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wasted ink
12-08-2008, 01:02 PM
Machining (and Routing) Aluminum

Here is a quick write-up I did (on another board) on a few things you should know about machining/routing aluminum alloys. You might ask why this was posted on a fiberglass/car audio site. Aluminum, when worked correctly, can instantly take an install to the next step. There are many different ways to incorporate this material into installs, most of which require routing. As I have more experience actually machining aluminum than routing it, I will go over some basic things you should know that are similar between the two. Before I do that, let's take a look at some installs where aluminum has been incorporated.

http://i22.photobucket.com/albums/b339/ashezfal/2007%20sierra/PB080118.jpg
http://i22.photobucket.com/albums/b339/ashezfal/2007%20sierra/PB080115.jpg
(Courtesy of Jon Kowanetz, Handcrafted Car Audio)

http://i21.photobucket.com/albums/b277/hemiforme/IMG_0514.jpg
http://i21.photobucket.com/albums/b277/hemiforme/IMG_0526.jpg
(Courtesy of Chad Marra, Xtreme Audio & Design)

http://www.hzemall.com/wordpress/wp-content/uploads/2008/01/p1010527small.jpg
http://www.hzemall.com/wordpress/wp-content/uploads/2008/01/p10105981small.jpg
(Courtesy of Tim Baillie, HzEmall)

Also check out Robolop's BMW build (Fiberglassforums.com)
http://fiberglassforums.com/showthread.php?t=5267

First and foremost: Be safe. Make sure to wear long sleeves, along with eye protection and hearing protection. Routing aluminum throws hot "chips" away from the bit in all directions, meaning there is a large risk of eye injury involved. Also, Routing aluminum is a VERY loud process. Although this may not affect you right away (except for ringing ears) this can cause permanent hearing damage or loss down the road. DO NOT wear gloves. Gloves can easily be caught in the cutter, and pull fingers/hands into the cutter. I've witnessed this before, it is not pretty. This is my disclaimer.

The two most important things to keep in mind when machining any material are feed and speed.
Feed, typically measured in inches per minute (in/min), is especially important when routering aluminum, and any other material for that matter. Similar to MDF, forcing or running the router across the material too quickly will cause the router to "bog" down, burning the bit, and often the material, causing the router to smoke, and give of a horrible smell. Although this won't always be the case when feeding too fast, it is important to avoid forcing the bit. listen to the motor of the router, and let the bit do most of the work. If the work/bit is burnt, it is time to replace the bit and start again, watching your feed a little closer. When it comes to routing aluminum, take your time, and feed slowly. Remember, this is not MDF. After a few passes, you will get the feel for the best feed rate. Feeding too slow will cause excessive wear on the bit, or even heat it past critical temperature, which I will explain later.
Speed, measured in RPM, is harder to regulate when using a router. Although many routers have different speed settings, there are also many that have one speed. In this case, it is not critical, and the one speed will be fine for most applications. For those who have a router which allows them to control the speed, see below for an idea of where you want the speed of the cutter.

Material
So you're ready to get going, but you need material. Although most of the more common aluminum alloys will yeild the same result, some will offer easier and/or faster ways of getting there, different (better) finishes, and different chip charactersitics, which can make a big difference. Let's go over some of these alloys, to give a better idea of what we're dealing with.

1100 & 3003:
Good machinability, "gummy" in nature. This may lead to poor chip disposal.
5052:
Similar to 3003, this alloy offers good machinability and "stringy" chips. However, the machined finish is not as good as 3003.
5056: Good machinability with fairly easy chip disposal.
2017-T4/2014-T6: Both of these alloys machine to an excellent finish. 2014-T6 has better machinability because of the heat-treatment involved in making the alloy, but causes greater tool wear than 2017-T4.
2024-T3: Good machining characteristics, assuming the bit is sharp (new). This alloy provides excellent surface finishes.
6061-T6: More difficult to machine than 2000 series, sharp (new) cutters can be used with coolants to provide fine finishes, with slightly heavier cuts.
7075-T6: Highest strength AL alloy available; good machinability.

Note: I have had excellent results with 6025, and other alloys as well. If you have a question concerning these or any other alloys, feel free to ask.

