非密封的管螺纹不带锥度；密封用的管螺纹带1：16的锥度.是不是这样。或者说常用的螺纹是不是这样。
推荐回答（5个）
不是,各有各的用途.而且这些螺纹现在都在用.
管螺纹比较乱,但常用的就如下几种:
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NPT:60度密封管螺纹,GBT12716-2002,ANSI-B1.20.1
G:55度非密封管螺纹,GB/T-7307-2001,ISO228-1
Rp,R1:55度密封管螺纹,第一系列,柱锥配合,GB/T-7306.1-2000,ISO7-1
Rc,R2:55度密封管螺纹,第二系列,锥锥配合,GB/T-7306.2-2000,ISO7-1
===================================================
NPT过去在我国叫Z螺纹,现在改叫NPT,其实就是美国鬼子的管螺纹,这种螺纹是密封的,有1:16锥度.
G是最常用的,自来水管,压缩空气管什么的都是这种螺纹,螺纹只起连接作用,没密封作用,所以连接处要加点生料带,或螺纹胶,或垫片什么的.这种螺纹是没锥度的,但欧洲国家习惯给这种螺纹也加1:16锥度,其实有那个锥度也没用.
至于你说的Rp,Rc,R(R其实在我国又分为R1,R2)就比较麻烦了..细细道来:
这几种符号都是针对55度密封管螺纹的,除Rp是直的外其它的都有1:16锥度.
英国用Rp,而英国以外的欧洲大陆国家用Rc,而且各自的外螺纹都叫R.
内螺纹好办,但各自的外螺纹都叫R,但其实此R非鄙R,比如你拿到一张英国图纸和一张法国(德国,意大利)图纸,里面都有个R,呵呵,小心了,其实英国的R和法国的R是不同的2种外螺纹.
我国为了避免这种混乱的情况发生,所以把GB/T-7306分为2个系列,配Rp的标为R1,配Rc的标为R2.(R1,R2的"1""2"要写为下标,但这里写打字打出来,呵呵.)
另:不密封的G螺纹好办,但密封的管螺纹比较麻烦,Rp-R1,Rc-R2其实是不可混用的.必然你用了吃奶的力气拧好的螺纹也密封不住,这就麻烦了.还有,G螺纹不密封,加工精度可以粗些.但Rp,Rc,R1,R2,NPT这些螺纹加工不好可就没办法密封了,所以买标准件时要买质量好的.
我国以前一直是用Rp-R的(就是现在的Rp-R1),现在Rp-R1,Rc-R2都推荐,只要工程师自己明白自己用的是哪个系列就行(典型的国家技术监督局在和稀泥,呵呵).
这种说法基本正确，且国标中也是这么规定的。
以国家标准中的四个管螺纹标准为例，非密封的管螺纹不带锥度，GB/T7307-2001《非螺纹密封管螺纹》中规定的螺纹就是不带锥度的管螺纹；密封用的管螺纹带1：16的锥度，GB/T7306.1-7306.2-2000《用螺纹密封管螺纹》、GB/T12716-2011《60°圆锥管螺纹》、GB/T1415-2008《米制锥管螺纹》这个三种标准中的管螺纹都是密封螺纹且锥度为1：16。
根据GB国标：圆柱管螺纹英制螺距用G表示如G1/2"
根据GB国标：圆锥管螺纹英制螺距用ZG表示如ZG3/4"、锥度1：16
根据JIS标准：圆锥外螺纹用R表如R3/4.
根据JIS标准：圆锥内螺纹用RC表如RC1/2.
根据JIS标准：圆柱内螺纹用RP表如RP3/4.
你是对的.非密封的管螺纹不带锥度,也就圆柱形管螺纹,该螺纹靠本身是无法获得好密封的,只有在螺纹里加入密封材料(如水胶布等),才能起到密封效果.密封用的管螺纹(也叫自密封管螺纹)都是利用1：16的锥度上的螺纹牙相互挤压,从而实现自密封,不用加密封材料(但有些带锥度管螺纹,由于加工上的问题,在实际操作上,还是在圆锥螺丝上绕上一些密封材料,以求保险.).
Rp是圆柱内螺纹,Rc是圆锥内螺纹,R是圆锥外螺纹, 标准规定没有改变.
1楼的回答 好长号专业，我也不好意思 说 什么 了，这些标准很多很乱，关于那个 R R1/2 我曾经问过 老外 怎么换算 他也不是 很清楚 根本 和英寸对应不上，于是他说 ：no need to care about that ,you only buy the tools according tio the drawing and do that. 我们用那种锥度的螺纹作润滑的街头2，在结构上的螺纹没有锥度，但是 接头 1/8pf 是 锥度的
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