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南京理工大學(xué)泰州科技學(xué)院 畢業(yè)設(shè)計(jì)(論文)外文資料翻譯 系　　部： 機(jī)械工程系 專 業(yè)： 機(jī)械設(shè)計(jì)及其自動(dòng)化 姓 名： 張 偉 學(xué) 號(hào)： 05010145 外文出處：http://www.thefabricator.com/ToolandDie /ToolandDie_Article.cfm?ID=1423 附 件： 1.外文資料翻譯譯文；2.外文原文。 指導(dǎo)教師評(píng)語(yǔ)： 譯文基本能表達(dá)原文思想，語(yǔ)句較流暢，條理較清晰，專業(yè)用語(yǔ)翻譯基本準(zhǔn)確，基本符合中文習(xí)慣，整體翻譯質(zhì)量一般。 簽名： 年 月 日 附件1：外文資料翻譯譯文 模具的八個(gè)基本元件 A stamping die is a special, one-of-a-kind precision tool that cuts and forms sheet metal into a desired shape or profile.沖壓模具是一個(gè)特殊的，一次性的一種精密工具，通過(guò)切割與塑形的方法使金屬成為一個(gè)理想的形狀或外形。 Most dies are constructed of several basic components, including die plates, shoes, die sets, guide pins, bushings, heel blocks, heel plates, screws, dowels, and keys.大多數(shù)模具構(gòu)造有幾個(gè)基本組成部分，包括模板，防磨裝置，模套，導(dǎo)向銷(xiāo)，軸襯，墊塊，墊板，螺釘，銷(xiāo)釘，和螺栓。 Dies also need stripper, pressure, and drawing pads, as well as the devices used to secure them—spools, shoulder bolts, keepers, and retainers; and gas, coil, or urethane springs.模具還需要沖孔模板，壓力和沖壓成型板，以及可用來(lái)保護(hù)轉(zhuǎn)子，肩螺栓，銜鐵，保持架;和氣體，線圈，或聚氨酯彈簧的工具。 一、 模板，防磨裝置，及模具套 Die plates, shoes, and die sets are steel or aluminum plates that correspond to the size of the die (see introductory photo and Figure 1 ).模板，防磨裝置，及模具套或鋁板塊相對(duì)應(yīng)的大小模具（見(jiàn)圖片和圖表1 ） 。 They serve as the foundation for mounting the working die components.它們?yōu)樵絹?lái)越多的模具組件提供基礎(chǔ)的服務(wù)。 These parts must be machined—milled or ground—so that they are parallel and flat within a critical tolerance.這些零件必須通過(guò)機(jī)械球磨或拋光，以保證它們?cè)谝粋€(gè)可接受的范圍內(nèi)保持平行和平整。 Although grinding is the most popular, a milled surface now can be obtained that is as accurate as a ground surface.雖然磨削是目前最流行的，但碾磨成型可以說(shuō)是現(xiàn)在最準(zhǔn)確的。 Most die shoes are made from steel.大多數(shù)模具防磨裝置是由鋼材料構(gòu)成，而Aluminum also is a popular die shoe material.鋁也是一個(gè)受歡迎的模具防磨裝置材料。 Aluminum is one-third the weight of steel, it can be machined very quickly, and special alloys can be added to it to give it greater compressive strength than low-carbon steel.鋁的質(zhì)量是鋼的三分之一，加工該材料速度非常快，而且可以添加特殊的合金進(jìn)來(lái)，以便達(dá)到比低碳鋼更大的耐壓強(qiáng)度。 Aluminum also is a great metal for shock adsorption, which makes it a good choice for blanking dies.鋁是一種很好的吸振材料，因而用它來(lái)做沖裁模是一種很好的選擇。 The upper and lower die shoes assembled together with guide pins create the die set.上，下模具防磨裝置裝配在一起，與導(dǎo)向銷(xiāo)配合形成一副模具。 The lower die shoe often has machined or flame-cut holes that allow slugs and scrap created in the die to fall freely through the die shoe onto the press bed.下模具防磨裝置往往有加工或火焰切割孔，讓未燃燒著的燃料及廢料自然地通過(guò)模具防磨裝置孔到達(dá)沖壓機(jī)底座，以便排出。 The holes also may serve as clearances for gas springs and other die components. The die shoe thickness is based on how much force can be expected during cutting and forming.模具防磨裝置厚度是基于切割和成型的力度。 For example, a coining die, one that compresses metal by squeezing it between an upper and lower die section, requires a much thicker die shoe than a simple bending die.