What Does Power Feed on Lathe Do

Speeds & Feeds - Speed & Feed Settings

Engine lathe drive systems can be divided into two groups: geared head and belt driven.

The geared head engine lathe uses a series of gears to transmit power from the main motor to the spindle. The belt drive engine lathe uses a belt to transmit power from the main motor to the spindle. The type of drive system your machine incorporates will have a great deal of affect on the type of speed selection method it uses.

There are two main configuration of geared head lathes: the dial type and the lever type (Figures 1 and 2).
Figure 1 Dial type speed selection	Figure 2 Lever type speed selection

The dial type mechanism for speed changes uses a rotary motion to change the gears in the headstock. Dial types usually consist of an inner and outer ring. When the inner and outer rings are aligned in the proper configuration, the R.P.M. is set to a certain speed. The dial type speed selection in Figure 1 uses a color coding as the method of alignment for R.P.M. selection. Other dial type speed selections work similarly, but use a different method of alignment for R.P.M. selection. In Figure 3 you will notice the outside ring sets the high, medium and low range, while the inside ring sets the individual speed within that particular range.

Fig3.jpg (16975 bytes)
Figure 3

The lever type mechanism for speed changes usually uses two to three levers to change the gear settings in the headstock. The lever type speed selection in Figure 2 uses a color coding as the method of alignment for R.P.M. selection. Other dial type speed selectors work in a similar way but use a different scheme or alignment method (Figure 4). The alignment scheme in Figure 4 uses letters to define the handles.

Fig4.jpg (18015 bytes)
Figure 4

Belt-Driven Drive Systems

Most belt-driven type lathes in use today are of the variable speed configuration. The variable speed lathe uses either a mechanism to move a belt on a scheeve pulley or an electronically variable speed spindle motor. Most variable speed systems manufactured now use the electronic variable speed motor. Some machines also come equipped with constant surface footage allowing the machinist to optimize his or her cutting speeds.

The antiquated step pulley system of speed selection uses different size pulleys to achieve different spindle speeds (Figure 5). To change speeds you loosen the belt tension and slide the belt in one direction or the other. These machines are somewhat obsolete and are not used in many modern manufacturing facilities.

Fig5.jpg (16414 bytes)
Figure 5

The feed mechanisms move the tool along the ways of the lathe automatically. Through the use of gear settings we can control the rate of the feed. Lathe feed settings are generally configured in two ways: levers and quick change gear boxes (Figures 6 and 7).
Figure 6 Lever type feed selection	Figure 7 Gear box

The feed selection type in Figure 6 uses a series of three or four levers to obtain a particular feed selection. The operator looks at a chart on the lathe for a particular feed setting (Figure 8). The chart tells the operator which levers need to be positioned for the individual feed setting.

Fig8.jpg (14615 bytes)
Figure 8

To obtain the feed setting of 0.01 per revolution shown in Figure 8, the operator would need to set the levers to an LCR6 setting pattern. On the quick change gear box shown in Figure 7, the operator would slide the gear lever into the position shown on the feed chart positioned above the feed levers. On all lathes, no matter what configuration, there is a feed direction lever or feed change knob. (Figure 8). The feed direction lever reverses the lead screw or feed rod to obtain a change in the direction of feed.

Figure 8 Feed Direction Change Mechanisms