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你可能喜欢System.Threading命名空间是.Net多线程编程的基础。对于多线程编程在实际工作中一直用的不多，所以了解也就不多。尽管如此，随着多核，多个cpu的出现，大计算量的需要，多线程将越来越受关注。所以打算写个系列博客，以便更多的了解学习多线程的知识。听说.Net4.0中有一个更方便多线程的类库，可惜还没真的见识过，先熟悉System.Threading就当&温故而知新&了
第一篇：从Thread的线程单元状态ApartmentState说起
ApartmentState是一个枚举变量，用来设置线程的单元状态（单元状态的ApartmentState的中文msdn翻译，这个翻译很水，我不能从这四个汉字中确切的了解英文ApartmentState要表达的意思）。ApartmentState有三个枚举值，分别为STA：表示Thread将被创建并进入一个单线程单元，我猜想STA应该是Single Thread Apartment的首字母简拼；MTA：表示Thread将被创建并进入一个多线程单元，还有一个是Unknown，表示没有设置线程的单元状态。我在以前使用Thread的时候，从来没有设置过线程的单元状态，今天要做个试验把这三种状态搞清楚。
使用新new 一个Thread实例之后可以使用SetAppartmentState方法设置线程的单元状态，每个线程只可以设置一次，若再次设置会抛异常，若不知道是否设置了单元状态可以使用Thread类提供的TrySetApartmentState方法来设置；不设置时其线程单元在控制台应用程序中默认是MTA。
试验思路：1.&使用new 3个Thread的实例，什么都不执行，看两种不同的AppartmentState的Thread的执行顺序如何2.&同样new 3个Thread实例，执行一段计算代码，看两种不同的AppartmentState执行完全部计算耗时情况
具体的实验代码如下：
Codeusing&Susing&System.Collections.Gusing&System.Tusing&System.Tusing&System.Dusing&System.Cnamespace&MutiThread{&&&&class&Program&&&&{&&&&&&&&static&Stopwatch&swA&&&&&&&&static&Random&r&=&new&Random();&&&&&&&&static&Hashtable&hashT&&&&&&&&&&&&&&&&static&void&Main(string[]&args)&&&&&&&&{&&&&&&&&&&&&Start3Thread(ApartmentState.STA);&&&&&&&&&&&&Console.ReadLine();&&&&&&&&}&&&&&&&&static&void&Start3Thread(ApartmentState&appartmentState)&&&&&&&&{&&&&&&&&&&&&int&threadCn&=&3;&&&&&&&&&&&&hashTable&=&new&Hashtable();&&&&&&&&&&&&swAll&=&new&Stopwatch();&&&&&&&&&&&&swAll.Start();&&&&&&&&&&&&do&&&&&&&&&&&&{&&&&&&&&&&&&&&&&StartThread(appartmentState);&&&&&&&&&&&&&&&&threadCn--;&&&&&&&&&&&&}&while&(threadCn&&&0);&&&&&&&&}&&&&&&&&static&void&StartThread(ApartmentState&appartmentState)&&&&&&&&{&&&&&&&&&&&&Thread&t1&=&new&Thread(new&ThreadStart(CalcSomething));&&&&&&&&&&&&//Thread&t1&=&new&Thread(new&ThreadStart(DoNothing));&&&&&&&&&&&&hashTable.Add(t1.ManagedThreadId,&false);&&&&&&&&&&&&t1.SetApartmentState(appartmentState);&&&&&&&&&&&&t1.Start();&&&&&&&&}&&&&&&&&static&void&CalcSomething()&&&&&&&&{&&&&&&&&&&&&Stopwatch&sw&=&new&Stopwatch();&&&&&&&&&&&&sw.Start();&&&&&&&&&&&&int[]&arr&=&new&int[1000];&&&&&&&&&&&&for&(int&i&=&0;&i&&&arr.L&i++)&&&&&&&&&&&&{&&&&&&&&&&&&&&&&arr[i]&=&r.Next(1000);&&&&&&&&&&&&}&&&&&&&&&&&&//Console.WriteLine("线程"&+&Thread.CurrentThread.ManagedThreadId&&&&&&&&&&&&//&&&&&&&&+&"的单元状态是:"&+&Thread.CurrentThread.GetApartmentState()&&&&&&&&&&&&//&&&&&&&&+&"；线程状态："&+&Thread.CurrentThread.ThreadState&&&&&&&&&&&&//&&&&&&&&+&"；耗时："&+&sw.ElapsedTicks);&&&&&&&&&&&&hashTable[Thread.CurrentThread.ManagedThreadId]&=&true;&&&&&&&&&&&&&&&&&&&&&&&&if&(hashTable.Count&==&3)&&&&&&&&&&&&{&&&&&&&&&&&&&&&&bool&allFinish&=&true;&&&&&&&&&&&&&&&&foreach&(object&key&in&hashTable.Keys)&&&&&&&&&&&&&&&&{&&&&&&&&&&&&&&&&&&&&allFinish&=&allFinish&&&&(bool)hashTable[key];&&&&&&&&&&&&&&&&}&&&&&&&&&&&&&&&&if&(allFinish)&&&&&&&&&&&&&&&&{&&&&&&&&&&&&&&&&&&&&swAll.Stop();&&&&&&&&&&&&&&&&&&&&Console.WriteLine(Thread.CurrentThread.GetApartmentState().ToString()&+&"总耗时："&+&swAll.ElapsedTicks);&&&&&&&&&&&&&&&&&&&&if&(Thread.CurrentThread.GetApartmentState()&==&ApartmentState.STA)&&&&&&&&&&&&&&&&&&&&{&&&&&&&&&&&&&&&&&&&&&&&&hashTable.Clear();&&&&&&&&&&&&&&&&&&&&&&&&swAll.Reset();&&&&&&&&&&&&&&