Metal Removal Counts

The rate of metal removal is the first of many considerations a machine designer faces when developing new lathe.

Most jobbing shops are looking for this feature. They want high metal removal rates and high accuracy too and you have to combine these features with price. You also have to design a lathe that’s competitive and make it a quality product right up from the base and bed casting to the gears and headstock.

A potential user of an engine lathe or any other machine tool- would look for performance first. He would check out a machine as a car.

Spindle speeds are a major consideration today. Most engine lathes are around 2000 rpm but an equally important consideration is the lathe’s ability to take full horsepower cuts at the lower spindle speeds.

Due to its design, for example, a lathe safe at 5 hp may be able to utilize the full 5 hp at the higher spindle speeds; a good lathe, however, will comfortably take full horse cuts as low as 300 rpm.

In order to efficiently cut a variety of metals of various diameters at optimum surface speeds, the horsepower capability throughout the range of spindle is of prime importance.

Not only should the engine lathe be able to take a full horsepower cut at low rpm, but it should be rigid – there should be no chatter. That’s when the design and quality of the casting are important; a machine, which is not sufficiently rigid, will produce vibration under heavy cutting forces and consequently chatter.

Casting is a scientific process, and there’s no real way a manufacturer can assure a customer that one casting is better than another. The heavy machine is not necessarily the best machine. Although metal casting for machine bases are about three times more expensive to produce compared with welded steel fabrication their superior vibration absorbing qualities over long period continue to make them the preferred choice.

Accuracy, even in small engine lathes, has increased in recent year due to demand from tool-and-die shops. Some machine tool builders offer specifications that are much tighter that any user needs. It’s like buying a car that goes 160 mph when you can only drive in a 60 mph limit area.

Chucks are generally an option on engine lathes. The chuck’s performance is based on its accuracy and ability to grip the workpiece. You can buy a low cost chuck but you’re going to have problems if you want to grip the workpiece accurately and tightly. The chuck will likely have excessive run out, or, under cut will slip.

You won’t defeat your purpose if you buy a cheap chuck and put it on an expensive lathe. The chuck is just as important to your machine’s performance as your machine is.

The length of the bed is important too. It basically depends on what the lathe is being used for. Heavy metal removal means more horsepower and it’s important to get maximum metal off in one cut.

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