On that lathe there is a round piece with a radius of 1 foot. To understand the relationship between cutting speed (SFM) and spindle speed (RPM), think about a lathe. The chip load must be adjusted to 75% if you step down more than the diameter, and if you are stepping more than 2 times the diameter it should be adjusted to 50%. When working with wood, you should step down a minimum of the diameter with tools larger than and including 1/4 inch unless you are using a down spiral tool. higher step-down means fewer cuts and shorter time on table, as well as extended tool life. It’s almost always going to be most efficient to step down as much as possible with a given tool. Step Down– The amount of depth (change in Z per pass) that a tool makes as it cuts in each pass at each level. If the tool is cutting a dado or channel through the material It is effectively stepping over 100% of the tool diameter for examples profile cutting contours or engraving. Step Over– The amount of surface area which a tool is overlapping a previous cut at the same depth level- so a 1/4” Bit with a 50% Stopover cuts 1/8 in of new material with each pass.
This formula can also determine federate F = f * n * S Too Small causes dust, burning of material or overheating bits because of friction.Ĭhip Load is calculated in the following manner. Too big of chips are caused by aggressive cutting, which puts stress on material and driver motors, and dulls tooling. Often you solve for spindle speed because the cutting speed and tool diameter are known.ġ200 feet/min is a good Cutting speed (V) limit for hardwoods and plywood using a carbide tool, you can adjust the Cutting speed (V) between 900 SFM to 1600 SFM to find a sweet spot for your given material.Ĭhip Load– Refers to the size and volume of chips produced by a cutting tool. S is the spindle speed in revolutions per minute. V is the cutting speed in feet per min (Often this is known,)ĭ is the diameter of the cutting tool in inches (also known or easily determined) It can be calculated by the following formula. Spindle Speed– the speed in RPM which the tool is spinning. This number is generally calculated from the diameter of the bit and the speed of rotation in RPM This is also referred to as surface speed.įeed rate– is the speed of the entire cutter in relation to the material in terms of xyz coordinates. this is both rotational movement and directional. These settings also can be adjusted to accommodate differences in material or numerous other factors through experimentation and testing.Ĭutting Speed– Refers to the speed at which the tooth of a cutter moves through material.
While the spindle speed and feed rate are what we actually use in the CNC program, they are related to one another and affected by recommended cutting speed, in surface feet per minute (SFM) and chip load, which are assigned by tool and material. a Router which only has off and on as speed settings, In some cases this may be a constant value- i.e. Speeds refers to the speed at which the spindle is spinning for the tool. often Finding the correct settings is a process of trial and error, so save pieces of material to run tests on.//*įeeds generally refers to the Federate at which the machine tool is moving through space in terms of x,y and z coordinates. Remember that there these settings are not uniform and can change based on material, tooling or machine. *//Your instructor or Staff can advise you on Feeds and speeds for many different tools, however for some tools, it may take some calculation to determine the proper settings for your tool and material.