&&&&&&&&&&swAll.Start();&&&&&&&&&&&&&&&&&&&&&&&&Start3Thread(ApartmentState.MTA);&&&&&&&&&&&&&&&&&&&&}&&&&&&&&&&&&&&&&}&&&&&&&&&&&&}&&&&&&&&}&&&&&&&&static&void&DoNothing()&&&&&&&&{&&&&&&&&&&&&int&times&=&3;&&&&&&&&&&&&do&&&&&&&&&&&&{&&&&&&&&&&&&&&&&Console.WriteLine("线程"&+&Thread.CurrentThread.ManagedThreadId&&&&&&&&&&&&&&&&&&&&+&"的单元状态是:"&+&Thread.CurrentThread.GetApartmentState()&&&&&&&&&&&&&&&&&&&&+&"；线程状态："&+&Thread.CurrentThread.ThreadState);&&&&&&&&&&&&&&&&times--;&&&&&&&&&&&&}&while&(times&&&0);&&&&&&&&}&&&&}}
实验的结果是：1.&AppartmentState为STA或者MTA时的执行顺序都是不定的，每一次执行都可能不同，也就是说顺序上无法说明两种的区别。2.&两种不同的ApartmentState的执行效率上是有区别的，单线程单元状态模式所耗时间明显多于多线程单元模式状态3.&在不设置线程的AppartmentState时，默认值是MTA，也就是多线程模式的
我的测试CPU是单CPU的，具体如下：Intel(R)Pentium(R)4CPU3.00GHz2.99GHz,1.99GB的内存
阅读(...) 评论()纸业专业英语词汇翻译(T2)_新闻传媒英语词汇
纸业专业英语词汇翻译(T2)
tantqalum compound 钽化合物 tap water 自来水 tapa cloth 南洋树皮纸 tape 条；带；卷尺 tape line 卷尺 tape measure 卷尺 taper valve 锥形阀 tapered flow header 锥形进浆管 taqpered roller bearing 锥形滚珠轴承 tapering 锥形 tapping 割胶，割树脂 tapping machine 纸箱粘合机 tappi standard tappi标准 tar （煤）焦油 tar oil 焦油 tar-saturated(roofing)felt 油毛毡 target 靶（子）；挡板 tarred felt 焦油纸板tarnish 锈蚀，生锈 tarpaulin 防水布；桐油布；油布 tcc former tcc离心式混合纸板机 tea cartridge 茶叶包装纸 tea wrapper 茶叶包装纸 teak 柚木 tear 撕裂度；撕裂 tear factor 撕裂因子 tear out 撕开 tear outs 选出废纸 tear resistance 撕裂度 tear ratio 撕裂比率 tear strength 撕裂强度 tear test 撕裂度试验 tear tester 撕裂度测定仪 tearing 撕裂 tearing (breaking)strength 撕裂度 tearing test 撕裂试验 tearing tester 撕裂度测定仪 technical data 技术数据 technical feasibility 技术上可行性 technical schedule 工艺规程 technical term 技术名词，术语 technician 技术员 technique 技术 tee t型 teflon 聚四氟乙烯，特氟纶 telegram paper tape 打孔电报纸 telegraph blanks 电讯用纸 telegraph manila 电讯用马尼拉纸 telegraph tank 电报带 telegraph writing 电报纸，电讯纸 telescoped 窜边的；错开的 telescoped roll 窜边纸卷 telescopic screw 套筒螺丝 telescopic container 双层容器 teletype 电传打字（机） teletype oiled perforator tape 打孔电传打孔带 teletype tape 电传打字带 teller 数纸工；计算员；纸张计数器 temperature conductivity 导温率；传热性能 temperature factor 温度系数 temperature gradient 温度梯度 temperature persistance 恒温性能temperature raising period 升温期 temperature regulator 温度调节器 tempering 回火，退火 tempering tem perature 回火温度，退火温度 tempering tower 缓冲塔 template 字型，纸样 templet 样板 tenacious 粘滞的；强韧的 tenacity 韧性，韧度 tender 操作工 tending 照顾，操作 tending aisle 操作侧，操作面 tending side 操作侧，操作面 tensile 抗张强度 tensile breaking strength 抗张强度，拉力 tensile draw 牵引力 tensile energy absorption 抗张能量吸收 tensile properties 抗张性能 tensile strain 伸长度 tensile strength 抗张强度 tensile dstrength absorption 抗张强度吸收 tensile strength tester 抗张强度测定仪，拉力仪 tensile stress 拉应力 tensile stretch 伸长率 tensile test 抗张强度试验 tensile tester 抗张强度测定仪 tensiometer 张力测定仪 tension 张力 tension control 张力控制 tension dryer 张力干燥器 tension roll(er) 张力辊，松紧辊 tension wood 受拉木 terminal 端部；接头；线端；终点 termite damage 白蚁危害 ternion 三张纸双摺制成的小册子 terpene 萜烯，萜（烃） terpinene 萜品烯 terpenoide 萜烯酯 terra alba 无水石膏，硬石膏 tertiary aloohol 叔醇 tertiary lamella 三生壁 tertiary screen 三道筛 tertiary treatment 三级处理tertiary wall 三生壁 terylen 涤沦 tesi scrubber tesi湿法除尘器 test bench 试验桌 test board 试验板 test jute liner 麻浆挂面箱纸板 test liner 强韧箱纸板；高耐破纸板 test method 试验方法；检验方法 test run 试运转，试验 test sheet 试验用纸样 specimen 试样 test tube 试管 tester 测定仪 testing apparatus 试验装置，测定装置 testing