turning & Fits

Press Fit / Shrink Fit Calculator

Find interference amount and the temperature rise needed to shrink-fit a part over a shaft.

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Interference

Shaft & bore dimensions

Shaft OD (in)

Bore ID (in)

Diametral Interference—

Radial Interference—

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Shrink-Fit Temperature

Heat required to clear the interference

Bore Diameter (in)

Interference (in)

Material (outer part)

Required Temperature Rise—

Suggested Heating Allowance—

Coefficients are ×10⁻⁶ in/in/°F. Add 100–150°F margin beyond the calculated minimum for safe assembly clearance and handling time. Estimates thermal clearance only — does not calculate holding force/torque.

Shop Math & Reference

Fraction ↔ Decimal Converter

Convert between fractional inches, decimal inches, and millimeters.

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Fraction → Decimal

Enter a fractional inch measurement

Whole

Numerator

Denominator

Decimal (inch)—

Millimeters—

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Decimal → Nearest Fraction

Enter a decimal inch value

Decimal Inch

Precision

Nearest Fraction—

Exact Decimal of Fraction—

Error—

Millimeters—

Shop Math & Reference

Unit Converter

Quick conversions for length, angle, torque, and pressure.

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Length

in · mm · ft · mil

Value

From Unit

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Angle

decimal ° · DMS · radians

Value

From Unit

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Torque

in-lb · ft-lb · N·m

Value

From Unit

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Pressure

psi · bar · kPa · MPa

Value

From Unit

Shop Math & Reference

Material Weight Calculator

Estimate the weight of bar stock by shape, dimensions, and material.

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Stock Dimensions

Shape, size & length

Inch / lb Metric (mm / kg)

Shape

Material

Diameter (in)

Length (in)

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Results

Estimated weight & volume

Enter dimensions and click Calculate

Densities are typical values for common alloys — verify against your exact material certification for critical quoting.

Shop Math & Reference

Hardness Conversion Reference

Approximate cross-reference between Rockwell C, Brinell, and Vickers hardness scales for steel.

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Rockwell C → Brinell / Vickers

Select an HRC value for approximate equivalents

Rockwell C (HRC)

HRC	Brinell (HB)	Vickers (HV)

Approximate values for steel, based on common ASTM E140-style reference tables. Conversions between hardness scales are empirical and material-dependent — use a calibrated chart for certification or contractual purposes.

Shop Floor Reading

Tips & Tricks

Practical techniques, troubleshooting, and lessons learned at the machine — new articles posted regularly.

View All Tips & Tricks →

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