Why Surface Finish Matters Surface finish (or surface roughness) describes the texture of a machined surface. It affects sealing, wear, fatigue life, coating adhesion, and appearance. If you’re designing parts that mate, seal, or slide against each other, you need to specify surface finish on your drawing. Common Surface Finish Values Ra (µin) Ra (µm) … Read more
What is NPT? NPT (National Pipe Thread) is the US standard for tapered pipe threads. The taper is 1°47′ (3/4 inch per foot), which means the threads wedge tighter as you screw them together — creating a seal. NPT threads require thread sealant (Teflon tape or pipe dope) for a leak-free connection. NPT vs. NPTF: … Read more
Matching Nut Grades to Bolt Grades Using the wrong nut with a high-strength bolt is a surprisingly common mistake — and it’s dangerous. A Grade 5 nut on a Grade 8 bolt will strip the nut threads before the bolt reaches its rated clamp load. Always match (or exceed) the nut grade to the bolt … Read more
How to Identify a Hex Bolt’s Grade Every hex bolt has markings on its head that tell you its material grade and mechanical properties. Those radial lines, numbers, and letters aren’t decorative — they’re a specification. Knowing how to read them means you can verify the right bolt is in the right application without pulling … Read more
What is Machinability? Machinability is how easy (or difficult) a metal is to cut with standard machining operations — turning, milling, drilling. It’s expressed as a percentage relative to AISI 1212 steel, which is the baseline at 100%. Higher percentage = easier to machine = lower cost. If you’re selecting a material and you have … Read more
What is Galvanic Corrosion? When two dissimilar metals are in electrical contact in the presence of an electrolyte (water, salt spray, humidity), the more reactive metal corrodes faster than it would on its own. This is galvanic corrosion — and it’s one of the most common (and preventable) failure modes in mechanical design. The further … Read more
Why You Need This Table Working with international suppliers or drawings from outside the US? The same steel has different names in different countries. This table maps the most common structural and engineering steels across seven national standards. Carbon & Alloy Steel Cross-Reference EN (Europe) SAE/AISI (US) UNS DIN (Germany) BS (UK) UNI (Italy) JIS … Read more
Decoding Steel Numbers Every time you see a steel callout like “4140” or “1018,” there’s a system behind those digits. The AISI/SAE numbering system tells you the steel’s composition at a glance — once you know how to read it. How the System Works Steel designations are typically 4 digits: XXYY First digit (X) — … Read more
What is Sheet Metal Gauge? Sheet metal thickness in the US is specified by gauge number rather than direct measurements. Confusingly, the gauge-to-thickness relationship is different for different metals. A 16-gauge sheet of steel is not the same thickness as 16-gauge aluminum. The tables below give you the actual thickness in inches and millimeters for … Read more
NPS Pipe Dimensions NPS (Nominal Pipe Size) is the North American standard for pipe sizing. Like NPT threads, the “nominal” size doesn’t match the actual dimensions — it’s a naming convention that’s been around for over a century. The OD is constant for a given NPS size. The schedule (40, 80, etc.) determines wall thickness … Read more