{"id":72,"date":"2026-09-05T07:30:00","date_gmt":"2026-09-05T05:30:00","guid":{"rendered":"https:\/\/www.matai.cz\/blog\/?p=72"},"modified":"2026-08-31T17:20:00","modified_gmt":"2026-08-31T15:20:00","slug":"din-7991-zapustna-hlava-imbus","status":"publish","type":"post","link":"https:\/\/www.matai.cz\/blog\/din-7991-zapustna-hlava-imbus\/","title":{"rendered":"DIN 7991 z\u00e1pustn\u00fd \u0161roub s vnit\u0159n\u00edm \u0161estihranem: norma a mont\u00e1\u017e"},"content":{"rendered":"

\u0160roub se z\u00e1pustnou hlavou a vnit\u0159n\u00edm \u0161estihranem podle DIN 7991<\/strong> je standardn\u00ed volbou v\u0161ude tam, kde m\u00e1 hlava \u0161roubu zapadnout do roviny spojovan\u00e9ho materi\u00e1lu a z\u00e1rove\u0148 se utahovat imbusov\u00fdm kl\u00ed\u010dem v \u00fazk\u00e9m prostoru. Tato norma je dnes harmonizovan\u00e1 s evropskou ISO 10642<\/strong> (resp. \u010cSN EN ISO 10642), tak\u017ee ozna\u010den\u00ed DIN 7991 a ISO 10642 v praxi popisuj\u00ed tent\u00fd\u017e prvek. V tomto v\u00fdkladu projdeme geometrii hlavy, rozm\u011brovou \u0159adu, dostupn\u00e9 jakosti i specifika mont\u00e1\u017ee, na kter\u00e1 je u z\u00e1pustn\u00fdch imbus\u016f pot\u0159eba myslet.<\/p>\n

Co norma DIN 7991 popisuje<\/h2>\n

DIN 7991 definuje \u0161roub s plochou z\u00e1pustnou (ku\u017eelovou) hlavou a vnit\u0159n\u00edm \u0161estihranem (imbusem) pro pohon. Charakteristick\u00fdm znakem je \u00fahel hlavy 90\u00b0<\/strong> u rozm\u011br\u016f M3 a\u017e M16 (u v\u011bt\u0161\u00edch rozm\u011br\u016f typu M20\/M24 se setk\u00e1te s odli\u0161nou geometri\u00ed), d\u00edky n\u011bmu\u017e hlava po spr\u00e1vn\u00e9m zahlouben\u00ed dosedne do roviny povrchu a z\u016fstane \u201ev l\u00edci\u201c. Vnit\u0159n\u00ed \u0161estihran umo\u017e\u0148uje utahov\u00e1n\u00ed i v zahlouben\u00fdch otvorech, kde by vn\u011bj\u0161\u00ed kl\u00ed\u010d nem\u011bl prostor.<\/p>\n

Norma navazuje na rodinu \u0161roub\u016f s vnit\u0159n\u00edm \u0161estihranem, kam pat\u0159\u00ed i v\u00e1lcov\u00e1 hlava podle DIN 912<\/a>. Zat\u00edmco DIN 912 p\u0159en\u00e1\u0161\u00ed p\u0159edp\u011bt\u00ed p\u0159es plnou v\u00e1lcovou hlavu, DIN 7991 ho p\u0159en\u00e1\u0161\u00ed p\u0159es ku\u017eelovou dosedac\u00ed plochu, co\u017e m\u00e1 p\u0159\u00edm\u00fd dopad na \u00fanosnost spoje (viz n\u00ed\u017ee).<\/p>\n

Rozm\u011brov\u00e1 \u0159ada DIN 7991<\/h2>\n

N\u00e1sleduj\u00edc\u00ed tabulka uv\u00e1d\u00ed z\u00e1kladn\u00ed rozm\u011bry pro nejb\u011b\u017en\u011bj\u0161\u00ed metrick\u00e9 velikosti. Hodnoty dk<\/em> (pr\u016fm\u011br hlavy) a k<\/em> (v\u00fd\u0161ka hlavy) jsou maxim\u00e1ln\u00ed jmenovit\u00e9 hodnoty dle normy, s<\/em> je jmenovit\u00e1 velikost vnit\u0159n\u00edho \u0161estihranu a stoup\u00e1n\u00ed odpov\u00edd\u00e1 hrub\u00e9mu metrick\u00e9mu z\u00e1vitu.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n
Z\u00e1vit<\/th>\nStoup\u00e1n\u00ed (mm)<\/th>\nPr\u016fm\u011br hlavy dk (mm)<\/th>\nV\u00fd\u0161ka hlavy k (mm)<\/th>\nVnit\u0159n\u00ed \u0161estihran s (mm)<\/th>\n<\/tr>\n<\/thead>\n
M3<\/td>\n0,5<\/td>\n6,0<\/td>\n1,7<\/td>\n2,0<\/td>\n<\/tr>\n
M4<\/td>\n0,7<\/td>\n8,0<\/td>\n2,3<\/td>\n2,5<\/td>\n<\/tr>\n
M5<\/td>\n0,8<\/td>\n10,0<\/td>\n2,8<\/td>\n3,0<\/td>\n<\/tr>\n
M6<\/td>\n1,0<\/td>\n12,0<\/td>\n3,3<\/td>\n4,0<\/td>\n<\/tr>\n
M8<\/td>\n1,25<\/td>\n16,0<\/td>\n4,4<\/td>\n5,0<\/td>\n<\/tr>\n
M10<\/td>\n1,5<\/td>\n20,0<\/td>\n5,5<\/td>\n6,0<\/td>\n<\/tr>\n
M12<\/td>\n1,75<\/td>\n24,0<\/td>\n6,5<\/td>\n8,0<\/td>\n<\/tr>\n
M16<\/td>\n2,0<\/td>\n30,0<\/td>\n7,5<\/td>\n10,0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Pro v\u00fdb\u011br z\u00e1pustn\u00e9ho imbusov\u00e9ho \u0161roubu DIN 7991<\/a> je u n\u00e1vrhu zahlouben\u00ed rozhoduj\u00edc\u00ed pr\u00e1v\u011b dvojice dk<\/em> a \u00fahel 90\u00b0: zahlouben\u00ed v d\u00edlu mus\u00ed m\u00edt odpov\u00eddaj\u00edc\u00ed ku\u017eelovou plochu, aby hlava dosedla cel\u00fdm povrchem a ne jen hranou. Pozor tak\u00e9 na drobn\u00e9 rozd\u00edly ve v\u00fd\u0161ce hlavy mezi p\u016fvodn\u00edm zn\u011bn\u00edm DIN a aktu\u00e1ln\u00ed ISO 10642 \u2014 u p\u0159esn\u00fdch zahlouben\u00ed je dobr\u00e9 vych\u00e1zet z konkr\u00e9tn\u00edho v\u00fdkresu v\u00fdrobce.<\/p>\n

Materi\u00e1ly a jakosti<\/h2>\n

DIN 7991 se vyr\u00e1b\u00ed v ocelov\u00e9m i nerezov\u00e9m proveden\u00ed:<\/p>\n