Subject: How can a poor boy cut sheetmetal w/out a shear?

From: [email-masked] (John Anderson)
Date: 30 Jun 1996 20:46:54 GMT

I use lots of .040 pre-finished aluminum.  It comes in 4x10' sheets, and
I've been trying to reduce my reliance on outside metal shops simply to
cut pieces to size.

I've got a panel saw in which I've put a rather fine-tooted circular saw
blade (7 1/4").  It makes an acceptable cut on one side, but a horrible on
on the other side (a continuous, ugly "burr").  Don't really have a
precise method to check, but alignment seems good.

My question is if there is a way to get a good cut with a circular saw
blade on sheet aluminum.  The blade I'm using is an inexpensive one -
carbon steel with probably 10-11 tpi.  It's the only thing I've seen sold
for aluminum cutting.  I have the blad set to penetrate the material about
1/4 inch.  If there's something better for this application I'd love to
know about it.

Thanks for any help.

   -John Anderson

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From: [email-masked] (Blake Malkamaki)
Date: Tue, 02 Jul 1996 00:26:58 -0400

}My question is if there is a way to get a good cut with a circular saw
}blade on sheet aluminum.  The blade I'm using is an inexpensive one -
}carbon steel with probably 10-11 tpi.  It's the only thing I've seen sold
}for aluminum cutting.  I have the blad set to penetrate the material about
}1/4 inch.  If there's something better for this application I'd love to
}know about it.
}
}Thanks for any help.
}
}   -John Anderson

Put some oil or water on the metal before you cut it.  It will cut much cleaner.

Blake
Blake Malkamaki, Little Mountain Ironworks, Concord, Ohio <[email-masked]>
>>Steam engines - Cletrac Crawler Tractors - Maple Syrup - Metal Signs<<
http://www.ncweb.com/users/blake

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From: [email-masked] (Edward Haas)
Date: 2 Jul 1996 08:34:46 -0700

--The trouble with cutting al. with an abrasive blade is that it 
gums up. If you're using a fine-toothed circular saw blade running at 
high rpm the effedt may be the same. When I bandsaw al. I always go for 
less teeth per inch, although this is more a function of how thick the 
material is: you always want several teeth in the cut or else scary 
things can happen. If it's at all possible, I would recommend cutting the 
material at a *lower* rpm with this skillsaw-type approach. 
	--If you can make do with a slightly funkier surface finish and 
if you are cutting straight lines, one thing you might try is an 
air-nibbler: there's a cheapie available from Harbor Freight and it would 
be fine for .040" al. If you cut using a straightedge to keep it going in 
the right direction, you might see some improvement in the feedrate and 
there won't be such a mess...
-- 
	"Steamboat Ed" Haas	:	Yikes, I'm 50!!! 	
	COMING SOON		:	The second THIRD of Life...
	http://www.west.net/~steamer  	
		---Decks a-wash in a sea of words---

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From: Mike Rehmus <[email-masked]>
Date: 2 Jul 1996 17:32:14 GMT

I've succesfully cut thick aluminum with my radial arm saw using
a carbide tipped blade.  No burrs and no problem.  Cross-cut by
the way.  Don't think I'd care to try a rip cut.

Safety - 

With thin material, you might get into the situation where
the material catches in the blade and then the
sheet aluminum becomes the equivalent of a gear rack and
the saw blade acts as the pinion.  At, say, 3,600 rpm, the
aluminum is really going to be moving when it shoots
out of the saw.

I'd recommend you let the outside shops shear your material
or, if you need a lot sheared, purchase a shear.

Best regards,

Mike Rehmus

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From: [email-masked] (Bart Smaalders)
Date: 2 Jul 1996 18:55:06 GMT

I used a regular cheap carbide blade in my skill 77 to cut some 3/16" aluminum 
diamond plate for the back of my jeep.  Clamp the work and wear hearing
protectors - the chips are hot and _moving_, so stand clear of the rear of
the saw.  Needless to say, you're wearing good eye protection of course.

