Advice needed on new acrylic hatch lens install

[jkm]

It's time to replace one hatch on Penquin (35-2).

I'm a stickler for keeping my baby stock so I'll be using Acrylic. The original screw holes were counter sunk.

Would not it be safer to use a carbide Forstner bit first, then drill for the screws?

I would also consider a counter sink bit, then drill the screw hole.

Any advice on drill speed using acrylic?

John

 

[Martin King]

When drilling plastics, you are supposed to use a bit ground to
60 degrees. You can buy them, or modify a regular bit by grinding.
Start by drillling a small diameter pilot hole, and work up to your
desired diameter, taking off small amounts. Drill speed should be
checked against a chart with consideration given to bit diameter
and use of some form of coolant is advised. Finish off with the countersink.
Before you commit to the workpiece, practice your technique
on some scrap first, and use a drill press.

 

[mherrcat]

I second the practicing on scrap first.
A double second on using a drill press; it helps a lot to control the pressure on the bit and keep it from possibly grabbing, also keeps the holes straight.

 

[exoduse35]

Also drill into a block not unsupported plastic, the final push through binds up and will shatter or crack the piece . The block is an artificial end point beyond the hole. Edd

 

[Lucky Dog]

and...use drill press for the counter sinking. Once the counter sink drill bit grabs hold of the material it will want to go deeper than you may have wanted to.

 

[jkm]

Thanks all for the great advice!