When showcasing the capabilities of our digital finishing systems or routers, we are often asked why we insist on cutting on top of felt when using a knife attachment. Choosing the appropriate sacrificial material is very important for applications that require cutting all the way through a substrate. Felt is the ideal sacrificial material for knife cutting for a number of reasons.
First, felt is air permeable, which means that the table’s vacuum hold-down system can still create enough suction through the felt and on to the material being cut. Proper hold-down is important for cutting accuracy and repeat-ability. Felt is also very durable, flexible, and can be used hundreds of times on either side for knife cutting before replacement is necessary. The flexible fibers in the felt means that you can cut numerous different patterns into the felt over time, without the integrity of the material being compromised. Most importantly, felt is very soft. This soft-landing is important in the prevention of knife dulling or potential breakage.
Although individual tangential or drag knives are relatively inexpensive to replace, repeated breakage and replacement will cause significant unnecessary costs over time. Ensure that your shop is equipped with a roll of felt that is at least as long (and wide) as the cutting surface of your table. Most felts rolls come in widths of 5-6.5 feet.