舉例來(lái)說(shuō)，鑄幣模具，其中壓縮金屬受擠壓，在上、下模具剖面之間，要求有一個(gè)更厚的模具防磨裝置而不是一個(gè)簡(jiǎn)單彎曲模。 圖1 Die plates, shoes, and die sets, which correspond to the size of the die, serve as the foundation for mounting the working die components. Image courtesy of Eclipse Tool and Die.模板，防磨裝置，及模具套，是其它更多組建工作的基礎(chǔ) 二、 導(dǎo)向銷(xiāo)和軸襯 Guide pins, sometimes referred to as guide posts or pillars, function together with guide bushings to align both the upper and lower die shoes precisely (see Figure 2 ).導(dǎo)向銷(xiāo)，有時(shí)被認(rèn)為是引導(dǎo)或支柱，功能在于能夠引導(dǎo)軸襯，使上，下模具防磨裝置恰到好處的連接成一個(gè)整體（見(jiàn)圖表2 ） 。 They are precision-ground components, often manufactured within 0.0001 in. Although numerous specialty mounting methods can be used to install these components, there are only two basic types of guide pins and bushings—friction pins and ball bearing-style pins.它們是精密磨光管，它的內(nèi)部往往制造成0.0001英寸。盡管有許多專業(yè)的安裝方法，可被用來(lái)安裝這些組件，但只有兩種基本類(lèi)型的導(dǎo)向銷(xiāo)和軸襯——摩擦銷(xiāo)和球軸承式的銷(xiāo)。 圖2 導(dǎo)向銷(xiāo)（指南職位或支柱） ，并引導(dǎo)軸襯，使上，下模具防磨裝置。 Friction pins are precision-ground pins that are slightly smaller than the guide bushing's inside diameter.摩擦銷(xiāo)是精確的銷(xiāo)，它只略小于引導(dǎo)套管的內(nèi)徑。 Pins are made from hardened tool steel, while bushings often are made from or lined with a special wear-resistant material called aluminum-bronze.銷(xiāo)是由淬硬工具鋼構(gòu)成，而軸襯往往是由一份特殊的耐火材料組成或構(gòu)成的所謂的鋁青銅。銷(xiāo)和軸襯中通常采用The aluminum-bronze may contain graphite plugs that help to reduce friction and wear that occur to the pins and bushings.鋁青銅，它可能含有石墨，有助于減少摩擦與磨損發(fā)生。 Friction pins also help to heel the die shoes and prevent them from moving from side to side.摩擦銷(xiāo)，也有利于固定模具防磨裝置，以防止它們從一邊滑向另一邊。 Precision or ball bearing-style guide pins comprise precision-hardened pins, ball cages, ball bearings, and bushings.精密或球軸承式導(dǎo)向銷(xiāo)包括精密硬化銷(xiāo)，滾珠隔離圈，球軸承，軸襯。 Unlike friction pins, these pins ride on a series of ball bearings contained in a special aluminum ball cage that permits the bearings to rotate without falling out.不像摩擦銷(xiāo)，這些銷(xiāo)依靠一系列的球軸承來(lái)工作，其中包括專門(mén)的滾珠隔離圈，它們?cè)试S軸承轉(zhuǎn)動(dòng)而不會(huì)脫落。 These pins have several advantages.這些銷(xiāo)有若干優(yōu)點(diǎn)。 First, friction is reduced so the die can run at faster speeds without generating excessive friction and heat.首先，摩擦力減小，使模具的運(yùn)行速度更快，而不會(huì)產(chǎn)生過(guò)量的摩擦和熱量。 Second, they allow the diemaker to separate the upper and lower die shoes easily.第二，它們?cè)试S制模工輕松的分開(kāi)上，下模具的防磨裝置。 Third, because they use ball bearings, they can be manufactured with greater accuracy than friction pins.第三，因?yàn)樗鼈兪褂脻L珠軸承，因而制造出來(lái)的精度比摩擦銷(xiāo)更高。 Remember, guide pins are meant to align the upper and lower die shoes, not to align a poorly maintained or sloppy ram in a press!請(qǐng)記住，導(dǎo)向銷(xiāo)，在壓力下，是為了校準(zhǔn)上，下模具防磨裝置，而不是校準(zhǔn)不利于維護(hù)和濕滑的連桿！ Some companies try to compensate for a poorly maintained press by adding oversized guide pins or grinding the guide pin ends to a cone shape.一些公司試圖補(bǔ)償為維修不善壓力而加入過(guò)大的導(dǎo)向銷(xiāo)，或者將其磨削成錐形狀。 