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•The outside surface of the nose fits in the taper hole of the hood. •The inside of the collet is made according to the shape of the work to be held. •Collets are much more suitable than a self centering chuck in mass production work due to its quickness in action and accurate setting.
Collet chuck Hood Collet
Attachments used in lathes •Taper turning attachment •Copy turning attachments •Milling and cylindrical grinding attachments •Spherical turning attachments •Relieving attachment
Taper turning methods A taper may be defined as a uniform change in the diameter of a work piece measured along its length. Taper may be expressed in two ways: •Ratio of difference in diameter to the length. •In degrees of half the included angle. LDD2tan 21
Taper turning methods D - Large diameter of the taper. d - Small diameter of the taper. l - Length of tapered part. α - Half angle of taper. •Generally, taper is specified by the term conicity. Conicity is defined as the ratio of the difference in diameters of the taper to its length. •Conicity, ? =𝐷1− 𝐷2𝑙
Taper turning by a form tool •A broad nose tool having straight cutting edge is set on to the work at half taper angle, and is fed straight into the work to generate a tapered surface. •In this method, the tool angle should be properly checked before use. This method is limited to turn short length of taper only. This is due to the reason that the metal is removed by the entire cutting edge will require excessive cutting pressure, which may distort the work due to vibration and spoil the work surface.
Taper turning by swiveling the compound rest •This method is used to produce short and steep taper. •In this method, work is held in a chuck and is rotated about the lathe axis. The compound rest is swiveled to the required angle and clamped in position.
Taper turning by swiveling the compound rest •The angle is determined by using the formula •Then the tool is fed by the compound rest hand wheel. This method is used for producing both internal and external taper. •This method is limited to turn a short taper owing to the limited movement of the compound rest. •The compound rest may be swiveled at 45˚on either side of the lathe axis enabling it to turn a steep taper. •The movement of the tool in this method being purely controlled by hand, this gives a low production capacity and poorer surface finish. LDD2tan 21
Taper turning by offsetting the tailstock •The principle of turning taper by this method is to shift the axis of rotation of the work piece, at an angle to the lathe axis, which is equal to half angle of the taper, and feeding the tool parallel to the lathe axis. •This is done when the body of the tailstock is made to slide on its base towards or away from the operator by a set over screw. •The amount of set over being limited, this method is suitable for turning small taper on long jobs.