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L45-1001 Aluminum Fabrication Tips

Lear 45-1001 Build History

Aircraft Aluminum Fabrication Tips

Rev 28 Nov 2018

 The L45-1001 introduction contains useful background information on this build. If somehow you have arrived at this place and have not read the L45-1001 introduction you will find it HERE:

Let’s talk metal. Aircraft alloy aluminum in particular, and how a builder with average skills and limited tooling can obtain satisfactory results. When someone uses the term “aircraft grade aluminum” they are referring to certain aluminum alloys commonly used in aircraft construction.

2024
“This is one of the best known of the high strength aluminum alloys. With its high strength and excellent fatigue resistance, it is used to advantage on structures and parts where good strength-to-weight ratio is desired. It is readily machined to a high finish. Since corrosion resistance is relatively low, 2024 is commonly used with an anodized finish or in clad form (“Alclad”) with a thin surface layer of high purity aluminum. Applications: aircraft structural components, aircraft fittings, hardware, truck wheels and parts for the transportation industry.”

Information on other aircraft alloys may be found at Aircraft Spruce HERE: https://www.aircraftspruce.com/catalog/mepages/aluminfo.php

Aircraft alloy aluminum has unique workability characteristics. Unlike common soft aluminum it is harder and cuts much cleaner.   The aluminum “sawdust” produced from blade cutting an alloy like 2024T3 AlClad looks like little grains of salt. It’s rounded and does not clog a saw blade or drill bit. This characteristic is very helpful to fabrication with limited tooling.

Many years ago I learned simple aluminum fabrication techniques from an A&P mechanic on the field where our avionics operation was located. Much of what appears below is from that experience. The writing below does not describe a step-by-step process but rather a collection of useful tips.

The MOST IMPORTANT thing I can tell you is this: USE SAFETY GLASSES! You will find that cutting metal with a jigsaw involves watching the blade CLOSELY to follow the cut line. When it's cutting, that blade will throw little fragments of aluminum UP AT YOU. You DO NOT want those in an eye, so get and USE a good pair of full-coverage safety glasses.

(1) You *MUST* use the proper aircraft alloy aluminum. It costs more than the cheaper stuff but the workability of aircraft alloys is far superior to the soft gummy stuff found in home and hardware stores. Aircraft alloy aluminum cuts cleanly and won't gum up the teeth in the cutting tool.

(2) Buy and USE something called "Tap Magic" on your cutting tools, particularly saw blades. They make a formulation specifically for aluminum alloys. It is not expensive and will pay for itself many times over in savings on saw blades and drill bits. A TINY AMOUNT applied to the working area of the cutting tool does the trick. Ron Rollo has seen some of the aluminum I cut using this process and he thought it had been cut with a CNC. Tap Magic on the tool helps to make a superior quality cut.

(3) USE a GOOD QUALITY jigsaw! I can’t say this often enough. I have an inexpensive Black & Decker jigsaw, a DeWalt 317 corded jigsaw, and a DeWalt DC330 18 volt cordless. The DC330 cordless produces MUCH BETTER results than the other two. It is more properly balanced with the right amount of weight on the head, has a superior speed control, and has a soft plastic foot cover that will not mar the part under fabrication.

(4) Use the right BLADE in your jigsaw. Get blades useful for cutting metal. Generally these will come in an 18-tooth or 24-tooth (per inch) version and you can get them in different widths. You need a skinny blade for cutting tight radius turns and a wider blade for tracking along a straight line. Experiment a bit with your particular jigsaw to find the blade SPEED that works best for the material you are cutting. When selecting jigsaw blades, IGNORE the label printed on the blade and LOOK AT THE TEETH. The best narrow blades for cutting a tight radius are actually wood trim blades, but they cut 2024T3 Alclad aircraft aluminum well. I cut the two-inch holes for the AOA indicators using a narrow wood blade. Some file dressing of small holes is required because they are a tight radius, but a round file will quickly smooth out the edges.

(5) Tape some brown Kraft paper (or butcher paper) *tightly* over the metal before you start cutting. Lay out your cut lines on the paper then cut right through paper and metal together. This will also help to prevent the jigsaw from scratching the surface of the metal as you cut. A professional machinist would use self-adhesive layout film or layout fluid (ink) and you can too, but I found that ordinary paper produces satisfactory results and is inexpensive.

(6) Once you have your paper layout in place center punch ALL the drill holes through the paper BEFORE you start cutting. The center punch dimples will help to hold the paper pattern in place as you work. If a disaster destroys the layout paper all the hole centers will be in place as a guide should you need to make a new paper layout.

(7) CLEAN UNDER THE SAW FOOT FREQUENTLY as you cut along a line. The aluminum “sawdust” produced by a jigsaw blade looks like tiny grains of salt. It will get under the saw foot and scratch the surface of the metal. I stop about every 2-3 inches and clean the area with a soft brush. Flip the saw over and clean the foot too! It only takes a couple of seconds and it will help prevent scratches on the work.

(8) TAKE YOUR TIME! You will find that the very best quality cuts are obtained when you allow the saw to proceed "at it's own rate". If you push the blade it will wander off the cut line and generally make a ragged cut. Put a few drops of Tap Magic on the blade frequently as you cut. If you get tired stop and take a break. Don't push the saw just to complete the cut. Take your time and you will be rewarded with a beautiful clean cut.

(9) Occasionally your cutting blade may wander from the marked line. I missed the line here. I re-marked it and trimmed it with a file. Don’t panic if this happens – just take your time and work the error.

Here is a photo I made when checking the AOA raw hole size. Notice the cut edges in this photo. None of them had been dressed with a file when this photo was taken. This is an example of the results you can obtain with simple tools, correct technique, and patience.  There are surely more professional methods for working aircraft alloy aluminum, but these will produce satisfactory results for the average builder with limited tooling.

Pro tip: A supply of good cookies makes this task easier. Lesson learned: When cutting the MIP one bag ain’t enough cookies!

HOME: This link goes to the L45-1001 build history introduction. Links to other L45-1001 posts are found at the END of the introduction.

Hey DonnyRay,

Thanks for this presentation,  I am liking the cookies as well.  Of course I like using card board.   How are you?  Looks like you are doing well.