In a change from our scheduled 'can't get anything done without the
fanciest tool in the Axminster catalogue' transmissions... just had a
happy experience as summarised in the subject line. Needed to put a
plain blank ali plate in place of the perforated sheet which came with
the oversize-tower 'puter case (which is full of airflow management
tricks, and then puts a gert big passive-flow hole in the side - I guess
assuming most/all Case Modders will buy the perspex side window, so they
can watch their wiring all day long, and sod the EMI!).

2mm ali sheet sourced readily enough (hole just under 300mm diam, so
precut sheets of that minor dimension were OK). How to cut a neat
circle, though? At 2mm my hand nibbler was a bit strained, and doing 1m
of cutting (300mm x pi, close enuff) wasn't a fun idea. 12in hacksaw
round each of 4 corners would've been possible, but hard to follow the
curve precisely. So... though my jigsaw's just a B&D cheapie bought 10?
years ago, I checked through the blade collection to find a couple of
'Piranha' fine-tooth metal-cutting blades. Applied to the inner edge of
the circle drawn round the perforated sheet as resting on the plate -
turned out to be very controllable, no juddering with the plate clamped
to the workmate, easy to follow the line. (Sheet came with disposable
white placcy covering, so markout and soleplate marks didn't end up on
the ali surface).

Result of less than 5 mins cutting - a nice neat circle, fitting
perfectly; edges rounded off gently on the (Ferm cheapie) bench grinder.

I guess I hit pretty much the sweet spot for jigsaw use - cutting curves
in thin sheet. While for 18mm ply I'd always bring out the circular saw,
for thin sheet like this - MDF, hardboard, and as I now know ali - the
'consumer-grade' jigsaw's just fine, as the inevitable blade-bend
doesn't affect the cut on so thin a sheet.

As it happens the nibbler had been in use on a 1.2mm bit of ali sheet
earlier in the day - cutting the verge for the first time, the mower
(rotary, petrol, with plastick/GRP deck) unerringly found a small
discarded lorry-tie-down strap, which wrapped round the blade with the
ratchety bit smashing into said deck. Chunks of deck came away before
the motor stalled. So, I added to the collection of ali patches which
were already in place on the other side of the deck with one
underneath/inside, held in place with a few pop rivets. The mower was a
bit of a distress purchase anyway, and is in its 5th year of cutting:
bought after moving to a place with a far bigger, and somewhat rougher,
garden: a 'big-blade' electric Flymo self-destructed within a coupla
months - instant refund from B&Q - and this one bought at a Local Shoppe
for Local Lawnmowers in its stead. What the GRP buys you in corrosion
resistance, you pay for in fragility - it really doesn't stand up to
thumping from the kind of junk which ends up in the verge expecially.
Yes, I usually try to clear up any nasties before mowing, and keep my
eyes open; but expecially with over-long grass on a first cut, with the
revs up full, any little lurkers end up thrown against the deck with
some force...

Ah, the joys of spring... Stefek