Shop calculators,
free to use.
Built by an engineer-run sign & fabrication shop. Tap drills, unit conversions, spindle speeds, thread pitch and drill angles — fast, no ads, no login. Bookmark it.
Unit Converter
Length, plus inch ↔ fraction for the bench.
Type a decimal inch in “Value”, set From = inch, to read the nearest fraction above.
Tap Drill Finder
Pick a thread — get the tap drill (number/letter/fraction + diameter) and the clearance hole.
Inch tap drills use the 75% rule (adjustable). Metric uses the standard “major − pitch”. Always confirm on scrap — material and tap style change the ideal hole.
Thread & Pitch Reference
TPI ↔ metric pitch, plus a full tap/clearance chart.
| Size | Major Ø | Pitch | Tap drill (75%) | Clearance |
|---|
Spindle Speed — RPM
Mill, lathe or drill. Starting speeds for HSS & carbide.
For turning, Ø = the workpiece diameter. For milling/drilling, Ø = the cutter/drill diameter. Reduce ~30–50% for interrupted cuts, deep holes or no coolant.
Drill Point Angle by Material
Grind/select the point for what you’re drilling.
| Material | Point angle | Notes |
|---|---|---|
| Mild & medium steel | 118° | General-purpose standard. |
| Stainless / tool / hardened steel | 135° | Split point; less walking, less heat. |
| Cast iron | 118°–135° | 118° common; 135° for harder grades. |
| Titanium & tough alloys | 135° | Split point, slow speed, firm feed, coolant. |
| Aluminum & soft alloys | 118°–135° | High helix; 135° resists grabbing in soft metal. |
| Brass & bronze | 118° | “Dub”/zero the rake so it won’t self-feed and grab. |
| Copper | 100°–118° | Slower point; gummy — clear chips often. |
| Acrylic / plexiglass | 60°–90° | Low angle, slow feed — prevents cracking/chipping. |
| Hard plastics / Delrin | 90°–118° | Sharp, polished flutes; back off for thin walls. |
| Wood | ~60° (brad point) | Brad/spur point for clean entry, no wander. |
Angle = the full included point angle. When in doubt on metal, 118° is the safe default; switch to a 135° split point for anything hard, stainless or prone to walking.
From a single plate to a full building program.
We don’t just calculate — we cut, engrave, weld and install. Channel letters, engraved plates, wayfinding and more. Installed across BC, shipped worldwide.