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Westcott SW-51 6-Inch Protractor Ruler — main product image
Westcott

Westcott SW-51 6-Inch Protractor Ruler

★★★★★4.3 (25 reviews)

One versatile ruler handles angles, straight lines, and curves — a compact drafting essential for students and working designers alike.

$5.99*$6.98Save 14%
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*Price sourced from Amazon.com. Last updated:Jul 14, 2026.Price and availability are subject to change.

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Overview

The Westcott SW-51 is a 6-inch multi-function drafting ruler designed for students, designers, and anyone who needs accurate angle, line, and curve references without carrying a full set of separate instruments. Its 180° protractor gives you precise angle measurement across the full semicircle, while the built-in 45° and 60° triangle cutouts handle the most common drafting angles without needing dedicated triangles. The French curve symbol adds smooth arc-tracing capability for layouts and technical illustrations. All of this in a tool that fits flat in a notebook pocket or pencil case — it's the kind of Swiss-army-knife drafting aid that earns permanent desk residency.

Made from transparent plastic, the SW-51 lets you see your work clearly beneath the ruler — a small but meaningful advantage when aligning to existing guidelines or tracing over reference marks. The dual-scale calibration (16ths of an inch and centimeters) makes it equally useful for imperial and metric projects, and the 6-inch length keeps it manageable for close-up work on standard paper sizes. The plastic construction is functional rather than premium — it will take some surface wear over time — but for everyday drafting, geometry homework, and light design work, the SW-51 delivers reliable, accurate results in a compact, affordable package.

Key Features

Transparent 180* protractor ruler

45* and 60* triangle cut outs plus French curve symbol

Calibrated 16ths to the inch and centimeters

Transparent 180* protractor ruler ^45* and 60* triangle cut outs plus French curve symbol ^Calibrated 16ths to the inch and centimeters

Specifications

Size
6 Inch / 15cm
Material
Transparent Plastic
Protractor
180°
Triangle Cutouts
45° and 60°
Additional Features
French Curve Symbol
Scale (Imperial)
16ths to the inch
Scale (Metric)
Centimeters
Brand
Westcott
Model
SW-51

Pros & Cons

👍 Pros

  • Combines protractor, triangle references, and French curve in a single 6-inch tool — reduces how many instruments you need on your desk or in your bag.
  • Transparent plastic construction lets you see underlying guidelines and reference marks on your drawing while measuring — a genuine practical advantage over opaque rulers.
  • Dual-scale calibration (16ths/inch and centimeters) handles both imperial and metric work without switching tools.
  • Compact 6-inch size fits easily in a pencil case, notebook sleeve, or laptop bag — always there when you need it.

👎 Cons

  • Transparent plastic scratches over time, which can make fine graduation markings harder to read after extended daily use.
  • The 6-inch length limits its usefulness for longer straight-line work — larger drafting or layout tasks will still require a full-length ruler or straightedge.
  • The French curve cutout covers a limited arc range; complex or varied curves still need a dedicated French curve set for precise work.
  • Plastic construction means it can flex slightly under pressure, which can introduce small measurement errors when pressing firmly with a mechanical pencil or pen.

Frequently Asked Questions

For many everyday tasks, yes. The SW-51 combines a 180° protractor, 45° and 60° triangle cutouts, and a French curve symbol in one 6-inch tool, which covers the core geometry needs for most drafting, technical drawing, and geometry coursework without needing to juggle multiple instruments.
The ruler is calibrated to 16ths of an inch on the imperial scale and in centimeters on the metric side — standard precision for drafting rulers in this size class. It's well-suited for accurate work in technical drawing and geometry, though for extremely fine engineering tolerances you'd want a dedicated precision instrument.
The SW-51 is made from transparent plastic, which is lightweight and functional but will show scratches with heavy daily use over time — particularly if dragged across rough paper or stored loose with other hard tools. It holds up fine for normal classroom and desk use with reasonable care.
The French curve symbol is a functional template — you can trace inside the cutout to produce a smooth curve for technical illustration or drafting layouts. It's a simplified curve rather than a full French curve set, but useful for common gentle arc applications without carrying an additional tool.
Yes — the SW-51 is dual-scaled, with 16ths-of-an-inch markings on one side and centimeters on the other, making it practical for projects that switch between measurement systems, including international coursework and mixed-standard drafting environments.

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