A concave attachment is a versatile one to cut concave-convex profiles. A set of rotating plates have T-slots for the T-bolts that hold the boring bar. These plates are rotated by a train of gears. The bar is held roughly yet free enough to rotate. When the tool is built, the boring bar is first clamped with both pivots at lead centre. So, the tool describes a zero radius when the crank is turned.
At this time, one set up pin hole is drilled in each of the rotating plates, as indicated so that the pin touches the boring bar. Then to set the tool, for a desired radius, it is merely necessary to place a piece of flat stock the same thickness as the desired radius between the bar and the set up pins while securing the bar in position. At this point, data the flat stock and set up pin can be removed.
The concave attachment is fixed to the carriage of the lathe. The compound rest that is locked solid with its base is removed and the attachment is fixed on the cross lied of the carriage with its axis parallel to the lathe bed.
The work is secured rigidly in a chuck. By the concave-convex movement of the boring bar, the material is being removed. This attachment is used to produce contour profiles and round balls.
NEED FOR ATTACHMENT
In recent years, new fabrication techniques have been developed to satisfy the technological demands. Moreover, emphasis is stressed on attachments.
Attachments are used in various fields and machines depending upon the needs to be fulfilled and mode of operation. An attachment eliminates the purchasing of a new unit which serves the same purpose. For example, a lathe occupies a place opposite to that of a milling machine, the ten machines mainly used to produce cylindrical and plain surfaces respectively. By implementing an attachment to a unit, the capacity of the unit can be increased which is very economical.
The worm wheel is rotated with the help of a worm shaft. Rotating plates with T-slots that hold the boring are screwed to the worm wheel. The worm wheel in turn is screwed to its base with a simple gear train. The rotary motion is imported to the blank through two spur gears and an intermediate gear namely “Idler Gear”.
The idler gear serves to keep the rotation of rotating plates in the same direction. The worm shaft is rotated in clockwise direction, the boring bar machines a contour profile in the clockwise direction and vice versa. Thus a concave-convex profile is machined by boring bar by simultaneous engagement of the two plates.