Care must be taken when flipping die shoes over so that the guide pins are not bent.當(dāng)翻動(dòng)模具防磨裝置的時(shí)候必須小心，這樣導(dǎo)向銷(xiāo)才不至于被弄彎。 三、墊塊及墊板 Heel blocks are special steel blocks that are precision-machined, screwed, doweled, and often welded to both the upper and lower die shoes (see Figure 3 ).墊塊是特殊鋼塊，這種鋼塊是精密機(jī)械，被攻螺紋，并用暗銷(xiāo)接合，而且往往焊接在上，下模具防磨裝置上（ 見(jiàn)圖3 ）。They contain components called wear plates and function to adsorb any side thrust that may be generated during the cutting and forming processes.它們都包含了所謂的耐磨板，以及在切割和成型工藝中吸附任何一方推力的功能。 They are especially important if the generated force is one-directional.如果所產(chǎn)生的力量是一個(gè)方向性的，那么它們就顯得尤其重要。 Too much force generated from one direction only can cause the guide pins to deflect, which results in misalignment of critical cutting and forming components.很大的力量往往產(chǎn)生于一個(gè)方向，它們不僅能引起導(dǎo)向銷(xiāo)傾斜，而且可能導(dǎo)致關(guān)鍵切割和成型部件未對(duì)準(zhǔn)。 圖3 墊塊特殊鋼塊連接到上，下模具防磨裝置吸附任何一方推力可能產(chǎn)生的 圖4 Keys locate and heel die sections and components.螺栓的位置。 大多數(shù)Most heel blocks have steel heel plates, and the heel block on the opposite shoe has a wear plate made from aluminum-bronze or some other dissimilar metal.大多數(shù)大多數(shù) 墊塊是有鋼墊板的，并且墊塊對(duì)面的防磨裝置中有由鋁青銅或其他一些異種金屬制成的耐磨鋼板。 The plate selection process is critical.鋼板鋼板的選擇過(guò)程是至關(guān)重要的，Using two opposing plates made of the same metal type can result in high friction, heat, and eventually galling or cold welding of the wear plates.用兩種相同的金屬做的對(duì)立板，可導(dǎo)致高摩擦，熱，并最終成為咬焊或冷焊的耐磨板。 Heel blocks can be used to heel the die in any or all directions.墊塊，可以用來(lái)使模具在任何或所有的方向傾側(cè)。盒子殘料通常用來(lái)在各個(gè)方位上傾側(cè)模具 Box heels often are used to heel the die in all directions.盒子。 四、螺釘，銷(xiāo)釘，和螺栓 保障Screws fasten and secure the working components to both the upper and lower die shoes.上，下模具防磨裝置的螺釘，具有栓緊和保障零件工作安全的作用。 The socket head cap screw is the most popular fastener used in stamping dies.插座頭帽釘是目前最流行用在沖壓模具的扣件。 This hardened tool steel screw, often referred to as an Allen head screw, offers superior holding power and strength.這種淬硬工具鋼螺絲釘，常常被稱作是Allen頭螺絲釘，它能提供優(yōu)越的握力和力量。 Dowels are hardened, precision-ground pins that precisely locate the die section or component in its proper location on the die shoe.銷(xiāo)釘都是堅(jiān)固，精確的銷(xiāo)子，在模具防磨裝置的適當(dāng)位置，它能夠精確定位模具剖面或組件。 Although dowels have much heeling ability, their main function is to locate the die section properly.雖然銷(xiāo)釘具備一定的側(cè)傾能力，其主要職能還是在于合理的定位模具。 Keys are small, rectangular blocks of precision-ground steel that are inserted into milled pockets in the die shoes and sections called keyways (see Figure 4 ).螺栓通常是由小的矩形耐摩擦鋼材料構(gòu)成，是插入到小型銑過(guò)的模具防磨裝置和鍵槽的地方（ 見(jiàn)圖4 ） 。 Keys locate and heel die sections and components.螺栓可以定位，并用以傾斜零部件和其它組成部分。 五、襯 Pads墊 襯A pad is simply a pressure-loaded plate, either flat or contoured, that holds, controls, or strips the metal during the cutting and forming processes.墊只是一個(gè)負(fù)載壓力的板，無(wú)論是平坦或有波紋，它在切割和成型工藝期間把握，控制或卸下金屬。 Several types of pads are used in stamping dies.