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David,

Thanks for your care, I know, if you have to drill in brittle clear material.
(a lot is (pmma) perspex), then use one older blund drill.
A new drill is to sharp and byts directly in the material that give cracks.
Also use a low speed for drilling.
I learned this from my business neighbour, he has a plastics productionshop.
He laser cutted a small T-plotter for me, but I find it most times to  big for plotting.

Regards

HermanD