I searched high and low to find left-handed taps and dies, or even steel screws and nuts to use as taps and dies to make the rigging-screws, with no luck at all. I've also bee searching for more information about the rigging-screws themselves, especially images.

I haven't given up, but since I've had some luck with 3D printed parts, I figured I'd see if that would be up to the task.

I just got a new 3D printer that will print larger stuff at higher resolution (more detail), and was cheaper than my original machine cost back in 2020. I think it's a little faster too. (Elegoo Mars 3)

I made a 3D model in Anim8or; printed, adjusted the model, and printed it, a couple of times. I put a couple on the model under tension to see how they hold up, and after a few days of varying October temperatures in my unheated shop, it seems to be holding up alright.

I saw some videos on YouTube about using 3D printed masters for "lost-resin casting" and looked around to see what it would cost to have these cast in brass/bronze from my STL file. While that would be a great solution to my durability concerns, so far it looks like it would cost over $900 USD to get 60 raw castings. That ain't happening unless this lottery ticket on my desk is a winner. 😉

Looking at the portrait of the ship done in 1856 by Tomaso deSimone at Naples Italy, on which I'm basing my model's appearance; I discovered, while looking for something else, that she didn't have deadeyes and lanyards on her shrouds, lower or topmast.
I originally wrote this off as deSimone's corner-cutting, like how he leaves off ratlines on the far side of ships in his portraits. I figured the ship originally had dead-eyes and lanyards and was later fitted with rigging-screws, maybe around the Civil War. But the more I looked at deSimones other paintings, of Constellation and other ships, and photos of the ship after the Civil War, it seems Constellation had rigging-screws (turnbuckles) right up into 1910 or so.

So, how do I make these things? The chain plates up to the screws are the same as I've been planning, but I'm going to need taps and dies between 1mm and 2mm in both right-hand and left-hand threads to make what's shown in the little sketch, and the only left-handed tools I can find on-line are from MiniTaps and are very expensive.

A couple of 3D printed grates went into the companion way hatches, just so they wouldn't be a pair of gaping black holes. The pin rails were glued in place and holes drilled in the main mast rail for the fore-tops'l braces to pass through. The real ship had an iron band with eyes below the tops for the futtock shrouds to attach to. I didn't need these to be removable, so I simply wrapped a strip of styrene around the mast and inserted eye-pins through it. The tops themselves have also been drilled for the topmast shrouds to pass through to the futtocks.
About here I shifted work to Pride of Baltimore, but came back a couple of nights ago and glued down the hammocks on the starboard side. I tried to rig up something to cut down bass strips to 3/16 inch for the railings on the bulwarks that will hide the seam between the bulwark and the hammocks pieces. I couldn't get anything to work, so I opted to mark off the bottom with blue masking tape in two layers to form an edge to place the strip against. After being glued on, I trimmed it to to top of the hammock trays.

The outboard side of aft quarter of the starboard side is done this way so far.

Both pivot guns got some paint (no, not red) but still need some touch-up before they're fastened to the hatches they sit on.

Now I'm trying to make jigs and get a production line going to make 22 pairs of chain-plates.

Rigged the wheel to turn with the rudder's movement, which was a bit like being a contortionist, but I got it done without braking any bones. I have to install a couple more eyes with pulleys so everything will move more smoothly.

Printed some gratings for the companionway hatches on either side of the capstan, and glued down the bitts to the deck.
The hammocks were all glued down on the port side.
Printed gunport eyebrows and installed and painted them on the port side, so I turned the hull and removed the balsa on the bulwarks and the old wood eyebrows I'd installed a while back. The new eyebrows got installed and painted on the starboard side.
The 1mm square brass came in, so the outboard stuns'l irons were installed on the yards.
Next day, the olive paint I ordered came in, and I airbrushed the pivot gun carriages, touched up the over-spray, and started picking out the details with Flat Steel.

