Free, no sign-up
Machinist reference
The charts a machinist comes back to every day: threads, drills, codes. To work out your own sizes, use the online calculators.
Chart
ISO 286 limits and fits
Calculator for H7, h6, k6, g6, p6…: deviations, limits, mid-zone, fit clearance or interference.
Chart
Tap drill chart
Metric coarse and fine, UNC and UNF: tap drill size and the bore diameter for single-point threading.
Chart
Thread undercut
Relief groove at a shoulder for external metric threads per ISO 4755: diameter dg, width, radius for any thread.
Chart
Trapezoidal thread (Tr)
Screw and nut diameters, depth, clearances and tool tip width per ISO 2901 — any Tr, multi-start included.
Chart
Morse tapers and center holes
Morse 0–6 and metric: diameter, ratio, angle per ISO 296. Type A center holes per ISO 866.
Chart
Insert designation decoder
What each letter and digit means in CNMG 120408, DNMG, VBMT and inch CNMG 432. Online decoder.
Chart
Toolholder and boring bar decoder
PCLNR 2020K12, MWLNR, SVJBR and S20R-SCLCR09 boring bars: clamping, approach angle, shank, length, matching insert.
Chart
ISO groups P, M, K, N, S, H
Colors and letters on insert boxes: which material, what P10–P40 means, codes HC, HW, CA.
Chart
Surface roughness: Ra, Rz, N, µin
Convert Ra to N1–N12, microinches, Rz and old GOST classes, with typical machining methods.
Chart
GD&T symbols
The 14 drawing symbols — runout, concentricity, circularity, perpendicularity… — what they mean and how to hold them on a lathe.
Chart
Fractions, mm and drill sizes
Fractions 1/64–1″ in decimal and mm, drills #1–#80 and A–Z; convert any size with the nearest drill.
Chart
Hardness conversion: HRC, HB, HV
Convert between Rockwell, Brinell and Vickers with approximate tensile strength — chart and online converter per SAE J417 / ASTM E140.
Chart
Steel grade equivalents
1045, 4140, 4340, 52100, D2, M2, 304, 316L, 321, 420: EN name, 1.xxxx number, JIS, GOST and ISO group. Search any grade.
Article
UNC and UNF thread chart
TPI, pitch in inches and mm, thread depth, bolt and nut minor diameters.
Article
TPI and inch thread pitch
TPI to pitch, how many decimals the pitch needs, G20 vs G21.
Article
NPT and BSPT tapered threads
1:16 taper, pipe thread sizes, calculation and G-code.
Article
Three-wire thread measurement
Best wire sizes and measurement over wires for metric and UNC/UNF.
Article
Retaining ring grooves
Groove dimensions for external and internal retaining rings.
Article
Lathe G-codes and M-codes
LinuxCNC codes for turning, with explanations.