Reference chart
Belt Speed by Task Chart (SFPM)
Set your VFD by the job: working SFPM ranges for hogging, bevel grinding, hardened steel, handles and leather, with percentages for a direct-drive 2x72 setup.
ForgeBrain
Knifemaking calculators
Belt speed, grind height, honing angle, steel weight and the charts behind them. Run the numbers before the work reaches the grinder.
5 live tools · 3 reference charts · nothing to install
Shop math
8 tools, no sign-up
Every one runs in the page. The numbers you type stay in your browser, and the arithmetic is the same arithmetic printed underneath each tool.
Live tool2×72 Belt Speed Calculator
Find your 2x72's surface speed in SFPM from drive wheel diameter and motor RPM, with optional VFD frequency, and see how hard a belt cuts and how hot it runs.
Live toolGrind Height Calculator
Turn stock thickness, edge thickness and bevel angle into the scribe height for a flat grind, with notes on reading the answer and using it at the machine.
Reference chartQuench Oil Speed Chart
A chart that matches quench media, from fast Parks 50 oil to aluminum plates and still air, to the steels each suits, plus the mismatches that soften blades.
Live toolRazor & Fine-Edge Angle Calculator
Enter spine thickness and blade width to find the honing angle built into a straight razor, per side and inclusive, with guidance against the classic targets.
Live toolSteel Selector
Answer four questions - use, rust care, heat treat setup, sharpening gear - and get your three best-fit knife steels from the 33-steel database.
Live toolSteel Weight Calculator
Enter length, width and thickness to get a steel bar's weight in pounds and ounces at 0.284 lb per cubic inch. Useful for blanks, bar orders and sword math.
Reference chartSteel Temper Color Chart
The oxide temper colors of carbon steel from pale straw to blue, with temperatures, what each means for a blade, and grinder-burn diagnosis.
Why they exist
Numbers beat guessing at the machine
Each tool handles a calculation that comes up at the grinder or heat-treat bench.
Set the speed before you burn a belt
Drive wheel diameter and motor RPM decide surface speed. A VFD moves it, and the wrong end of that range glazes belts or burns an edge.Scribe the line before you grind
Stock thickness, target edge thickness and bevel angle fix exactly how far up the blade a flat grind reaches. Scribe it, then grind to the line.Know the weight before you order
Steel runs 0.284 lb per cubic inch. That one number sizes a blank, a bar order and the shipping on both.
Keep reading
The guides behind the math
Where each of these numbers comes from, and what to do when the answer surprises you.
- Abrasives
Belt Buyer’s Guide: Which Abrasives to Actually Buy
Belts are the single biggest recurring cost in this hobby, and buying the wrong ones wastes money twice: once on belts that wear out fast, and again on…
- Abrasives
Choosing a Motor & VFD for Your 2×72
Every Torus ships as a complete assembled chassis with the motor sold separately — which hands you the one decision that shapes the machine’s personality…
AbrasivesThe Complete 2×72 Attachments Guide
A 2×72 out of the box is a platform; the attachments are the machine. Every serious grinder task — flat bevels, hollow grinds, fullers, handle curves…
Same bench
The machine the numbers assume
These tools assume a grinder that holds its setting. I machine the parts, hand-assemble, track and test Torus grinders in Sterling, Illinois.
Nova 2×72 Aluminum Belt Grinder
Current dual-axis platform with a fiber-laser-cut 6061 chassis and single-knob tracking.
Starts at$1,295
Nebula 2×72 Steel Belt Grinder
Current dual-axis platform with a steel chassis, more mass and less vibration.
Starts at$1,295
Torus 2×72 Classic Aluminum Belt Grinder
Prior-design aluminum chassis, 90-degree tilt and 1.5-inch tooling arms.
Starts at$995
One-man shop
Need a number that is not here?
Send me the calculation you keep doing on the back of a belt sleeve so I can evaluate it for ForgeBrain.