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Cutting doors out of aluminum skins

PostPosted: Wed Mar 20, 2019 8:44 pm
by lfhoward
I skinned my trailer back in 2016 with aluminum. At the time I needed to get camping quickly and covered over some side utility door openings that I had designed into my trailer from the beginning.

Before skinning the sides. Note the rectangular openings for side utility doors.
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Close up of the passengers side utility compartment:
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Doors on the workbench being urethaned.
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As it sits now with the side utility door openings covered over (wooden doors not installed):
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It’s 3 years later and I am wanting to have better access to these compartments. On the drivers side is the electrical equipment door. On the passengers side I want to store my Coleman stove and other kitchen related things. I already made the wooden doors and they’ve been sitting for 3 years. My question is about cutting holes in the existing trailer skin. Here’s the problem:

I don’t have any more matching aluminum. The rectangles that I cut out of the trailer need to become the door skins. Thus, I can’t make any mistakes while cutting. The margin of error is a 1/4 inch gap between the frame and the door.

How would you cut the aluminum out? I did my cutting with a jig saw when the aluminum was on my workbench, but I can’t see using a jigsaw here and having a good outcome. Is this a job for a router with a flush cut bit? Who has cut doors out after skinning with aluminum?

Re: Cutting doors out of aluminum skins

PostPosted: Wed Mar 20, 2019 9:40 pm
by halfdome, Danny
What you are asking I've done it on 6 teardrops.
I contact cement my aluminum skins on making a solid place to cut out the doors with a carbide flush bit.
I first drill from the inside plywood edge a 1/4" hole to pop the router bit through from the outside to the inside.
I keep constant pressure to my plywood walls but not too heavy or the bearing will sink into the plywood, ruining the cutout.
You'll need to route in a clockwise direction.
I use Amana Tool 51430 Solid Carbide InVectra Aluminum Laminate Trim 1/4 D x 5/8 CH x 1/4 SHK x 2-3/8 Inch Long Router Bit
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It's an expensive router bit but has out performed anything else that I've tried to use.
The double bearings are very helpful. :thumbsup:
With other router bits they start to give up half way around my door cutouts.
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:D Danny

Re: Cutting doors out of aluminum skins

PostPosted: Thu Mar 21, 2019 5:42 pm
by lfhoward
Danny, thank you so much for this helpful post. I didn't know that kind of router bit existed.

Today I measured my router's flat surface from the edge to the bit, and found out that I need 1-3/4" of space between the line I'm cutting and any other objects in the vicinity. That made me a little nervous so I went down to the trailer to see what might be in the way of a smooth cut.

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I see a few things that could get in the way. First, the screws that hold the aluminum down have raised heads. I would have to remove those, I think, in order for the router to slide across the surface. Second, there is a raised lip of Sikaflex caulk where the aluminum meets the trailer that makes a nice waterproof seal. This lip would keep the router from sitting flat and potentially mess up the cut. Third and last is the green metal fender (or at least the front corner of it). The distance between the fender and the door cut is going to be exactly the thickness of a 2x2... which is in reality 1-1/2 inches... not tall enough to clear the flat work surface of the router, which is 1-3/4".

This would have been so much easier if I had cut the rectangle out of the aluminum skin prior to permanently installing it. But I didn't have time to fit the doors then, unfortunately.

So thinking about what tools I do have that can cut the line and be less than 1.5" from the fender... that leaves the jigsaw. I'm thinking about drilling small holes through the aluminum from the inside to mark the 4 corners of the rectangle, then widening them with a 1/4" drill bit to fit a jigsaw blade. Then I'd trace the middle of each cut using a straightedge from hole to hole, and cut the line with my jigsaw. This will leave roughly 1/8" of aluminum around the edges that will need to be trimmed. I could probably get some of that with a flush bit for my router, at least on certain parts of the opening. Where there isn't room for the router I could shave the excess aluminum off with a file.

Does anyone have any better ideas? Is there such a thing as a mini-router with a smaller base plate?

Re: Cutting doors out of aluminum skins

PostPosted: Thu Mar 21, 2019 7:02 pm
by Treeview
Yes...small base routers are available. Do the big areas with your router then treat yourself to a new tool...and do the small areas. I’ve bought many refurbished Dewalt tools with no regrets

Re: Cutting doors out of aluminum skins

PostPosted: Thu Mar 21, 2019 8:42 pm
by halfdome, Danny
I think an offset laminate trim router would work for your situation.
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I've used mine for trimming the scribed laminate top splash edge to wall on many kitchen counter tops.
From a search it looks like Porter Cable doesn't make them anymore, and used ones are going for more than the original new price, what a shame.
Other brands have off set bases available for their small trim routers.
Here's one for the Bosch.
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I'm thinking it should fit the Bosch trim routers I'v bought at Home Depot for $99.00 each, very nice rack & pinion feature. :thumbsup:
They run on that serrated belt in the picture.

:D Danny

Re: Cutting doors out of aluminum skins

PostPosted: Fri Mar 22, 2019 6:55 pm
by lfhoward
Thanks again Danny and Treeview. My router is a Bosch and that second photo you posted was the exact fit for my unit. I ordered it and the bit you suggested. I may not get around to installing those side doors for a while but I’m glad I now have a way to do it!

Re: Cutting doors out of aluminum skins

PostPosted: Fri Mar 22, 2019 7:28 pm
by halfdome, Danny
I'm happy I was of some help to come up with a solution to your question. :thumbsup:
:D Danny

Re: Cutting doors out of aluminum skins

PostPosted: Mon Jul 01, 2019 2:29 pm
by lfhoward
Hi Danny,

I’m getting ready to do this project soon and I was wondering what speed you used on your router as you cut the aluminum? Is it slow to keep it from melting or medium or fast? I don’t want to destroy the bit or the surface I’m trying to cut.

Thanks,
Lauren

Re: Cutting doors out of aluminum skins

PostPosted: Mon Jul 01, 2019 3:24 pm
by halfdome, Danny
Lauren, I think a medium speed would work best, you could make adjustments as you go along. :D Danny

Re: Cutting doors out of aluminum skins

PostPosted: Mon Jul 01, 2019 6:54 pm
by tony.latham
You won’t destroy a carbide bit but you do need to stop and check it to make sure it’s not galling up. I wear safety glasses and a full face mask. You’ll get sand blasted.


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Re: Cutting doors out of aluminum skins

PostPosted: Mon Jul 01, 2019 8:35 pm
by lfhoward
Thanks a lot Danny and Tony. I’m working on the doors now. Once I get them finished I’ll get to the cutouts on the trailer next.

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Re: Cutting doors out of aluminum skins

PostPosted: Tue Jul 02, 2019 1:08 pm
by lfhoward
Metal cut and test fitted.

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Next up is fabricating the edge moldings that will allow the door to seal against the trailer.