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Cutting thick aluminum and metal temper

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brothapig(at)HOTMAIL.COM
Guest

Posted: Thu Feb 07, 2008 6:50 am Post subject: Cutting thick aluminum and metal temper

Guys and gals, I am scratch building and last night I cut out my spar root fitting (I don't have the number right in front of me) for my 701.  It is 3/16" 2024 T4 aluminum, and I used an angle grinder with a cut-off wheel to make the rough cut, and then finished it with a disk sander, and finally a hand file.  Turned out pretty nice if I must say so myself   However, I'm now sitting here at work thinking about what I had done last night, and I am now wondering; could I have heated the bar stock up enough to change the temper?  It never got extremely hot, but it was too hot to hold onto.  It air cooled from that point.  I'm not real familiar with the heat treatment of aluminum, so I thought I would post the question here.  Any thoughts, or am I just being too worried?

  [quote][b]

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bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Thu Feb 07, 2008 8:24 am Post subject: Cutting thick aluminum and metal temper

I'm no expert on metallurgy, this is just information I've picked from my personal research: The "T4" means the metal has been solution heat treated and then allowed to naturally age harden. The heat treatment takes place at 300º-450ºC. I don't think you'll effect the strength of the metal much unless you heat it above 300ºC.

A saw blade will generally work better than a grinding wheel for cutting aluminum. The grinder tends to load up with aluminum, which slows down the process and generates a lot of heat. A band saw is ideal but I've found that even a hack saw works better than a grinder in most cases. Some people say a circular saw with a laminate blade works well also but a face shield is mandatory equipment.

On Feb 7, 2008, at 9:46 AM, Ryan Vechinski wrote:

 	  Quote: 	
		  Guys and gals, I am scratch building and last night I cut out my spar root fitting (I don't have the number right in front of me) for my 701.  It is 3/16" 2024 T4 aluminum, and I used an angle grinder with a cut-off wheel to make the rough cut, and then finished it with a disk sander, and finally a hand file.  Turned out pretty nice if I must say so myself   However, I'm now sitting here at work thinking about what I had done last night, and I am now wondering; could I have heated the bar stock up enough to change the temper?  It never got extremely hot, but it was too hot to hold onto.  It air cooled from that point.  I'm not real familiar with the heat treatment of aluminum, so I thought I would post the question here.  Any thoughts, or am I just being too worried?

	


 -- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.



 



 [quote][b]

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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

pilotdna(at)HOTMAIL.COM
Guest

Posted: Thu Feb 07, 2008 9:53 am Post subject: Cutting thick aluminum and metal temper

Hi Ryan,

Don't worry, you didn't hurt the 2024.  



It is common practice at Delta TechOps and Northrop Grumman to trim aluminum parts on-wing with a die grinder and thin cutoff wheel then final trim with a 90 degree die grinder and 50 then 120 grit sanding disk.  I'm sure it is done elsewhere in industry.  Even in this CNC era, a lot of jets have "trim to fit" in the drawing notes.



At Delta, it was normal to leave aluminum fittings on composite parts that were being repaired with a hotbonder at 350F for several hours, as long as the fitting was not directly under the repair.  300F was considered a safe cutoff for the aluminum part.  For metalbond repairs, 2024T3 is directly heated to 200F for several hours to cure the film adhesive.



Happy Building,

Doug E.

601XL TD Corvair



do not archive

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ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Thu Feb 07, 2008 12:24 pm Post subject: Re: Cutting thick aluminum and metal temper

A metal cutting blade in a jigsaw works really well. I have a horizontal/vertical bandsaw and I still wind up using the jigsaw all the time.



[quote="brothapig(at)HOTMAIL.COM"]Guys and gals, I am scratch building and?last night I cut out my spar root fitting (I don't have the number right in front of me) for my 701.  It is 3/16" 2024 T4 aluminum, and I used an angle grinder with a cut-off wheel to make the rough cut, and then finished it with a disk sander, and finally a hand file.  Turned out pretty nice if I must say so myself   However, I'm now sitting here at work thinking about what I had done last night, and I am now wondering; could I have heated the bar stock up enough to change the temper?  It never got extremely hot, but it was too hot to hold onto.  It air cooled from that point.  I'm not real familiar with the heat treatment of aluminum, so I thought I would post the question here.  Any thoughts, or am I just being too worried?

   	  Quote: 	
		  [b]

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macstar(at)raider.co.nz
Guest

Posted: Fri Feb 08, 2008 12:56 am Post subject: Cutting thick aluminum and metal temper

I wouldn't take the risk of overheating such a critical part. An angle

grinder spinning at 12,000 RPM could possible generate enough heat to cause

problems. There is only a 5 deg tolerance when this metal is heat treated.

Would have to look up the temps - its around 400 Deg F I think. If this is

exceeded it can have a dramatic effect on its metallic state and of course

mechanical properties. 



Ian McClelland

601XL

Working on Fuselage. 



 

8:57 p.m.

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cj.tremblay(at)videotron.
Guest

Posted: Fri Feb 08, 2008 5:47 pm Post subject: Cutting thick aluminum and metal temper

Hi Ryan,  

   

For myself I cut the flat bar with a band saw (diagonal cuts)  and with a circular fix table (transversal cuts), with an soft 56 toot soft metal blade  ( waxed with a candle). No heat at all, metal stay cold, I can hold it anytime during the cutting process, by hand with no gloves. The AC-4313-1B from FAA, always recommend (like a general rules) not heat aluminum, in the cutting or sanding process, metal cutting process should always permit to handle it by hand to not alter electrical or mechanical properties. But, cutting aluminum with a band saw requires very long experience with a band saw. This operation could be dangerous and can scraps the flat bar easily.  

   

Note : negative impacts for your spar depend on where are located the cut on the bar and the spars.   

   

   

See following pages for more info on the process that used for cutting my spares flat bar.     

http://www.zodiac640.com/Garage_page.htm/  

Christian Tremblay  

A guy who build a CH640 aircraft from plan  

http://www.zodiac640.com/  

  

         

  

De : owner-zenith-list-server(at)matronics.com [mailto:owner-zenith-list-server(at)matronics.com] De la part de Ryan Vechinski

 Envoyé : Thursday, February 07, 2008 9:46 AM

 À : zenith-list(at)matronics.com

 Objet : Cutting thick aluminum and metal temper  

  

   

Guys and gals, I am scratch building and last night I cut out my spar root fitting (I don't have the number right in front of me) for my 701.  It is 3/16" 2024 T4 aluminum, and I used an angle grinder with a cut-off wheel to make the rough cut, and then finished it with a disk sander, and finally a hand file.  Turned out pretty nice if I must say so myself   However, I'm now sitting here at work thinking about what I had done last night, and I am now wondering; could I have heated the bar stock up enough to change the temper?  It never got [i]extremely[/i] hot, but it was too hot to hold onto.  It air cooled from that point.  I'm not real familiar with the heat treatment of aluminum, so I thought I would post the question here.  Any thoughts, or am I just being too worried?   	  Quote: 	
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