3.6 LAB-CUTTING

3.6.1 Cutting Forces

The objective of this laboratory was to study the relationship between speed, feed and cutting forces.

For this laboratory, the lathe was set up with a hollow section of aluminum pipe. The cutting tool was equipped with a dynamometer which was able to measure the cutting forces. The laboratory consisted of making various cuts at different speeds and feeds. Based on this data, horsepowers were calculated, and compared to the theoretical values.

The estimated cutting forces, horsepowers required for each cut, calculated HPu, correction factors c, and the calculated percent errors can be seen below.

CASE 1: Variable Feed

CASE 2: Variable Speed

For variable feed, the Cutting Forces vs. Feed graph can be seen here.

For variable speed, the Cutting Forces vs. Velocity graph can be seen here.

3.6.2 Surface Texture

The objective of this laboratory was to study the relationship between speed, feed and surface roughness.

Both a steel and brass bar were used to study the effects of speed and feed on surface roughness. The collected data can be seen here.

Graphs of Roughness vs. Feed can be seen here: Brass Steel

Although we were not able to test the effect of tool radius in lab, we did discuss it in lecture. As the radius of the tool is increased, and everything else is held constant, the surface roughness should decrease. This effect is a result of an increased cutting surface.

The range of roughness from the notes for boring or turning is 16-250 microinches. This is the average range that is used for this operation.

From the graphs it can be seen that steel was generally rougher than brass for a given feed rate. However, the speed was not held constant for the two different materials, so it is possible that the reduction in speed from 1000 RPM for brass to 255 RPM for steel, caused the increased roughness.