Every big industry nowadays uses TOS boring mills for their machining operations. Even machining shops find the TOS boring mills as indispensable to their operations particularly when customers demand for increased productivity in a relatively short period of time. Boring is a process that requires a machine with lots of versatility to ensure the accuracy of holes produced on the workpiece.
Why will you bore when you can drill?
The TOS boring mill is used for enlarging a hole that has been previously drilled or for roughing and finishing the internal surface. There is an advantage to using the boring mill instead of other machine tools because very large parts can be efficiently machined due its large configurable envelope. Boring mills are frequently used on workpieces that have dimensions beyond a 60” envelope because traditional machining centers are not capable of handling large envelopes. Another advantage of the TOS boring mills is the spindle that advances from its headstock to allow the operator to reach into the smaller cavities. Tool deflection is minimized because the live spindle provides the opportunity to keep tooling short from the cutter point to where it fixes on the spindle.
Making a choice for a boring mill
There are two types of TOS boring mills – horizontal and the vertical boring mills - but while they have similar functions, they are configured differently. The horizontal boring mill has a spindle that is mounted horizontally. In vertical boring mills, the spindle is mounted vertically. In the horizontal boring mill, the workpiece remains stationary while the cutting tool turns. On vertical boring mills, it is the workpiece that turns while the cutting tool is stationary. Most industries use the horizontal boring mill because it does not limit part size. It is easy to place a 10-foot tall part on the table whereas on the vertical boring mill, the largest part size would be about 3 feet. The two TOS boring mills are different from each other but both get the same amount of work done.
The process of boring
There are different factors that have to be taken account in boring – tool overhang and the diameter of the tool, chip control, insert nose radius and geometry, cutting fluid, damped tools and tool coupling. The length with which the spindle extends from the anchor is referred to as the overhang. End users tend to limit overhang to avoid the risks of deflection that can result into chatter and insert failure. For each length equal to the tool diameter that the tool is extended, deflection can increase 8 times so that it is important to use the largest tool diameter possible and the shortest overhang possible.
To ensure that proper chip control takes place, cutting speed should be reduced to about 50% of the recommendation. Rough boring with three cutting edges can generate a lot of chips. In order for the chips to be efficiently evacuated from the hole, the maximum depth of the cut should not exceed half of the cutting edge length.