In this article we will discuss about tool and tool-layout for turret lathe used in industries.
Tools for capstan and turret lathe are similar in construction to those of centre lathe tools, except material. The tools used are made of H.S.S. or tungsten carbide because the machines are more rigid and also operated at higher cutting speeds. The tools mounted on cross-slide are used for tuning, facing, necking, parting etc. and those mounted on the turret head are used for drilling, boring reaming, etc.
The tool layout for a job constitutes the pre-determined plan for machining operation of a particular component. The layout is dependent upon the number of pieces to be manufactured, i.e. lot size. As a general rule, standard tools should be used as much as possible and also for small batches of work, the layout should be simple.
For large quantities and long run special tools should be used as they minimise machining time and retain their cutting qualities for the maximum period. The accuracy and cost of component largely depends upon the tool layout.
For preparation of the tool layout, it is necessary to have the finished drawing of the part to be machined and if it is a forging or casting, the forged, or cast blank will determine how much machining has to be done on various faces.
After a preliminary list-giving the order of operations has been decided upon with details as the tools required, a tool layout to the scale is prepared on the tracing paper by super-imposing the layout of the machine capacity chart, drawn to the same scale with the component in position.
For any layout in which there may be a doubt regarding sufficient travel, clearances, etc., a simple preliminary trial is conducted on the drawing board before it is put on the machine. For many jobs, their comfortable adaptation to a machine will be obvious by simple estimates and more elaborate precautions will prove unnecessary.
Examples of Tool Layout:
A few typical examples of tool layout are given below:
1. Tool Layout for Front Wheel Axle:
Tool layout shows the types of tools required and the sequence in which they are to be used. While preparing tool layouts, the capacity chart of machine showing the capabilities of machine should not be lost sight of. It also ensures that tool movements and turret indexing, etc. clear the various machine parts. Machining time can be established by listing the operations required systematically in the form of tool layout.
To machine the front wheel axle from 18 mm steel bar, shown in Fig. 32.20, the following operations are required:
(1) Feed out the bar.
(2) Turn 14.5 mm diameter with the tool box.
(3) Turn 13.75 mm diameter with the tool box.
(4) Round end with roller steady end tool.
(5) Centre with centre drill.
(6) Cut thread with Coventry die.
(7) Form 17 mm diameter and chamfer with tool in the square turret.
(8) Part off with stepped cut-off tool in the rear-tool post.
A typical layout to be used for various operations is shown in Fig. 32.21.
To machine a ball-bearing part shown in Fig. 32.22 the following operations are performed:
(1) Rough face end with tool in the back tool post.
(2) Finish face end with tool in the front tool post.
(3) Bore diameters O and P and chamfer C with tools in boring bar in hexagonal turret.
(4) Recess diameters X and Y using double recess cutter held in recessing tool slide.
(5) Size bore diameter O using fine adjustment boring bar.
(6) Tap bore P using tap and die holder. A typical layout of tools to be used for various operations is shown in Fig. 32.23.
Table 32.1 shows the description of operation at various tool stations, spindle speed, feed rate and machining time, etc.
Draw a tool layout for the component shown in Fig. 32.24. Also determine the machining time for all the operations, the manipulation times and the overall machining time for producing the component on a turret lathe.
Fig. 32.25 shows the various tools and the tool layout required to produce the component shown in Fig. 32.24.