Thread Ruler Large Multi-Geometry Drafter

An all-in-one precision drafting instrument engineered by Sahra Industrial Design, uniting the functions of a beam compass, focal-thread ellipse drafter, protractor, parallel rule, and straightedge into a single seamless chassis[cite: 8].

Apparatus & Structure

The Instrument

Multi-Function Geometry Hub

Replaces multiple cumbersome drafting tools by integrating a 14-inch calibrated linear beam, integrated protractor head, and specialized sliding carriage into one rigid instrument[cite: 8].

Thread Ruler Large 14-inch model with pencil holder carriage, protractor head, and guide thread[cite: 8]

Universal Surface Deployment

Optimized for standard drafting paper, technical drawing tables, chalkboards, and classroom dry-erase marker boards alike.

Integrated Systems

5-in-1 Capabilities

1. Sliding Carriage & Pen Clamp

Smooth-gliding cursor locks onto the main slide beam, holding pencils, technical pens, or dry-erase markers firmly at an adjustable radius[cite: 8].

2. Tension-Thread Ellipse System

Features an extended stem and guide thread anchoring to the ruler body, allowing continuous string-tension tracking to construct mathematically perfect ellipses[cite: 8].

3. Beam Compass & Radial Arcs

Anchors via a pivot point on the protractor head, transforming the rigid 14-inch arm into a wide-radius compass for arcs and large circles[cite: 8].

4. 180° Integrated Protractor Head

Graduated semicircular head indexed in fine degree divisions with a thread-lock fixture for angular layout and alignment[cite: 8].

5. Parallel Guide & Linear Ruler

Dual-edge linear scale for measuring lengths, setting step offsets, and striking parallel lines across large formats[cite: 8].

Operation & Procedures

Drafting Benchmarks

Geometric Mode Matrix

Figure	Tool Configuration	Operational Action
Ellipse	Stem + Thread Anchor[cite: 8]	Tensioned Loop Glide[cite: 8]
Circle / Arc	Center Pivot + Slide Lock[cite: 8]	Radial 360° Sweep[cite: 8]
Angles	Semicircle Protractor[cite: 8]	Direct Degree Layoff[cite: 8]
Parallel Lines	Slide Beam Tracking[cite: 8]	Offset Edge Stroke[cite: 8]

Focal Ellipse Construction Principle

By tethering the guide thread between the stem and the ruler base, the sum of distances from both focal anchors remains constant:

d₁ + d₂ = 2a (Constant Thread Length)

Yields uniform ellipses with precise major and minor axes in a single fluid motion[cite: 8].