100mm hole through 5mm acrylic sheet

[woodchucker]

Maybe I got lucky (twice) on that sheet metal box I cut through. Thanks for the idea on modding the bits for plastic drilling. Haven't done much plastic drilling, so I just blunder my way through it. If I need to drill plastic, I will keep this in mind.

For smaller holes in plastic, and step bit (Christmas tree bit) works great, for sheet metal too.

 

[usamech]

Others have great answers on how to make the circle. I can recommend a bit I used in a router to cut straight lines in 1/4" acrylic for a showcase project for work.

From my notes I used an "Amana 51504" "slow spiral" bit. Solid carbide for 30$, but it worked like a charm. Beautiful edge like glass, no burrs. I never cut plexiglass, but after a couple trial cuts, really worked well. Speed/feed was important. Too fast and material can crack and too slow will melt the material. My records say I cut off a 48" sheet in 15 seconds, of course using a stiff straightedge.

Good Luck!

 

[Firstram]

Use a circle cutter to make a MDF pattern and route it out with a pattern bit like Martin mentioned. Practice on some scrap to get a feel for it before you make your part.

 

[Parlo]

When using a circle cutter I recommend locking the quill and raising the bed.