Cutting 20ga galvanized sheet metal

Aviatordave · Jul 29, 2020

Hey folks,

I got a project that I’m starting on that involves some 20ga galvanized steel. I haven’t picked up the metal yet. I’ll have it tomorrow, will probably start work on it this weekend.

I have to cut several pieces out of a 48”x96” sheet. All straight cuts. No curves.

I’ve fabricated a lot but have very little experience with large, thin sheets. I own a set of aviation snips. Think I’ll be ok with the straight snips on 20ga galvanized steel or am I asking for really sore hands?
Should I be looking at a different tool? A nibbler? I can use a grinder with a cut off wheel but I’m hoping to avoid the mess.

What’s your experience?

-Dave

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sberry · Jul 29, 2020

Depending on how much I wanted to cut might get a Menards shear, about 60$ and cut 20 well.

harley jim · Jul 29, 2020

Harbor freight

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sberry · Jul 29, 2020

Yup, that be it.

Aviatordave · Jul 29, 2020

Might just have to go to HF.

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DTE · Jul 29, 2020

harley jim said:
Harbor freight

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I have that same one. That is one of the best/most useful tools I have ever bought.

BD1 · Jul 29, 2020

I bought the Milwaukee Metal cutting circular saw. It's a amazing tool for flat sheets. I cut 20 gauge with it.
Depending if this is a one of two time deal. Have a, sheetmetal shop shear what you need. OR invest in a 48" shear.

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Lwel9226 · Jul 30, 2020

I have one of those.... It cuts 16-18-20 ga very well....
I know they are rated for 14 ga ****....
I burned up the first one I had on the first day cutting 14 ga.... Brand new tool didn't even last a day.....

LynnW

cvairwerks · Jul 30, 2020

Depending on length of cuts, nibbler or power shears would be better. Galvanized will be hard on the aviation snip blades....

sberry · Jul 30, 2020

I ruined mine on 14 also, couldnt help myself and absolutely didnt need to do it. I should buy another one and will next real sheet job.

Aviatordave · Jul 30, 2020

Longest cut will be 48”. I ordered a metal cutting blade for my circular saw from Amazon. Picking up metal today. Blade will be here Saturday. From the reviews it looks like it works well out of the gate but doesn’t last long. I don’t need it to last that long so we’ll see. Was the least expensive option that should produce the few, straight, clean cuts I need.

I’ll report back after the weekend.

Thanks for the tips!

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gayler · Jul 30, 2020

Make sure to use PPE. Ears, eyes and lungs. Zinc from cutting or welding will make you sick. http://dtspecializedservices.com/blog/posts/view/196/risk-factors-in-cutting-galvanized-steel

Aviatordave · Jul 30, 2020

Always good advice, gayler,

I’m a welder, so I’m very familiar with the dangers of zinc/galvanized metal and the resulting metal fume fever. ; -)

That’s a good tip to pass on to anybody and everybody.

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Graham08 · Jul 30, 2020

Lwel9226 said:
I have one of those.... It cuts 16-18-20 ga very well....
I know they are rated for 14 ga ****....
I burned up the first one I had on the first day cutting 14 ga.... Brand new tool didn't even last a day.....

LynnW

The Kett shears those are a copy of actually will cut 14 gauge. They cost a bit more than $49.95, though.

Richard D · Jul 30, 2020

My supplier will shear it for a dollar a cut, did you ask them if they can cut it for you?

slopdog · Jul 30, 2020

hands down the best (cheap) tool for cutting sheet metal (imo)

joeswamp · Jul 30, 2020

Lots of folks don't know this, but aviation snips are really precision tools for trimming off that last 1/8-1/4", although you can use a pair of them to cut a strip in the middle of a sheet.

This guy shows how they're properly used:

HMCFab9 · Jul 31, 2020

I'd go to a sheetmetal shop, or HVAC place & have them shear it for you.

It only takes seconds to shear it & it might cost you less than having to buy a specific tool to do it. (& it will be a better cut than anything you could do yourself)

danski0224 · Jul 31, 2020

slopdog said:
hands down the best (cheap) tool for cutting sheet metal (imo)

On 20ga, the side of the cut passing over the throat will be distorted using a Unishear.

A double cut shear might only distort the sheet a tiny bit, right next to the cut.

