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一、旧国标普通螺纹的牙底形状分析 1.在旧国标中,外螺纹牙型槽底形状,不做规定,制造时可在原始三角形下部H/6处削平,或倒圆。圆角半径r=H/6=0.1443t 式中: H—原始三角形高度 t—旧国标螺纹螺距 2.外螺纹牙底最小削平宽度或最小倒圆位置,在原始三角形下部H/8处,最小圆角rmin=H/8=0.1082t,这是设计刀具的原始数据。 3.外螺纹内径偏差不规定,但应保证外螺纹内径与内螺纹内径之间有间隙,并由螺纹刀具来保证。其螺纹牙底是用对螺纹成型刀具的牙顶来控制的。 4.内螺的牙底允许呈圆弧形状,刃磨其外径上偏差不规定。二、新国标普通螺纹的牙底形状分析 1.新国标内、外螺纹牙底实际轮廓上的任何点,均不应超越按基本偏差所规定的最大实体牙型。 2.新国标对于高强度螺栓的牙底形状做了明确而又比较严格的规定。这是因为应
First, the old national standard general thread shape of the bottom of the tooth 1. In the old national standard, the shape of the outer thread groove bottom groove, do not make provisions, the manufacture of the lower triangle in the original H / 6 flat, or round. Fillet radius r = H / 6 = 0.1443t Where: H - the original height of the triangle t - the old national standard thread pitch 2. External thread bottom minimum flattening width or minimum rounding position, in the lower part of the original triangle H / 8, the minimum Rounded corner rmin = H / 8 = 0.1082t, which is the original data of the design tool. 3. External thread diameter deviation is not specified, but should ensure that there is a gap between the internal thread diameter and internal thread diameter, and by the thread cutter to ensure. The thread bottom of the thread is used to control the top of the thread forming tool to control. 4. The internal thread of the tooth bottom allows arc shape, sharpening the deviation on the outside diameter is not specified. Second, the new national standard tooth shape analysis of the common thread 1. The new national standard, the external thread at any point on the actual contours of the outline, should not exceed the basic deviation of the maximum entity tooth shape. 2. The new national standard for the strength of the tooth bottom shape made clear and more stringent requirements. This is because of it