spiral staircase construction

I also posted this in the metalworking forum..
After spending too much time trying to find plans for a spiral staircase, or
a kit for a reasonable cost, I've decided to start from scratch and make my own. What I plan to do is weld 4" angle iron "tread brackets" to a 3" pipe at 30 degree spacing (all material is 1/8 inch). Each tread is 8 " higher than the next one - this gives 11 treads for an 88 inch rise. I'll cut a 1 1/2" radius curve into the horizontal part of the angle iron to match the pipe I'm welding it to. The tread brackets will have welds on both sides of the vertical and horizontal surfaces. Then I'm going to drill and bolt 2 by 12 wooden tread to each bracket. Brackets will probably be 36 to 40" long as will wooden treads. I still haven't figured out the balusters, but probably will use a single rod welded to each tread bracket and somehow curve a metal railing for a hand rail (the rail will be a problem). This may sound like a lot of work, but I have all the materials on hand, a Miller 175 MIG welder and a plasma cutter. There are only 11 treads to attach, so I can get this part cut and done in a day, provided I can layout the degree spacing without botching it. The big problem I see is the railing, but I do have a small bender which I could bend short sections of pip in, and weld them together as I work my way up. I looked for kits, and none had wooden treads for less than about $2500 shipped to me in Colorado, so I have some financial incentive. Any help would be much appreciated. Thanks for being a great group.
John
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<snip>
There are only 11 treads to attach, so I can get this part cut and done in a day, provided I can layout the degree spacing without botching it.
<snip>
Speaking from a carpenters point of view, I can tell you you want to do the layout full size on the floor....Start with the diameter of your center pipe....then draw the finished diameter of the staircase...then add the tread bracket layout at 30 degrees....Startin to look like a BIG clock face on the floor.
Stand your center pole up on the layout.....plumb and brace well. Then you can level each tread bracket as you go and plumb bob down to the layout for your 30 degree spacing.
FWIW - most steel spiral stairs that I have seen have a long triangular gusset under each tread bracket and welded to both the bracket and the center pole. Wouldn't be too hard to make these decorative as well.....
For the railing, it might be possible to wrap a length of tubing around something of the correct diameter ( kinda like a spring ) and then expand it lengthwise to the correct height.....just guessing here but it may work :)
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Jeff Sellers wrote:

<snipped sound words of wisdom>
What about making individual brackets for each tread that drop over a core pipe ? That way you get to adjust out your mistakes, and you can make some simple jigs to align the parts Jeff just described ?
The coolest spiral stair I saw was shown in Fine Homebuilding a while back - the centre of the spiral was cut out of a 24" thick wall tube in a double helix !
The second coolest was the one with a huge tree trunk as the stair core.
But wood is terribly hard to weld....
Steve
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Thanks for the inputs from Steve and Jeff - The kit stairs do come with each stair as a single unit which drops onto to center pipe - you then tighten a large nut on the top of the assembly to hold it all in place - or at least this is how it was described to me. Seems the fabrication would be simpler and more solid if each stair tread bracket was welded to the central tube, but I know this leaves less room for error. I had thought about using a peeled log for this stair center support, as its going into a small log cabin, but then I'd have to attach either metal brackets or wood treads directly to the log, and making it sturdy sounds harder than just welding up an all steel one. BTW, I just went out to check my steel stock and it looks like everything will be 1/4 inch thick. Anyway, please keep the ideas coming. I will start this project soon, and the more brain parts, the better. Thanks!
John

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Doctor John wrote:

One big advantage of using the center pole and dropping treads over would be that you can weld the treads and their gussets on a bench where you don't have to contort yourself and weld out of position. Then you drop them on and you could still plug weld them to the core and weld them to each other, if you felt the need.
As for the railing, I'd lean toward welding on tabs at each vertical stanchion, then laminate a big bunch of small wood squares (say 1/4" square by as long as you can get) into the sweeping ever-changing compound curve of the rail. Either attach it to the tabs or encapsulate the tabs inside the rail.
Stuart
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I was looking at some spiral stairs on Sat. These used a pipe core. The treads slipped over the pipe and then tightened to the pipe with some set screws. There were no gaps between the pieces that slipped on the pipe core. At the other end of the tread, there was a piece that came down from one tread to the next tread and was secured with a large nut to the lower tread. These stairs were all metal, but you could do the same thing with a metal frame for each tread and then wood attached to the frames.
Dan
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If you take a spring like that and expand lengthwise it will diminish diameterwise, so it would need some bending to get in shape. I missed the start of the thread, will it be built in place or first built and then moved in place. If the former, getting such a "springroll" in position would be sort of tricky, probably easiest to lower it down from upstairs. Or make it in shorter sections. Henning
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| I also posted this in the metalworking forum.. | | After spending too much time trying to find plans for a spiral staircase, or | a kit for a reasonable cost, I've decided to start from scratch and make my | own. What I plan to do is weld 4" angle iron "tread brackets" to a 3" pipe | at 30 degree spacing (all material is 1/8 inch). Each tread is 8 " higher | than the next one - this gives 11 treads for an 88 inch rise. I'll cut a 1 | 1/2" radius curve into the horizontal part of the angle iron to match the | pipe I'm welding it to. The tread brackets will have welds on both sides of | the vertical and horizontal surfaces. Then I'm going to drill and bolt 2 by | 12 wooden tread to each bracket. Brackets will probably be 36 to 40" long | as will wooden treads.

The core pipe is the way to go. You jig up each step to a short piece of pipe that fits over the core pipe, and on the outside diameter you have, at the leading edge corner (where you would step, I guess) a vertical piece of pipe with a length to match the rise. Same diameter on the other side of the tread is a threaded coupling welded on. When you slip all these over the core pipe, you screw in a pipe through the vertical pipe into the coupling below it. This attaches the outside edge of the risers together and also serves as a way to attach a rail. Not sure if it's all clear, but this builds a whole lot faster as you just do the same thing over and over again in a jig where you can comfortably weld it up.
There's a lot of math that goes into getting this right, so feel free to find someone with a spiral staircase and trade beer (or nice wine, guessing about the owners!) for time with their staircase and a tape measure.
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The centepost concept is best. Your handrailing can be rolled. It is important to give the custom rolling outfit all the particulars and they will roll the helix for you. One has to make sure that the rotation is in the right direction. ( CW or CCW) We did a 14 for high one for a movies set a few months ago. I have pics if you are interested. In our case we did not have the luxury of fourteen foot plus handrailing height clearance so we built it on the horizontal. Anything to make life interesting. Randy

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Thanks Randy for the photos, and everyone else who has helped me with this. I figure the stair treads will be slices of a pie with a diameter equal to the distance across two treads. So if I make the treads 40 inches across the long axis and imagine them coming to a zero point at the center of the support pipe, the circle is 80 inches in diameter, or about 251 inches around. If I cut this into 12 slices (the top one will be the upper landing, so it isn't actually used), then each tread is a triangle 21 inches deep at the outside edge. If these are all laid out, they would form a circle with one pie wedge missing, with a small circle cut inside for the support pipe. These treads are then mounted on the support pipe with the edges exactly lined up one 8 inches above the other. Then I'd run a baluster on the back corner of each tread to tie into the front face of the tread above it. Since the treads will be wood, I'll probable use wooden balusters and maybe a wooden handrail. Since the wood treads will bolt to the angle iron bracket below it, the brackets have a small margin for error, as long as I keep them square. The first angle iron brace would be 6 inches off the floor to allow for the 2 inch thick rough cut lumber I'm using. I still think welding 11 angle iron braces uniformly spaced to an 8 foot long pipe is doable, even for a bonehead like me. When the weather is good, I can do this outdoors and set up a couple braces to hold the center pipe horizontally so I can rotate it into position. Does this layout sound correct and doable? Thanks!!!
John

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Building vertically on a circular layout on the floor is a safer way if you can do it. If you build horizontally you have to calculate every angular increment of your treads then using a bevel on a square and a level set each tread. You can confirm by chordal distances on the edge of each adjacent tread. If you build vertically you can plumb bob down to confirrm tread angular locations and a tape for vertical location. I will crunch some numbers you will need. You might notice that that house picture showed just that method but set on a spiraled channel. Randy

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