instrument 试验仪表，测定仪 testing strip 试验纸条 testing surface 试验表面，测定表面 tetrahedral formula 四面体式 tetraose 四糖 tetrasaccharide 四糖 tex 相当于1克/1000米 texrope belt v型皮带 text finish 中等光泽装饰 textile 织品；织物 textile fiber 织物纤维 texture 组织；外观；纹理 texture of paper 纸张外观 theoretical duty 理论负载（荷）；理论功率；理论能力 theory of micelle 胶束学说 theory of retention 留着学说 thermal capacity 热容量；热功率 thermal compression evaporation 热压蒸发 thermal coefficient of expansion 热胀系数 thermal conduction 热传导 thermal conductivity 导热率 thermal content 热含 thermal decomposition 热解 thermal diffusion 热扩散 thermal diffusivity 热扩散率 thermal equilibrium 热平衡 thermal expansion 热膨胀 thermal gradient 热量梯度 thermal insulating material 绝热物质 thermal insulating properties 纸热性质thermal insulation 热绝缘；保温层 thermal losses 热量损耗 thermal pollution 热污染 thermal properties 热力性质 thermal radiation 热辐射 thermal regulator 温度调节器 thermal sensitivity 热敏性 thermal stability 热稳性 thermal stress 热应力 thermal treatment 热处理 thermal unit 热量单位 thermal value 热值 thermochemistry 热力学 thermochromism 热色现象 thermocolor period 热色周期 thermocompressor 热压机 thermocouple 热电偶 thermocouple pyrometer 热电偶高温计 thermodiffusion 热扩散 thermodynamic efficiencyt 热力（学）效率 thermodynamics 热力学 thermofiner 热磨机 thermoforming 热成形 thermography 凹凸印刷 thermophillic 亲热性 thermo-planisher 加热平滑辊 thermoplastic adhesive 热塑性胶粘剂 thermoplastic fiber 热塑性纤维 thermoplastic fiber bonding 热塑性纤维结合力 thermoplastic material 热塑性材料 thermoplastic resin 热塑性树脂 thermoplasticity 热塑性 thermoplastics 热固性塑料 thermo-regulator 温度调节器 thermoset plastics 热固性塑料 thermosetting 热固（性） thermosetting plastics 热固性塑料 thermosetting resin 热固性树脂 thermostability 热稳性 thermostat 恒温器 thermo(tro)graph 温度记录器 thexotropic index 融变性指数 thick walled fiber 厚壁纤维thicken 增浓；浓缩 thickener 浓缩机 thickener vat （圆网）浓缩机底槽 thickening 增浓；浓缩 thickening agent 增浓剂 thickness gage 厚度计 thickness scale 厚度计 thickness tester 厚度计 thickol 聚硫橡胶（商业名称） thief tester （试料取样）刺管 thin film 薄膜 thin wall cell 薄壁细胞 thin walled fiber 薄壁纤维 thinness number （裂断长计算用）薄度值 thinning 稀释 thinning water 稀释用水 thinnings 间伐材，疏伐材 thiocatbamate 硫代氨基甲酸酯 thiocatbonate 硫代碳酸盐 thioester 硫酯 thiolignin 硫代木素 thiosulfate 硫代硫酸盐 thiosulfonate 硫代磺酸盐 thiosulfonic acid 硫代磺酸 thiosulfonic acid 硫代硫酸 third hand 卷纸工 third press 第三压榨 third press felt 第三压榨毛毯 third wash 三段洗涤 thirds 三级破布 thirty-two mo 32开 thixotropy 触变性 thorne barker thorne袋式剥皮机 thorne bleacher thorne高浓漂白塔 trash 破布除尘；松散；捶击 thrasher 松散机 thrashing 打散；捶击 thread 螺纹；线 thread burr 环纹刻石刀 thread-like molecule 线状分子 threaded felt 埋线毛毯，高强毛毯 threading 领纸，引纸 threading speed 领纸抄速，引纸抄速 three drum reel 三鼓卷纸机three plane watermark 亮暗水印 three ply 三层 three pocket grinder 三袋磨木机 three section dryer control 三段通气操作 three shaft turret winder 三轴塔式卷纸机 threshold value 阀值，界限值 thrity-two mo 32开 thriving tree 主伐林 throat 狭口，狭道 throttle 节流 throttle down 节流；关闭阀门 throttle valve 节流阀，减压阀 through drying 穿透干燥 through-put capacity 通过量 through station 中间站 throughway valve 直通阀 throw of pump （泵）扬程 thrown outs 选出废品 thru dryers 穿透干燥器 thrust 推力 thrust bearing 推力轴承 thyratron 闸流管 thyristor 闸流晶体管 ticker tape 电报纸条 ticket 标签 tie coat 中间涂布 tie water 结合水 tight knot 活节，紧密节 tight roll 张紧辊 tightener 张紧装置，张紧器 tile 瓷砖，瓦片 tile liner 屋瓦用衬纸 tile tank 瓷砖贴面槽 tilt clolth 帆布 tilting 倾斜 tilting digester 回转式蒸煮器 