幾種類(lèi)型的墊片被用在沖壓模具中。 Depending on their function, pads can be made from soft low-carbon steel or hardened tool steel.根據(jù)其功能，襯墊可以由軟低碳鋼或淬硬工具鋼制造。 Contoured pads must fit very closely to the mating die section.等高墊必須配合非常密切，以便配合模具剖面。 Precision requirements determine whether the pads are positioned with guide pins and bushings or left unguided.精度的要求決定了墊片是否定位于導(dǎo)向銷(xiāo)和軸襯，而非位導(dǎo)向。 Stripper Pads/Plates. Stripper pads are flat or contoured spring-loaded plates that pull, or strip, the metal off the cutting punches (see Figure 5 ). 模板墊/板。模板墊片是平坦或波形的彈簧負(fù)載板，它從剪切沖頭上拉或卸下鋼材料。（ 見(jiàn)圖5 ） 。 When it is cut, metal naturally tends to collapse around the body or shank of the cutting punches; this is especially true during piercing.當(dāng)它被切斷，金屬自然坍塌在切割鉆孔周?chē)蚣羟袥_頭的鉆頭部位。這種情況尤其發(fā)生在沖孔的時(shí)候。 The stripper pad surrounds the cutting punches and mounts to the upper die shoe.模板墊環(huán)繞在切割鉆孔周?chē)?，并安裝到上模具防磨裝置上。 As the punch exits the lower die, the spring-loaded pad holds the metal down flush with the lower die section, which allows the cutting punches to withdraw from the sheet metal or piece part.當(dāng)沖頭退出下模具 ，彈簧負(fù)載墊隨金屬向下沖洗，并隨下模具運(yùn)動(dòng)，它使切削鉆孔退出金屬板或零部件。 圖5 Keys locate and heel die sections and components.螺栓的位置，和模具部件。 Often stripper pads are inserted with a small block of steel called a pad window.模板墊片常常插入一小塊稱為墊孔的鋼。 This pad window usually is small and lightweight and can be removed easily to allow the die maintenance technician to remove the ball lock-style pierce punch from the retainer without removing the entire stripper pad.墊孔通常是小而輕便，可輕易移走，使模具維修技師在消除球鎖式?jīng)_床穿透時(shí)不至于移除整個(gè)模板墊。 Stripper pads also function to hold the metal flat or to the desired shape during the cutting process.模板墊同樣在切削加工過(guò)程具有控制金屬的平坦或到形成理想的形狀的功能。 Pressure Pads/Plates. During the wipe bending process, the metal must be held down tightly to the lower die section before the forming punch contacts the metal. 壓力墊/板。在彎曲過(guò)程中，在用以成形的沖頭接觸到金屬之前，金屬必須穩(wěn)穩(wěn)地固定在下模具部位。 Pressure pads must apply a force that is at least equivalent to the bending force (see Figure 6 ).壓力墊，必須提供的力量至少相當(dāng)于抗彎力（ 見(jiàn)圖6 ） 。 Most pressure pads use high-pressure coil or gas springs.大部分壓力墊用高壓力的線圈或氣體彈簧。當(dāng)When loaded with very high-pressure springs, contoured or flat pads also can form sheet metal.負(fù)載非常高的壓力彈簧，等高或平面墊，也能形成金屬板材。 These pad types often are referred to as power punches.這些墊被稱為重?fù)粜蛪|。 圖6 During the wipe bending process, the metal must be held down tightly to the lower die section before the forming punch contacts the metal.在消滅彎曲過(guò)程中，金屬的，必須控制下來(lái)，緊緊到下模具節(jié)，然后才形成沖壓接觸金屬。 Pressure pads must apply a force that is at least equivalent to the bending force.壓力墊， 必須提供的力量是至少相當(dāng)于彎曲的力量。 Draw Pads. Draw pads control metal flow during the drawing process (see Figure 7 ). 沖壓成型板。沖壓成型板在成型過(guò)程中控制著金屬的流動(dòng)，（ 見(jiàn)圖7 ） 。 In drawing, the amount of pressure, or downward force, exerted on the sheet metal determines how much metal is allowed to flow and enter the draw die cavity.