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Discussion Starter #1
I would appreciate some advice. I am installing skylight shades (unfortunately 20 feet up...) that have metal tracks on the sides. While I assume the metal tracks are aluminum, I don't really know. They are also finished with white paint. Unfortunately, I have to trim about a quarter inch off the ends of them. The profile is "U" shaped with a few different ridges and indentations. I would have attached a photo, but didn't see how to do that on the site. The base of the "U" is about 3 inches long and then one side is 1 inch tall and the other side is half an inch tall. Everything but the bottom of the "U" is visible once the track is installed.

I'd like to know how to trim them in a way that retains the shape of the metal (doesn't mangle the little ridges, etc.), and also leaves clean edges with minimal damage to the paint. The tools I have: miter saw, hacksaw, and tin snips. My initial thought is to put a piece of wood inside the "U" of the track and then cut it with the miter saw using just a regular wood blade. I'll probably be doing a total of less than 10 cuts.
Some questions:
1) what is the best way to do this, especially given my current set of tools
2) IF it is a good idea to put a piece of wood inside the track to help, does it need to be a tight fit or can I have a quarter or half inch gap between the wood and the side of the "U"?
3) To get the cleanest edges, and the least damage to the shape of the metal or the paint, do I cut it with the "U" facing upward or downward? I think this is the same as asking is the cleanest where the blade first starts the cut or where it ends the cut
4) Is it helpful to put on masking tape and then cut through the tape?
5) Do I need any lubricant on the saw blade?

Thanks in advance for you advice! Hopefully its not too many questions in one post.
 

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johnep
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I would just confirm metal is alloy with a magnet.
There are special alloy blades available. In the pas, I have used Bosch blades on a jig saw to cut alloy.
johnep
 

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First determine if it is aluminum or not. If it is aluminum, I have used a miter saw with a carbide tipped blade and had good results, but I cut very slow. Even then you will need to remove any burs with a knife or file. Be SURE to wear goggles to protect your eyes and hold the part tightly to the miter saw. If it is some other metal, someone else will have to chime in on that. But I would use a diamond angle grinder or as stated, metal cutting saber saw.
 

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He does not have a jig/saber saw.


I am assuming that the 20" high comment has nothing to do with the cutting.


From your description I cannot tell just how much metal you will need to cut through. If not a lot then I would just use your hack saw.


George
 

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He does not have a jig/saber saw.


I am assuming that the 20" high comment has nothing to do with the cutting.


From your description I cannot tell just how much metal you will need to cut through. If not a lot then I would just use your hack saw.


George
I didn't read too well, I didn't catch he didn't have a saber saw. Man I need some coffee. lol
 

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As BigJim said, IF it's aluminum, a miter saw will cut it. Holding it securely is very key. Because the teeth are pointing up when cutting small stuff near the fence, the blade wants to pull the material up, bending it or worse. In my experience, a hand Usually isn't enough to hold it securely. A clamp is better, especially to keep your hands out of there. Your idea of making a wood sandwich is a good idea. A blade with more teeth is good too. And as BigJim said, go slow. The teeth tend to grab if you cut too fast.
 

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The tin snips will deform the shape, no way around that.
Sawing would be your best option.
The key to a clean cut, regardless of which saw you use, is fine tooth count 32 for hacksaw , 60 for miter saw. You want the blade to "cut" not grab the material. Light pressure and a slow feed rate should do the trick. Start the cut where the piece is the weakest, do not cut the strongest side first or you lose all the support. If this means you must use a wooden spacer block inside the "U" then it should be a snug fit.
 

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CharleyL
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Might be a good time to go to Harbor Freight and pick up a carbide metal cutting blade for your miter saw. You won't need a 14" if the needed blade hole size can be found in a smaller diameter. It will actually work better if it's smaller in diameter. They work better at lower shaft speed, but will do what you want very quickly.

