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Cast Iron Spiral Assembly


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#1 grinninggrunny

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Posted 11 February 2014 - 07:26 PM

Anybody had experience of re assembling an old cast spiral staircase? We have the steps, handrail, spindles, platform for the top, but the pole for the centre looks like an old scaffold pole. I've seen other info that this works. The internal diameter of the steps column seems to be around the 54mm mark at its smallest, while the pole is 49mm, leaving a 5mm gap for play? A dry run this last weekend to check for assembled height from the new wooden groundfloor to the mezzanine (still to be floored out properly) had the set up looking not too bad, but you could see a very slight deflection in the centre of the spiral without having the centre pole in the column. We now know what orientation and packing is required.

So, my idea is to use to 3 wedges of dry hardwood at each step, with the centre pole in, to make sure the assembly stays true, if anybody with experience of these items has any suggestions/questions it would be appreciated, ie. without wedging the centre pole, if this is not necessary, it could be dropped in post assembly and also mean the steps would not need to be taken up and dropped, sorry, placed over the pole. Each step has a rounded profile on the bottom of its column which fits into the top of the previous step, the socket on the top of each step is hollowed out slightly and seems to self centre the join, there is a space as though for some packing of some sort.

Thanks for reading, any helpfull comments appreciated.

Chris

#2 ProDave

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Posted 11 February 2014 - 07:33 PM

As an engineer, drill and tap 3 or 4 equally spaced holes around the centre of each section, then insert hex grub screws to tighten down on the centre pole.

#3 Nickfromwales

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Posted 11 February 2014 - 08:40 PM

If they're cast, would that specific point pressure not split the cast? When the treads are stepped on, there will be a lot of pressure applied to those points. :-/
I think I'd approach an engineering works and ask them to produce some sleeves that fit in to complete the surface contact deficit right the way around the pole, but you'll probably find that it would be cheaper, and better, for them to turn down some steel dowel to the right diameter and do away with all the above. Engineering works are cheaper than you'd think, as they do this day in day out so ask for a price before you dismiss it. Offer cash as they'll probably do that "on the side".
Regards, nick.

#4 temp

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Posted 12 February 2014 - 07:00 AM

I agree with Nick. I recently had the commutator on a washing machine motor skimmed in a lathe. Was surprised how little they charged me. You might find it's not too expensive to get a new pole made?

#5 wmacleod

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Posted 12 February 2014 - 08:56 AM

Your local engineering shop should be able to order in the right sized steel tube from their steel supplier which will probably be a lot quicker and easier than adapting an undersized scaffolding tube to fit it, just give them a call and ask for a price.