Happiness: cheapie jigsaw, metal-cutting blade, 2mm ali sheet, neat 30cm circle!

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
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My 'book' says don't use ally on a grinder - it clogs the wheel. Same with normal metalwork files. Those 'tile' type files seem fine, though.
--
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Dave Plowman (News) wrote:

grinder.
with
putting chalk on the wheel first helps a lot. Whether thats enough to avoid the problem i dont really know. Grind wheels can be resurfaced though.
NT
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ISTR chalk being used on a normal file to give a fine finish on steel when draw filing.
At school, we had to use old files kept specially for ally.
But as I said, those grit coated files - usually meant for ceramics - don't get clogged with ally. They're handy for wood too - for a bodger like me. ;-)
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Stefek Zaba wrote:

So it just happened to cut to the same amount and direction of wonkiness that you nedeed for this job :)
Seriously, you can get lots done with cheaparse tools, and I think that does get overlooked sometimes here.
NT
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Very true. Too often in this group discussions of "what can I get away with buying to finish the job cheaply" descend into flame wars of "my tool's bigger than yours" which always read to the casual observer as "I'm a bigger tool than you" :-)
henry
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With most of the common power tools I end up replacing a cheap one with a decent one if it gets much use. Done this with jigsaw, router, bench grinder, pillar drill as well as ordinary drills, etc.
Of course if they're only used occasionally, the most basic might do.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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