Using Boring Tools with a CNC Router Collet

Boring tools can be adapted to a CNC router for use at slower RPMs. October 3, 2007

I have a couple of very basic questions regarding tooling for a CNC router. The 5mm brad point bits I've seen all have a flat on the shank. Our machine does not have a boring unit, so can these bits be used in the router? Will the flat cause problems with the collet? Will it cause vibration? What rpm and plunge rate should be used?

The tool holders on the router accept tools with shanks up to .625 inches. Is there a source for bits for MDF routed raised panel doors that have a shank diameter less than .75in?

We (2 man shop) have been using a used Multicam 3000 for a couple of months now, and in spite of the learning flubs, are very happy with it.

Forum Responses
(CNC Forum)
From contributor F:
I also have a 3000 on which I use Vortex tooling. I have used them because of their knowledge and because they have very good tooling. You are better off using just one tool company, rather than shopping around for price, because of the help they can give you.

From contributor C:
I believe most boring tools have flats, and require an adapter to be used in a typical collet. The one I use has a 10mm shank on it, thus requiring a 10mm collet. But you can then use any readily available (i.e. cheap) boring drill. I personally use Courmatt; they have been great, but any of the guys that post on WOODWEB should be able to set you up.

As far as the tool shank diameter, it sounds like you have a small spindle (up to 7.5 HP), which only allows use of an ER25 collet. The ER25 collets only go to .625 diameter, because that is as large as the machine that holds the collet is intended to run. To use .75 shank or larger, you need ER32 collets, which typically are found on larger 10HP+ spindles with larger shafts to accommodate a larger shank.

That said, you can have the shank turned down on a tool if you must, but don't go any further than you have to. My fly cutter was turned down from .75 to .625, and I've had a .75 ball-end turned down as well. Most people don't recommend this; bits that require large shanks are going to put more stress on your spindle than it is intended/designed to take, and can lead to premature failure, as well as being unsafe. The bigger spindles not only make more HP, they have sturdier frames and larger bearings, often with air assisted holding to keep things steady on a big cut.

So, if you must turn a tool down, make sure you take light passes with it or reduce your feed rate as far as you can. In MDF, this is a pain, as you probably need to slow down past the point where ignition occurs, and fire in a wood shop is no fun.

From contributor G:
You have an ER25 collect system. Use a 10mm collet. The flat will not affect any balance issues, as you need to slow your rpm's to 3600, with a plunge rate of 75IPM. Any custom tool can be made with a .625 shank, depending on the diameter.

From contributor H:
If you use the correct adapter, the balance should not be a problem. Yes, we [Southeast Tool] have MDF bits with a 1/2" shank. Most of the others are correct; 3000 to 3600 IPM is what most will run correctly at.