Fasteners
Frequently asked questions
Should I choose metric or inch threads for plant equipment?
Match the thread system of the existing tapped hole or mating part. European, Japanese and Chinese machines mostly use ISO metric threads, while US equipment often uses UNC/UNF. The two do not interchange: M6 and 1/4 inch are close in size but differ in pitch, and forcing one into the other damages the thread.
When is zinc-plated steel enough and when is stainless required?
Electro-galvanized property-class steel suits dry indoor use. Outdoors, hot-dip galvanizing is the better choice, and in wet, chemical, food processing or coastal areas A2 or A4 stainless is preferred. Note that A2-70 stainless has lower tensile strength than class 8.8 steel, so it is not a direct substitute in highly loaded joints.
What information does KIT need to quote the right fastener?
Please state the thread system and diameter, pitch, length, head type, property class or stainless grade, coating, and the standard (ISO, DIN, JIS, ASME) if known. A photo of a sample next to a ruler also speeds up identification. Send the request to sales@kit.com.vn; CO/CQ are available on request.
What role does tightening torque play in a bolted joint?
Torque is an indirect way of creating preload, the clamp force in the bolt. Most of the applied torque is lost to friction in the threads and under the head, with only about 10 to 15% becoming clamp force. The same torque on dry, oiled or plated threads therefore gives noticeably different preload.
Thread locker or lock washers: which prevents loosening?
Anaerobic thread locker fills the gap between mating threads and stops the transverse slip that drives self-loosening under vibration. Split lock washers do little in a properly tightened joint. For vibrating joints, the effective approach is adequate preload combined with thread locker, prevailing-torque nuts or wedge-locking washer pairs.
When does galvanic corrosion between metals occur?
When two metals with different electrode potentials touch in the presence of moisture or an electrolyte, the less noble metal corrodes faster. It is worst when the less noble part is small relative to the other, such as a zinc-plated screw in a large stainless sheet. It can be limited by choosing metals close in potential, insulating with plastic washers, or keeping the joint dry.
