Re: ATM stainless steel

["Alan and Marie-Jo Cairncross" <acairnx@onaustralia.com.au>]

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> From: J. v. Gastel <m043653@home.vu.nl>
> To: ATM <atm@shore.net>
> Subject: ATM stainless steel
> Date: Thursday, September 17, 1998 6:56 AM
> 
> 
Hi Jan. I haven't read Berry's book and I'm not aware of the reason why
they advise the use of stainless steel. Perhaps because it is stronger than
aluminium (thickness for thickness). However, stainless is a real pain to
work. It work hardens, which means that as you drill it or cut it it
hardens and it will harden to the extent that it will burn the end off a
drill in no time flat. It can be worked but only with great care. Another
thing is that the filings can cause cuts and nicks on your fingers to
become infected because of the chrome content in it. I'm building a 22"
reflector and I have made an 18 point cell from 10mm (3/8") aluminium sheet
which I picked up at a scrap dealer for $10. For average builders I would
recomend aluminium. it is easy to work with hand tools and will not work
harden. Also it is 1/3 the weight of stainless steel. If you want to be a
bit fancy you can use aluminium alloys which have about the same strength
as mild steel but less than half the weight. If you go that route I would
advise 2024 alloys and not 7075 alloys. 2024 isn't much harder to work than
aluminium. 7075 work hardens although no where near as bad as stainless
steel. I only use stainless when absolutely necessary and it is not
necessary for mirror cells. Regards Alan