The Curta.org Bulletin Board

[RAPA]

[stenella]

definitely watching

[Axel]

So many parts...[/quote]

I recognize those ten carry springs ! I had to manufacture several to fix my 500713 type 2 😊

[thomasmanegiste]

Hello everyone,

Sorry for being offline for that long, I was way too busy these last months to be able to focus on that project (exams, work, urgent works...).

I juste realised I forgot to translate my last post on usinages.com, so here we go.

21st of december, 2025

I'm currently working on the gear sectors and sliding gears (10076 and 10053):

Sliding gears (10053):
https://drive.proton.me/urls/R3GF6RF928#MoZwe8rYuhBL

Up to this point, I tried to stick to the original design, machining the gear in sheet steel and mounting it onto a brass bushing. But this process causes some problems:
-It implies machining a 2.3mm bore, with a built-in key to ensure rotational linkage with the bushing. I tried to machine it using rotary broaching, obtaining mediocre results, but the process is not suited for semi-production, and I got a scrap rate of about 50%.
-When the previous step is successful, I then turn the 4.4mm diameter (head of teeth diameter), maintaining the part on a 2.3mm grooved arbor. Cutting forces often deform the part, or destroy the keyway by making the part turn onto the arbor.

https://drive.proton.me/urls/S463Q07P4M#WgN2UXE0LmkU

Picture above depicts the best result yet: we can see that the key is too small on the unmounted gear, the part moved when machining. I also tried to make a through bore, without key, soldering the gear onto the bushing.

I suppose that those gears were punched (seeing the statement "Stanzgrat entfernt", "remove punching burrs"), maybe prior to a remachining operation (I don't know if the tolerances are feasible by punching only. If anyone has experience with this technique, or a constructive opinion don't hesitate to share your view).

The most serious solution I found is to machine this assembly in a single part:

https://drive.proton.me/urls/91V7A1CMA0#drnmSwFmPKTS
https://drive.proton.me/urls/X6M5TYSFV0#M8bNW6RDaCoM

The profile of this part is turned out from bar stock, leaving enough material to hold it for milling. Then, I create the driving key by deforming the integrated bushing.

https://drive.proton.me/urls/GVX8W0G7E8#EBbFpFbDw0cO
https://drive.proton.me/urls/3046N2XNS4#2Hl0xWx8S4AR

Gear sectors and gear sectors holder (10001, 10213) :

https://drive.proton.me/urls/1P8C1Y0JKM#G35w9iPONFbR

I tried to find a solution to machine the gear sectors without slowly sinking into madness. I suppose that those were also punched, allowing to obtain the inner sharp corners.

https://drive.proton.me/urls/RYEV6P5KWW#4zYAADjVe0St
https://drive.proton.me/urls/QPKSP60NGG#HzwgZRdfAsyq

Current solution :
I'm using a two-pin design, allowing easy manufacturing and assembly. On usinages.com, I said that I didn't know if this was the final solution, but it seems to work quite well.

https://drive.proton.me/urls/Z78T07K90M#OD8opEVsk4Ln
https://drive.proton.me/urls/8W69CE3970#G1u3we3Jy8VL

That was the translation of the previous post. I will soon post the rest of the news, hopefully later this week.

Have a nice day!