Drill Mill in a Shapeoko

John,

That’s another insightful, thoughtful and really useful post from somebody with directly relevant specialist knowledge.

I, for one, am more than happy to see your posts, especially because you have the specialist knowledge, you clearly declare the potential conflict of interest so we know. I don’t see a problem with your employment, the value of your info outweighs any concern I might have with the potential confict.

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All,

Thank you for your input and suggestions. I was able to complete my two cribbage boards this week without any major issues (outside of my Fusion model being a little different than my stock). Here is a picture the finished piece.

One follow up question I had was regarding the what sounded like chattering when the drill mill was removed from the stock. I had my DeWalt router set to 1 (~16500 RPM) and my plunge rate for the drilling operation was 25 in/min with peck drilling of 0.125", the video can be found here.

Thoughts on what is causing the sound and is it something to be concerned about?

Thanks,

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First, an odd bit of trivia: There are drill mills, and mill drills, and they are not the same thing.

A drill mill is just an end mill that also has a drill point. They don’t have 118-degree drill points, though, so they are not self-centering. Typically, they have 90 degree points and are used for chamfering and little else. There are situations where a machining center may have a limited number of pockets in the magazine, and it would make sense for the chamfer mill to also have some contouring work in regular jobs.

Except in that very specific scenario, drill mills are not the best tool for the job.

@veteranbicycle

Thanks for the tip, I didn’t know about both types. I selected a drill mill because several other people indicated that it was better for a drilling operation than a standard flat end mill. Are you say that a drill mill is not the best tool for this? If not I’m open to other suggestions.

Thanks,

It’s more of a specialized end mill that also has a pointy end rather than an end mill that can also drill. The drill in its name is more about its looks than anything else. Think of it either as a chamfer mill that also has side-cutting flutes or as an end mill with an integrated chamfer mill.

Drilling on an amateur machine like a Shapeoko is a special case because of the high RPMs. Your best bet is to spot using a spot drill, followed by a small drill to clear the center, followed by boring with a small end mill.

The spot drill is a short, rigid short flute drill whose only job is to put a little pip in the surface. That pip creates a boundary for the little drill, so it doesn’t wander, and the spot drill should have at least as high a tip angle as the drill that follows it. The little drill has a much better chance of starting out straight with that pip.

All of that is probably irrelevant considering how much of an effort it is to change tools on the Shapeoko, and even more so how the Bitsetter isn’t especially well engineered.

As to your original question… are your holes meant to be cylindrical or conical?

That sounds fairly normal to me for a plunge into a non-clearance hole, is it the sound on the secondary plunge that you’re concerned about?

I am at work and can’t listen to the video, but if it is what I expect (high pitch chattering, almost like “screaming” or “nails on chalkboard”), I used to get it when my RPM was too high, so I dropped my RPMs down to the 10K RPM range. I believe it is the bit just bouncing around in the hole.

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I have been using a 1/4 inch shank, 2.4degree tapered 1/16th ball end mill for the cribbage board holes…

But, I have only drilled a couple of thousand holes with it.
Seems the taper of the bit matches the taper of the cribbage pegs pretty well.

fwiw… I like how the peg set’s into the tapered hole.

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