Machining Calculators & Engineering Tools
32 free calculators we built because we use them — tolerances and fits, threads, feeds and speeds, materials, inspection. Every one computes from formulas shown on screen, works in both directions, and tells you honestly when a number is exact and when it is an estimate. Results are linkable, so you can send a colleague the exact answer.
Tolerances & fits
Getting the numbers on the drawing right — and knowing what they cost.
ISO 2768 General Tolerances
Permitted deviation for any dimension — or the reverse: does the general tolerance cover what you need?
OpenISO 286 Limits & Fits
H7/g6 to H7/p6: exact limits, clearance/interference range, fit diagram and a measured-parts checker.
OpenPress Fit Force
Lamé equations: contact pressure, press force, hub hoop stress and the shrink-fit temperature.
OpenTolerance Stack-Up
Worst-case vs RSS side by side, per-feature contributions, and the per-feature budget for an assembly limit.
OpenGD&T Symbol Decoder
Build a feature control frame and read what it demands — plus whether the combination is even legal, and how ASME Rule #1 differs from ISO.
OpenTrue Position (MMC)
TP from measured coordinates with bonus tolerance at MMC, drawn on the tolerance circle.
OpenGauge R&R (MSA)
Is the gauge lying to you? EV, AV, GRR and ndc, reported against both total variation and the drawing tolerance.
OpenCpk Process Capability
Cp, Cpk, PPM defective and yield from spec limits and data, with the normal curve drawn against the tolerance band.
OpenMaterials & stock
Choosing the grade and knowing what it weighs — before the quote.
CNC Material Selector
Filter 50 grades we machine by strength, machinability and density; compare side by side; look up alternatives.
OpenMetal Weight
Bar, plate, tube and hex weight across real grades — or how much material fits a weight budget.
OpenThermal Expansion
Growth with temperature, and how much temperature swing a tolerance can survive. Why 20 °C is the law.
OpenHardness Conversion
HRC ↔ HV ↔ HB and approximate tensile strength for steel, from the ASTM E140 / ISO 18265 tables, both ways.
OpenBar Stock & Yield
Parts per bar after parting kerf, facing and the chuck remnant — plus swarf percentage and the real material cost per part.
OpenMaterial Equivalents
Cross-reference EN, BS, DIN Werkstoff, JIS and AISI/UNS designations — search any system, with honest notes on where grades differ.
OpenNitriding Case Depth
Cycle time for a target nitrided case depth and back (d = K√t), on the diffusion curve, with the process guide.
OpenThreads & fasteners
From tap drill to torque wrench.
Tap Drill & Engagement
Tapping drill and ISO 273 clearance holes M1.6–M30, thread engagement worked both ways, full chart.
OpenThread Dims & 3-Wire
Pitch/minor diameter and measurement over wires — plus measured-over-wires back to actual pitch Ø.
OpenBolt Torque & Preload
M3–M30 in 8.8/10.9/12.9 with adjustable K and utilisation — reproduces the published charts and shows why they disagree.
OpenThread Engagement
Minimum tapped depth so the bolt breaks before the thread strips — from the real materials, not a generic multiple of diameter.
OpenDrill Point & Countersink
Drill point length and tip depth to program, plus countersink plunge depth to a target diameter — both drawn in cross-section.
OpenCutting: speeds, power & time
The shop-floor numbers, checked against our actual machines.
Feeds & Speeds
RPM, feed, chip load and MRR with chip-thinning warning — checked against our real spindle list.
OpenCutting Power & Torque
kW from removal rate and kc, torque at RPM, and which of our spindles can carry the cut.
OpenMachining Time
Cycle time with a visual cutting-vs-everything-else breakdown — and the feed needed for a target time.
OpenTurned Finish (Ra)
Theoretical Ra from feed and nose radius — or the max feed for the Ra on the drawing.
OpenTool Deflection & Chatter
Cantilever push-off from core diameter and stick-out, with the published L:D chatter limits and the fix hierarchy when it rings.
OpenScallop & Stepover
Ball-nose cusp height from stepover and back, drawn to scale, with the cycle-time consequence.
OpenSetup & inspection
On the surface plate and at the machine.
Bolt Circle (PCD)
X/Y coordinates for any hole pattern, drawn to scale — or PCD from the measured gap between holes.
OpenSine Bar
Gauge block stack for any angle and back, with the real resolution at your angle drawn on screen.
OpenTaper
Angle, ratio and taper-per-foot from diameters; 7:24 and metric ratios; tailstock offset.
OpenSurface Finish Converter
Ra ↔ RMS ↔ Rz ↔ N grades in any direction, with honest confidence labels per conversion.
OpenTrig / Triangle Solver
Right-triangle sohcahtoa with the triangle drawn live as you type, plus a sine/cosine-rule solver for any triangle.
OpenCost & DFM
What your part will cost — and why.
Printable reference charts
Five A4 sheets from the same verified data — tap drill sizes, ISO 286 tolerance grades, hardness conversion, GD&T symbols and surface finish. Free to print, pin up and photocopy.
Open the charts → For students & lecturers →Send Your Drawing for a Same-Day Quote
Talk directly to the engineers who will machine your parts — no account managers, no trading-company markups. Complimentary DFM review with every enquiry.