Cutting CGI - Corrugated Galvanised Iron?

ttm

I'm fixing an old roof, and have about 20 sheets of Corrugated Galvanised Iron to cut to lenght anyone got any ideas what the best method is.

I've cut the stuff before but only ever a couple of sheets with either a jigsaw (very noisy) or a small angle grinder but its been slow.

I don't mind buying new tools for a job (any excuse) so what do you think I should get? While I can hide the cut end under another sheet it wuld be best if the cuts were really clean and straight.

I've one other question as I might add a lead flashing on one edge of the galvanised to get a good weather proof seal (another option is felt) so how do galvanising and lead flashing react?

btw the reason I'm cutting the sheets is that I either got a very heavy gauge sheets for free or had to pay about 350euro for the correct length sheets that were that really crappy thin gauge (0.5mm afaik) and I really wanted to use the thickest gauge I could get the stuff I have is like they used to use 50 years ago on barns and the like.

CJhaughey

I used a 4.5" grinder with a stainless steel cutoff disc.
The cutoff discs are very thin 1.5-2mm and cut corrugated very well.
You would be advised to get a few as they can wear fast.

ttm

CJhaughey wrote: »

I used a 4.5" grinder with a stainless steel cutoff disc.
The cutoff discs are very thin 1.5-2mm and cut corrugated very well.
You would be advised to get a few as they can wear fast.

Just been out practising on an old sheet and a small angle grinder seems to be the easiest way to go. Was only using some cheap Lild disks and looks like one disk will do at least 3 or 4 sheets. I might see if I can get some longer jigsaw blades as the jigsaw did a cleaner job but obviously bounced off the troughs with a blade that was a little to short. Because I have a load to cut and a flat 8'x4' bench I can put the sheet I am cutting over then end of the bench with the bit to cut off sticking out between two sandwiched others this holds everything nice and firm for both the grinder and jigsaw.

I'm really just prevaricating about the job as its a real pain, just discovered half the sheets I'm removing are held by nails through the sheets above which makes the job bigger. I was hoping to pull out the bottom sheets and push in the new ones without touching then next row of sheeting above.

Also discovered I can't use lead flashing which I had guessed anyway, this Australian site had some useful info all very obvious stuff but first place I found a warning not to mix with other metals such as lead.

CJhaughey

ttm wrote: »

Also discovered I can't use lead flashing which I had guessed anyway, this Australian site had some useful info all very obvious stuff but first place I found a warning not to mix with other metals such as lead.

I think thats referring to zinc/aluminium type sheeting not galvanised steel.
I have never had a problem using lead flashing on corrugated galv.

ttm

CJhaughey wrote: »

I think thats referring to zinc/aluminium type sheeting not galvanised steel.
I have never had a problem using lead flashing on corrugated galv.

I'm not sure on that one, having read bits and bobs all over the web I was under the impression that most if not all new CGI was Zn/Al coated? But who knows what the stuff is I've got?

slimjimmc

CJhaughey wrote: »

I think thats referring to zinc/aluminium type sheeting not galvanised steel.
I have never had a problem using lead flashing on corrugated galv.

It's the same as the galvanised iron sheeting we get here.

They recommend (and I recall reading similar advice elsewhere) that you don't cut with a disc as it can damage the coating, I suspect due to excessive heat.

Handling and Cutting of CGI
For safety, wear gloves when handling CGI. Ensure your hands or gloves are clean, especially when handling zinc/alum which can mark. Use a coloured pencil for marking steel, as lead or black pencils contain graphite which promotes rusting. CGI is best cut using tin snips, but for larger cuts it may be necessary to use a power saw with a steel cutting blade or a power nibbler. Avoid using abrasive discs as they can cause burred edges and coating damage. Where possible cut sheets on the ground, and always clean off any swarf and metal filings progressively during the installation. Dispose of off-cuts carefully.

[Edit]
Alternatively you could try just tearing it, it seems to work for this guy :eek: http://njhurst.com/blog/01275442740
[/Edit]

ttm

CJhaughey wrote: »

I used a 4.5" grinder with a stainless steel cutoff disc.
The cutoff discs are very thin 1.5-2mm and cut corrugated very well.
You would be advised to get a few as they can wear fast.

After testing various methods thats what I did.

I got some of the very thin discs about 1mm thick and while they don't last long they cut very quickly and accurately. The much thicker cheap Lidl disc's (also marked for use on stainless steal) lasted twice as long but were slower to cut as they had to grind away more metal.

Anyone recommending using tin snips especially on the heavier gauge sheets must have some magic tin snips I've never managed to find.

CJhaughey

ttm wrote: »

After testing various methods thats what I did.

I got some of the very thin discs about 1mm thick and while they don't last long they cut very quickly and accurately. The much thicker cheap Lidl disc's (also marked for use on stainless steal) lasted twice as long but were slower to cut as they had to grind away more metal.

Anyone recommending using tin snips especially on the heavier gauge sheets must have some magic tin snips I've never managed to find.

I know, I tried various things but the thin discs worked the best for me.
They do wear fast but its not like you do this job all the time.

ttm

Discs I used were marked as being 1.2mm thick, they do about 15ft (7sheets) before they need changing.