Thanks JIM
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There are numerous ideas for constructing ladders or stairs for shipmodels. Together with gratings, this seems to be something that pre-occupies the the mind of shipmodellers. Perhaps because spacing saw-cuts evenly is a challenge with hand-tools. Having machines with tool-slides, controlled by spindles with graduated dials, at one’s disposal takes away most of that challenge, at least in theory. It seems logic to transpose the common techniques for making ladders just to a smaller scale, say with thinner saw-blades to cut slots into the spacing device.
Preparing a spacing device for stairsHowever, the sizes of the materials to be used in itself poses a challenge. Treads in (wooden) stairs are typically 25 to 30 mm thick, which translates to roughly 0.2 mm in the 1:160 scale. The stringers of stairs may be somewhere between 40 and 60 mm thick, which translates into 0.3 to 0.4 mm on the model. The treads are usually notched into the stringers, so that the outside of the sides are smooth. This is a technique that would be very difficult to reproduce at this small scale because milling notches 0.2 mm wide and 0.2 mm deep into material that may be as thin as 0.3 mm is practically quite difficult to do consistently. The other difficulty is to cut the treads to exactly the right lengths. This problem also appears, if one tried to simply butt the steps against the sides for glueing. The clean glueing, without fillets appearing, also was a challenge, at least for me.
Cutting notches for treads into stair-stringers of bakelite-paperInitially, the material of choice was bakelite-paper, which is very stiff, but rather brittle at a thickness of 0.2 mm and has attracted all the issues mentioned above. I then tried polystyrene, which is much less brittle, but also much less stiff. It has the advantage that it can be glued, or rather welded, using dichloromethane, allowing nearly invisible joints between close-fitting parts. While all these properties are useful, the styrene proved to be too flexible to be sanded to size on the milling machine, compared to the bakelite-paper.
After various trials the most promosing method for stairs that emerged was the following:
1. cut strips somewhat wider than the stringers of the stairs from 0.2 mm bakelite paper.
2. arrange these strips in a pack on the micro-vise; count as many strips as needed for the stairs, plus a few spares, and a couple of sacrificial/protective ones at each side of the pack.
3. push the strips down into the vise and then sand them as a pack to equal width.
4. incline the vise to the angle of the stairs and cut slots at the required distances with a fine-toothed saw-blade of 0.2 mm thickness.
Cutting slots for steps into stair-stringers of polystyrene5. cut strips slightly wider than the width of the treads from 0.2 mm bakelite-paper, clean them up and round one edge slightly.
6. cut the treads slightly longer than the final length from those strips.
7. take two stair-stringers and insert the treads, which should be a tight fit, with the rounded side first.
8. adjust one side so that it is straight and the steps are only protruding slightly – everything should be square, of course.
Glueing together the stair components9. infiltrate thin cyanoacrylate cement into the slots and let set thoroughly.
10. adjust the opposite side to the right distance and repeat as above.
11. nip-off excess tread material on the outside.
12. file the outside of the stringers flush with a diamond nail-file and/or the disc sander
13. glue a second layer of 0.2 mm bakelite paper to the outside of the stair-stringers
Sanding to thickness the stairs14. transfer to the vise on the milling machine, slots down, and sand down the stair-stringers to just above the steps.
15. turn the stairs over and sand them down to to the scale width of the stringers.
16. sand the stair-stringers to the required thickness.
17. clean-up all burrs etc.
18. the stairs are now ready to be trimmed to length.
Selection of stairs (not yet trimmed to length)I have tried to follow the same procedure with brass-sheet and soldering, but using bakelite-paper gave crisper results. Perhaps one should have etched the components and then soldered them together, as I had envisaged at the very beginning. This would have allowed to hold close tolerances of the individual parts, requiring less clean-up. However, I found setting up the etching process to onerous and also wanted to see, whether I could fabricate the stairs usind classical workshop techniques.
The hand-rails and other fittings will be produced later, together with the railings, as they will be very delicate.
To be continued ... soon ... first I have to go to Helsinki on business – and to have some Rudo-steak, now that Christmas is over