CNC Routers: Applications and Technology: Spiral Router Bits

Question:-I have a question about spiral router bits as I have no experience using them. I have a chance to get a couple but with limited funds right now, I only want to get ones that I would use frequently. What type (up/down/compression), what diameter, and what function would you use them. From everything I’ve read it looks like an up-cut bit is used for hand-held routing when doing mortises and a down cut for router table work for dadoes, rabbets grooves. What are your thoughts? Thanks and keep up the great work!

Answer:- Quality solid carbide spiral bits combine effective chip removal with a continuous shearing action cut not obtained from a standard straight bit. You’ll get smoother cutting action with better results.

Up-cut Bits provide faster cutting while they pull chips up and out of the work or towards the router. They are excellent bits to use when cutting material in a router table since they tend to hold the work piece to the table itself. Ideal for mortise and tenons, grooving, slotting or routing deep blind holes. Down-cut Bits cut slower and push chips away from the router to eliminate top surface splintering. Use for pattern cutting or when going completely through the board as it allows clear vision of the cutting line. Ideal for fine finish work such as veneers, laminates, inlays and repairs because they prevent upper edge tear outs. Use Down-cuts for trimming and sizing.

Compression Bits Cuts through stock and gives clean cuts in both top and bottom. No tear out as bit is designed to pull work into the center of the stock. Ideal for double sided veneer plywood, melamine, and laminates. As for size recommendations, it really depends on the specific application you intend to use the bit for. We find that the 1/8″, 1/4″ and 1/2″ Up-cut and the 1/4″ and 1/2″ Compression bits are the most popular for our customers applications.