{"id":67416,"date":"2026-10-10T12:06:16","date_gmt":"2026-10-10T04:06:16","guid":{"rendered":"https:\/\/sfxtec.com\/stainless-fastener-galling\/"},"modified":"2026-10-10T12:06:16","modified_gmt":"2026-10-10T04:06:16","slug":"stainless-fastener-galling","status":"publish","type":"page","link":"https:\/\/sfxtec.com\/de\/stainless-fastener-galling\/","title":{"rendered":"Why stainless fasteners seize, and how to stop it"},"content":{"rendered":"<p class=\"lead\" style=\"font-size:16px;color:var(--ink-soft)\">Galling is not cross-threading and it is not a manufacturing defect. It is cold welding: two metal surfaces, clean and under pressure, welding together at a microscopic level until the thread tears itself apart. Stainless is the material it happens to most, and it has a handful of very practical fixes.<\/p>\n<h2>Why stainless, specifically<\/h2>\n<p>Stainless steel protects itself with a chromium-oxide layer that re-forms instantly when it is scratched. That is exactly what makes it corrosion resistant &mdash; and it is also why it galls. When a bolt is tightened, the oxide layer is stripped from the high points of the thread, bare metal is exposed on both parts, and the two surfaces weld before a new oxide layer can form. Stainless also has a high coefficient of friction and low thermal conductivity, so the heat generated by tightening stays in the contact area and accelerates the process.<\/p>\n<p>The problem gets worse with:<\/p>\n<ul>\n<li><strong>Large diameters.<\/strong> More contact area, more heat, more torque.<\/li>\n<li><strong>Long thread engagement.<\/strong> More surface in sliding contact.<\/li>\n<li><strong>Power tools.<\/strong> Speed generates heat far faster than hand tightening.<\/li>\n<li><strong>Clean, degreased, unlubricated threads.<\/strong> Nothing between the surfaces.<\/li>\n<li><strong>Repeated assembly.<\/strong> Each cycle removes more oxide and work-hardens the surface.<\/li>\n<\/ul>\n<h2>Six ways to prevent it<\/h2>\n<ol>\n<li><strong>Lubricate the thread.<\/strong> This is the single most effective measure. A nickel- or molybdenum-based anti-seize compound, or a moly-based grease, cuts the friction that generates the heat and keeps the surfaces apart. A wax-based dry film works where an oily residue is unacceptable. Note that lubrication lowers the torque needed for a given preload &mdash; reduce the torque setting accordingly, or you will over-tighten the joint.<\/li>\n<li><strong>Slow down.<\/strong> Use hand tools, or a driver on its lowest speed with a torque cut-off. If a fastener starts to feel hot, stop &mdash; the damage is already happening.<\/li>\n<li><strong>Torque to the correct figure, once.<\/strong> Over-tightening is the most common cause in practice. Work to the torque the size and grade call for, and do not &#8220;give it a bit more&#8221; as insurance.<\/li>\n<li><strong>Mix the alloys.<\/strong> A 316 (A4) nut on a 304 (A2) bolt, or a fastener with a nylon-insert nut, reduces the tendency to weld because the surfaces are not identical. Mating two identical stainless parts is the worst combination.<\/li>\n<li><strong>Use coarse threads and the minimum sensible engagement.<\/strong> A coarse thread has fewer, larger contact points and clears itself better. More thread engagement is not automatically better.<\/li>\n<li><strong>Do not re-use stainless fasteners indefinitely.<\/strong> After several assembly cycles the thread is work-hardened and the oxide has been repeatedly stripped. Treat frequently dismantled joints as consumable, or move to a lubricated or coated fastener.<\/li>\n<\/ol>\n<h2>If it has already seized<\/h2>\n<p>In order:<\/p>\n<ol>\n<li><strong>Stop turning.<\/strong> Continuing is what shears the shank or strips the hexagon.<\/li>\n<li><strong>Penetrating oil and time.<\/strong> Apply, leave it to creep for several hours, then try a small back-and-forth movement rather than a single hard turn.<\/li>\n<li><strong>Impact rather than torque.<\/strong> A sharp tap on the head of the fastener &mdash; not on the thread &mdash; often breaks the weld where steady force will not.<\/li>\n<li><strong>Local heat, carefully.<\/strong> Differential expansion can break the joint free, but heat will discolour stainless and can destroy a coating, and it must be kept away from anything painted, plated or polymeric.<\/li>\n<li><strong>Cut it off.<\/strong> When nothing else works, a cut-off disc is faster and cheaper than a damaged component. Then replace the fastener with a lubricated one.<\/li>\n<\/ol>\n<h2>What we stock for it<\/h2>\n<p>Stainless lines in <a href=\"\/de\/material\/304-stainless-steel\/\">304<\/a> and <a href=\"\/de\/material\/316-stainless-steel\/\">316<\/a>, with <a href=\"\/de\/surface-finish\/plain\/\">plain<\/a>, <a href=\"\/de\/surface-finish\/brushed\/\">brushed<\/a> and <a href=\"\/de\/surface-finish\/sandblasted\/\">sandblasted<\/a> finishes so you can pick a thread surface that suits assembly, plus nylon-insert <a href=\"\/de\/product-category\/nuts\/lock-nuts\/\">lock nuts<\/a> that avoid the stainless-on-stainless pairing entirely. Sold by the piece, no minimum order.<\/p>","protected":false},"excerpt":{"rendered":"<p>Galling is cold welding, not cross-threading. Six practical measures that prevent it, and what to do once a fastener has locked up.<\/p>","protected":false},"author":0,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-67416","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/sfxtec.com\/de\/wp-json\/wp\/v2\/pages\/67416","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sfxtec.com\/de\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sfxtec.com\/de\/wp-json\/wp\/v2\/types\/page"}],"replies":[{"embeddable":true,"href":"https:\/\/sfxtec.com\/de\/wp-json\/wp\/v2\/comments?post=67416"}],"version-history":[{"count":0,"href":"https:\/\/sfxtec.com\/de\/wp-json\/wp\/v2\/pages\/67416\/revisions"}],"wp:attachment":[{"href":"https:\/\/sfxtec.com\/de\/wp-json\/wp\/v2\/media?parent=67416"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}