Small Holes (Speed)

I am using my Shapeoko for a small production environment (it works great), but one of the very slow steps of the operation is “drilling” holes. It takes forever! This isn’t a question on how to make the machine do a drill operation, but more looking for feedback on an idea I had to speed this process up.

My material is HDPE that is 3/8" thick, so it is pretty soft and I am using a 1/8" O Flute bit. Instead of setting the toolpath to start at the top of the work piece, then slowly core out the hole, I was thinking I could set the start depth to something 5/16" (tricking the machine into drilling straight down at the start). It seems like one variable I would need to control is the plunge rate to make sure the bit doesn’t get lowered too fast. The holes I am drilling are only slightly larger than the 1/8" bit. Before I send work pieces flying and bits shattering… thought I would ask if anyone has tried this? or you see any issues with my logic.

*** This is soft-ish plastic and wouldn’t expect this method to work on hardwood etc.

Is an “O-flute bit” basically just a single-flute endmill?

Do you mean you’re currently doing a helical bore toolpath and you’re wondering if you can just plunge straight down?

If so, yes, you should be able to just plunge. Might be worth doing a peck drilling cycle to help clear the chips. Though technically there are sometimes endmills that aren’t bottom-cutting.

If you’re doing a lot of drilling, it might also be worth trying a drill instead, though I can’t say how well it would work, I’ve only done it in metals.

To be honest, I don’t know what the difference is between a single flute and an O-flute other than O-flute is the recommended type of bit to use for plastic.

I am using Carbide Create, so limited to “pocket” for creating a hole. Helical would probably be much faster. It sounds like I should go ahead and do some experimenting. Carbide Create is weird with small holes. Sometimes it plunges, circles, lifts out of the hole and other times it plunges, circles, plunges without lifting back out. Can’t seem to find a reason why it does that.

The previous solution I came up with was to use an actual drill to drill the holes using a jigg I had made to ensure exact placement of the holes. The problem with using the drill was that it left a flared edge on the bottom of the work, which wasn’t as clean as I would like.

The closest example I did to what you describe is this:

HDPE is butter, in that example I’m straight plunging at 60ipm (if anything, plunging too slow is the problem, in soft plastics).

O-flute is a specific type of single flute designed to curl up chips, for milling plastics. The shape/rake angle is specific, and it’s super sharp.


This helps a lot! Good call on the plunge rate and I should have known better because I get better results running my regular cuts faster.

So are you plunging almost to the bottom, then letting it cut out the pocket? My holes are slightly bigger than the bit, so my approach was to plunge it down almost to the bottom, let it do its pocket, then one more plunge to the bottom and let it do its pocket (2 passes). The other option would be to plunge just slightly further than the bottom and letting it pocket (one pass).

plunging 3/8" deep and pocketing in one pass might be pushing it with a 1/8" endmill, I would probably try two passes. Regular pockets, 5mm per pass. Maybe even start with 1/8" DPP, test to verify that it doesn’t break a sweat, then increase DPP. You may get away with 3/8" in one go, but don’t go breaking bits for me.

I can feel all metalheads having a stroke right now, good thing you are only milling HDPE :slight_smile:

I appreciate the advice! I wouldn’t even consider this with metal or hardwood, but HDPE is so soft that I figured it was worth asking to see if anyone has tried it.

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Not sure if this will help you or not, CC 530 has a drill option on the toolpaths now. I’ve used it once and it worked fine.


Oh, that is interesting. Do you know if you have to use the exact size bit? Or does this just create a path that is more efficient at creating a hole?

The endmill used will move straight up/down, so the resultant hole will be endmill diameter + runout.

@myersd08 The drilling tool path added in 530 is awesome. It has saved me a lot of time on drilling holes in cribbage boards. I actually switched to high speed drill bits and dropped the RPM as low as it will go and am able to go way faster on each board now. Not sure how the HDPE will work with that but I would hope it would go much better for you. You should be able to choose the option to plunge right to the bottom with a drill bit and then it should be in and out quick.

This sounds like a great option! I have been buys making stuff, so haven’t upgraded and it seems like I have a good reason to go to the new version now. It sounds like if I need to drill a slightly bigger hole than my 1/8 bit (which I do), I could run a drill operation, then run a 2nd full depth “pocket” operation to get the hole to size. Obviously this has limitations, but doesn’t seem like a stretch to make a 3/16 hole this way. I do a full depth finishing pass on all my cutouts anyway, so I know this produces good results.

One question though… What do you use for a collet with your high speed drill bits? I only have 1/8 and 1/4 collets. HDPE is pretty soft, so I think i should be fine with my end mill but it would be nice to know for other applications.

The only problem I see is that I lose all that time staring at the machine while it slowly pockets holes out :grinning:

I just use the 1/8 and 1/4 precision collets I got when I bought the machine.

If you want to drill the holes, they make various sizes of carbide circuit board drills that have 1/8" shanks (including sizes larger than 1/8"):

3/16" diameter and 10,000 rpm will get you to 491 SFM, which is right at the upper end of the recommended range for drilling polyethylene:

0.004 to 0.012 feed per rev at 10,000 rpm works out to 40 to 120 IPM plunge rate. Thinking an air blast for cooling / chip clearance along with peck drilling would help.

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