[Droid Incredible Android Development] enohand:
well i have been out of the programming game for quite some time & have only dabbled in Android within the last few months.

I am trying to write a program that will calculate RPM speed for me.

below is the formula, i have been trying to get this to work for a few days now & cannot get past certain point.

so i figured i would reach out tot the community to see if anyone (who actually knows how to code...lol, ) could whip this up for me....

it shouldn't take that long & doesn't have to be pretty, just functional

Calculating RPM

The RPM setting depends on the cutting speed and the diameter of the part. The RPM setting will change with the diameter of the part. As the diameter of the part gets smaller, the RPM must increase to maintain the recommended surface footage. Again, take the case of the wheel. Think of the part as a wheel and the cutting speed as a distance. A larger wheel (part) will need to turn fewer revolutions per minute to cover the same distance in the same amount of time than a smaller wheel (part). Therefore, to maintain the recommended cutting speed, larger diameter parts must be run at slower speeds than a smaller diameter part.

The lathe must be set so that the part will be operating at the proper surface speed. Spindle speed settings on the lathe are done in RPMs. To calculate the proper RPM for the tool and the workpiece, we must use the following formula:

This simplified version of the RPM formula is the most common formula used in machine shops. This RPM formula can be used for other machining operations as well.

Let's put this formula to work in calculating the RPM for the machining example below. Use the recommended cutting speed charts in Table 4.

A cut is to be made with a high-speed steel (HSS) tool on a 2-inch diameter piece of 1018 steel with a brinnel hardness of 200. Calculate the RPM setting to perform this cut.

Cutting Speed = 100 (fpm)

Diameter of part = 2.0

Since the available spindle speed settings are generally not infinitely variable, the machine cannot be set precisely to the calculated RPM setting. Some judgment must be made in selecting the speed to use. Try to get to the speed which is nearest to the calculated RPM, but if you can’t, consider these conditions. Are you roughing or finishing? If you are roughing, go slower. If you are finishing, go faster. What is your depth of cut? If it is a deep cut, go to the slower RPM setting. Is the setup very rigid? Go slower for setups that lack a great deal of rigidity. Are you using coolant? You may be able to go to the faster of the two settings if you are using coolant. The greatest indicator of cutting speed is the color of the chip. When using a high-speed steel cutter the chips should never be turning brown or blue. Straw-colored chips indicate that you are on the maximum edge of the cutting speed for your cutting conditions. When using carbide, chip colors can range from amber to blue, but never black. A dark purple color will indicate that you are on the maximum edge of your cutting conditions. Carbide cutting tools are covered in much greater detail in other sections of your learning materials.

Let’s try some more examples.

A cut is to be taken with a (HSS) turning tool on a 0.75 inch piece of 1045 steel with a brinnel hardness of 300. Calculate the RPM setting to perform this cut.

Cutting Speed = 60 (fpm)

Diameter of part = 0.75

A 1-inch (HSS) drill is used on a 4-inch diameter piece of 1012 steel with a brinnel hardness of 100. Calculate the RPM setting to perform this drilling operation.

Cutting Speed = 140 (fpm)

Diameter of the drill = 1.00

Note that in the R.P.M. calculation, we used the diameter of the drill and not the workpiece. This was done because the cutting takes place at the diameter of the drill, not on the outside diameter of the workpiece.

A turning operation is to be done on a 3.00-inch piece of 4140-alloy steel with a brinnel hardness of 200. A carbide turning tool is to be used. Calculate the RPM setting to perform this cut.

Cutting Speed = 400 (avg. fpm)

Diameter of part = 3.00