tilting trap 倾斜式水汽分离器 timber 木材，木料 timber and lumber standardizstion 木材标准化 timber assortment 木材分类；选材 timber histology 木材组织学 timber mill 锯木厂 timber science 木材（科）学timber stain 木材变色 timber treating plant 木材处理车间 timber worm 木材害虫 timberland 林场 time at maximum temperature 保温时间 time card bristol 时间表卡纸 time lag 时间滞后 time of beating 打浆时间 time of storage 贮存时间 timed pulses 时控脉冲 timer 计时器，定时器 timing device 计时器 tinctorial power 染色能力 tincture 着色，染色；色泽 tinctural value 染色值 timder 易燃物 tingle 色调，色彩 tingle (bromine)number tingle漂率，溴化值 tint 色调，色彩 tinted 着色 tinted back 纸板底面染色 tinted cards 染色卡纸 tinted white 白色涂布 tinting 着色，染色 tinting strength 着色能力 tintometer 色调计 tip 纸卷芯塞 tipot side 紧边 tipper 倾卸车 tire container 轮胎箱用纸板 tire cord （轮胎）帘布，帘子线 tire wrapper 轮胎包装纸 tissue 薄（页）纸 technical tissue 工业用薄纸 textile tissue 织物包装纸 toilet tissue 卫生纸，手纸 towel tissue 毛巾纸 tracing tissue 描图纸 twisting tissue 纸绳用薄纸 two-ply toilet tissue 双层卫生纸 tissue fillers 薄纸用填料 tissue former 薄页纸成形装置，薄页纸成形器 tissue machine 薄页纸造纸机 tissue winders 薄页纸复卷机titanium dioxide 二氧化钛，钛白 titanium white 钛白 titratable acid 可滴定酸 titratable alkali 可滴定碱 titration 滴定 toilet roll 卷筒卫生纸，手纸卷 toilet roll cutter and perforator 卷筒卫生纸裁切与打孔机 toilet winder 卫生纸复卷机 token 半令 tolerance 容许范围 toluene 甲苯 tomlinson furnace tomlinson喷射式碱回收炉 toner 调色剂；涂料调剂 toothed wall 齿形管壁 top coating 表层涂布 top couch (roll) 上伏辊 top felt 上毛毯
纸业专业英语词汇翻译(T2) 相关内容:查看更多>>From Wikipedia, the free encyclopedia
Threading is the process of creating a . More screw threads are produced each year than any other . There are many methods of generating threads, including subtractive methods (many kinds of thread cutting and grinding, as detailed below); deformative or transformative methods ( molding and casting);
methods (such as ); or combinations thereof.
There are various methods for generating screw threads. The method chosen for any one application is chosen based on constraints—time, money, degree of precision needed (or not needed), what equipment is already available, what equipment purchases could be justified based on resulting unit price of the threaded part (which depends on how many parts are planned), etc.
In general, certain thread-generating processes tend to fall along certain portions of the spectrum from -made parts to mass-produced parts, although there can be considerable overlap. For example, thread lapping following thread grinding would fall only on the extreme toolroom end of the spectrum, while thread rolling is a large and diverse area of practice that is used for everything from
leadscrews (somewhat pricey and very precise) to the cheapest deck screws (very affordable and with precision to spare).
Threads of metal fasteners are usually created on a thread rolling machine. They may also be cut with a , . Rolled threads are stronger than cut threads, with increases of 10% to 20% in tensile strength and possibly more in fatigue resistance and wear resistance.
Thread cutting, as compared to thread forming and rolling, is used when full thread depth is required, when the quantity is small, when the blank is not very accurate, when threading up to a shoulder is required, when threading a tapered thread, or when the material is brittle.
