The illustration above shows the splintering that’s typical when cutting conventional. This end grain splintering can be avoided by climb cutting…HOWEVER…when climb cutting the chip is formed from max size tapering off to minimum size. This and the forces created by the router bit trying to “climb” out of the cut result in a finish that’s not as smooth as a conventional cut.The solution to this dilemma is to cut to each methods strength. Climb cut an object allowing .01” - .015” then make a final pass, full depth without allowance in a conventional direction. This method will often result in the best possible finish on a part.NOTE: When the finish of a part is poor, check the scrap. If the scrap finish is better, change the direction of the tool path.Typical Splintering that occurs when routing in the conventional directionCCWCW
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Practical suggestions...Putting It All Together…Now that you know the basics about router bits, It’s time to put that knowledge to use! After you have chosen the material for the job and the correct bit and chip loads, some people feel the hardest part of CNC work is next… Holding the material in place. There are several techniques for holding material, Vacuum, double stick tapes, cams, screws, tabs, and plastic nails to name a few. Hold down methods are outside the scope of this article, but there is a cutting strategy that many of us use to help whatever method of hold down you use. It’s called the “Onion Skin Strategy”.When using this method you make an initial cut in the climb direction cutting away from the finished product about .005 --.010 and about .015--.020 less than the total material thickness. You then make a finish pass at full depth in the conventional direction and on the product cut line. This method leaves a continuous “tab” in place while the heavy cutting forces are being realized and then makes the final cut full depth eliminating the “water” or step marks of multi pass cuts. The Example below assumes .5” material.Rough or first path of an Onion skin StrategyFinish or Second path of an Onion skin Strategy