This is the second part of our previous article: How to use router bits properly
The rate at which the router is fed along the work (or the work is fed across a router table) is very important to the overall quality of the cut to the longevity of the bit. You should feel a constant, even pressure when the work meets the cutter. Feed rate ultimately depends on the type of material being cut, the amount of material being removed and the type of bit being used.
The most common feed rate mistake is excessive restraint. And feeding too slowly is a quick way to ruin a bit. Letting the bit “dwell” in the cut will lead to a burned cut, caused by the bit heating up, which in turn reduces the bit’s life immensely. Remember, heat can ruin a sharp tool. So keep the router (or the work) moving.
If you are concerned about bogging the router down, make several light passes to complete the cut instead of trying to hog away too much material in one pass. This is especially true if you are using large-diameter bit. This will reduce the stress on the bit and will generally be a safer practice.
The speed at which the bit turns can be important. The typical router runs at somewhere between 20,000 and 24,000 rpm, depending upon the brand and model. Router bits are designed to cut at this operating speed. If you were to run the typical router bit at a reduced speed, say 10,000 to 12,000 rpm, you might be surprised at how poor a job it does. The finish of the cut probably will be rough and choppy.
This is true of most bits. But as the diameter of the bit increase, the router’s high operating speed becomes a problem. The cutter is too darn big to be revolving at 22,000 rpm. While there’s little dispute that large-diameter bits — for example, 3 to 3 1/2-inch-diameter panel raisers should be spun at about 12,000 to 14,000 rpm, opinions vary as to the appropriate speeds for other sizes of bits.
Once bit source recommends operating any bit larger in diameter than 1/2 at no more than 17,000 rpm and cutting that speed to no more than 14,000 rpm when the diameter exceeds 1 inch. More commonly, you’re advised to slow the bit when its diameter hit 2 inches.
What’s working here is confusion between safe operating speed and an appropriate balance between bit speed and feed rate. We slow down big bits simply because they’re unsafe at “full router speed”. But we often slow down midsized bits so a workable balance can be struck between bit rpm and feed rate. As I mentioned before, a feed rate that is too slow is common. The bit moves too slowly through the cut, the heat builds up, the wood scorches.
The prevalence of plunging operations fuels this problem. Say you have a short slot to cut. Each time you want to plunge the bit deeper, you tend to pause, allowing the spinning bit to dwell in the cut. You can just smell the wood scorching. The cut is short, and each change in direction brings another slowing of the feed rate, another pause. One way to moderate the problem is to slow down the bit’s revs — even when the cutter is relatively small in diameter.
Check out this video to see u “how to make a shaker style cabinet door using tongue and groove router bits AKA rail and stile router bits”. This is my favourite video when it comes to getting started with router and router bits.
This concludes our topic of using router bits. If you still haven’t found a router bit set to your needs, check out this article. Consider learning know how to clean and sharpen if you already own a router bit set.