I'm making a solar air heater using aluminium drinks cans. I'm using a hole saw in a pillar drill to cut out the top and bottom. The
problem is that the hole saw is quite grabby and if the can isn't well centred, the saw pulls the can and chews it up. The metal is very thin
and with one end removed and the other being cut, the wall isn't that strong to be clamped up tight.
Would changing the drill speed help? I'm guessing that slower would be better. What else would help?
hole saw is probably not the best on such thin material
I wonder if you could punch them out with a makeshift punch and wooden block?
Interested in the design too, I "find" a lot of cans. :-/
Edited to add ignore the punch idea, but a sharp pair of side cutters or an old fashioned stabby can opener migh5 work.
I was thinking you needed the hole to be almost the size of the can , but had a look online for the ide and see like Steve says that you only need a
smallish hole, so perhaps a standard drill .
Good luck, let us know how you get on with. It
[Edited on 25/3/19 by ReMan]
I made one years ago, with Fosters cans, as I do seem to have a few 
I didn't bother cutting any hole in the top just left the ring pull hole for that,
In the bottom just drilled a 10mm hole
Heat rises, so doesn't matter to much how big the hole is 
My contraption was "no nailed" together and sprayed matt black, and lived in the lounge window for a while, until swmbo objected that
although the heat off it was impressive (it really did get VERY hot) the downside was not much light was getting in !
Cloudy days it did nothing, !
steve
Interesting - i'd never heard of these before (or paid much attention to solar panels either!)
http://www.reuk.co.uk/wordpress/solar/make-a-simple-solar-air-heater/ uses flat wood bits
I'm going to agree with Reman - hole saws aren't the best way to cut a hole in very thin, Aluminium.
But if you've got no other option - speed it up (not down) and go through VERY VERY slowly.
Aluminium cut's best at high speed with a high rake angle (on the cutting teeth). Your hole saw is probably not designed for Aluminium (rake
angle won't be optimum) so the best you can do is speed it up and feed it through VERY slowly 
Thanks. I wasn't sure whether faster or slower would be the way to go.
I've been feeding the saw very slowly until it just touches the can to make sure it is centred, then feeding it further until there is just the
first sign of cutting resistance, then waiting for it to cut through. If it snatches, it does so on its first contact with the can.
Would a hole as small as 10mm not restrict the flow? I've been using a 44mm hole saw in the bottom and a 50 for the top as they're almost a
perfect fit for the recesses top and bottom.
quote:
Would a hole as small as 10mm not restrict the flow?
Just bang a decent size cold chisel through the bottom.
Drinks cans are that thin you can cut them with scissors if need be.
I tend to agree, just jab a hole in the bottom with something sharp. Your not after massive flow rate anyway. I'd build one too but not sure where to get all the cans...
I would try a 'step drill'
something like
https://www.screwfix.com/c/tools/drill-bits/cat12140001?drillbittype=step