Drill bits for plastic ?

[weeksy]

I'm very short on drill bits, i don't need many/often, but for drilling things like number plates, as you'd expect, this happens more here than in some houses

My last 4mm snapped and my 5mm is blunt...

Maybe i'm using the wrong type though, so what would you say i need ?

[KungFooBob]

I buy the cheap ones in the middle aisle of Lidl or Aldi, they always seem to have them in.

It's a good job they're cheap, because they're shit, I dunno why I keep buying them.

[Skub]

Any old drill bit should deal with plastic. No need for spendy cobalt stuff or anything.

If you have a bench grinder you could sharpen the blunt drills.

[Yorick]

Any old drill bit should deal with plastic. No need for spendy cobalt stuff or anything.

If you have a bench grinder you could sharpen the blunt drills.

Please don't let Noggers read that

[David]

For number plates (I have done a few...) I would use a very sharp steel (for drilling steel, I noes they are made of steel ) drill of the appropriate size.
For softer plastics, a wood drill....sharp again. BTW I often mark/drill holes in plaster board with a wood drill.

[Yorick]

Just smash a big fucking nail through

[demographic]

Not exactly a recommendation, more of what I have to hand and generally use for perspex.
Err, its the HSS cobalt drills I use for most holes in aluminium, steel, stainless steel (high feed, low speed in stainless though) and the sub 13mm holes in wood.

Above 13mm in wood its either an auger bit, or a holesaw and if I'm doing masonry its an SDS TCT bit.

I would say that your best to have a bit of wood/MDF behind the plastic your drilling into though.
Pretty much the same as for steel.

In an ideal world I think industry uses a tip ground to a different angle to get a better efficiency but I'm not dicking about with that, I have far too many types of drill/holesaws as it is.

Basically, whatever you use for drilling steel at the small sizes you'd be doing for numberplates.

[demographic]

Forgot to mention, too fast a speed drilling or cutting perspex just melts it.
Not so much an issue for a 6mm hole but a real thing if your ripping a sign with a circular saw (the better ones have sometimes have a speed setting) or drilling the thick stuff.

[Mr Moofo]

Sticky velcro is you friend ....

[mangocrazy]

In any material I'd always drill a pilot hole first with a small (c. 2mm) drill bit before taking it out to its final size. Always use sharp drills and either sharpen blunt ones or throw them away. You only really need fancy cobalt drills when working with stainless or tool steels. And invest in a centre punch so the drill bit doesn't wander.

[weeksy]

I used the ones with the pointy bit on the end as easier to be accurate

[mangocrazy]

I used the ones with the pointy bit on the end as easier to be accurate

Yeah, they're good and tend to be decent quality. But you can't beat a centre drill when starting a hole off precisely. The body is chunky, so they're not going to snap on you like a thin HSS drill will, and they also give a countersunk lead in for the big dog drill to follow.

https://www.cromwell.co.uk/shop/cutting ... c/39151102

[demographic]

I used the ones with the pointy bit on the end as easier to be accurate

In theory I should be using them for small holes in wood as they cut a neater hole.
In reality they don't handle much site abuse so I don't have any and the cobalt drill index I use for most things is from Machine Mart and not that spendy anyway.

[Horse]

And invest in a centre punch so the drill bit doesn't wander.

But not on plastic

Put a strip of masking tape on the surface, use a gimlet or bradawl to create a small indentation.

The masking tape eases marking the required location, it also means that if the dril skids it won't scratch the surface.

And treat yourself to a set of hex shank drill bits, much easier to swap and tighten.

[mangocrazy]

I have used a centre punch on plastics, but there are so many different types of plastics that you can't generalise. Engineering plastics like Acetal, Delrin, Nylon and UHMWPE are fine with a centre punch. Brittle pastics, less so...

Masking tape is always a good idea when drilling. Makes marking out more visible as well.

[Felix]

I would never buy a set of them again. Bought to many that would have a slight wobble when in use like they were never set properly. Cheap and branded.

[Horse]

I would never buy a set of them again. Bought to many that would have a slight wobble when in use like they were never set properly. Cheap and branded.

I deliberately only showed an image, not a link to any specific product. I've only bought reputable brands.

If they wobbled, they would have gone back.

[demographic]

I would never buy a set of them again. Bought to many that would have a slight wobble when in use like they were never set properly. Cheap and branded.

I deliberately only showed an image, not a link to any specific product. I've only bought reputable brands.

If they wobbled, they would have gone back.

IMO the slight wobble is an inherent feature of the rattle gun chuck which is the main reason people use those bits. Just quickly pushing them into a rattle gun is often faster than changing bits in a three jaw chusk.
If theyre used in a three jaw chuck instead they usually have a lot less runout.

I usually have two (or more) drills on the go. A rattle gun with screwdriver bits, a combi drill with normal drill bit/auger bit/holesaw/spade bit and maybe an SDS drill with masonry bit depending on my needs.

[Horse]

IMO the slight wobble is an inherent feature of the rattle gun chuck

I had really bad wobble a few minutes ago, with one in a three jaw.

Mind you, I'd managed to wedge it off-centre between two of the jaws after using a bigger drill bit

[Taipan]

I bought these as I was low and they were on offer as Bunnings was closing down. I'd buy them again.

https://tinyurl.com/5n8ucmdk