刀具和刀夹CUTTING TOOLS AND TOOLHOLDERS

刀具和刀夹CUTTING TOOLS AND TOOLHOLDERS(中文6500字,英文4300字)
想顺利的加工工件，就必须做到：
1．    刀具或刀片的种类要恰当。
2．    刀夹的类型要合适。
3．    刀具的切削刃要锋利。
4．    刀具要安装或调整到适当的位置和高度。
刀具的材料
制造车床上使用的刀片的基本材料有以下六种：水淬硬化钢，高速钢，硬铸有色合金，烧结硬质合金，陶瓷和金刚石。使用材料的选择取决于许多因素：刀具成本，刃磨费用，刀具的尺寸和类型，金属切削速率，使用时间的长短，零件的光洁度和公差，以及机床的条件和性能。由于有着许多因素，选择材料常常是根据一般的经验而不是精确计算。然而，对各种不同刀具材料的某些一般特性是应该有所了解的。

CUTTING TOOLS AND TOOLHOLDERS
To machine a workpiece successfully you must have :
1.    the correct kind of cutting tool or tool bit
2.    the right type of toolholder
3.    a tool with a sharp cutting-edge
4.    the cutting tool set or adjusted to the correct height and position.
Cutting-tool materials
Tool bits used on the lathe are made form one of six basic materials: water-hardening steels,high-speed steels,hard-cast,nonferrous alloys,sintered (cemented) carbides,ceramics,and diamonds. The selection of the material used depends upon many factors including:tool cost,size and design of tool ,metal-removal rate ,length of run ,finish and tolerance of part,and condition and capability of the machine tool . Because of these factors ,material selection is more often based on general experience than on precise evaluation . There are, however ,certain general characteristics of the different cutting-tool materials you should understand.
Water-hardening Steels.These include the high-carbon tool steels (either plain carbon or those with minor additions of chromium , vanadium,or tungsten) .The different grades of water-hardening tool steels are classed as W steels in American Iron and Steel Institute’s system of classification . Tools made from these materials have very sharp ,smooth cutting-edges when properly heat-treated. They are adequate for limited turning at a relatively low cutting speed or when old ,low-speed equipment ,such as a flat-belt lathe , is used .