A saw with a metal cutting blade can provide a nice cut using a guide. But it will be noisy as ****, and instead of sawdust, you get hot tiny metal chips everywhere. Definitely need earplugs. Safety glasses alone won't be good enough if your eyes have any value to you.

matt_i · Aug 1, 2020

You can score it with a utility knife against a straightedge and snap it back and forth like trim coil.

However its 1 blade per cut.

The other tool I used for my ductwork was a Knipex hand nibbler. Leaves a tiny serration on the cut but since its double shear it leaves no stress in the material like aviation snips.

Monza Harry · Aug 1, 2020

slopdog said:
hands down the best (cheap) tool for cutting sheet metal (imo)

I have the Princess Auto version of those power snips [HF's northern copy cat] I haven't used mine much yet but my buddy has the Makita version and they F@#$%@G CUT! No kerf loss either same with having it done with a foot shear. Keeping it straight will be a challenge though.

danski0224 said:
On 20ga, the side of the cut passing over the throat will be distorted using a Unishear.
A double cut shear might only distort the sheet a tiny bit, right next to the cut.
A saw with a metal cutting blade can provide a nice cut using a guide. But it will be noisy as ****, and instead of sawdust, you get hot tiny metal chips everywhere. Definitely need earplugs. Safety glasses alone won't be good enough if your eyes have any value to you.

As Captain Kirk said to Scotty: Get those F#$%^*G Shields UP! And taping up your sleeves and neck line for long cuts will NOT seem silly if you try it first without, Don't ask for details on how I know this I'm taking the "Fifth on this matter, please pass the "Polysporin and band-aids "

For using the saw I usually try and put a piece of sacrificial wood (ply, Masonite)over as the thin material can and does grab and create mayhem. Some angle clamped to the top [and well supported from the bottom] will act as an awesome fence keeping things nice and straight. Harry

danski0224 · Aug 1, 2020

I'll wear a long sleeve hoodie if I have to use a circular saw to cut metal.

The specific metal cutting saws aren't too bad because they have a completely enclosed guard system. The Milwaukee corded one is quite good.

A regular wood circular saw or miter saw with a metal cutting blade is another matter entirely.

At a minimum, I'll wear a face shield over safety glasses. The preferred method is goggles over safety glasses and a face shield. The industrial places I've been to witb an actual safety program will require Spoggles.

The face shields that fit over a hard hat will trap debris in the groove that the hat fits into. This is a disaster waiting to happen, and it happened to me.

Only the MSA face shield has a rubber deflector to keep debris from getting into that groove. Otherwise, the other style needs to be taped so it is sealed.

Brush/shake/blow out your hair and above the goggles or glasses before removing them.

Aviatordave · Aug 2, 2020

You guys are giving some great advice. I’ll definitely load on the PPE. I’ve got plenty of it. It’s a pretty common practice for me to wear safety glasses under the face mask. I’ll have ear muffs and a hood for this as well as long sleeves. I’ve been the recipient of too many lessons over my years to be cavalier about it.

Somebody above asked me what my supplier would charge per cut. I’m not sure about sheet metal but they charged me $25 to cut three pieces of 1-1/2” angle iron in half so I could fit it on my 10’ trailer. And I’m pretty sure they did all three pieces in one cut. I didn’t even bother asking for the cut cost for sheet metal.

I’ll be cutting it with the new saw blade soon. I’ll upload some pics with the results. For now, it sure looks pretty as a temporary top for my project table!

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bobabuee · Aug 8, 2020

dam $25 dollars for 3 cuts that more than what 3 peices cost me... holy **** going on there

ttpete · Aug 10, 2020

slopdog said:
hands down the best (cheap) tool for cutting sheet metal (imo)

That's a Desoutter style throatless shear. I have one that's rated for 14 gauge steel. Works great.

Terry D · Aug 11, 2020

I just did a project with 20 gauge galvanized sheet metal. I used the Lenox blade for thin metal in my cordless circular saw. Clamped a straight edge on the metal for a guide, Worked great. Its pricey, but I use it for cutting conduit and Unistrut for my job.

https://www.amazon.com/gp/product/B00279PAI4/?tag=atomicindus08-20

Aviatordave · Aug 17, 2020

Well, it all came out great. Went with a carbide circular saw blade. Nice, clean, smooth cuts. I used a piece of sacrificial 2x12 under the sheet metal, clamped a straight edge to it and went to town. (After changing the depth of cut on my saw so I did’t cur down i to the work bench.

Thanks for all the good advice!

Here’s some pics.

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Cutting 20ga galvanized sheet metal

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