How to best cut a large diameter (~14") circle out of sheet metal?

I need to cut out a 13.875" circle out of some .063" Al.  Its already formed so I can't put it on a router or anything.

I've seen large diameter, drill operated fly cutters, but the biggest I've seen has a diameter of about 6".

I can break out the tin snips, or drive an hour and a half one way to a friend's shop and use his electric shears, but I was hoping to hear a better idea for less effort than those

Hand held jig saw if you need to watch closely, sawzal if you don't?

Have you seen those little nibblers that chuck into a handheld drill? I've seen something that combines that idea with a pin and string compass for cutting HVAC ducting in place. 

Robbie (Forum Supporter) said:

Have you seen those little nibblers that chuck into a handheld drill? I've seen something that combines that idea with a pin and string compass for cutting HVAC ducting in place. 

I haven't.  I think I can picture how that would work though

matthewmcl (Forum Supporter) said:

Hand held jig saw if you need to watch closely, sawzal if you don't?

I was hoping for something with a prettier edge than that without a lot of post processing

The nibbler idea can work, but I think a jig saw may actually get you to the cleanest edge the fastest.

Find someone local with a plasma table and 5 minutes.

0.063" Aluminum? 

I would have pulled out my aviation snips and been done before you had finished making this post.

Sometimes the simplest tools are the best.

Ron's latest video can teach almost anyone new things about a tool everyone thinks they know

I have nothing to add, but the title "Tips for snips" would be perfect for a circumcision how-to. 

eastpark said:

I have nothing to add, but the title "Tips for snips" would be perfect for a circumcision how-to. 

There are some things I just don't want to see tutorials for on YouTube.

In reply to Trent :

Thank you! I definitely learned something new today. 

Keith Tanner said:

eastpark said:

I have nothing to add, but the title "Tips for snips" would be perfect for a circumcision how-to. 

There are some things I just don't want to see tutorials for on YouTube.

^^^^This.  I sure as heck ain't watching no videos with "mohel" in the title.  

Keith Tanner said:

eastpark said:

I have nothing to add, but the title "Tips for snips" would be perfect for a circumcision how-to. 

There are some things I just don't want to see tutorials for on YouTube.

I assume when you say you can't put it on a router you mean a router table but can you put a router on it? It would probably be the fastest way to get an accurate circle if you can find exact center and make a little bracket with the proper radius to tie the router to the center point.

It takes a bit to set it up, but I use a band saw.  The plate on my band saw has pre-threaded holes for accessories, but it's easy to fab this up.

I took a 4' aluminum ruler and clamped it to the baseplate flush with the blade.  Under the ruler on the edge of the baseplate I put chunk of angle steel.  Clamp the ruler and angle together and drill/fasten.  I'll be using flathead machine screws with a countersink and nylock nuts (this is as far as I've gotten on this current project).

Take the whole thing off and cut the ruler flush with the steel angle.  Now hold the angle up to the baseplate to mark for holes to mount it.

Now I can drill a wee hole every 1/16" (offset a little so they don't overlap).  Anytime I want a circle, I put a pin in the center of the material, drop it in the hole that is half my desired diameter, and bingo.  Perfect circle.

If I want to do thin sheet metal, I just dust some spray adhesive on a piece of cardboard and stick the sheet metal to the cardboard to give it a little support

In case you're more visual:

Trent said:

0.063" Aluminum? 

I would have pulled out my aviation snips and been done before you had finished making this post.

 

Sometimes the simplest tools are the best.

 

Ron's latest video can teach almost anyone new things about a tool everyone thinks they know

https://www.youtube.com/embed/x8PDRAsMDXc?rel=0

 

This is what I'd probably do. Snips will typically require 2 passes if you want a really nice edge though. (I have a rotory shear I'd do a rough pass with then a clean up pass with hand shears.) A Beverly type shear or electric shears would be the easiest, fastest way to get a finish quality edge though.

I can name 20 or 30 different tools that can do this job.  But you haven't told us what you've got. 
 

It would start for me with knowing what tools I've got, and how they work. I don't own a Beverly shear, so I wouldn't do it that way. I own a band saw, a router, jig saw, power snips, and good aviation snips. All of those would be possible, depending on my mood.

Can you have a small pilot hole in the middle?  It's gonna be easier if you can pivot off the center point. 

Jigsaw with Bosch aluminum cutting T127DF100 blade and aluminum cutting fluid. 

If you need a perfect circle, I'd use a router with a guide attached to a hole drilled at the center.  Wood working tools will absolutely cut aluminum, just go slow.  If the piece is really important you could even cut an outside guide out of MDF 

SVreX (Forum Supporter) said:

I can name 20 or 30 different tools that can do this job.  But you haven't told us what you've got. 
 

It would start for me with knowing what tools I've got, and how they work. I don't own a Beverly shear, so I wouldn't do it that way. I own a band saw, a router, jig saw, power snips, and good aviation snips. All of those would be possible, depending on my mood.

Can you have a small pilot hole in the middle?  It's gonna be easier if you can pivot off the center point. 

Part of the problem, I don't have a wide range of sheet metal tools, I was going to use this as an excuse to expand my tools.  I am on the lookout for quality aviation snips, but I'd rather something with less effort.

It does have a pilot hole in the center already.

I've done stuff like this on a table saw.  WARNING THIS VIOLATES OSHA RULES.  Put a metal cut off wheel in the table saw.  Clamp a piece of wood to the bed of the table saw.  Insert a screw half the diameter (aka radius) of the circle you want from the metal cut off wheel.  Use said screw as your center point.  Put on your safety glass, Kevlar gloves, and all the other PPE you may own.  Turn on saw and rotate material until you you have a perfect circle.  Drink an adult beverage of your choice if you still have all body parts attached.  If not tip your ER doctors and nurses.

EDIT - I just realized I've been a dumbass several times.  You can use a stick or other materials to feed the stock into the cut off wheel.  Amazing I still have my fingers.

Stampie (FS) said:

EDIT - I just realized I've been a dumbass several times.  You can use a stick or other materials to feed the stock into the cut off wheel.  Amazing I still have my fingers.

In reply to Trent :

Thanks for posting that. I learned a lot there. I used to read Ron Covell's column in Street Rodder.

Depending on what type of aluminum it is... sometimes aircraft grade .063 is mighty hard to cut even with good aircraft snips.  Just saying.

Maybe tape it off with masking tape (so the jig saw won't mar the finish), and cut with a jig saw.   File to nice finish.