Main articles:
A common method of threading is cutting with taps and dies. Unlike , hand taps do not automatically remove the
they create. A hand tap cannot cut its threads in a single rotation because it creates long chips which quickly jam the tap (an effect known as "crowding"[]), possibly breaking it. Therefore, in manual thread cutting, normal wrench usage is to cut the threads 1/2 to 2/3 of a turn (180 to 240 degree rotation), then reverse the tap for about 1/6 of a turn (60 degrees) until the chips are broken by the back edges of the cutters. It may be necessary to periodically remove the tap from the hole to clear the chips, especially when a
is threaded.
For continuous tapping operations (i.e., power tapping) specialized spiral point or "gun" taps are used to eject the chips and prevent crowding.
Single-point threading, also colloquially called single-pointing (or just thread cutting when the context is implicit), is an operation that uses a
to produce a thread form on a cylinder or cone. The tool moves
while the precise rotation of the workpiece determines the
of the thread. The process can be done to create external or internal threads (male or female). In external thread cutting, the piece can either be held in a
or mounted between two . With internal thread cutting, the piece is held in a chuck. The tool moves across the piece linearly, taking chips off the workpiece with each pass. Usually 5 to 7 light cuts create the correct depth of the thread.
The coordination of various machine elements including , slide rest, and change gears was the technological advance that allowed the invention of the , which was the origin of single-point threading as we know it today.
lathes are the commonly used machines for single-point threading. On CNC machines, the process is quick and easy (relative to manual control) due to the machine's ability to constantly track the relationship of the tool position and spindle position (called "spindle synchronization"). CNC software includes "canned cycles", that is, preprogrammed subroutines, that obviate the manual programming of a single-point threading cycle. Parameters are entered (e.g., thread size, tool offset, length of thread), and the machine does the rest.
All threading could feasibly be done using a single-point tool, but because of the high speed and thus low unit cost of other methods (e.g., tapping, die threading, and thread rolling and forming), single-point threading is usually only used when other factors of the manufacturing process happen to favor it (e.g., if only a few threads need to be made, if an unusual or unique thread is required, or if there is a need for very high
with other part features machined during the same setup).
A diagram of a solid single-form thread cutting tool
A solid multiple-form thread .
The path a multiple-form thread cutting tool travels to create an external thread.
Threads may be
with a rotating
if the correct
toolpath can be arranged. This was formerly arranged mechanically, and it was suitable for mass-production work although uncommon in job-shop work. With the widespread dissemination of affordable, fast, precise , it became much more common, and today internal and external threads are often milled even on work where they would formerly have been cut with taps, die heads, or single-pointing. Some advantages of thread milling, as compared to single-point cutting or taps and dies, are faster cycle times, less tool breakage, and that a left- or right-hand thread can be created with the same tool. Additionally, for large, awkward workpieces (such as a
casting), it is simply easier to let the workpiece sit stationary on a table while all needed machining operations are performed on it with rotating tools, as opposed to rigging it up for rotation around the axis of each set of threads (that is, for the "arms" and "mouth" of the hydrant).
There are various types of thread milling, including several variants of form-milling and a combination of drilling and threading with one cutter, called thrilling.
Form-milling uses either a single- or multiple-form cutter. In one variant of form-milling, the single-form cutter is tilted to the
of the thread and then fed radially into the blank. The blank is then slowly rotated as the cutter is precisely moved along the axis of the blank, which cuts the thread into the blank. This can be done in one pass, if the cutter is fed to the full thread depth, or in two passes, with the first not being to the full thread depth. This process is mainly used on threads larger than 1.5 in (38 mm). It is commonly used to cut large- or multiple-lead threads. A similar variant using a multiple-form cutter exists, in which the process completes the thread in one revolution around the blank. The cutter must be longer than the desired thread length. Using a multiple-form cutter is faster than using a single-form cutter but it is limited to threads with a helix angle less than 3°. It is also limited to blanks of a substantial diameter and no longer than 2 in (51 mm).
Another variant of form-milling involves holding the cutter's axis orthogonally (no canting to the thread's helix angle) and feeding the cutter in a toolpath that will generate the thread. The part is usually a stationary workpiece, such as a
on a valve body (in external thread milling) or a hole in a plate or block (in internal thread milling). This type of thread milling uses essentially the same concept as contouring with an endmill or ball-nose mill, but the cutter and toolpath are arranged specifically to define the "contour" of a thread. The toolpath is achieved either using helical interpolation (which is circular interpolation in one plane [typically XY] with simultaneous linear interpolation along a third axis [typically Z]; the CNC control model must be one that supports using the third axis) or a simulation of it using extremely small increments of 3-axes linear interpolation (which is not practical to program manually but can be programmed easily with CAD/CAM software). The cutter geometry reflects the thread pi the lead (thread helix angle) is determined by the toolpath. Tapered threads can be cut either with a tapered multiple-form cutter that completes the thread in one revolution using helical interpolation, or with a straight or tapered cutter (of single- or multiple-form) whose toolpath is one or more revolutions but cannot use helical interpolation and must use CAD/CAM software to generate a contour-like simulation of helical interpolation.
