{"id":4353,"date":"2026-03-13T13:03:17","date_gmt":"2026-03-13T05:03:17","guid":{"rendered":"https:\/\/machinedwasher.com\/?post_type=product&p=4353"},"modified":"2026-03-16T15:58:43","modified_gmt":"2026-03-16T07:58:43","slug":"countersunk-bolts","status":"publish","type":"product","link":"https:\/\/machinedwasher.com\/th\/products\/countersunk-bolts\/","title":{"rendered":"304 Stainless Steel Countersunk Bolts M3-M20 Hex Socket Flat Head Screws"},"content":{"rendered":"

What are Countersunk bolts?<\/strong><\/h2>\n
Countersunk bolts<\/strong> feature a conical head that sits flush with or below the workpiece surface when installed into a pre-machined countersink hole. [Standard number to be confirmed: ANSI B18.3 (hex socket) or B18.6.3 (Phillips)]<\/div>\n
Unlike socket head cap screws<\/strong>, countersunk bolts eliminate surface protrusions, reducing fluid drag and interference risks. Compared to square head bolts<\/strong>, they deliver concealed installation for precision aesthetic surfaces and tight-clearance applications.<\/div>\n
\n

Materials<\/h2>\n
Stainless Steel Series<\/strong><\/div>\n
\u2022 A2-70 (304 equivalent)<\/strong>: 700 MPa tensile strength, general corrosion resistance, indoor\/light outdoor environments<\/div>\n
\u2022 A4-80 (316 equivalent)<\/strong>: 800 MPa tensile strength, molybdenum-enhanced chloride resistance, marine\/chemical applications<\/div>\n
\u2022 A2-50\/A4-50<\/strong>: Cold-worked, moderate strength, cost-sensitive projects<\/div>\n
\n

Surface Finishes<\/h2>\n
\u2022 Plain (Uncoated)<\/strong>: Native stainless passivation layer, cleanroom\/medical equipment compatible<\/div>\n
\u2022 Electropolished<\/strong>: Ra \u22640.8 \u03bcm surface roughness, eliminates micro-cracks, medical\/semiconductor preferred<\/div>\n
\u2022 PTFE Coating (Xylan\u00ae)<\/strong>: 0.05-0.10 friction coefficient, anti-galling, 260\u00b0C service temperature<\/div>\n
\u2022 Uncoated SS<\/strong>: Maintains intrinsic corrosion resistance, avoids galvanic coupling risks<\/div>\n
\n

Specifications<\/h2>\n
Metric Standard<\/strong><\/div>\n
\u2022 Diameter<\/strong>: M3-M24<\/strong> (coarse\/fine thread optional)<\/div>\n
\u2022 Length<\/strong>: 6-200mm<\/strong> (full thread\/partial thread)<\/div>\n
\u2022 Drive Type<\/strong>: Hex Socket \/ Phillips \/ Slotted<\/strong> \u2022 Head Angle<\/strong>: 90\u00b0 countersink<\/strong> (standard) \/ 82\u00b0 (imperial)<\/div>\n
Imperial Standard<\/strong><\/div>\n
\u2022 Diameter<\/strong>: #4-1″<\/strong> (UNC\/UNF thread)<\/div>\n
\u2022 Length<\/strong>: 1\/4″-8″<\/strong> \u2022 Drive Type<\/strong>: Hex Socket \/ Phillips \/ Slotted<\/strong> \u2022 Standard<\/strong>: ANSI B18.3 (hex socket) \/ B18.6.3 (Phillips)<\/div>\n
\n

Application Scenarios<\/h2>\n
Scenario 1: Precision Sheet Metal Enclosures<\/strong> Square head bolt protrusions disrupt stackable shipping. Countersunk bolts enable zero-gap panel mating with M4-M6<\/strong> and A2-70<\/strong>, achieving IP65 enclosure ratings.<\/div>\n
Scenario 2: Automated Conveyor Systems<\/strong> Socket head screw protrusions snag conveyed materials. Countersunk bolts’ flush installation eliminates interference points; PTFE coating<\/strong> reduces friction against polymer slide blocks, extending maintenance intervals.<\/div>\n
Scenario 3: Marine Decking<\/strong> Square head bolt protrusions create trip hazards and water pooling. Countersunk bolts with A4-80<\/strong> and electropolish<\/strong> maintain surface integrity in salt spray, meeting USCG safety codes.<\/div>\n
\n

Customer Case<\/h2>\n
Situation<\/strong>: A precision medical equipment manufacturer used standard socket head cap screws for CT scanner housings. Screw head protrusions caused surface dents during stacked shipping, and disinfectant pooled around protrusions, creating corrosion spots.<\/div>\n
Task<\/strong>: Required a fully flush-mount, hydrogen peroxide-resistant fastening solution compliant with FDA 21 CFR 888.30.<\/div>\n
Action<\/strong>: Supplied A2-70 electropolished countersunk bolts<\/strong>, M6\u00d720mm, 90\u00b0 head angle matching countersinks, Ra \u22640.4 \u03bcm surface finish, with material certificates and batch traceability codes.<\/div>\n
Result<\/strong>: Eliminated surface denting and corrosion risks; cleaning cycle reduced by 30%; equipment surface rating upgraded to Class A (reported).<\/div>\n
\"\"<\/div>","protected":false},"excerpt":{"rendered":"

304 Stainless Steel Countersunk Bolts M3-M20 Hex Socket Flat Head Screws<\/p>","protected":false},"featured_media":4357,"comment_status":"open","ping_status":"closed","template":"","meta":{"_acf_changed":false},"product_brand":[],"product_cat":[3086],"product_tag":[3133,3167,3135,3166,3140,3139,3136,3097,3098,3165,3168,3134],"class_list":{"0":"post-4353","1":"product","2":"type-product","3":"status-publish","4":"has-post-thumbnail","6":"product_cat-machined-bolts","7":"product_tag-countersunk-bolts","8":"product_tag-countersunk-bolts-m12","9":"product_tag-countersunk-bolts-m8","10":"product_tag-flat-head-countersunk-bolts","11":"product_tag-m10-countersunk-bolts","12":"product_tag-m3-countersunk-bolts","13":"product_tag-m8-countersunk-bolts","14":"product_tag-machine-bolts","15":"product_tag-machine-bolts-and-nuts","16":"product_tag-socket-countersunk-bolts","17":"product_tag-square-countersunk-bolts","18":"product_tag-stainless-countersunk-bolts","20":"first","21":"instock","22":"shipping-taxable","23":"product-type-simple"},"acf":[],"_links":{"self":[{"href":"https:\/\/machinedwasher.com\/th\/wp-json\/wp\/v2\/product\/4353","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/machinedwasher.com\/th\/wp-json\/wp\/v2\/product"}],"about":[{"href":"https:\/\/machinedwasher.com\/th\/wp-json\/wp\/v2\/types\/product"}],"replies":[{"embeddable":true,"href":"https:\/\/machinedwasher.com\/th\/wp-json\/wp\/v2\/comments?post=4353"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/machinedwasher.com\/th\/wp-json\/wp\/v2\/media\/4357"}],"wp:attachment":[{"href":"https:\/\/machinedwasher.com\/th\/wp-json\/wp\/v2\/media?parent=4353"}],"wp:term":[{"taxonomy":"product_brand","embeddable":true,"href":"https:\/\/machinedwasher.com\/th\/wp-json\/wp\/v2\/product_brand?post=4353"},{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/machinedwasher.com\/th\/wp-json\/wp\/v2\/product_cat?post=4353"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/machinedwasher.com\/th\/wp-json\/wp\/v2\/product_tag?post=4353"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}