A reader's question about drilling acrylic is answered by one of PBO's experts

QUESTION: 

Are there any special things I should know about drilling acrylic? I want to drill some holes quite close to the edge of a piece around 8mm thick. Any tips would be greatly appreciated.

Bill Carr
By Email

DICK EVERITT REPLIES:

Special acrylic drilling bits are

ideal, but I’ve managed with

ordinary twist drills. Practise on a

scrap piece of acrylic and if there

is a tendency for the drill to dig in

and chip the surface, grind the

drill’s cutting edges back a bit.

Simply fl atten them against the

side of the grinding wheel, as

shown in the photo.

A drill press is great for keeping

everything square, but a manual or

powered hand drill also works fi ne.

Clamp the acrylic down carefully,

being careful not to scratch the

surface, and have a scrap piece of

acrylic or hardwood underneath.

This gives the right resistance to

the drill point as it keeps cutting

and prevents the sides of the drill

from bursting through and

chipping the edge of the hole.

Use a slow speed, drill a pilot

hole and make a circular dam of

plasticine around the hole to hold

water to lubricate and cool the job.

Work slowly and keep taking the

load off the drill so it doesn’t heat

up and crack the plastic.

If the hole is for a bolt, drill it

slightly oversize and rub off the

sharp edges with a countersink or

larger drill, to prevent stresses

building up as you clamp

everything down.

There are all sorts of acrylic

plastics: some drill like soft cheese,

others seem to work-harden and

always want to chip, so good luck!
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