Tutorial - DIY Inside Corner Bracket

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Senior member Navig has graced the our forums with another detailed how-to. This time he tells us how to make a corner bracket for connecting aluminum square tube together. There is even a bonus how-to make endplugs for the open end of the square tube you’re left with.

Navig’s thread will be merged into this article’s comments thread so the tutorial will be in the Comments section below. If the photos don’t load properly, just click this link and head straight to the forum post to read his superb tutorial.

Thanks for sharing your craft with us Navig!

– Jeremy Vaughan (hokiealumnus)

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  1. Thanks,

    I've been looking for a long time, so I went DIY.

    The project using these brackets is coming soon...I'm working 2 projects simultaneously right now both of which are about 3/4 done.

    Then I'll be doing the project based on these brackets.
    Silver solder/Plumbers solder wold work better for the next batch, its strong enough to support a structure/load but the melting point is low enough for it not to melt the joining metals. The main difference between the different solders is the melting temp of the filler material, Lead -> Silver -> Brass.

    Great guide.
    I must agree with Lord of Decay. My father is a master plumber and I have also worked as a plumber and have very much the same techniques instilled in myself.

    When soldering materials such as brass or copper a hot joint is the best method to use. This means that you heat the material up enough that simply touching it with the solder will melt the solder. This method requires more heat, but creates a much better joint.

    I can't remember if the same holds true with brass, but a simple method for knowing when copper is hot enough to apply the solder is that the flame coming off of the copper will turn green (its pretty cool looking if you havent seen it before).

    Silver solder is probably a good choice here, but keep in mind here are that silver solder costs a decent amount more than standard solder. Though in small quanities you wont end up spending too much more.

    One last thing, using enough flux is very important. If you dont have enough flux or it is not covering enough of the joint you will get a bad solder. So dont be skimpy on the flux, having more than needed isnt a bad thing.

    great guide though.
    I was thinking about this Navig and I cam up with an idea. I'm not sure if you have thought of it or considered it, and not that I don't like your idea (because I do). But this way would be less work, and not take as long. See attached below. It is whatever size angle aluminum that you would want to use. .75-1" or something. Cut your 2 45s on one side, then put it on the side of a table and use the rigidity of the table to bend the piece into a 90 meeting the 45s up. At the angle use a piece of aluminum to reinforce the angle (also at a 90). I'm not sure what screws you could use to go through the aluminum that would have a low profile, or you could counter sink them using pan head or flat head screws. I don't know, it was just an idea.
    Thanks for the info. My knowledge base = exactly what was posted above, and not a bit more.

    Literally, I was working with a machinist on a different project--"not so DIY outside corner brackets", and I mentioned how I could put together an inside corner bracket with 2 pieces of stock angle aluminum. A local company could TIG weld that for me for $80/hour. But this machinist mentioned that I could try soldering brass. I had some solder for volt mods, I had a plumber's torch for plumbing, I found some angle brass, and so I gave it a go!

    With my batch, it seems plenty sturdy as is. By design the corner brackets aren't really load bearing--the solder joint really is for resisting torquing and separation. I guess we'll see when I put together a frame.

    So, then, you recommend silver solder for the next batch?

    ps. Honored for the front page!
    Nice write up but soldering techniques need some work. Using the process in the videos you created a "cold solder joint" by not heating the base material hot enough to melt the solder without direct heat applied. Also using basic lead based solder the joint is not structurally sound to support a load or for rigidity.

    A hard style soldering method should be used when dealing with any joint which will support a load or for rigidity, aka silver soldering.

    My father was a machinist by trade and I had soldering/brazing/welding techniques instilled in me through childhood.
    And here’s what makes these 2 little mods work so great:

    After simply mounting the corner brackets together and plugging the holes, you are straight ready to flush mount plastic paneling to the frame.

    If you finish your frame nicely or paint/powder-coat it, you can even offset the plastic paneling for a little reveal:

    Step #7

    Pop the end plug out.

    Vice the square tube jig piece, then pop the end cap out. It may be stuck a bit if glue leaked to the edges.
    Step #4

    Apply superglue to aluminum end plate and plastic cube and fit them together.

    I’m using a little scrap piece to make sure the it’s nice and square.
    Step #2

    Sand your cube.

    Sand the cube down until it fits snug into the square tube piece.

    Also sand the surface that is going to receive glue.

    Snug fit:

    Step #1

    Stock material.

    I start with some strip ¾” wide, 1/16” thick bar aluminum.

    Then I cut off a ¾”+ piece (use: bandsaw, cutoff, hand miter box). Make it just slightly larger than ¾” because you can plan on sanding it down. Getting an exact ¾” square piece is too difficult without robotic aid.

    I also start with some ⅝” plastic cubes, available for very cheap at various plastic suppliers.

    You can also start with some ⅝” aluminum square bar and cut off lengths (I recommend from ½” to ⅝”).

    Finally, have a small piece of de-burred ¾” aluminum square tube (1/16” thick walls), approximately ½” length--this is going to be our jig.

    Part 2

    End plugs

    As a corollary project to my DIY Inside Corner Bracket, I will also include some instructions for fabricating my DIY End Plugs.

    As you can see from the above picture, once you’ve got your corners secured with the bracket, if you do standard straight cutting of your square tubes, you will end up with exposed tube inside.

    So let’s close it up with an end cap.