The tooling used for thread milling can be solid or indexable. For internal threads, solid cutters are generally limited to holes larger than 6 mm (0.24 in), and indexable internal thread cutting tools are limited to holes larger than 12 mm (0.47 in). The advantage is that when the insert wears out it is easily and more cost effectively replaced. The disadvantage is the cycle time is generally longer than solid tools. Note that solid multiple-form thread cutting tools look similar to taps, but they differ in that the cutting tool does not have a backtaper and there is not a lead-in chamfer. This lack of a lead-in chamfer allows the threads to be formed within one pitch length of the bottom of a blind hole.
Thrilling is the process of threading and drilling (accomplished in the reverse order) internal threads using a specialized cutting tool on a CNC mill. The cutting tool tip is shaped like a drill or center-cutting endmill, while the body has a thread-shaped form with a
form near the shank. The cutter first plunges to drill the hole. Then the thread is circularly interpolated just like the multiple-form cutter described above. This tool drills, , and threads a hole all in one compact cycle. The advantage is this process eliminates a tool, , and tool change. The disadvantage is that the process is limited to hole depth no greater than three times the diameter of the tool.
Thread grinding is done on a
using specially dressed
matching the shape of the threads. The process is usually used to produce accurate threads or threa a common application is ball screw mechanisms.[] There are three types: center-type grinding with axial feed, center-type infeed thread grinding and centerless thread grinding. Center-type grinding with an axial feed is the most common of the three. It is similar to cutting a thread on a lathe with a , except the cutting tool is replaced with a grinding wheel. Usually a single ribbed wheel is used, although multiple ribbed wheels are also available. To complete the thread multiple passes are commonly required. Center-type infeed thread grinding use a grinding wheel with multiple ribs that is longer than the length of the desired thread. First, the grinding wheel is fed into the blank to the full thread depth. Then the blank is slowly rotated through approximately 1.5 turns while axially advancing through one
per revolution. Finally, the centerless thread grinding process is used to make head-less
in a similar method as . The blanks are hopper-fed to the grinding wheels, where the thread is fully formed. Common centerless thread grinding production rates are 60 to 70 pieces per minute for a 0.5 in (13 mm) long set screw.
Rarely, thread cutting or grinding (usually the latter) will be followed by thread
in order to achieve the highest precision and surface finish achievable. This is a
practice when the highest precision is required, rarely employed except for the
of high-end machine tools.
Internal threads can be
(EDM) into hard materials using a sinker style machine.
The thread forming and rolling concept
Page 23 of Colvin FH, Stanley FA (eds) (1914): American Machinists' Handbook, 2nd ed. New York and London: McGraw-Hill. Summarizes screw thread rolling practice as of 1914.
Thread forming and thread rolling are processes for
screw threads, with the former referring to creating internal threads and the latter external threads. In both of these processes threads are formed into a blank by pressing a shaped tool, commonly called a 'thread rolling die' against the blank, in a process similar to . These processes are used for large production runs because typical production rates are around one piece per second. Forming and rolling produce no
and less material is required because the blank size starts smaller than a blank required there is typically a 15 to 20% material savings in the blank, by weight. A rolled thread can often be easily recognized because the thread has a larger diameter than the blank rod from wh however, necks and
can be cut or rolled onto blanks with threads that are not rolled. Also, the end of the screw usually looks a bit different from the end of a cut-thread screw.
Materials are limited to
materials because the threads are . However, this increases the thread's yield strength, surface finish, , and . Also, materials with good deformation characteristics are n these materials include softer (more ductile) metals and exclude
materials, such as . Tolerances are typically ±0.001 in. (±0.025 mm), but tolerances as tight as ±0.;in (±0.015 mm) are achievable. Surface finishes range from 6 to 32 micro-inches.
There are four main types of thread rolling, named after the configuration of the : flat dies, two-die cylindrical, three-die cylindrical, and planetary dies. The flat die system has two flat dies. The bottom one is held stationary and the other slides. The blank is placed on one end of the stationary die and then the moving die slides over the blank, which causes the blank to roll between the two dies forming the threads. Before the moving die reaches the end of its stroke the blank rolls off the stationary die in a finished form. The two-die cylindrical process is used to produce threads up to 6 in (150 mm) in diameter and 20 in (510 mm) in length. There are two types of three- the first has the three dies move radially out from the center to let the blank enter the dies and then closes and rotates to roll the threads. This type of process is commonly employed on
and . The second type takes the form of a self-opening . This type is more common than the former, but is limited by not being able form the last 1.5 to 2 threads against shoulders. Planetary dies are used to mass-produce threads up to 1 in (25 mm) in diameter.
Thread forming is performed using a fluteless tap, or roll tap, which closely resembles a cutting tap without the flutes. There are lobes periodically spaced around the tap that actually do the thread forming as the tap is advanced into a properly sized hole. Since the tap does not produce chips, there is no need to periodically back out the tap to clear away chips, which, in a cutting tap, can jam and break the tap. Thus thread forming is particularly suited to tapping blind holes, which are tougher to tap with a cutting tap due to the chip build-up in the hole. Note that the tap drill size differs from that used for a cutting tap and that an accurate hole size is required because a slightly undersized hole can break the tap. Proper lubrication is essential because of the
involved, therefore a lubricating
is used instead of .
