I had this interesting question posed to me recently by Kevin (from California).
It is interesting to me, because back when I was contemplating (and then purchasing) a drill press, the same thought crossed my mind. After all, both machines grip a cutter in some form of chuck, and spin it. So what is stopping one doing the role of the other?
Since then I have formulated the following justifications why I feel that the two tools should not be used to perform the role of the other. (In particular, I am looking at it as to why the drill press shouldn’t be used as a router).
1. The chuck doesn’t hold the bit anywhere near as tightly as a router bit collet, so they are a lot more prone to slippage (and if a router bit slips, it is likely to change height, and therefore change the profile that’s being cut (at best….a kickback or a grab of the workpiece is not desirable!), if a drill bit grabs the work, hopefully it does slip!) The slippage will also scar the shaft of the router bit badly, making unusable in a router later – either simply because it won’t fit, or because those scratches make the bit more prone to breakage. My wheel cutter bit (which is designed only for use in the drill press) has a badly scarred shaft – doesn’t matter for that bit as it will only ever be used on the drill press, but I’d hate some of my other router bits getting damaged like that.
2. The average router bit speed is 8000 RPM to 20000 RPM. The average drill press is 200 RPM to 3000 RPM. A drill press simple can’t drive a router bit at the speeds required to obtain a reasonable finish, and without horrendous tearout that can occur when running a router bit way too slow.
3. The bearings on a drill press are designed to be thrust-loaded – ie you drive a drill bit down into the workpiece. A router bearing is designed for axial (horizontal) loading. If a drill press is used as a router too much, the bearings will wear out a lot faster than desired.
4. The chuck of a drill press is typically on a morse taper. Axially loading up the chuck often will loosen it to the point that it suddenly falls off!
5. Finally, although it seems expensive, even a $320 router (such as the 2400W Triton) isn’t actually that expensive compared to the router bits. Each of my bits range in price from 10% the cost of the router up to 50%. Add it altogether, and the router itself is only a small portion of the total cost (spread over time) of the ‘tool’. My collection of router bits is worth something like 5 times the value of the router itself.
I guess, in an emergency, you could use a drill press to do a little routing job (small bit, light passes, soft wood), but I wouldn’t make a habit of it for those reasons. The reason the wheel cutting bit works well on a drill press, is it is designed to plunge into the workpiece, not run along an edge, so really it is just a glorified drill bit. It is also designed to work at the slow speeds of the drill press – you’d kill yourself trying to use it in a router!