Boring Tips: Creating the Perfect Hole

In machining, boring is the process of enlarging a hole that has already been drilled by means of a boring machine such as the. TOS boring mills Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole. There are many types of boring machines such as TOS boring mills. Here are some tips on how to bore a hole better.

1. Make a Preliminary Speed Selection

Considering the material specification, select a speed that allows you to cut the material without buildup on the cutting edge and without undue tool wear. You can either consult your carbide manufacturer's instructions, or use a machining data handbook. In other words, select a speed at which you obtain safe cutting operation without undue overload, vibrations or tool wear.

2. Select a Chip Load in Inches per Revolution

All carbide inserts have an acceptable range with regard to chip load. For roughing operations, most inserts will start breaking steel chips from about 0.007 ipr and up. By selecting starting speeds and feed rates according to these recommendations, you normally will get reasonable initial cutting conditions.

3. Check the Projection Ratio of Your Boring Bar

Divide the total bore depth of your tool by the largest boring bar diameter at the root of the tool. If the ratio obtained is within 4:1, you will virtually never have to worry about vibration or chatter. If the ratio is 5:1 or greater, you may have to reduce your cutting speeds progressively to avoid chatter. By following the principles for optimum boring performance, bores on this work piece are completed with maximum efficiency.

4. Take a Trial Cut

After establishing steps one, two and three, take a trial cut. Listen to the sound of the machining, the smoother the noise the better. Look at the chips. If you get long, curling chips, you must increase your feed rate. If you get chips that look like corrugated iron, then the feed rate is too high. Another way to verify optimal cutting conditions is to observe the return spiral made by the inserts. When free cutting conditions are achieved, the spiral lines on the return groove will be virtually invisible.

5. Optimize Cutting Speeds

After consulting your load meter, listening to the chip formation and looking at the surface finish obtained, you may want to increase your cutting speed. For safety's sake, do this in steps of about ten percent each. For steel, especially low-carbon steels, higher cutting speeds lead to better cutting conditions. Ideally, the heat created by the cutting action should be carried away by the chip so that the cutting edge and the work piece remain cool.

6. Watch Insert Wearing In

It is important to observe how an insert is wearing in. In the first phase, the cutting edge will wear relatively fast, and diameter adjustments on the first work pieces may have to be made frequently. Over the long, middle phase, the insert should remain stable, wearing down only gradually, so that adjustments for diameter need to be made less frequently. At the end of the useful tool life, the insert will wear down rapidly. It is, therefore, important to watch for that critical point and to change the insert promptly.