Best way to enlarge hole in sheet metal?

[syncropatrick]

Got a couple of circular 16mm holes in metal dash which need opening out to 20mm for new switches. What's best way to do this?
I've got an electric drill and bits for making fresh holes in thin sheet metal, but nothing for enlarging.
I can buy a 20mm HSS bit with a taper shank http://www.tracytools.com/metric-drill- ... 1625-220mm, will that fit in my DIY drill chuck?

Doubt a Dremel would help here.
Maybe a manual circular file will do...

[nicq]

Try something like this. http://www.axminster.co.uk/halls-tapere ... tAodEFAAuQ" onclick="window.open(this.href);return false;

[T3luestar]

I'd say a cone cutter is as good option, like said above.

http://www.ebay.co.uk/sch/i.html?_trksi ... &_from=R40" onclick="window.open(this.href);return false;

[gtavalanche]

A step drill would be the way forward.

[Plasticman]

the above are a bit rough and ready and leave nice fat choddies on the reverse. i use
https://www.cromwell.co.uk/QMX0451124B" onclick="window.open(this.href);return false;
fleaba or simminlar about £20 i use them all the time .quick and neat
mm

[syncropatrick]

ooh, those q-max cutters look the bizz - no tidying up needed afterwards and no danger of wandering drill bits. one ordered from feepay.
thx all.

[Plasticman]

round ones are cheap , when i was m aking power amps we had to have rectangular holes for switches, they cost

[sarran1955]

Hello,

Still got a couple..

Great for prototyping.. and cheaper than a fly press tool..

Cordialement,

[syncroandy]

Q-Max cutters rock ! Stepped cone drills are pretty usefull to IMO, and definitely have a place in the toolbox.