When considering the blank diameter tolerance, a change in blank diameter will affect the major diameter by an approximate ratio of 3 to 1. Production rates are usually three to five times faster than thread cutting.[]
Flat die thread rolling
Planetary thread rolling
Two-die cylindrical rolling
Three-die cylindrical rolling
Tool styles
Description
Application
Machine, tapping and wood screws
Cylindrical in-feed 2 dies
Large or balanced screws, threaded bar stock
Cylindrical in-feed 3 dies
Tube fitting, spark plugs, threaded bar stock
Planetary dies
High volumes screws, sheet metal screws, and drive screws
Production rates
Thread diameter [in.]
Flat dies [pieces/min]
Cylindrical [pieces/min]
Planetary [pieces/min]
450 to 2000
250 to 1200
100 to 400
the threads are directly formed by the geometry of the mold cavity in the
or . When the material freezes in the mold, it retains the shape after the mold is removed. The material is heated to a liquid, or mixed with a liquid that will either dry or cure (such as plaster or cement). Alternately, the material may be forced into a mold as a powder and compressed into a solid, as with .
Although the first thoughts that come to mind for most machinists regarding threading are of thread cutting processes (such as tapping, single-pointing, or helical milling), Smid points out that, when plastic bottles for food, beverages, personal care products, and other consumer products are considered, it is actually plastic molding that is the principal method (by sheer volume) of thread generation in manufacturing today. Of course, this fact highlights the importance of the
getting the mold just right (in preparation for millions of cycles, usually at high speed).
Cast threads in metal parts may be finished by machining, or may be left in the as-cast state. (The same can be said of cast
teeth.) Whether or not to bother with the additional expense of a machining operation depends on the application. For parts where the extra precision and surface finish is not strictly necessary, the machining is forgone in order to achieve a lower cost. With
parts this means a but with molded plastic or die-cast metal, the threads can be very nice indeed straight from the mold or die. A common example of molded plastic threads is on soda (pop) bottles. A common example of die-cast threads is on
(connectors/fittings).
Many, perhaps most, threaded parts have potential to be generated via additive manufacturing (), of which there are many variants, including , , , , , , and . For most additive technologies, it has not been long since they emerged from the laboratory end of their historical development, but further
is picking up speed. To date, most additive methods tend to produce a rough
and tend to be restricted in the
that they can produce, and thus their earliest commercial victories have been in parts for which those restrictions were acceptable. However, the capabilities are continually growing.
Good examples of threaded parts produced with additive manufacturing are found in the
fields, where
have produced threaded titanium implants.
Often subtractive, additive, deformative, or transformative methods are combined in whatever ways are advantageous. Such multidisciplinary manufacturing falls under classifications including , , , , , , or .
of the finished screw threads can be achieved in various ways, with the expense of the method tailored to the requirements of the product application. Shop-floor inspection of a thread is often as simple as running a
onto it (for male threads) or a bolt into it (for female threads). This is plenty good enough for many applications (e.g.,
or hobbyist work), although it is not good enough for most commercial manufacturing. Higher-precision methods are discussed below.
Commercial-grade inspection of screw threads can involve most of the same inspection methods and tools used to inspect other manufactured products, ; ; ; ; and
(CMMs). Even
(including ) can be used, for example, to inspect internal thread geometry in the way that an optical comparator can inspect external thread geometry.
Conical micrometer anvils, specifically suited to resting on the sides of the thread, are made for various , with 60° being the most common. Mics with such anvils are usually called "thread mics" or "pitch mics" (because they directly measure the pitch diameter). Users who lack thread mics rely instead on the "3-wire method", which involves placing 3 short pieces of wire (or ) of known diameter into the valleys of the thread and then measuring from wire to wire with standard (flat) anvils. A
(produced by a straightforward trigonometric calculation) is then multiplied with the measured value to infer a measurement of the thread's . Tables of these conversion factors were established many decades ago for all standard thread sizes, so today a user need only take the measurement and then perform the table lookup (as opposed to recalculating each time). The 3-wire method is also used when high precision is needed to inspect a specific diameter, commonly the pitch diameter, or on specialty threads such as multi-start or when the thread angle is not 60°. Ball-shaped micrometer anvils can be used in similar fashion (same trigonometric relationship, less cumbersome to use). Digital calipers and micrometers can send each measurement (data point) as it occurs through an interface (commonly ) to storage and as input to software, in which case the table lookup is done in an
can be achieved using .
