How to Make a Basic Pentagon Stool/Side Table

In this Instructable I'll show you how to make a simple stool/side table. I needed a workshop stool so I could sit while welding but I also want to learn to make things that are good enough for the house so I learnt a lot making this since I'm new to welding. Originally it was meant to have a detachable top but I didn't have any suitable material in the colour I wanted. When I do make it, I'll create another Instructable and attach the link here.

-Steel and wood cutting tools

-Welding machine

-Angle grinder

-Measuring and marking tools

-Angle measuring

-Smooth finish sheet

-Steel square tubing

-Steel flat stock

-Drill

-A few short screws

-Clamps

-Something to sand with

-Spray paint of your choosing and primer

-Scrap wood/sheet goods are generally helpful but not necessarily needed to complete the project

-PPE

I'll be using 25mm square tubing because that's what I had lying around. Ideally I would have used something in the range of 35-45mm square tubing. I don't have a protractor so I'll be using my table saw to cut a piece of timber at the angle I need. The interior angle of a pentagon is 108°. Since we want the 2 pieces to meet in the middle we need to half that. You may be tempted to cut everything at exactly 54° but when it comes to interior angles where the outside corner is more important than the inside, you should always under cut. I'd recommend undercutting by 0.5°. I usually work with timber and 1° is what I'm used to but I found the interior gap to be too large when welding.

The length of each side of the pentagon is 200mm. You will need 10 pieces.

The length of the "legs" is 490mm. You will need 5 pieces.

The tabs are 35mm. You will need at least 6 pieces, 10 if you want to be extra careful. Remember to drill the holes first.

Now that you've got the material ready to go, it's time to cut them.

I'll be cutting the 2 pentagons out first. Each need to be 200mm from the long ends. This can be done by marking each end at 200mm and then marking the interior angle with a protractor. I just used my table saw to cut a piece of timber at the angle I need and butted it up against my steel cutting saw. If you use this method, make sure you're cutting trapiziums and not parallelograms by flipping the stock after each cut. It's more important that all pieces are the same length rather than exactly 200mm. If all the pieces are 202mm, that's fine!

Once you're done, line things up and make sure it looks good before moving forward.

To find the length, I spaced 2 pieces of the pentagon on the floor and eyed it. The length turned out to be 490mm. The angle is 15°. Unlike the pentagon, you do want parallelograms so don't flip after each cut.

Now is a good time to drill your holes in the flat stock and cut your tabs out. My tabs were around 35mm.

First things first, remove the burrs. You can use a file. I have a bench grinder so that's what I used.

Set your pieces up. I'm tacking 3 pieces at a time. Use your angle find tool to line things up. You can use a piece of cut timber if that's all you have. Once you're happy with the set up, clamp it and begin tacking. I'm new to welding so I won't be advising you to copy me exactly but doing it my way will still work.

I then tacked the other 2 pieces together before placing them to form a pentagon. Adjust everything so the angles are more or less the same and weld it.

My square tubing had holes in it so I filled those up.

Before you do this, please check step 6 first as it will save you time and make it easier for you. Same sort of deal as before. Tack first, make adjustments, clamp, and weld. You can use timber to align everything up. Just make sure the pentagons are parallel to each other.

Assuming you read through step 6, now you should be able to weld the tabs. Take a scrap piece of the sheet good you plan to use and use that to space your tabs from the top. I wanted it to be flush so I just layed it on upside down and welded it.

Once you're done, grind your welds flat or leave them if that's the look you prefer. If you gind them flat, be gentle. I didn't and I've learnt from that mistake.

I used a spray on metal primer. Any will do but the cheaper stuff may require 2 coats. I gave it a light coat of the colour I wanted to use as well but there's no need to unless you want to see how it'll look.

Once it was dry enough to touch, I placed it on top of my smooth sheet goods and marked the interior with a mechanical pencil. When you do it, you should do the marking before you weld the legs; It'll be easier and save time. I then used a cutting tool(in my case it was a jigsaw) and cut just outside of the line. Sanded to the line. Knocked the corners off a tad and then tried to fit it. Your pentagon's won't be perfect either so make markings to indicate which one is the top and which one is the bottome, as well as which side of the sheet fits best to which side of the frame. I used an 18mm sheet. I tried it with a thinner sheet but it was too flexible.

Once I was happy with the fit, I sprayed the pentagon top and bottom glossy black.

I gave it all a few more coats and then just screwed the bottom and the top to the tabs.

That's pretty much all there is to it. Quite basic but as I mentioned earlier, there was meant to be more to it but I didn't have the right materials.

I hope you've enjoyed my first Instructable. If there's anything I forgot to mention please let me know. Thanks!