Router Bits Versus Drill Bits for Boring with a CNC Router

It's best to use drill bits for boring holes, especially if you have to bore a lot of them. August 5, 2010

I am purchasing tooling for a 3 axis CNC, and would like to know if you guys are using 5mm drill bits with 10mm shanks, or a 5mm router bit for line boring? My tool supplier recommends drill bits and the router manufacturer recommends 5mm router bits with 5mm shank. We will be machining through and stop holes in 3/4 melamine.

Forum Responses
(CNC Forum)
From contributor J:
Use 5mm dowel drills with 10mm shank. We seldom thru bore, but when we do we have good results without a v point as the spoilboard backs the panel up to prevent blowout.

From contributor E:
I use router bits for some drilling, but if you are going to do a lot of drilling like large jobs and lots of adjustable shelf holes then I'd recommend you use the drill. It is designed for that and the side compression torque on the bearings will be a lot less.

From contributor T:
I am unsure from your post - does your machine have a dedicated boring unit? If so you would definitely want to only use drill bits. Typically the RPM are limited to a preset RPM on boring units and most only accept a standardized shank. By design they are intended to be used with drill bits. If you will be drilling with a piggy back drill or using the router spindle itself, sometimes you have more options available.

From the original questioner:
We will be using the main spindle for drilling line bores in vertical panels. No drill bank. Contributor E - I am not sure what you mean by side compression torque on the bearings. I would think the bad pressure would be on the end of the shaft as it is plunging straight down?

From contributor S:
Drills are for drilling router bits are for routing! Your tool supplier is correct.

From contributor T:
Consensus is correct. Drill bits only for drilling, unless you are pocketing holes.
Keep in mind also that the proper speed for a drill bit is very low compared to a router bit. Brad points on a spoilboard work great at around 4000 RPM for through drilling. Since you are drilling with the spindle, check whether it spins that slowly. You lose torque at slow speeds, but it isn't a problem for drilling small holes. Also router bits don't plunge well especially at small diameters even if they are theoretically set up for plunging since there is no lead in or lead out.

From the original questioner:
Do you guys put the drill bit with the flat on it right into the router collet, or is there an adapter that you use?

From contributor M:
They can be had without a flat, but I often just bridge one split and chuck it in. You need a 10mm collet. Personally I like the solid carbide for the router. You can get them lots of places; Vortex is one.

From the original questioner:
Drill bits make sense.

From contributor G:
Definitely go with solid carbide drill bits. We had been using carbide tip ones and had all the issues of a cheap tool. Once we changed over to solid carbide the quality of thru holes increased mega times and the tools last forever as compared to tipped tooling. Once again, you get what you pay for.

From contributor P:
Avoid using router bits for boring holes. The carbide gets too hot and loses its edge (sharpness). Even doing a short cut with a router bit reduces its life span (toe kick notches on the gable). As soon as I cut a custom diameter hole (small) with the router bit I can smell the wood burning, especially with compression bits where the chips aren't evacuated enough and the machine can't reach the bit's cutting speed/chip thickness.