Earlier machines had a cutting head supported by a beam cantilevered inside the cylinder. This resulted in finished radius increasing as the cantilever moved along the cylinder. In this machine the cutting head is supported at both ends. Accuracy was improved drastically, and for the first time the gap between piston and cylinder wall could be reduced to the thickness of a coin. Efficiency of the new atmospheric engines was improved. James Watt's engines could not have worked properly without them.