Going Insane from Issues with Acrylic

Hi guys I’m a little frustrated with trying to do some 0.118" cast acrylic.

I’ve broken three bits today experimenting with feeds and speeds.
They are all 1/32" bits. DW611 at 16k (lowest)

First try was going fine at Easel’s recommended 25IPM, 9in plunge, .02 DOC but after about 10min the stuff started melting and the bit got stuck and broke (it’s a really long cut length)

A little upset because money gone, but I gave it another try (bought 10pc 1/32" since I’m a beginner) This time, brought it down to 20IPM, 9in plunge, .01 DOC. Went fine again for the same amount of time and melted, broke the bit.

Took a break for the whole day, went back to do a different cut in the same acrylic. Tried again, 25 IPM, 8in plunge, .02 DOC, went fine for first few minutes (have been clearing using canned air) then it started melting so I immediately stopped everything and brought the spindle up. It’s the Chemcast cell-cast acrylic, which I read is a lot different from Plexi.
Take 4: Realized that the bit is 5 flutes. (Five. Flutes. Wow. The rest of my bits are 2F) So maybe it just needs to clear it faster, went 50 IPM, 8in plunge, .02 DOC. Immediately breaks, it cut for about 3 seconds before the end broke and got stuck in the plastic.

Should I change the DOC? The length of cut is rather long (~3/8") so my dad and I think that it’s just cutting too deep. Three bits gone so I’m afraid to change any numbers.

Do a search for acrylic. There are many posts about this material.

5 flutes is a lot of flutes for a 1/32" bit, and a lot of flutes when your slowest spindle speed is 16k. My first thought is your feed is way too slow, especially with that many flutes. I am usually in the 40-50 IPM range with single and 2-flute bits.

The other thing might be that with that many flutes, you don’t have enough open area on your bit for the chips to leave the cut and bit, and those are melting to your workpiece. Do you have anything single or 2-fluted from Inventables you could try?

I second Larry’s post. There are lots of acrylic posts and tips on here.

what is your design?

I do have a solid carbide 2F 1/32" (need to do lettering) but the acrylic seems just a little too thick for it.

I have searched for acrylic threads before but only found one thread that had similar problems, and it’s a little hard for me to estimate especially like you said this thing has 5 flutes.

I just ordered new material and a new bit yesterday so I may have to wait a while to get some other new ones, but is there anything I can try with the old one? I was thinking maybe bump up to 100IPM, and going much shallower at say maybe .001" DOC

It’s this design here, originally it had lettering on the bottom but before I even started I decided I’ll try it later and wanted to test a simpler area first

“Design is not shared publicly” error.

How deep are you trying to cut with your 1/32" 5-flute?
Inventables 1/32" fishtail might make it all the way through your acrylic sheet. If you aren’t getting through with your current bit, give this one a try at a shallower max depth and see if you have success.

Oops. Didn’t hit save. Should be good now.

All the way through, so 0.118". It’s a keychain so the hole on top and the circle are full depth. The arrow part will be too if I can figure out a way around things.

Yeah it seems that both diameters should be able to cut through. even the 1/32". I’m a little low on personal spending though so I’ll have to think about it. Thank you though for the suggestion.

Try the “R” as a fill like the arrow. What about making it a 2-stage cut and using a larger bit for the final cutout?

I did a similar job last week. Also my first try on acrylic. Went without a hiccup.

my settings:
1/16" 2-flute bit
60 ipm
0.01" doc
spindle at lowest setting

very crisp cuts with no melting whatsoever

I think your bit is the problem; too small and too many flutes. How they can fit 5 flutes on a 1/32 bit is beyond me, but it can’t be very good for chip clearance…

btw this:

is generally accepted, but i’d beware with large diameters. I would never do a 4mm doc on hardwood with an 8mm bit. not even close


Plastic, shallow and fast. Or it will melt and stick

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@SteveLittlepage I thought about a 2-stage, but realized I’d still have to do the arrow fully in the finish pass. I’ll think about that more though, so thanks

@PhilJohnson One day I will maybe try a laser conversion. I haven’t worked with engraving bits before but maybe I should give it a try, it seems a lot of people are using that for acrylic. And yes I realized that maybe I shouldn’t trust Easel on the DOC, thanks for the headsup

@anon68752607 That’s a really neat cut you did, it looks good. You’re right about the flutes, I completely forgot about it because the bit is so small and I had to take a jeweler’s loupe to it to count.

@DavidAnnetta I think Easel likes to do things in as little passes as possible so yeah that would explain deep & slow not working. Thank you for the advice, I’ll stick (no pun intended) with that for plastics

One other thing I didn’t see in this thread, if it is here…nevermind.

Your bit should be an upcut bit, that helps it evacuate the chips.


I hate to be a downer, but forget cutting acrylic with a 1/32" bit, dewalt 611 and no coolant system.

I am going to be adding a vfd spindle to my setup for this very reason. The Dewalt is just too fast, even on 1.


@ErikJenkins Yup, I haven’t bought any downcut bits yet

@JDM Yeah I’m thinking I should just avoid doing 1/32". I may look into coolant systems later though but only for when I know more, I plan to cut mostly aluminum but I’ll try to figure out acrylic first.
I haven’t thought about a slower spindle though, I guess that’s now on the list with a new laser

I can get good cuts if I really need it but have to sit there the entire time with a spray bottle and brush.

I’m about 50/50 between needing the slower variable speed and the power of the dewalt so having both will be ideal.

I’m pretty sure you can get a VFD that is more torque a slower rpms than the dewalt.

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Or buy a Makita 700.

To cut acrylic with a .03125 bit you will need to slow the IPM down to a crawl. I cut acrylic on occasion and I have plenty of experience with speeds and feeds and if you are going faster than 6 IPM with that small of a bit then you are going way too fast. You also need to pay attention to your depth per pass. I would set it at .005 per pass. Try that and see if helps. Also forgot to mention that you need to clear the chips as quickly as possible. You may also want to try a single flute upward cut.

onsrud acrylic bits single “o” flute works great for flawless cuts on acrylic. 40ipm with a .125" bit at doc of .0625" produced flawless weldable cuts with dewalt 611 on setting 2.

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