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◆挤压丝锥是利用金属塑性变形原理而加工内螺纹的一种新型螺纹刀具，挤压丝锥挤压内螺纹是无屑加工工艺，特别适用于强度较低、塑性较好的铜合金和铝合金，也可用于不锈钢和低碳钢等硬度低、塑性大的材料攻丝，寿命长。
◆定义：
是一种加工内螺纹的刀具，沿轴向开有沟槽。也叫螺丝攻。丝锥根据其形状分为直槽丝锥, 螺旋槽丝锥和螺尖丝锥。直槽丝锥加工容易，精度略低，产量较大。一般用于普通车床，钻床及攻丝机的螺纹加工用，切削速度较慢。螺旋槽丝锥多用于数控加工中心钻盲孔用，加工速度较快，精度高，排屑较好、对中性好。螺尖丝锥前部有容削槽，用于通孔的加工。工具厂提供的丝锥大都是涂层丝锥，较未涂层丝锥的使用寿命和切削性能都有很大的提高。
◆特点：
用挤压丝锥挤出的螺纹表面光洁度高，螺纹的金属纤维不断裂，并在表面形成一层冷硬层，可提高螺纹的强度和耐磨性。它从根本上解决了攻丝的排屑困难问题，因无屑，更有利于螺纹的装配。在电子，塑料行业应用广泛。
◆用途：
供加工螺母或其他机件上的普通内螺纹用（即攻丝）.机用丝锥通常是指高速钢磨牙丝锥，适用于在机床上攻丝；手用丝锥是指碳素工具钢或合金工具钢滚牙（或切牙）丝锥，适用于手工攻丝。

◇Extrusion tap is by using the theory of metal plastic deformation and machining internal thread of a new type of thread tools, thread in the extrusion tap extrusion is a chipless machining process, especially suitable for the low strength, good plasticity, copper alloy and aluminum alloy can also be used for stainless steel and low carbon steel hardness is low, the large plastic material such as tapping, long service life.
◇Low definition：Is a kind of machining internal thread cutting tools, have grooves along the axial direction. Also called a tap. Tap according to its shape can be divided into straight slot tap, spiral tap and screw tap. Slightly less straight flute tap easy processing, precision, larger output. Commonly used in ordinary lathe, drilling and tapping machine of screw thread processing, cutting speed is slow. Spiral tap drilling blind holes with more used in nc machining center, processing speed, high precision, good chip removal, good to neutral. Tap screw tip anterior yu-jong cutting groove, used for hole processing. Tool factory provide tap tap are mostly coating, less coating tap service life and cutting performance are greatly improved.
◇Low characteristic：With extrusion tap extrusion screw thread surface finish high, threaded metal fibre
Don't break, and form a layer of cold hard layer on the surface, can improve the thread strength and abrasion resistance. It fundamentally solves the tapping of chip removal difficult problem, because there was no crumbs, more conducive to screw assembly. Widely used in electronics, plastics industry.
◇Low usage：For processing on the nuts or other parts of ordinary female with (that is, tapping). Machine tap is usually refers to the high speed steel grinding taps, suitable for tapping on machine tools; Hand tap refers to carbon tool steel or alloy tool steel rolling teeth (or incisor) tap, suitable for manual tapping.
挤压丝锥: 设计原理、优缺点
Extrusion tap: design principles, advantages and disadvantages
挤压丝锥是一种先进的无屑成型螺纹加工刀具，加工后螺纹精度高，被广泛应用在汽车、航空、电子等精工行业。
由于挤压成型无切屑干扰，因此加工螺纹精度可高达4H，螺纹表面粗糙度可达Ra0.3左右。
用切削丝锥加工的螺纹的金属组织纤维是间断的，而挤压螺纹的金属组织纤维则是连续的。因此，挤压螺纹强度较之切削螺纹可提高30%左右。
此外，由于挤压导致的冷作硬化现象，螺纹表面硬度较之芯部可提高40%-50%，同时螺纹表面的耐磨性也得到极大提高。
挤压丝锥无切削刃、无容屑槽、丝锥强度高，通常不会出现崩刃现象。此外，挤压丝锥较之一般切削丝锥（比如螺旋槽丝锥）寿命可提高3倍以上，攻丝速度也会有较大提高。但是，挤压丝锥也有其局限性，具体体现在以下两个方面：
1、丝锥规格
由于是挤压成型，需要较高的“挤压力”，因此，挤压丝锥普遍制成小规格丝锥，一般M12以下（常用规格为M3-M8）。
2、底孔直径
一般切削丝锥底孔尺寸：D=d1-P。以M16×2为例，底孔尺寸D=16-2=14。
然而，挤压丝锥则对底孔要求较为苛刻。一般来说可按以下公式计算大致底孔尺寸：
D=d1-0.49P。仍以M16×2为例，底孔尺寸：D=16-0.49×2=15.02
事实上，不同螺纹旋合度及不同材料、不同孔深的推荐的底孔直径也会不一样。这点可参看攻丝底孔直径计算中有关介绍。
 
Tap is a kind of advanced chipless extrusion molding thread cutting tools, thread after processing of high precision, is widely used in automotive industry, aviation, electron, etc., seiko.
Because of interference without chip extrusion, the thread machining precision can be up to 4 h, the screw thread surface roughness can reach Ra0.3 or so.
With cutting tap thread of metal fibre is intermittent, and extrusion screw metal tissue fiber is continuous. Therefore, the extrusion thread strength than cutting thread can be increased by about 30%.
In addition, the cold work hardening phenomenon, due to extrusion thread surface hardness than the core can be increased by 40% - 50%, thread surface wear resistance have been greatly improved at the same time.
Extrusion tap without cutting edges, no crumbs slot, tap the intensity is high, usually do not appear collapse edge phenomenon. In addition, the extrusion tap than average cutting tap (such as spiral tap) life can be increased by more than 3 times, tapping speed will have improved greatly. But, extrusion tap also has its limitations, embodies in the following two aspects:
1. tap specifications
Is due to the extrusion molding, need higher "extrusion", therefore, extrusion tap tap is generally made from small specification, under general M12 (commonly used specifications for the M3 - M8).
2. the diameter of bottom hole
General cutting tap base hole size: D = d1 - P. M16×2, for example, bottom hole size D = 16-2 = 14.
Extrusion taps, however, the bottom hole is more demanding. In general can be bottom hole size roughly by the following formula:
D = d1-0.49 P. Still M16×2, for example, bottom hole size: D = 16-0.49 ×2 = 0.49
In fact, screw different degree and different materials, different hole deep base hole diameter of the recommended will be different. This can see the tapping of the bottom hole diameter calculation about the introduction.

丝锥与底孔 Tap and bottom hole