Question 1

What is a spur gear generator?

Accepted Answer

A spur gear generator is an engineering tool that calculates the mathematical geometry of straight-toothed cylindrical gears (spur gears) and creates 2D CAD vectors. GearDXF uses the involute curve formula to generate precise tooth flanks that provide smooth meshing, constant velocity ratio, and minimal sliding friction. The resulting profiles can be exported directly into DXF and SVG formats for digital manufacturing.

Question 2

How do you calculate spur gear pitch diameter and outside diameter?

Accepted Answer

For metric gears, Pitch Diameter (d) equals Module (m) multiplied by Number of Teeth (z): d = m * z. The Outside (Tip) Diameter (da) equals Module multiplied by (z + 2): da = m * (z + 2). The Root Diameter (df) equals Module multiplied by (z - 2.5): df = m * (z - 2.5). In imperial units using Diametral Pitch (DP), Pitch Diameter is z / DP, and Outside Diameter is (z + 2) / DP. GearDXF computes all these dimensions in real time as you adjust parameters.

Question 3

Which pressure angle should I select for spur gears?

Accepted Answer

The 20-degree pressure angle is the modern industrial standard, offering the best balance of tooth strength, load capacity, and smooth meshing without excessive tooth undercutting. A 14.5-degree pressure angle provides whisper-quiet operation and higher contact ratio, but has lower tooth bending strength and requires more teeth to prevent undercutting (minimum 32 teeth without profile shift). A 25-degree pressure angle provides maximum tooth bending strength for heavy-duty, high-torque applications.

Question 4

What is the minimum number of teeth on a spur gear to avoid undercutting?

Accepted Answer

For standard 20-degree full-depth involute spur gears, the theoretical minimum number of teeth without undercutting is 17 teeth. If you use a 14.5-degree pressure angle, the minimum is 32 teeth. For a 25-degree pressure angle, gears can have as few as 12 teeth without severe undercutting. GearDXF accurately models the true involute profile and root fillet so you can verify tooth clearances before manufacturing.

Question 5

How do I export spur gears for laser cutting or CNC routing?

Accepted Answer

In the GearDXF sidebar or properties panel, click 'Download DXF' or 'Download SVG'. The exported files consist of continuous, single-loop closed polylines without duplicate overlapping nodes or broken segments. This guarantees compatibility with CAM tools including LightBurn, SheetCAM, Fusion 360, Vectric Aspire, and LaserCAD.

Question 6

Can I add weight-saving spokes and center bore keyways?

Accepted Answer

Yes. GearDXF includes built-in controls to specify the shaft hole diameter, keyway width, and keyway depth to lock the gear onto a keyed motor shaft. For large spur gears, you can activate the spoke generator to create circular or rectangular cutouts, drastically cutting material weight while retaining structural torsional rigidity.

Question 7

How does backlash compensation work on spur gears?

Accepted Answer

Backlash is the intentional space between mating gear teeth that prevents binding due to thermal expansion, manufacturing tolerances, and center distance errors. GearDXF includes a backlash slider that thins the tooth profile symmetrically by your specified offset. This is critical for 3D printing (compensating for filament squish/over-extrusion) and laser cutting (offsetting beam kerf width).

Question 8

How do I calculate the center-to-center distance between two spur gears?

Accepted Answer

The theoretical center distance (a) between two meshed external spur gears equals the sum of their pitch diameters divided by 2: a = (d1 + d2) / 2 = m * (z1 + z2) / 2. When you connect gears in GearDXF, the software automatically snaps them to this exact theoretical center distance so their pitch circles touch tangentially.

Free Spur Gear Generator - Involute Spur Gear Calculator, Simulator & DXF Export

Precise Involute Tooth Geometry & Formulas

Spur Gear Calculator: Metric Module & Imperial Diametral Pitch

Backlash Compensation for Real-World Tolerances

Center Bores, Drive Keyways & Weight-Saving Spokes

Interactive 2D Gear Simulator & Multi-Gear Trains

Clean DXF, SVG & 1:1 Scale PDF Export

Frequently Asked Questions (Spur Gears)

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