|Machine Shop Home|
|Introduction | Safety | Milling Machines | Speeds/Feeds | Cutting Tools | Broaching | Projects | Tests|
"Horizontal Milling Machine"
Operating the horizontal milling machine is not much different than operating the vertical milling machine until you begin using the over-arm supports and arbor driven cutters. When we use the horizontal milling machine in this way, a new set of operating principles need to be addressed. In the information that follows please pay close attention to the details. The information will help you not only make better parts and keep the machine running in proper order, but it may also keep you from getting seriously injured.
When selecting the proper cutter always make sure that the cutter is not in need of sharpening (Figure 1). Dull cutters cause tool costs to increase.
The tooling costs will increase, because if a dull cutter is run too long the cutting edges can suffer permanent damage. The damage may be in the form of heat build up, edge chipping, and in extreme cases breakage of the cutter. Dull cutters produce poor quality surface finishes. The power consumption of the machine increases with dull cutters. Dull cutters also cause excessive strains to be put on the machine, the fixture, and the arbor.
Coarse Tooth Cutters-Vs-Fine Tooth Cutters-When possible select a coarse tooth cutter over a fine tooth cutter (Figure 2). A coarse tooth cutter has larger gullet areas for chips an therefore will not clog up as quickly.
The teeth on a coarse tooth cutter are much larger and can withstand a greater chip load. Coarse tooth milling cutters dissipate heat faster because of the tooth configuration. The coarser tooth cutters can also help to eliminate chatter. Finer tooth milling cutters should be used on thin materials where more teeth need to be in contact with the work. Fine tooth cutters should also be kept away from deep grooving operations.
Setting Up Arbor Driven Cutters-When assembling or disassembling a setup using the over-arm support, always leave the support in place when loosening or tightening the arbor nut(Figure 3).
Figure 3: Tightening the arbor nut without the overarm in place will ruin the arbor.
The arbor nut should be tightened by hand with a reasonable length wrench. A hammer should never be used to tighten the arbor nut (Figure 4). Over tightening the arbor nut can cause the nut to crack or the threads within the nut to stretch.
Figure 4: Over tightening the nut can crack the nut or stretch the threads.
The remove the arbor, loosen the jam nut and then loosen the draw-in bolt a few turns. Do not unscrew it totally from the arbor. Tap lightly on the draw-in bolt with a soft faced hammer to break the taper engagement (Figure 5).
If you unscrew the draw in bolt totally from the arbor, and strike the bolt with a hammer, the threads on the bolt and the arbor will become ruined.
Handling Cutters-Protect your hands with a cloth when handling cutters, particularly large side and face milling cutters(see Figure 6).
|Reassembling the Arbor on the Machine|
When ever you have two tapered or mating surfacing contacting one another it is good practice to make sure the two parts are
clean (Figure 7). If the arbor and spindle are not clean before assembly, arbor runout will result. Also, jamming the dirt in between the two mating surfaces will damage the arbor and the spindle. Clean the arbor and all of itís components before assembling them.
Figure 7: Clean all mating surfaces before assembling them.
Keying the Cutter to the Arbor-All cutters need to be keyed to the arbor (Figure 8). Do not rely on friction to drive the cutter.
Figure 8: Never operate an arbor driven cutter without the drive key(s) in place.
Use a key that is long enough to cover the cutter as well as the bushings on either side of the cutter (Figure 9). Assembling a narrow cutter with a short key can cause the cutter to split the key losing the positive drive to the cutter. If the cutter fails to turn while feeding in the cut, catastrophic failure to the cutter, the arbor, and the workpiece will result.
Figure 9: Assembling a narrow cutter with a short key is a bad practice.
As stated earlier, make sure that the arbor collars are clean and free of burrs before they are mounted on the arbor. When using thin metal slitting saws, support the saw blade on both sides with large diameter collars. The larger arbor collars will help support the thin slitting saw blade and keep the cutter from vibrating and possibly breaking.
|The Arbor Support-The arbor support houses the arbor bushing (Figure 10).||
Figure 10: The Arbor support.
The arbor bearing collar slides into the bushing and provides the support surface between the arbor and the arbor support (Figure 11). The fit of the arbor bearing and the bushing is very important.
Figure 11: The fit between the bushing and bearing is critical.
An adjusting ring is available for adjusting the fit of the bushing to the bearing collar (Figure 12). Too loose a fit will cause inaccuracies in the cut or chatter will occur. Too tight a fit will cause friction and seizing between the bearing and the bushing.
When you are running the machine check for heat build up in the arbor bearing. If adjustments need to be made consult your instructor. Make certain that the oil reservoir is filled with the proper grade of oil. Finish the setup with a squirt of oil between the arbor bearing and the arbor bushing.