The first step in CNC programming is to select the appropriate tool for the operation. You need to consider the type, size, shape, material, and coating of the tool, as well as the number of flutes, teeth, or edges. The tool selection depends on the type of operation (such as drilling, milling, turning, or threading), the material and geometry of the part, and the surface finish and accuracy required. You should also take into account the availability, cost, and durability of the tool, and avoid using tools that are too large, too small, or too worn for the job.
You can use pretty much any type of tool when it comes to machining any metal for the most part. For example, if you want speed without investing in tooling - buying a bunch of cheaper HSS Endmills can do most jobs but they will be disposable, specifically if you're trying to run steel parts fast. Drills and taps are different in a sense but it also depends on what type of hole you're approaching ( blind, through ... etc. ) If time isn't a factor getting proper tooling for each specific material would be ideal, but programs should be proofed out with the less expensive tooling so the high-end tools don't get wasted.
The feed rate is the speed at which the tool moves along the workpiece or the workpiece moves along the tool. It is usually measured in inches per minute (IPM) or millimeters per minute (mm/min). The feed rate affects the productivity, quality, and tool life of the CNC operation. A higher feed rate can reduce the machining time and improve the chip removal, but it can also increase the heat generation, vibration, and tool wear. A lower feed rate can improve the surface finish and accuracy, but it can also increase the machining time and the risk of tool breakage. The optimal feed rate depends on the material and hardness of the workpiece, the type and diameter of the tool, the spindle speed, and the depth of cut.
One thing I've learned is to find the tool's limit, once you've done that make sure to leave an appropriate stock to leave for the finish tool to prevent unnecessary and when possible make sure the coolant flow is optimal to help relieve the heat and help chip evacuation. The key takeaways from my career are to make sure to have a separate tool doing a finishing pass also depending on the material and tool engagement, coolant flow, chip evacuation, adjust the ramp angle, helical ramp diameter, plunge feed rate, and tool lift.
The spindle speed is the rotational speed of the tool or the workpiece. It is usually measured in revolutions per minute (RPM) or surface feet per minute (SFM) or meters per minute (m/min). The spindle speed affects the cutting forces, temperature, and chip formation of the CNC operation. A higher spindle speed can increase the cutting efficiency and reduce the heat generation, but it can also increase the centrifugal force, noise, and tool wear. A lower spindle speed can reduce the cutting forces and tool wear, but it can also increase the heat generation and chip size. The optimal spindle speed depends on the material and geometry of the workpiece, the type and diameter of the tool, the feed rate, and the depth of cut.
Personally, I use some formulas to find optimal feed and speeds or find out a range for the SFM and then I'll adjust the feed and speed appropriately, once experimenting is done then you can push the limit if your feed and speeds are correct your tool should bearly wear away because the heat will dissipate correctly - again beside those reasons remember to check ramp angle, helical ramp diameter, optimal load, and tool lift.
The depth of cut is the distance that the tool penetrates into the workpiece or the workpiece penetrates into the tool. It is usually measured in inches or millimeters. The depth of cut affects the material removal rate, power consumption, and surface finish of the CNC operation. A higher depth of cut can increase the material removal rate and reduce the number of passes, but it can also increase the cutting forces, heat generation, and tool deflection. A lower depth of cut can reduce the cutting forces and heat generation, but it can also increase the number of passes and the machining time. The optimal depth of cut depends on the material and hardness of the workpiece, the type and diameter of the tool, the feed rate, and the spindle speed.
It's always good to take the most optimal cut, for example when cutting still or certain bronze you don't want to take too small of a depth of cut because even though you may machine through the first couple of layers the material will start to work harden and then your tool well get torched or it may flash weld and snap the tool clean from the collet.
in my experience there is another factor to all the calculations and examples. The quality of the material and the tool it self. In addition to all the variables above there comes the condition of the machine. The best tool can't handle a worn out machine(vibration, chatter). In my life(40years) of machining and programming i had to overcome many obstacles to get the job done. The basics are always a good starting point. CNC is fun :)