7.12) Item 2, Index Arm Assembly

Now the index arm assembly is a big thing to do and see. It looks like the picture below:-

There are a few items that need to be made before we get to assembling the arm though.

First, you need 14 nuts (Item 32). These could be bought, but I wanted thin nuts, and the standard M3 nut is 2.5mm. So, I ended up making 2mm thick nuts, as below:-

While you're at it you may as well make a further 6 nuts that are required for the main sextant assembly. In actual fact, I was able to get 5mm A/F stock myself rather than the imperial specified, very satisfactory.

The next item to make is the Index Mirror (Item 34), from stainless steel. Take a careful look at the stainless steel sheet. You may have to polish it - if you do, make it as good as you can without polishing in distortions.

The micrometer stop screw, (Item 46). This is not really necessary, but I prefer to have it.

You need two pillars (Item 48)

And a spring (Item 54, not drawn) – which I leave up to you to sort out. I reckon a segment off a spring from an old Biro should do.

Then assemble the whole lot together:-