- Bart

---
Bart Smaalders			Solaris Clustering	SunSoft
[email-masked]		(415) 786-5335		MS UMPK17-301
http://playground.sun.com/~barts			2550 Garcia Ave
							Mt View, CA 94043-1100

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From: robert brown <[email-masked]>
Date: Tue, 02 Jul 1996 09:12:24 -0700

> 1/4 inch.  If there's something better for this application I'd love to

You'll do well to cut straight aluminium with a saw, John, without 
raising a burr. If your saw is a bit on the fine side the teeth may be 
gagging on the chip, which is somewhat adhesive. Use kerosene as a 
lubricant and set the saw depth just to penetrate through. An air shear 
or nibbler is the better method, if your wallet will stretch that far.

			Regards
				Rob. Brown

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From: [email-masked] (Reg H. Beardsley)
Date: 3 Jul 1996 17:06:16 GMT

The sheet metal trade commonly uses either a screwdriver or a knife
driven w/ a hammer to cut ductwork.  I've seen it done twice.  There
is some metal deformation, so it may not suit your needs, but it
does work and it's VERY quick, albeit a bit noisy.

Friction sawing w/ a circular saw w/ a steel blade put on BACKWARDS
also works.  It's noisy and flings shreds of metal everywhere.  I've
never seen the edge it produces, so it also may not be suitable.

BTW a sheetmetal deburring tool at $5-10 will eliminate the burr quite
quickly and a very reasonable price.

Have fun!

-- 

------------------------------------------------------------------------
               I am solely responsible for the contents...

Reginald H. Beardsley                                      [email-masked]

                       Consultant/Programmer 
------------------------------------------------------------------------

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From: [email-masked] (Adrian Whichello)
Date: 3 Jul 1996 23:18:55 GMT

You could use a router and an end mill (although if you're too poor to buy a
shear, maybe a router is beyond your pocket as well :-).  I once used this
combination for a project to build a low cost microwave antenna that was made
>from  a stack of several sheets of 1/16th Al. The router followed special curves
cut on a master, but a straight cut would be no problem. Left a very nice edge,
with no burring.

Adrian Whichello                           Phone: +61 2 351 4824
Imaging Science and Engineering Laboratory  Home: +61 47 588 319 
Sydney University Electrical Engineering     Fax: +61 2 351 3847
Australia                                  Email: [email-masked]

"I wish to God these calculations had been executed by steam!" - C. Babbage

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From: [email-masked] (PARSEK)
Date: 4 Jul 1996 16:52:38 GMT

robert brown  <[email-masked]> wrote:

>lubricant

Kerosene?!?  Isn't that asking for a conflaguration?  (It is July 4th and
all, but still...)

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From: [email-masked] (Jonathan M. Elson)
Date: 5 Jul 1996 05:52:43 GMT

John Anderson ([email-masked]) wrote:
: I use lots of .040 pre-finished aluminum.  It comes in 4x10' sheets, and
: I've been trying to reduce my reliance on outside metal shops simply to
: cut pieces to size.

: I've got a panel saw in which I've put a rather fine-tooted circular saw
: blade (7 1/4").  It makes an acceptable cut on one side, but a horrible on
: on the other side (a continuous, ugly "burr").

Well, maybe you need to get a de-burring tool.  I don't know how severe
the burr is.  There are tools sold by machine shop suppliers (Enco, MSC,
KBC, Grand Tool, etc.) that you run down the edge of the cut to slice off
the burr.  This is actually necessary in nearly ALL cutting operations on
aluminum, due to the plastic flow of that metal.  These tools are
disposable, as they only cost about $4.00.

: My question is if there is a way to get a good cut with a circular saw
: blade on sheet aluminum.  The blade I'm using is an inexpensive one -
: carbon steel with probably 10-11 tpi.  It's the only thing I've seen sold
: for aluminum cutting.  I have the blad set to penetrate the material about
: 1/4 inch.  If there's something better for this application I'd love to
: know about it.

The problem is that the surface speed is WAY too high for metal cutting!
You want about 100 - 150 SFPM for HSS on Aluminum, you are probably
running 1500 - 2000 SFPM, good for sawing wood.  Look for a worm-drive
saw with the slowest blade RPM you can find.  Otherwise, there are
hand-held bandsaws for this purpose, but the throat is really limited on
those.  If the work allows, a band saw would work better, if it has slow
speeds for metal.

You could try supporting the metal on a surface, attaching a guide to it,
and scoring the metal with a sharp knife, like the carpet installers use.
Those knives with the extendable blades, for cutting open boxes are what
I have in mind.  .040" aluminum is quite thin, and should cut through in
a few passes.  You will still get a burr, but it will be quite small, and
easily removed.