Each method of thread generation has its own detailed history. Therefore a comprehensive discussion is beyond the s but much historical information is available in related articles, including:
[various sections]
and its family of articles (e.g., )
and its family of articles
Various specific
articles (e.g., , , , , )
The first patent for the cold rolling of screw threads was issued in 1836 to William Keane of Monroe, N.Y. However, the dies for rolling the threads onto the screw blanks were made of cast iron, which is brittle, so the machine was not successful. The process languished until 1867, when Harvey J. Harwood of Utica, New York filed a patent for the cold-rolling of threads on wood screws. Further efforts to cold-roll threads on screws followed, but none seemed to meet with much success until Hayward Augustus Harvey () of Orange, N.J. filed his patents of 1880 and 1881. Charles D. Rogers of the American Screw Co. of Providence, Rhode Island made further refinements to the process of rolling threads onto screws.
, p. 741.
, pp. .
, p. 1842
, p. 758.
, pp. 149–150.
. www.Cutwel.co.uk. Cutwel.
Accessed on January 11, 2009
(1996). . Instructions for Using Milling Machine Accessories. Sherline.
, p. 755.
, p. 754.
, pp. 433–442.
, p. 443.
, p. 435.
, p. 442.
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Komet customer, .
, p. 756.
, p. 324.
, p. 260.
William Keane,
U.S. Patent no. 9,398X (issued: Feb. 13, 1836).
The screw "cutting" machine of William Keane and his partner, Thaddeus Sellick of Haverstraw, N.Y., is mentioned in the North River Times (Haverstraw, New York), reprinted in: The Pittsburgh Gazette, March 19, 1836, . From page 2: "Important Invention. Mr. William Keane.of Haverstraw, has in conjunction with Mr. Thaddeus Selleck, obtained letters patent for a machine for cutting screws, which probably excels any thing of the kind now in use in Europe or America. The principle of the machine consists in circular dies, which have a motion towards each other, while, at the same time, they make upwards of 500 revolutions a minute. These dies receive the screw at the top of a cast iron pot in which they are secured, and when it obtains its proper thread, it is thrown off by means of an inner spindle, and another instantly takes its place, the dies preserving their usual velocity, without changing their rotary motion. The saving of screws is another important consideration in favor of these machines, as it is difficult to spoil one upon them. Their construction is simple, and we understand that one, containing four sets of dies, and upon which a boy can turn off thirty gross per day, can be built at a cost not exceeding $150. They are now in operation at Selleck & Keane's Screw Factory, at Samsondale, in this town [i.e. Haverstraw, N.Y.]."
For a brief review of the history of screw making, see:
Charles D. Rogers (July 11, 1901)
The Iron Trade Review, 34 (28) : 20-21.
Christopher White (ca. 2005)
(Museum of Fine Art ; Boston, Massachusetts).
Harvey J. Harwood,
U.S. Patent no. 65,567 (issued: June 11, 1867). In his patent, Harwood states:
"In the manufacture of wood-screws the thread has been formed hitherto by removing the metal between the turns of the thread by means of dies or cutters.
By my invention the blank is rotated between rotating or reciprocating dies, suitably formed, and set in motion, by means of which the thread is impressed on the blank without removing any part of the metal."
Apparently Harwood and the patent examiner were ignorant of Keane's 1836 patent.
See, for example:
Benjamin D. Beecher,
U.S. Patent 77,710 (issued: May 12, 1868).
James M. Alden,
U.S. Patent 110,532 (issued: Dec. 27, 1870).
Treat T. Prosser,
U.S. Patent 181,010 (filed: Dec. 30, ;; issued: August 15, 1876).
Hayward A. Harvey,
U.S. Patent 223,730 (filed: Oct. 15, ;; issued: Jan. 20, 1880).
Hawyard A. Harvey,
U.S. Patent no. 248,165 (filed: April 7, 1881; issued: October 11, 1881).
Thomas Wm. Harvey, Memoir of Hayward Augustus Harvey (New York: 1900), "The Rolled Screw,"
[Anon.] (August 28, 1897) "Hayward Augustus Harvey," Scientific American, 77 (9) :  ; .
Charles D. Rogers,
U.S. Patent no. 370,354 (filed: May 11, ;; issued: Sept. 20, 1887).
Degarmo, E. P Black, J T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley,  .
Green, Robert E. et al. (eds) (1996),
(25 ed.), New York, NY, USA: Industrial Press,  .
Smid, Peter (2008), CNC Programming Handbook (3rd ed.), New York: Industrial Press,  ,  .
Stephenson, David A.; Agapiou, John S. (1997), , Marcel Dekker,  .
Stephenson, David A.; Agapiou, John S. (2006),
(2nd ed.), CRC Press,  .
Todd, Robert H.; Allen, Dell K.; Alting, Leo (1994), , Industrial Press Inc.,  .
(1947), Sixty Years with Men and Machines, New York and London: McGraw-Hill,  . Available as a reprint from Lindsay Publications (). Foreword by .
Roe, Joseph Wickham (1916), , New Haven, Connecticut: Yale University Press,  . Reprinted by McGraw-Hill, New York and London, 1926 ( ); and by Lindsay Publications, Inc., Bradley, Illinois, ().
Roe, Joseph Wickham (1937), , New York, New York, USA: ,  ,  , ;.
(2000), , Scribner,  ,  ,  . Various republications (paperback, e-book, braille, etc).
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