膨胀螺丝Anchors一般说的是金属膨胀螺丝，膨胀螺丝的固定是利用楔形斜度来促使膨胀产生摩擦握裹力，达到固定效果。螺钉一头是螺纹，一头有锥度。外面包一铁皮(有的是钢管)，铁皮圆筒(钢管)一半有若干切口，把它们一起塞进墙上打好的洞里，然后锁螺母，螺母把螺钉往外拉，将锥度拉入铁皮圆筒，铁皮圆筒被涨开，于是紧紧固定在墙上，一般用于防护栏、雨篷、空调等在水泥、砖等材料上的紧固。但它的固定并不十分可靠，如果载荷有较大震动，可能发生松脱，因此不推荐用于安装吊扇等。
膨胀螺丝Anchors由螺杆和膨胀管等部件组成，螺杆尾部为圆锥状，圆锥的内径大于膨胀管内径。当螺母拧紧的时候，螺杆向外移动，通过螺纹的轴向移动使圆锥部分移动，进而在膨胀管的外周面形成很大的正压力，加之圆锥的角度很小，从而使墙体、膨胀管及圆锥间形成摩擦自锁，进而达到固定作用。
膨胀螺丝Anchors上的弹簧垫是标准零件，因为它的开口错开并具有弹性，所以叫做弹簧垫圈，弹簧垫圈的作用是利用错口的锐利尖角刺入螺母和平垫中，防止螺母松动。
平垫也是标准件，它的作用是把螺母的压力均匀分布于被连接的零件上。
膨胀螺栓的等级分为:45、50、60、70、80，
膨胀螺丝的材料:主要分奥氏体A1、A2、A4，
马氏体和铁素体C1、C2
45号钢，对于重要的或特殊用途的螺纹联接件，可选用15Cr ，20Cr，40Cr，15MnVB，30CrMrSi等机械性能较高的合金钢。
根据墙体实际情况选用不同膨胀螺丝。一般有以下几种6×60、6×80、6×120、6×150。
6×60:总长60 mm，套管长45 mm、直径8 mm、壁厚0.7 mm、表面是镀彩锌;螺杆长60 mm、直径6 mm、螺纹的部分35 mm、底部杆锤8mm的圆锥形，表面是镀彩锌;螺母外径10 mm的八角形、厚度5 mm、表面是镀白锌;垫片外径13 mm、厚度 1mm、内径6 mm、表面镀白锌;弹片是外径9 mm、内径6 mm、厚度1.6 mm圆环。
6×80:总长80 mm，套管长65 mm、直径8mm、壁厚0.7 mm、表面是镀彩锌;螺杆长、螺母、垫片、弹片同上。
6×120:总长120mm，套管长105mm、直径8mm、壁厚0.7 mm、表面是镀彩锌;螺杆长、螺母、垫片、弹片同上。
6×150:总长150mm，套管长135mm、直径8mm、壁厚0.7 mm、表面是镀彩锌;螺杆长、螺母、垫片、弹片同上。
Expansion Anchors generally speak of metal expansion screws. Expansion screws anchors use wedge slope to force expansion to produce friction and grip to achieve anchors. The screw is threaded at one end and tapered at the other. The outer bread is a tin (some steel pipe), the tin cylinder (steel pipe) half has a number of notches, put them together into the wall hole, and then lock the nut, the nut pulls the screw outward, the taper pulls into the tin cylinder, the tin cylinder is opened, so tightly fixed on the wall, generally used for guardrail, awning, air conditioning and so on cement, brick and other materials. But its fixing is not very reliable, if the load has a large vibration, may loose, so it is not recommended for the installation of ceiling fans.
Expansion screw Anchors consist of screw and expansion tube and other parts. The tail of the screw is conical. The inside diameter of the cone is larger than the inside diameter of the expansion tube. When the nut is tightened, the screw moves outward, and the cone part moves through the axial movement of the thread, and then forms a great positive pressure on the outer surface of the expansion tube, and the Angle of the cone is very small, so that the friction between the wall, the expansion tube and the cone is self-locking, and then achieves the fixing effect.
Expansion screwanchors spring Anchors are standard parts. They are called spring anchors because their openings are splintered and elastic. Spring anchors are used to insert the nut and pad with the sharp Angle of the splintered opening to keep the nut from loosening.
The flat washer is also a standard part. Its function is to distribute the pressure of the nut evenly across the connected parts.
Expansion bolt grades :45, 50, 60, 70, 80,
Expansion screw material: main austenite A1, A2, A4,
Martensite and ferrite C1 and C2
45 steel, for important or special purpose threaded connection, can choose 15Cr, 20Cr, 40Cr, 15MnVB, 30CrMrSi and other alloy steel with higher mechanical properties.
Select different expansion screws according to the actual situation of the wall. Generally there are the following kinds of 6×60, 6×80, 6×120, 6×150.
6×60: the total length is 60 mm, the casing length is 45 mm, the diameter is 8 mm, the wall thickness is 0.7 mm, the surface is coated with colored zinc; Screw length 60 mm, diameter 6 mm, thread part 35 mm, the bottom rod hammer 8mm conical, the surface is painted zinc plating; The nut is octagonal with an outer diameter of 10 mm and a thickness of 5 mm. The surface is white zinc plated. Gasket outer diameter 13 mm, thickness 1mm, inner diameter 6 mm, surface coated with white zinc; The shrapnel is a ring with an outer diameter of 9 mm, an inner diameter of 6 mm and a thickness of 1.6 mm.
6×80: the total length is 80 mm, the casing length is 65 mm, the diameter is 8mm, the wall thickness is 0.7 mm, the surface is coated with colored zinc; Screw length, nut, gasket, shrapnel as above.
6×120: the total length is 120mm, the casing length is 105mm, the diameter is 8mm, the wall thickness is 0.7mm, and the surface is coated with colored zinc; Screw length, nut, gasket, shrapnel as above.
6×150: the total length is 150mm, the casing length is 135mm, the diameter is 8mm, the wall thickness is 0.7mm, the surface is coated with colored zinc; Screw length, nut, gasket, shrapnel