In my metal fab shop I have special metal cutting saws very similar to miter saws, but designed for cutting only metal. The only real difference is the shaft speed, which is usually about 60-80% of woodworking saw blade speeds. I gave this same info to a friend and he is very happy with his blade. They will cut mild steel and non ferrous metals very well, and will last quite a while, if you don't bind the blade in the cut, or cut so slowly that you heat up the work so it hardens at the cut point. Feed it a little aggressively, and you won't have this problem. Be certain to wear safety glasses, a full face shield, long sleeves, and leather gloves when you do this. The saw dust from cutting metal is very hot. Make certain that your shirt is fully buttoned up as well, or you may break into a welder's hot chip dance immediately following the cut. After your first successful metal cut with this I'm certain that you will find other metal things to cut with this blade, so hang it up nearby for your next metal project.

Charley
 

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Ive cut this sort of thing many times with a mitre saw. But if you have a really nice blade, swap it out for a less expensive spare, or if you want to be certain, they make metal cutting blades for mitre saws.

Put the U channel with the main flat pointing upwards (meeting the blade first) far less likely to deform the material this way, in my experience.

If its thicker, then a grinder with a cut off blade would be best.

In any case, the paint will burn slightly.

A hack saw may work, but good chance the cut will not be perfectly straight and possible to deform aswell.

Perhaps there is a recommended tool to trim the parts down in the manual. Surely your not the first to need to do so. Check there first.


Sent from my iPhone using Tapatalk
 

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Discussion Starter #10
Thanks for all the replies, including the safety information and specific instructions from experience. It is really helpful guidance and I am close to giving it a shot. Here's some extra information
-the metal that is bent into this "U" shape is about the thickness of a penny...if anybody remembers what a penny looks like. I can't tell if the material is aluminum. It is light in weight and is NOT magnetic. There is nothing like a data sheet that tells me.
-Mentioning it is 20 feet up is just me whining.
-I forgot to mention that I also have a Dremel if that would be useful
-In answer to a question, these tracks were custom cut to the "proper" length and so there is no standard guidance on how to cut. The skylights are recessed and my measurements were off.

I admit that it would not have thought to clamp this or even roll down my sleeves due to flying metal bits.
 

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I would bet that is aluminum as it is non magnetic. If you can fit a piece of wood inside that would be a plus. I would cut it standing on edge with the open side toward the back of the miter saw, to me that would be less chance of the blade grabbing the metal. Just cut really slow and that should do it. Also with the wood inside, it may not bur as bad.
 

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Because the metal is fairly thin, the blade may have a tendency to deform it, especially at the edges where the blade will enter or exit the cut. Your idea to put a board inside is a good one.


I bought one of these metal cutting blades from Harbor Freight for under $10 years ago. I was skeptical but was amazed at how well it worked on steel. I’m sure it would work on aluminum too. Just make sure your saw’s RPM doesn’t exceed the rating on the blade.
 

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Hopefully you have plenty of extra track. Do some practice cuts with your extra. Having done it myself, I would be tempted to use the miter saw with a carbide blade. As suggested, putting a piece of pine inside helps keep the track from deforming. Cut right through the wood or position the wood just inside your mark so you miss it. Whatever works best for you.
 

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Discussion Starter #16
Here's what I ended up doing:
-miter saw, carbide blade (42 teeth on 8.25 inch blade)
-wood block inside the "U" to help prevent it from deforming
-positioned it faced down, so the back of the wide base of the "U" was what got hit first by the blade. while someone mentioned positioning it with one of the sides on the top, the shape made it too hard to keep it in position
-gloves, long sleeves, and of course eye protection
-cut slowly

It ended up being a nice clean cut, didn't deform the metal, little bits of metal went flying everywhere (including my gloves), and lots of cleanup. If I had any spare track to practice on, I'd test using a hacksaw just to have less cleanup. But, otherwise I'd do it the same way.
Thanks again.
 
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