在成型過(guò)程中，壓力或向下的力量，施加于金屬板材，決定著多少金屬允許流入模腔。 Too much pressure may stop the metal from flowing and cause splitting; too little downward force may allow excess metal to flow inward and cause loose metal or wrinkling.壓力太大可能會(huì)阻止金屬流動(dòng)，并造成破裂;太少向下的力量可能讓多余的金屬流動(dòng)松散或起皺。 Draw pads, often referred to as binders or blank holders, usually are made from hardened tool steel.沖壓成型板，往往被用于粘合劑或控制齒輪，通常是由淬硬工具鋼制造。 They can be flat or contoured, depending on the piece part shape.它們可以持平或等高，這取決于其零部件的形狀。 Most drawing dies use a single draw pad; however, in special cases, some use two.多數(shù)成型模板使用單一沖壓成型板，但在特殊情況下，一些會(huì)用兩個(gè)。 圖7 Draw pads control metal flow during the drawing process.沖壓成型板和控制金屬流動(dòng)，在繪畫(huà)的過(guò)程。 6.六六、 Spools, Shoulder Bolts, and Keepers轉(zhuǎn)子，肩螺栓，以及銜鐵 Spools, shoulder bolts, and keepers are used to fasten pads to the die shoes while allowing them to move up and down.轉(zhuǎn)子，肩螺栓，以及銜鐵，是用來(lái)栓緊墊和模具防磨裝置，同時(shí)也允許它們上升和下降。 They are secured to either the top or bottom die shoe with screws and often dowels for precision location.它們使頂部或底部模具防磨裝置與螺絲釘固定，往往銷(xiāo)釘作精確定位。 Of all of the components used for securing pads, spools are the most common, especially in larger dies ( Figure 1 and Figure 8 ).所有的部件用于固定墊板，轉(zhuǎn)子是最常見(jiàn)的，尤其常見(jiàn)于較大的模具中（ 圖1和圖8 ） 。 圖8 Spools, shoulder bolts, and keepers are used to fasten pads to the die shoes while allowing them to move up and down. Image courtesy of Anchor Lamina Corp.轉(zhuǎn)子，肩螺栓，以及銜鐵用來(lái)栓緊墊，以模具防磨裝置，同時(shí)也允許它們提出上升和下降。 7.七七、Retainers保持架 Retainers hold or secure cutting or forming die components to both the upper and lower die shoes (see Figure 9 ).保持架能使上、下模具防磨裝置保持或安全切割成形模具部件（ 見(jiàn)圖9 ） 。 One of the most popular retainers is a ball-lock retainer, a high-precision, accurately manufactured die component that secures and aligns both cutting and forming punches.其中最流行的保持架約是一個(gè)球鎖保持架，高精密，準(zhǔn)確地制造模具組件，可以使切割和成型沖頭得以安全使用，并排列成一行。It uses a spring-loaded ball bearing to locate and secure the punches, which feature a precisely machined teardrop or ball seat.它是用彈簧負(fù)載球軸承位置，并確保鉆孔，其中具有精密加工的淚狀物或球座。 The spring-loaded ball bearing locks into the teardrop shape and prevents the punches from coming out of the retainer.彈簧式球軸承鎖住淚狀物，并防止沖頭從保持架中漏出。 圖9 保持架使上，下模具防磨裝置保持或安全切割成形模具部件。 球鎖保持架的好處是他們?cè)试S模具維護(hù)師移除和快速重新安裝打孔器The advantage of ball-lock retainers is that they allow the die maintenance technician to remove and reinstall punches quickly.球所 。 The punch is removed by depressing the spring-loaded ball bearing and pulling up on the punch.該沖床去除抑制彈簧負(fù)載的球軸承，并拉動(dòng)了沖床。 Specialty retainers also can be made to hold and align irregular punch shapes, as well as headed-style punches and pilot pins.特殊的保持架，也可以鉆孔和銷(xiāo)來(lái)對(duì)準(zhǔn)不規(guī)則形狀。 八8.八八 八、 Springs彈簧 Springs supply the force needed to hold, strip, or form metal.彈簧供應(yīng)保持、卸下或成型金屬時(shí)所需要的力量。 Many different springs are used in stamping dies (see Figure 10 ).許多不同的彈簧用于沖壓模具（ 見(jiàn)圖10 ） 。 