The irons made to the diagram didn't really fit the yard well. The stalk that holds the hoop off the yard was too close on the outboard fitting, and too far on the inboard one; so I adjusted the 3D model and printed them again. These worked out much better.
Now I have to find, or produce some brass square stock to install into the ends of the yard for these things to attach to.

I made the stanchions and rails for all three top railings. I need to make a jig to weave up the netting that gets stretched out across them.

I redid the skylight again. The center bar was widened so the sashes would lay down, and new sashes with the bars inside instead of top were made.
There's four pairs of bitts on the spar deck, and those were modeled after the ones in the earliest photos I could find. I held off gluing on the hammocks because I though I needed to install hawse pipes near the bitts, but the ship didn't have any, so I've started gluing on the hammocks.
I modeled the stuns'l yard fittings, but I have to find, or make some brass square stock for the ends of the yards.

Looking at the diagrams from the manual for operating the pivot guns, I felt my gun circles needed a bit more to them. I added circles for the center skid of the chassis to the plan, printed them, primed them, painted them with Testors' "Steel," and CAed them to the deck.
The ones on the bow overlap the edges of the access hatch, and had to be trimmed and the overhanging parts glued to the fixed part of the deck. I drilled holes for pins of some sort, to back up the CA, though I haven't decided what to use. I'm thinking Delrin rod, but I'm have to by some first.

The last sections of hammocks were printed today. Before they get installed I have some work to do on the bulwarks; hawse holes, that sort of thing. I'm planning on using slow-setting epoxy mixed with fine saw-dust to attach them.
In the last two pics, the port-side hammocks are sitting in place, I haven't removed the balsa from the starboard side yet.

I hung an anchor on the cathead just to see how it looked there, and get some idea what it would require to get the thing lashed up as it is in the painting - which reminds me, I have to make a cat head for the cathead.
I tweaked the model for the oars and tried printing 45 all at once. I got what was either a Borg cube or some sort of electrical heat-sink thing. I've managed to dig out 27 or them with only 4 total losses so far, but I don't hold much hope for the rest.
I did up the bob-stays with the 3D printed bulls-eyes and temporarily lashed them up - I have to walk some line for the permanent lashings.
Years ago now, the bulwarks were covered with several layers of balsa sheet, rounded over and painted black to look a bit like tarpaulins over the hammocks until I could figure out how I was going to make exposed hammocks as appears in nearly all the paintings and photos of the ship. 3D printing settled that for me, but just printing them outright would use too much expensive resin, so I needed to make them hollow. 200 hammocks will be visible when it's all done, and I have just under half of them printed in groups of 9 hammocks. I primed them in gray, then painted a first coat of "canvas" which is my custom mix of flat white with about 1/8 of it flat tan.
I sawed of the wheel-stand, of the new 3D printed wheel and used the wood stand from the old 3D printed wheel, which means the wheel can properly spin now. So I'm going back to plan A and connecting the wheel to the rudder servo so it's move when the rudder does. The skylight and wheel also got painted, though the skylight bars need some touch-up (that flash really brings out every little flaw!)
I finally finished the 3D model of the gun rings for the pivot guns. I modeled in holes so I could pin them down as well as CA them to the deck. I mounted them to print all together at once, but left more space between things so as not to repeat the above oar-block problem-turns out I needed to leave more space still. The holes I modeled were too small and printed as dimples, so I wound up drilling them anyway. They got a base coat of black, but will get a "gunmetal" or "steel" paint job at some point.

Then, while printing 2 more hammock trays, I broke the printer, again. Last time the LCD screen went bad. This time the resin vat stuck to the LCD and tore off the ribbon cable when I was trying to remove the vat. Before this happened, I had ordered an upgrade screen kit that's supposed to speed up printing times by as much as 2x, but it hasn't arrived yet.
If any of you are trying this at home, put a sheet of film over the LDC so if the vat sticks, it pulls the film, and not the screen.