Fastener selection most often looks only at size, ignoring strength and operating conditions. Our approach starts with the load, then sets material and surface treatment.
Three rules
- General equipment assembly works with grade 4.8; upgrade to 8.8 for heavy loads or vibration;
- Indoor dry environments use black oxide; outdoor or humid conditions require zinc or dacromet;
- Food and medical equipment go straight to 304/316 stainless, do not make do with coated carbon steel.
The same three rules apply to matching nuts and washers.