Spring selection is based on many factors, including the required force and travel, the spring's life expectancy, and, of course, cost.彈簧選擇，是基于許多因素，包括所需的力量和用途，彈簧的預(yù)期壽命，當(dāng)然還有成本。 Among the most popular are gas springs, which, when filled with nitrogen, can supply a great deal of force.其中最受歡迎的是氣體彈簧，其中，當(dāng)其充滿氮?dú)?，可供?yīng)大量的力量。 They also have an excellent life expectancy.它們也有一個(gè)很好的預(yù)期壽命。 圖10 彈簧供應(yīng)卸下或成型金屬需要保持的力量。 Other types are coil and urethane springs, often called marshmallow springs.其他類(lèi)型的盤(pán)簧和聚氨酯彈簧，通常被稱為軟性彈簧。 Coil springs are very popular when a reasonable amount of force is needed and budget constraints are present.螺旋彈簧是很受歡迎的，它有一個(gè)所需的合理的力量和可以展現(xiàn)出的預(yù)算的強(qiáng)制力量。 Urethane springs work well in short-run or prototype stamping operations.聚氨酯彈簧在短期運(yùn)行或原型沖壓業(yè)務(wù)中很好用， 并且They also are inexpensive.它們還很便宜。 附件2：外文原文（復(fù)印件） Die basics with eight basic components A stamping die is a special, one-of-a-kind precision tool that cuts and forms sheet metal into a desired shape or profile. Most dies are constructed of several basic components, including die plates, shoes, die sets, guide pins, bushings, heel blocks, heel plates, screws, dowels, and keys. Dies also need stripper, pressure, and drawing pads, as well as the devices used to secure them—spools, shoulder bolts, keepers, and retainers; and gas, coil, or urethane springs. A stamping die is a special, one-of-a-kind precision tool that cuts and forms sheet metal into a desired shape or profile. The die's cutting and forming sections typically are made from special types of hardenable steel called tool steel. Dies also can contain cutting and forming sections made from carbide or various other hard, wear-resistant materials. Most stamping dies are constructed of several basic components, including die plates, shoes, die sets, guide pins, bushings, heel blocks, heel plates, screws, dowels, and keys. Dies also need stripper, pressure, and drawing pads, as well as the devices used to secure them: spools, shoulder bolts, keepers, and retainers, as well as gas, coil, or urethane springs 1. Die Plates, Shoes, and Die Sets Die plates, shoes, and die sets are steel or aluminum plates that correspond to the size of the die (see introductory photo and Figure 1). They serve as the foundation for mounting the working die components. These parts must be machined—milled or ground—so that they are parallel and flat within a critical tolerance. Although grinding is the most popular, a milled surface now can be obtained that is as accurate as a ground surface. Most die shoes are made from steel. Aluminum also is a popular die shoe material. Aluminum is one-third the weight of steel, it can be machined very quickly, and special alloys can be added to it to give it greater compressive strength than low-carbon steel. Aluminum also is a great metal for shock adsorption, which makes it a good choice for blanking dies. The upper and lower die shoes assembled together with guide pins create the die set. The lower die shoe often has machined or