The advantages of reversible knives over solid brazed edges
I am increasingly hearing customers asking about bits with reversible knives, although not everybody knows about the advantages of bits fitted with them. If a customer doesn't know of these benefits, he won't be able to utilize the bit's potential or may even shorten their service life.
General information about reversible knives
These bits are easy to recognize because of a reversible knife secured with a screw, wedge or an extending wedge. And because of the requirements for final sharpness, high emphasis is placed on every operation during the production of these knives. Compared to a brazed tool, there is no need for final sharpening and levelling of the final cutting diameter. This important parameter specifies the accuracy of the routed so-called bed, which is accurate in the hundredths of a millimetre.
Reversible knives - how to choose the right strength 
The reversible knives are available in tungsten carbide in different variations of hardness It doesn't necessarily mean the harder the knife the better. The knife should be selected according to the material, which you are routing now or usually. You can choose knives from the following materials: Wood, Wood+, Universal, Laminates and MDF+. Should you use knives labelled for laminate or MDF on wood, the knife will probably break when it encounters a knag. This knife is very strong, but also brittle. And the other way around, the knives for wood may be used on laminates. But you have to count with fast dulling of the blade. If you rout all kinds of material, then the Universal knife is just right for you. This type of knife is usually supplied with new tools.
Cutting diameter
The most important feature of the knives is a constant cutting diameter. When using a brazed tool you always have to resharpen it, which reduces the diameter by 0,1-0,2 mm. And when using a tool with a bearing, the difference between the edge of the knife and the bearing may be up to 0,5 mm after a while. An undesirable difference in the majority of woodworking operations. Either when copying using a ring or joining a worktop along a template.
Geometry - selecting a proper tool
Bits with reversible knives are the only tools made in various geometries (angle of the face). The tool geometry is one of the main features influencing the durability of the edge and cleanliness of cut, depending on the type of material. The basic three geometries are ideal for work with laminates, wood or for universal use. Diamond tools are equipped with a geometry ideal for cutting laminates and the spiral cutters have a geometry ideal for work with wood. Brazed tools feature only one universal angle. Each type of reversible knife bits has different geometries depending on the type of work. For example, the F041-12521 bit is ideal for routing of laminates and kitchen tops.
Setting up the knife
The set up of the knife is very simple. Just insert it into the bed and place it on its inner side. By applying slight pressure, the knife falls into its place and is ready to be secured with screws. The screws have to be tightened securely to ensure strong hold of the knife. A second option of the knife set up can be seen with mini-knives, which are fitted with a locking groove. In this case, a wedge is used to secure the knife. These knives fit into the long groove created in the bed, this defines the ideal position of the knife, now just secure the wedge and tighten the screws.
Sharpening of knives
The knives are not designed to be resharpened and should be used on a one-time basis. Each knife has 2-4 perfectly sharp edges. When an edge gets dull, just rotate or replace the knife. The price of the knives begins at 46 Kč (1,70 €) If the knife costs about 60-70 kč, then the cost of a brazed toll will be the same as replacing the whole knife. You don't have to worry about sharpening and wait for a tool for a whole week, just rotate the knife and you're ready to rout in a matter of seconds.
To sum up
One must look at the bits with reversible knives in a long run to truly appreciate its time-saving and most importantly cost-effective features. We recommend using the replaceable knife bits when regularly routing laminates and DTD and when variation of the cutting diameter is not required. The cutter is also ideal for copying and routing along a template. A huge downside of brazed cutters is the waiting period when you're having it sharpened. When using reversible knives, sharpening is non-existent and production of a new sharp edge takes minutes.
The reversible knives offer lots of advantages, to ensure long life, however, it is imperative that you use high-quality knives, strong securing screws and we also recommend to clean the bed of the knife after use with a CMT Emulsion for tools (code C99800101) and to continuously use the lubricant for wood when routing (code C99800201) A continuous care of your tool will prolong its life and save you money.
Should you have any questions about the use of these tools, don't hesitate to contact us and we will gladly answer your inquiries.
Back to what's new