[sdiy] Making holes in plastic

[Seb Francis]

>
> 1. Use a flat wood-boring bit. They are available in large diameters 
> and produce a very neat hole in plastic - I used them on some plastic 
> electrical backboxes with good results. Downside is that they may not 
> be precise enough for you positionally.
>
I always use flat wood bits for large holes in plastic panels.  They are 
pretty accurate if you are careful and you:
(a) Drill a *small* pilot hole first for the point of the bit to fit 
into (drill a hole that the point locates into nicely)
(b) Use a drill & drill bit without any wobble (some cheap drills and 
drill bits are 100% straight)

> 2. Use a step drill bit. These are always recommded here for getting 
> neat large holes in metal panels, so should make short work of 
> plastic. However, without a drill press, the position of the hole can 
> wander quite a bit from your pilot hole (this happened to me just 
> yesterday - I don't have a press either).
>
Step drill bits are excellent for metal panels, but it's definitely true 
that they can wander a bit without a press.  Also, for drilling by hand 
I find it better to use a high-torque, slow speed drill/driver rather 
than a mains drill - this gives you much more control and reduces the 
risk of accidently going through the next step (especially if your step 
drill is rather sharp it will cut very quick!)

But I would not recommend a step drill for large holes in plastic.  I 
imagine you would get the same problems as you do with large HSS bits in 
plastic - the bit (especially if sharp) tends to cut too deep into the 
plastic and rip and tear it, resulting in a mess.

So, personally I'd go with the flat wood bit :)

Seb