Drill bits for plastic

[hermit100]

I need to make some holes in a plastic storage box and lid (don't ask!). I've attempted this in the past with an ordinary drill bit but it hasn't worked very well and leaves very rough edges. I need a smooth finish, what sort of drill bit should I be looking to get for this task?
Thanks.

[vrdiver]

I've used drill bits designed for wood, which seems to work provided you can put something behind the plastic you are drilling into, so that the pressure of the drill doesn't push the plastic out. A bit of old wood usually does the job.

VRD

[Itsallaguess]

I've used drill bits designed for wood, which seems to work provided you can put something behind the plastic you are drilling into, so that the pressure of the drill doesn't push the plastic out. A bit of old wood usually does the job.

VRD

I'd also recommend those types of drill bits for drilling through plastic. For the avoidance of doubt, this is what you'd be looking for -

http://www.wilko.com/power-tools/drills+drill-bits/icat/drills-and-drill-bits#esp_cf=pdxttype&esp_filter_pdxttype=Drill%20Bits%20Brad%20Point

They are called 'Brad Point Drill Bits', and if you've not got a Wilko nearby then they're also available from Screwfix quite cheaply -

http://www.screwfix.com/c/tools/brad-point-bits/cat5930022

Cheers,

Itsallaguess

[hermit100]

I do have a Wilko, will check those out. Box is v large so putting something behind is more difficult than it sounds but it seems I will have to try to figure out a way to do it. Thanks both.

[WessexMario]

whether you use a hss or a wood drill, if you want a clean hole in plastic
- use a sharp drill and
- use a slow drill speed !

[hermit100]

I don't think my drill has variable speed, it's either 'go' or 'stop' (and 'hammer' or screw, I am obviously using the latter); I will try to 'go' gently!

[WessexMario]

I do have a Wilko, will check those out. Box is v large so putting something behind is more difficult than it sounds but it seems I will have to try to figure out a way to do it. Thanks both.

One way to do it would be to put a piece of scrap wood on the ground outside, rest the relevant face of the box/lid that you want to drill on the wood, then drill out from the inside of the box.
and... measure twice, cut/drill once.

(I'm assuming you have little in the way of workbench, clamps etc)

[hermit100]

(I'm assuming you have little in the way of workbench, clamps etc)

[/quote]

You would be correct, nothing at all in fact. But I do have some bits of wood and if I can get the drill in at vaguely the correct angle from inside I'll do that, it's certainly the most sensible way of going at it. Thanks.

[Wizard]

The important thing is that the piece of wood used needs to have a decent amount of pressure applied to it, sufficient that it isn't just dislodged when the drill comes through. As a drill breaks through there is a tendency for the forces pushing to overcome the cutting action, in wood the result is that the fibres around the hole are pushed away from the edge of the hole and not cut. Often referred to as "blow out".

The function of the piece of scrap wood is therefore to support those fibres and allow the drill to cut them before they are pushed away, hence the advice to use a sharp drill above. I would have thought it would be less of an issue in most plastics that are not as fibrous as wood.

If the material is thick and it is hard to hold a block behind where the drill will come through an alternative would be to use a small drill to make a pilot hole. Then, using that as a centre point drillhalf way through from one side finishing the hole by drill the other half of the hole from the other side.

If none of this pros you could try using a countersink to clean up the hole after it has been drilled.

Terry.

[brightncheerful]

Bosch do a range of hole saws that care be used for hard plastic

[hermit100]

Oh for a recs button!
Thank you, virtual recs all round.

[foundone]

If it's soft plastic bodge a hole through with a hot nail.