The Tool Mill

Workshop calculators

46 calculators for the wood shop and the metal shop — joinery layout, saw and router setup, lumber and fasteners, machining, welding and belt drives. Every page shows its formula and checks its answers against worked examples you can redo by hand.

What you will find here

The Tool Mill is a small, independent collection of calculators for jobs where a measurement and a formula beat a guess: the blade a used band saw needs, the dado stack that matches a sheet of plywood that is not really ¾ in, the pivot distance for a router circle jig, the drill for a #8 screw in oak. Each tool asks for things you can measure in the shop and returns a number you can act on, with the arithmetic shown so you can see where it came from.

20 of the pages are full guides. Alongside the calculator they explain when to use it, how the math works in plain words, give a reference table produced by the calculator itself, walk through two or three worked examples with real numbers, and list the mistakes and safety points that matter for that job. The rest are shorter calculator pages with the formula, worked checks and limits.

Everything runs in your browser. There is no account, and your measurements are not sent anywhere to get an answer. The pages are planning and setup aids; a machine manual, a blade or bit maker’s chart, a welding procedure or an inspector always takes priority.

Start with a guide

The most-used topics, written out in full:

Box joint — finger count, pins and sockets, even-division pin width
Dado stack — chippers and shims that add up to your measured plywood
Mortise and tenon — one-third rule tenon, cheeks, width and mortise depth
Half-lap joint layout — cut depth and shoulder length, equal or unequal stock
Dovetail layout — tail width, half-pins and slope angle
Polygon miter angle — flat frames and splayed boxes, miter and bevel
Face-frame rail stile — stile and rail cut list, mid stiles and mid rails
Drawer box — box size, parts and bottom panel from the opening
Circle jig — router pivot distance for discs and openings
Band saw blade length — blade length from wheel size and axle spacing
Bandsaw blade tension stretch — dial-indicator stretch for a target tension
Crosscut sled runner fit — runner width and depth for a snug miter-slot fit
Router bit tip speed — tip speed and safe RPM for big bits
Forstner bit RPM — drill press speed by bit diameter
Wood lathe RPM — roughing and finishing speed by blank diameter
Linear feet to board feet — board feet both ways, nominal or dressed
Wood screw pilot hole — pilot and clearance drills for #4–#14 screws
Threaded insert pilot depth — pilot and depth for inch and metric inserts
Fly cutter RPM — spindle speed and feed for a single-point fly cutter
Pulley RPM / belt drive — driven speed, ratio and belt speed

How to get a trustworthy answer

Measure the real thing. Wheel diameter over the tire, the miter slot with calipers, the plywood in three places. Nominal sizes are the most common source of wrong answers.
Keep one unit system. Most tools default to inches; many accept millimetres. Do not mix them within one calculation.
Compare with the worked example. Each page shows the steps. If your answer surprises you, put the example numbers in and check you get the same result.
Test on scrap. A test cut, a test hole or a test bead is still the final check.

All 46 calculators by job

Filter tools

Joinery & layout (13)

Joints that need numbers before they need a saw: how many fingers fit, how deep a lap goes, how wide a dado stack must be, and what a frame or drawer cut list looks like from the opening you actually built.

Box joint — finger count, pins and sockets, even-division pin width
Dado stack — chippers and shims that add up to your measured plywood
Mortise and tenon — one-third rule tenon, cheeks, width and mortise depth
Half-lap joint layout — cut depth and shoulder length, equal or unequal stock
Dovetail layout — tail width, half-pins and slope angle
Scarf joint length — scarf length from stock thickness and slope ratio
Polygon miter angle — flat frames and splayed boxes, miter and bevel
Crown molding miter — nested miter and bevel from spring angle and wall corner
Face-frame rail stile — stile and rail cut list, mid stiles and mid rails
Drawer box — box size, parts and bottom panel from the opening
Cabinet overlay — finished door size from opening and overlay, single, pair or inset
Shelf pin hole layout — hole centers for 32 mm, 1 in or 1¼ in systems
Circle jig — router pivot distance for discs and openings

Saw, router & lathe setup (10)

Machine setup in the wood shop. Blade length and tension on the band saw, sled runners and blade height on the table saw, and speed choices for router bits, Forstner bits and lathe blanks, where diameter changes everything.

Band saw blade length — blade length from wheel size and axle spacing
Bandsaw blade tension stretch — dial-indicator stretch for a target tension
Band saw drift angle — drift angle from a test cut, to skew the fence
Crosscut sled runner fit — runner width and depth for a snug miter-slot fit
Table saw blade height — blade height above the stock for through cuts
Table saw taper jig — jig opening, rise and angle for tapered legs
Router bit tip speed — tip speed and safe RPM for big bits
Forstner bit RPM — drill press speed by bit diameter
Wood lathe RPM — roughing and finishing speed by blank diameter
Hand plane cutting angle — bed angle plus back bevel or bevel-up angle

Lumber, glue & fasteners (8)

Buying, preparing and fastening wood: board feet at the yard, seasonal movement, strip yield, bending, glue-line clamping, and the right pilot hole for screws and threaded inserts.

Linear feet to board feet — board feet both ways, nominal or dressed
Lumber shrinkage — width change with moisture content
Rip strip yield — how many strips a board gives after kerf
Steam bending time — steaming time from thickness
Wood glue clamp pressure — clamp count and force for a glue line
Brad nail length — brad or finish-nail length from trim and substrate
Wood screw pilot hole — pilot and clearance drills for #4–#14 screws
Threaded insert pilot depth — pilot and depth for inch and metric inserts

Machining & drilling (5)

Drilling, tapping and turning in the metal shop: tap drills, hole saw and fly cutter speeds, tailstock taper set-over, and torque wrench corrections.

Tap drill size — 75% thread drill for inch and metric taps
Hole saw RPM — hole saw speed by diameter and material
Fly cutter RPM — spindle speed and feed for a single-point fly cutter
Tailstock offset taper — tailstock set-over for turning a taper
Torque wrench extension — dial setting when an adapter lengthens the wrench

Welding & cutting gas (6)

Starting settings and quantities for stick, MIG, TIG and oxy-acetylene work. These are starting points to strike a test bead with, not welding procedures.

Stick welding amperage — starting amps from rod diameter
MIG wire speed — wire feed speed from plate thickness and wire size
Welding heat input — kJ per inch from volts, amps and travel speed
Welding travel speed — travel speed from weld length and time
TIG tungsten grind — point angle, grind length and tip for TIG tungsten
Acetylene withdrawal rate — safe draw per cylinder and cylinders per torch tip

Belt drives & shop power (4)

Belt and chain drives, motor current and the voltage lost on a long cord or circuit to a shop machine.

Pulley RPM / belt drive — driven speed, ratio and belt speed
Roller chain length — chain pitches for two sprockets and a center distance
Motor FLA — full-load current by horsepower and voltage from the NEC tables
Voltage drop — drop on a long run to a shop tool

About this site

The Tool Mill publishes original calculators with the formula and worked examples on every page, so you can check the math yourself. Pages are corrected when a reader reports a confusing input or a wrong number. It is not a store, a brand catalog or an engineering service. More about how the calculators are checked · Contact.