Mechanical Engineering Toolkit vs Poly

Mechanical Engineering Toolkit is a professional engineering calculator for students, researchers, and practicing engineers. Choose a formula, enter your variables, and get instant results — with calculation steps, formulas, diagrams, and unit conversions shown along the way. Switch between SI and Imperial units anytime, save favorites, and find the right tool fast with recommendations by major. Save your inputs as named projects, and export any result as text, image, CSV or PDF. Categories and tools: Mechanics of Material • Moments of inertia of plane areas • Force-displacement relation of a bar • Torsion formula and angle of twist • Flexure formula of a beam • Transverse shear stress • Deflections and slopes of cantilever and simple beams • Plane stress transformation and Mohr's circle • Principal stresses and planes • Spherical shell and thin-walled pressure vessel stresses • Buckling load of a column • Thermal deformation and stress • Combined loading • Bolted / riveted joints • Fatigue safety factor • Shaft power and torque Statics • Centroid of an area • Resultant of a force system • Beam reactions • 2D truss analysis Machine Design • Helical compression springs • Spur gear geometry and stresses • Shaft fatigue design (DE-Goodman) • Bearing L10 life • Belt and chain drives • Bolt preload / torque-tension • Fillet weld strength • Press / shrink-fit interference • Shaft critical speed (Dunkerley) • Beam natural frequency (five end conditions) • Torsional natural frequency (one or two rotors) Fluids & Thermal • Reynolds number and flow regime • Pipe pressure drop (Darcy-Weisbach with Colebrook) • Pump and fan power • Composite wall conduction • Fin efficiency • Heat exchanger sizing by LMTD Theory of Elasticity • Constitutive relation of linear elastic material • Stress/strain of linear elastic material Composite Material • Lamina and laminate stress/strain • Lamina engineering constants • Laminate plane and 3D properties • Rule of mixtures • Failure criteria (Tsai-Hill, Tsai-Wu) Reference Tables • Drill & tap chart (metric and imperial thread series) • ISO 286 fits & tolerances • Standard sections (AISC W, IPE, HEB) • Unit converter No account required. Works offline. Available in English, Chinese, German, French, and Japanese.

Poly-PDF — Scanner, PDF Editor & Annotator Pay once, own it forever — no subscriptions, no in-app purchases, no surprises. Poly-PDF is a complete PDF editor for iPhone and iPad. Edit text directly on the page, annotate documents, fill forms, sign, and organize your files. EDIT TEXT IN PLACE Tap any text on a PDF and start typing. PolyPDF lets you edit the actual content of a document right on the page, preserving the original font, size, and layout. Change a date, fix a typo, or rewrite a paragraph. ANNOTATE ANYTHING Add sticky notes, text boxes, shapes, arrows, and freehand ink drawings anywhere on a page. Highlight, underline, or strikethrough selected text. Every annotation is saved directly into the PDF so it opens correctly in any other app. FILL FORMS & SIGN Tap any form field to fill it in. Add your signature from a saved library or draw a new one. Insert images and stamps with a single tap. SHAPES & DRAWING Draw rectangles, ovals, lines, and arrows with full control over stroke color, fill color, and line width. Sketch freely with the pen tool or highlight with the highlighter. Smart alignment guides help you center and align objects on the page. ORGANIZE YOUR LIBRARY Keep your PDFs tidy with folders, search, and sort options. Drag a file onto a folder to move it instantly. Open PDFs directly from iCloud Drive and save changes back in place. SCAN DOCUMENTS Turn paper into PDFs with the built-in document scanner. Scan multi-page documents in seconds and save them straight to your library. POWERFUL PAGE TOOLS Reorder, rotate, insert, and delete pages. Export a clean flattened copy of any document. Redact sensitive information permanently with the redaction tool. BUILT FOR iPAD Open two documents side by side in split view with synchronized scrolling. Use the full-screen reading mode for distraction-free viewing. Keyboard shortcuts make editing faster than ever. MORE FEATURES · Table of contents navigation · Bookmarks and go-to-page · Full-text search across pages · Password-protected PDF support · Dark mode support · Undo and redo for all edits · Works entirely offline — no account required Poly-PDF is built for people who work with documents every day. Whether you're reviewing contracts, editing reports, filling out forms, or marking up study notes, Poly-PDF gives you the tools to get it done — right on your device.