Cutting sheet metal question


I have some sheet metal that I need to cut for a project. It needs to be a cleaner cut and more accurate than can be achieved with tin snips.
I considered buying a 7 1/4 inch cutting wheel (if they make them in that size) and using it in my Skill saw.
My brother said he had heard that taking a regular saw blade and turning it over so it rotates in the wrong direction, works well for metal cutting.
Anyone ever used this method or have any suggestions - pro or con?
Thanks in advance
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Bob wrote:

Andy writes: The normal procedure for checking this technique out is to get a small piece of scrap and try it out. If it works well, please post it back here....
I haven't found a way to cut metal that is cleaner than tin snips, tho. If you are referring to the serrations that happen when you move the snips forward, you are doing it incorrectly, or have the wrong kind of snips.
By the way, the finer the teeth on the blade, the cleaner the cut. Also, a metal cutting blade put into a skill saw may work also, tho it actually 'grinds' rather than cuts.
I've also used a jigsaw with a metal cutting blade. But nothing has done it as clean for me as a shear, which is what tinsnips are....
Andy in Eureka, Texas
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you might find a local ductwork or metal shp who can shear it for you. best cut that way.
so what are you building?
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" snipped-for-privacy@aol.com" wrote:

A sheet metal shop may have plasma and/or CNC plasma as well which will give you nice clean cuts for non-linear stuff that a shear can't do.
Pete C.
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i have used the 'reverse' saw blade before and it worked ok.
I have some sheet metal that I need to cut for a project. It needs to be a cleaner cut and more accurate than can be achieved with tin snips.
I considered buying a 7 1/4 inch cutting wheel (if they make them in that size) and using it in my Skill saw.
My brother said he had heard that taking a regular saw blade and turning it over so it rotates in the wrong direction, works well for metal cutting.
Anyone ever used this method or have any suggestions - pro or con?
Thanks in advance
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They make carbide saw blades for cutting metal. I have a 12" Makita blade in my chop saw I've cut unistrut, cast iron pipe and other metals. I do no the blades come in deferent sizes, you should find them with web search. Also a good building supply should have them.
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I've used the reverse blade a few tims and it works really well. Once the blade is installed backwards you need to make a new cover for the blade so that there is very little room left around the blade sticking through the table saw. I use a piece of wood just to the left of the blade to hold the metal against the table, otherwise it tends to want tot run over the top of the blade. Take your time and wear ear and face protection...

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A "zero-clearance insert";you fasten a piece of hardboard to the saw with the blade raised then drop the blade (under power) down thru the hardboard to cut a slot only as wide as the blade. (if a table saw,lower then raise the blade) This gives more support to the workpiece.
--
Jim Yanik
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Bob wrote:

This suggestion comes up pretty regularly w/ answers on both sides, generally. I've never tried abusing a blade in such a way, but can't imagine you could possibly get as clean a cut as w/ a good set of snips.
Alternatives --
Best possible cut, accuracy dependent on the operator you find is to take it to a tin shop and have them shear it.
Depending on the gage of material, you should be able to get as accurately dimensioned cut as needed w/ snips if the snips are of good quality capable of cutting the material. You can always clean up the edge w/ a good file if you leave it a tiny bit proud.
For thicker material, an abrasive blade is certainly an alternative, but it may color and/or distort the material from the temperature.
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I own a compressor, air nibbler, shears and cut off wheels. Everything except a brake, though a friend does own one. All of the other mentioned forms of cutting "shrink" or "expand" the metal leaving a very lightly rolling edge or small marks. The table saw is the nicest cut I've made though you need to make sure you don't scratch the aluminium.

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rent a compressor and a air nibbler.(used on autos to install sunroofs)
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Jim Yanik
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Bob wrote:

It might help if you could be more specific than "metal", since that includes annealed aluminum to stainless steel. IOW, a huge range of physical properties.
Huge variation of machinability.
Shear and deburr.
J
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Cutting sheet metal is tricky, even when you do it right. I have used a pneumatic tool that looks like three fingers stuck out. I have used snips. I have used a blade on a saw, but it makes so much noise and jumps so much I think I only used it once.
Accurate cutting is difficult. For me, there was a lot of time finishing. Taking an electric wire brush, and knocking down the razor sharp edges. BUT, this is tricky, and it is easy for the material to kick. Always have the material clamped down, and always feed the material in such a way to avoid kicks. Hand files and a good old sanding block are standard tools, too.
I have heard people using electric snips and hand scissors, but I have no experience with them. I believe if I had a lot of it to do, I'd invest in one of them, but only after much investigation and trial use. Manual hand cutting is very hard on the hands, both muscularly and lots of cuts. I'm sure there's something that would work for you that would give you the cut you need. It may cost a few bucks, but when you get a finished product without much additional finishing, it's worth the cost.
Steve
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wrote:

If you don't have much to cut you can get good results by sandwiching it between 2 pieces of plywood and cutting with a circular saw.
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Bob wrote:

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Bob wrote:

It might work, but ... do NOT use a carbide tipped blade!! The chips may fly off it.

I've had some luck with sandwiching it between two pieces of 1/4" plywood and cutting. But, it depends on lots of things.
WHAT are you trying to cut and what specific problems are you getting/seeing?
Pop`

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Bob wrote:

I use a circ. saw with an abrasive blade to cut sheet metal all the time. This is probably the quickest, easiest way to get a nice straight cut.
Putting a saw blade on backwards so it spins the wrong way? Sounds like the wrong way! If you really wanna try this, just be sure that you are NOT using a carbide tipped blade.
Mike
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wrote:

It will depend a lot on how thick the sheetmetal is. If you're really concerned about the clean-ness of the cut, clamp the metal between two hunks of scrap wood, and cut through the whole stack. You might also consider cutting 1/16th" beyond the line, and then grinding your way back with a sandng wheel, if the workpeice is small.
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wrote:

As is usually the case here, you don't say how thick the sheet metal is. I've had tremendous success cutting aluminum siding with a small bandsaw, which is all I could afford, and a metal cutting blate.
There is a little edge left of shredded aluminum, but I think it would brush off with my fingers. Instead I use the slightest touch of a wire wheel on a bench grinder axle. And I mean the lightest touch, because I didn't want to hurt the brown finish, which matched where I was putting the item.
I'm sure the bandsaw would work very well with much thicker pieces and with steel etc., to the limits that are given in the specs.

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