flame-cut holes that allow slugs and scrap created in the die to fall freely through the die shoe onto the press bed. The holes also may serve as clearances for gas springs and other die components. The die shoe thickness is based on how much force can be expected during cutting and forming. For example, a coining die, one that compresses metal by squeezing it between an upper and lower die section, requires a much thicker die shoe than a simple bending die. 2. Guide Pins and Bushings Guide pins, sometimes referred to as guide posts or pillars, function together with guide bushings to align both the upper and lower die shoes precisely (see Figure 2). They are precision-ground components, often manufactured within 0.0001 in. Although numerous specialty mounting methods can be used to install these components, there are only two basic types of guide pins and bushings—friction pins and ball bearing-style pins. Friction pins are precision-ground pins that are slightly smaller than the guide bushing's inside diameter. Pins are made from hardened tool steel, while bushings often are made from or lined with a special wear-resistant material called aluminum-bronze. The aluminum-bronze may contain graphite plugs that help to reduce friction and wear that occur to the pins and bushings. Friction pins also help to heel the die shoes and prevent them from moving from side to side. Precision or ball bearing-style guide pins comprise precision-hardened pins, ball cages, ball bearings, and bushings. Unlike friction pins, these pins ride on a series of ball bearings contained in a special aluminum ball cage that permits the bearings to rotate without falling out. These pins have several advantages. First, friction is reduced so the die can run at faster speeds without generating excessive friction and heat. Second, they allow the diemaker to separate the upper and lower die shoes easily. Third, because they use ball bearings, they can be manufactured with greater accuracy than friction pins. Remember, guide pins are meant to align the upper and lower die shoes, not to align a poorly maintained or sloppy ram in a press! Some companies try to compensate for a poorly maintained press by adding oversized guide pins or grinding the guide pin ends to a cone shape. Care must be taken when flipping die shoes over so that the guide pins are not bent. 3. Heel Blocks and Heel Plates Heel blocks are special steel blocks that are precision-machined, screwed, doweled, and often welded to both the upper and lower die shoes (see Figure 3). They contain components called wear plates and function to adsorb any side thrust that may be generated during the cutting and forming processes. They are especially important if the generated force is one-directional. Too much force generated from one direction only can cause the guide pins to deflect, which results in misalignment of critical cutting and forming components. Most heel blocks have steel heel plates, and the heel block on the opposite sh