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milling Acrylic

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John Alexander Stewart10/07/2020 13:13:59
771 forum posts
52 photos

Hi all; was given a task to mill a pocket and outline in a bit of 3mm Acrylic.

The searching I did here mentions turning, on-line it's with high speed spindles.

What have YOU done with a slowish (say, max 5,000rpm) spindle on either a manual or CNC mill? Say, 3mm or 4mm 2 flute cutter.

I expect to hold this piece down with double sided tape, hopefully I can get it off of the carrier again. :-|

Advice more than welcome. Thanks - JohnS.

Tony Pratt 110/07/2020 14:03:51
1149 forum posts
5 photos

If you go too fast the plastic will melt.


Barrie Lever10/07/2020 14:40:18
653 forum posts
75 photos


There are two types of acrylic sheet, extruded and cast, the extruded material clogs up/melts around the cutter very easy so keep temperatures down.

I have heard of people using tap water as a coolant.

Two pieces of masking tape and join with super glue is how I hold this sort of part down, do it every day with big chunks of carbon fibre.


Adam Mara10/07/2020 15:45:11
110 forum posts
3 photos

I use Carbide Create on a 3018 CNC router, usually with a 3mm or 1.5mm bit. Speed is set at around 4000rpm, depth per pass 0.5mm, feed rate 150mm and plunge of 100mm. Not fast, but works for me!

FLguy10/07/2020 16:47:11
15 forum posts

At the medical company I worked for we used lots of WD-40; HSS tool bit with approx. .015 radii at it's tip and spindle speeds about 600 to 650 RPM. Slow feed. Hardly ever a need to polish afterwards.

Kevin Hodgkins10/07/2020 16:51:06
1 forum posts

I cut and engrave cast acrylic (perspex) with my cnc router, and find it a fairly easy material to work with.

I usually cut a high spindle speed ( 20,000 rpm,1200mm/min, 1mm DOC with 1/8" cutters ) but that is mainly for chip clearance. I've found lower speeds cut fine, but chips accumulate in the cuts.

As an experiment I took an off-cut and tried it in my manual mill at 2000 rpm this afternoon and quite happily machined some pockets and slots with no drama.

I tried machining extruded acrylic once, I'll not be trying again.

Georgineer10/07/2020 17:52:37
367 forum posts
16 photos
Posted by Barrie Lever on 10/07/2020 14:40:18:


There are two types of acrylic sheet, extruded and cast, the extruded material clogs up/melts around the cutter very easy so keep temperatures down.


What he said. The extruded stuff goos up like chewing gum, puddles the cut, and sets rock hard when you stop. The cast stuff machines beautifully and smells nice while you're doing it. I've never used coolant, but I keep the depth of cut down and the feed rate up to get the heat away quickly. Talking two-flute end mills up to about 4 mm diameter; no idea off the top of my head what speeds and feeds I used.

George B.

John Alexander Stewart13/07/2020 17:48:20
771 forum posts
52 photos

Many thanks - the support and guidance was appreciated.

The Acrylic faceplate machined with absolutely no issues, and results delivered to owner. (doing this for a friend of a friend, he's a radio nut, and had ONE piece of Acrylic of the correct size - no screw-ups allowed.

I decided to mill on my manual mill - Centec 2B, the part barely fit with maybe 5mm extra Y travel, but fit it did. On the Centec, I could have my nose down close, and adjust the feed as appropriate; next time I'll know better how to do this on CNC.


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