Bits, Feeds and Speeds
When machining aluminum, it is best to use carbide or ceramic cutters, opposed to High Speed Steel (HSS) cutters. Where most router bits sold are in fact carbide or carbide tipped, this should not pose a problem.
Although in most cases of routing aluminum a single speed router will be used, there are different speeds at which multi-speed routers should ideally be run for best results. If the router does not have speeds in adjustments of RPM's, check the manual to see the equivalent of speed settings to RPM's. I'd recommend 8-10krpm.
As mentioned above, feed is a very important variable in machining/routing aluminum. One part of feed is the direction in which the piece is fed into the cutter. There are two variations of this.
Conventional Cutting/Milling: This is the generally "correct" way to cut with a router. This is when the work is fed against the cutter rotation. In machining applications, and also in the case of routing aluminum, conventional cutting is used to "rough cut" a piece of material. See picture below.
http://www.sperdvac.org/cutting_speeds_and_feeds/tool_conventional_milling.jpg

Climb Cutting/Milling: This is the opposite of Conventional cutting. The work is fed in the same direction as cutter rotation. Although the operator must use caution while doing this, climb cutting is the ideal way to achieve the best finish when routing aluminum. See picture below.
http://www.sperdvac.org/cutting_speeds_and_feeds/tools_climb_milling.jpg


Setup
Start by finding yourself a nice, spacious workplace. Cover anything and everything you do not want to get covered in aluminum chips. Next, decide whether you will use the router conventionally or in a table.

Conventional Routing: Start by fastening your work piece to something. I like to drill the piece ill be routing with a few holes on the edges. Make sure these screws will not get in the way of the face of the router. If there is no way to avoid this, countersink the screws to sit below the surface. I like to screw the piece to a large piece of MDF. Then, once the piece is fastened to that, I clamp the MDF to my workbench. Again, do a dry run with the router off, and make sure it will clear the clamps. You're ready to start.

Router Table: Similar to the way described above, fasten the piece being cut to a piece of MDF. Make sure the piece of MDF is the same shape as what you want the aluminum to be. Place the aluminum, fastened to the MDF, face down on the table. Using a flush trim bit and some lubrication*, feed the piece into the bit slowly, allowing the bearing to ride the temple (MDF). Keeping the bearing tight to the piece, go around your work completely, shut the router (making sure the bit is not touching the material) and clean your piece of chips/lubricant.

*I recommend A9 or any other cutting oil, I wouldn't personally recommend WD40 or similar oils.

In conclusion, there are endless possibilities when using this process. Please remember to take safety into consideration when using this information, as there is a great risk for injury here. I will continue to update this as I complete more projects using aluminum. Please feel free to PM me with any questions or suggestions you have.

probmxstyle
12-08-2008, 01:07 PM
Good write up. Glad to see people actually putting informative info up

helotaxi
12-10-2008, 02:15 AM
Feed it either too fast or too slow and the cutter is toast in a really big hurry. Much faster than with a mill thanks to the tool RPM. Important to use good bits. HSS works better on AL than on MDF and is cheaper than carbide.

And I really wouldn't suggest climb milling with AL. It's scary enough having a piece of wood flung at you. Unless you're working a thick piece, it's easier to just take a file, emory cloth and finally a buffer to the edge if you want a nice finish.

ngsm13
12-10-2008, 02:26 AM
Cools.

nG

wasted ink
12-10-2008, 10:16 AM
Feed it either too fast or too slow and the cutter is toast in a really big hurry. Much faster than with a mill thanks to the tool RPM. Important to use good bits. HSS works better on AL than on MDF and is cheaper than carbide.

And I really wouldn't suggest climb milling with AL. It's scary enough having a piece of wood flung at you. Unless you're working a thick piece, it's easier to just take a file, emory cloth and finally a buffer to the edge if you want a nice finish.

HSS may be a better case for a beginner, where the bit is going to get warn down faster, but carbide tools are the best to use on aluminum, hands down.

Climb milling is dangerous, but it is done often, by machinists too. i agree, id much rather rough cut with conventional milling, and then finish the piece myself.

helotaxi
12-13-2008, 10:04 AM
Climb milling is dangerous, but it is done often, by machinists too. i agree, id much rather rough cut with conventional milling, and then finish the piece myself.

Milling and routing are very different in that with a mill you have the piece clamped to the machine and the tool is in a rigid fixture as well. Either the tool or the work is free with a router. I know the benefits of climb milling (and the hazards) on a mill, no way it's worth the risks with a router.