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View Full Version : how to cut a 14 inch hole



Five Seven
05-02-2016, 09:46 PM
I am trying to make a fan shroud for 14 inch fans and I am not sure how to go about cutting the large holes. Is there a particular tool I should use that would work best? Thanks in advance.

NickP
05-03-2016, 06:50 AM
What material? What gauge? Do you have aviation shears? Plasma Arc? Jig Saw (questionable)?

JT56
05-03-2016, 09:44 AM
I think HF has different sizes lol

https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcQP3EveGPPQUY-NVj8nVewKPOvEjnSBugzIpIR_QoogQByzJ7hyGA

WagonCrazy
05-03-2016, 09:50 AM
depending on the material and thickness, I would think aviation shears would do it.
5993

chevynut
05-03-2016, 11:46 AM
I think it would be best to know what tools and resources Five Seven has before one can answer this question. For example, to me the easiest and best way to do this would be using a CNC laser. Does he have access to one? Next would be CNC Plasma. Again, does he have access to one?

Using the tools I have I would use my manual plasma cutter and cut close to the line that I made with a large compass, dinner plate, or whatever. Then I would use my die grinder with a burr to cut close to the line, and finish with a sanding drum on my die grinder or drill press.

Without a plasma cutter I would use my die grinder and a cutting wheel to rough it out, then finish as I described.

I've never liked using any kind of snips on sheetmetal as they always roll the edge or distort the metal, and are difficult to use, imo. I have a few pairs from my aircraft mechanic days, but rarely use them.

I made these pieces for my 12" fans using the method I described. There are multiple pieces but the method would be the same if it was one. And no, it's not heavy.

http://www.trifivechevys.com/attachment.php?attachmentid=5994&stc=1

55 Rescue Dog
05-03-2016, 02:33 PM
An electric shear like this, is by far the best way to cut distortion free radius cuts in sheet metal. I have a milwakee with the center moving cutter, which works great on straighter cuts, but one like this is the way to go. There are cheaper knock-offs. Works similar to a Beverly shear. Otherwise, just clamp it to thin plywood, and cut it with a jig saw. Much cheaper than a CNC plasma cutter for a one off cut.
http://www.ebay.com/itm/MAKITA-JS1602-Electric-Metal-Cutting-Shear-16-Ga-/272222887204?hash=item3f61bf9d24:g:bzsAAOSwxcRW9ff M

567chevys
05-03-2016, 03:16 PM
I have used the MAKITA JS1602 Electric Metal Cutting Shear. They are nice units

Sid

chevynut
05-03-2016, 07:19 PM
We still don't know what the OP has at his disposal in the way of tools and equipment. It's often cheaper to pay someone to do the work than to buy a $300 tool like an electric shear for a one-time deal.

MP&C
05-03-2016, 07:29 PM
I would suggest offset snips in right and left hand. This will explain why.....



https://www.youtube.com/watch?v=qAOQfUaRZyw&feature=related

chevynut
05-03-2016, 07:47 PM
Even if you use tin snips to finish the hole, you still have to rough-cut the hole out with something. You can't just plunge the snips into the sheet. Five Seven, tell us what tools you have.

Five Seven
05-04-2016, 07:11 AM
Sorry guys I have been traveling. I have an air compressor and don't mind buying additional hand tools. I am working with 18 gauge steel.

Five Seven
05-04-2016, 07:28 AM
I have tin snips, angle grinder, typical hole cutters in the 4 inch range. I have been doing a bit of sheet metal work, but never large holes.

chevynut
05-04-2016, 07:41 AM
Five seven, I would take your hole cutters and remove as much of the metal as you can, getting fairly close to the line. Be careful that it doesn't grab the metal and spin it, or it can be dangerous. Clamp the metal down somehow when drilling. Then I'd trim it with tin snips and finally clean it up with an angle grinder. If you don't have one, I'd suggest getting a small 90 degree air die grinder and some carbide bits for it. I use the hell out of mine and I have 4 of them. Mine are Ingersoll-Rand and they're only about $50 but you can get cheaper ones that work well at Harbor Freight.

Custer55
05-04-2016, 01:06 PM
If you need something to draw your 14" circle you can make compass for large holes with a yard stick or something similar. Just make holes 7" apart in this case, 1 for a screw or pointer and the second one for a pencil, scribe or marker of your choice. With the pointer and marker points 7" apart you can make a perfect 14" dia. circle to cut to.
Brian

Five Seven
05-05-2016, 07:23 AM
Thanks everyone for the input.

NickP
05-05-2016, 09:29 AM
I wonder; in this instance, were one to remove up to a 1/16 or 1/32 of finished size, could one use a plunge router with a carbide bit? If you had a circle maker for it and of course if you had the router it might be a bit less work and certainly a cleaner finish - just make certain you don't try to climb cut it.

chevynut
05-05-2016, 09:50 AM
I've used a carbide tipped router on aluminum but never on steel. Not sure how that would work but it might.