You are probably aware of these terms in reference to setting up your CAM program when deciding which is going to be the best direction to follow to get your part's cleanest and most accurate finish.
The main difference between climb and conventional cutting is how the cutter bites into the material.
A conventional cut deflects the bit, causing it to dig in and produce a rougher surface, whilst a climb cut pushes the bit away leaving a smoother finish. Because of this when cutting Hardwoods it is generally believed that the best finish will be achieved using a climb cut for the gear teeth on the gears of the clock.
A simple visual check of any off-cut you have made will quickly tell you whether your set-up is correct, if the off-cut is cleaner than your part you have it the wrong way round.
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I would personally always use the Climb cut for all but the last layer where I swap to a single pass with a Conventional cut. This for me gives the best tool usage and the cleanest and most accurate finish.
It should always be remembered when setting up for cutting that you need to change the direction of cut when you move from cutting an Outside profile to cutting an Inside profile. As the cutter only spins in one direction all the time changing to an inside cut always necessitates the cutting direction is reversed.
The illustration below is taken from the Vetric Cut2D worksheet for one of my clocks. This shows all of the parts for a clock laid out on a single sheet ready for cutting. All outside cuts are shown in Blue and all inside cuts are in green along with other colours and layers for non-cutting items like text.
