I am a Newbie. What Bits Should I Buy?

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Hi, Everyone. I’m a raw newbie here, so please forgive me if I ask some really silly or uninformed questions. I will finally have some time during the holidays to start using my machine. I have a Shapeoko 4, all set up and ready to go.

First question. I make very expensive guitar picks, ranging in price, for one pick, from $40 to $99 each. These are made from engineering plastics such as Ultem, PEEK, DuPont Vespel, and the like. Although so far I have not cut these materials with a CNC, in my experience they cut, sand and grind very similarly to Delrin, Acrylic, PE, etc.

I need to buy a basic combination set of entry-level bits. I don’t necessarily want to buy the cheapest stuff out there, but I also don’t want to buy Snap-On bits. From the little I know, I believe the kind of bits I’m seeking would be called End Mills, correct? Right now, I’m looking at this set. Is this a good place to start?


For my initial jobs, I will never be cutting anything thicker than .080" (2 mm). Therefore, because my materials are so very expensive, to minimize material loss I would like to work with the thinnest possible bits that won’t break. (To give you an idea of my material expenses, a 12" x 12" x .060" square of PEEK can sell for upwards of $300.) I am thinking initially of trying to cut with a 1/32" bit.

Is it possible that I can go with a bit thinner than 1/32"? If so, what bits might you recommend?

Suggestions accompanied by direct URL links would be a huge help.

Thanks Much,
Routing Success

The smallest tools we offer are:


either of which should work well.

@TDA runs a business selling such small tooling and may have better options:

Also see:

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Thank You! I will take a look at these and go from there.

I have purchased bits from both drillman1 on EBay and from drillbitsunlimited.com and have been happy with those I’ve purchased. For the ones sold by drillman1, read the description carefully. He does sometimes sell used bits and the description will say so. They have plenty of life left and I haven’t had any issues using them; they just won’t last quite as long as new ones.
I have no affiliation with either seller, just a happy customer.

Hi Scott,

I recommend you initially go for larger endmills, because 1/32" endmills are very fragile and you will break a lot of them while you dial in your feeds and speeds, dust collection/air blast, etc…Try your hand at 1/16" first, possibly even 1/8" for first cuts.

In addition to Will’s recommandation, I like Amana single flute (O-flute to be precise) endmills for plastics.

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Also you’ll still occasionally break them after you’ve dialed in feeds and speeds

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Usual preface, I’m with PreciseBits so while I try to only post general information take everything I say with the understanding that I have a bias.

Sorry, couldn’t get to this until today.

Yes and no. Endmill is a fairly generic term. As an example those linked cutter are endmills. However, they would be a horrible choice as they are a grinding geometry that is intended to cut composites and will typically melt plastics. What you’re looking for are endmills but specifically 1-3 flute tools design for cutting soft media (realistically 1-2 flute right now as each flute added requires more feed). Won’t get into too much more specific here due to my previously stated bias.

In general I personally would side with Julien here. Start with bigger tooling and preferably start with similar but less expensive material. That will let you find all the pitfalls in your process without burning through expensive material and tooling.

When you do go to the expensive stuff, I’d recommend sticking at least initially to single flute cutters from a decent company. They are effected much less by runout which will start being a bigger issue in that size tooling and under. Additionally, if designed correctly the single flutes will give you a better cut in plastic anyway. Although, they won’t last as long in like for like cutting as there’s one less flute to dull.

This is also true. Some of this is unavoidable as tooling dulls. Some of it can be from material variation. You’re also more likely to unexpectedly run into it with multi-flute cutters with runout that’s a significant percent of the chipload. With expensive material or high labor/tool cost final products some companies will actually retire tools after X hours to address this. Although, that requires a pretty good understanding of your process, feeds and speeds, material, etc.

Just as clarification, I’ve worked at the company for decades but I’m not an owner.

Hope that’s useful. Let me know if there’s something I can help with.

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Hey, guys, I’ve had a long day in the shop, so I’ll make this short for now.

There’s a couple really cool Shapeoko groups on Facebook, and between your feedback and theirs, it’s pretty clear that I will want to start with a 1/8" bit and make my mistakes, then work on slowly to try and go thinner. I suspect that 1/32" is probably not a realistic expectation for my application, but I’m hoping in time I can get to 1/16" without breaking bits. And, yes, agree as well to start with cheaper plastics. I have super cheapo Acrylic and a few other sheets of other cheap plastics.

One other thing. Everyone I’ve spoken to has told me that I definitely want to use an UPcut bit when machining plastics, not a Downcut.

Appreciate any additional comments, and thanks so much for your time and shared experience.


For cheaper plastic note that you will want to avoid certain types — cast acrylic cuts well, extruded acrylic is difficult to the point where most folks don’t even bother.

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As Will said extruded acrylic will probably not be a good choice as it’s hard to machine. It’s actually not even the same mix as cast acrylic and has an intentional lower melting point. This is both for the manufacturing method and for applications like thermoforming.

Yes, you definitely want an up-cut. A down-cut will force the chips to the bottom and will complicate things heat and finish wise. This is especially true if you are going to be slotting as the chips are trapped in the flute longer.

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