Help finding bobbin carriage for Necchi 840-100 (~Pfaff 335~)

[solowiej]

Hello! I finally found a reasonable sounding deal on a cylinder arm machine. When I went to pick it up the small parts that were pictured in the sale: Bobbin case, bobbin cover and presser foot, had all been lost. I had already paid for the machine and driven there so I took it home with me. 

I haven't found much info on the Necchi 840-100. Based on this thread on the very similar Pfaff 335, I ordered some cheap bobbins and cases online. 
They don't fit. The center hole for the bobbin case is slightly too snug to fit onto the center pin on the Necchi. 

The bobbin post on my rotary hook measures 4.4 outer diameter.

These bobbin cases measure 4.3mm inner diameter.

Could this be a matter of polishing the (cheapo) bobbin cases a bit further open so they fit? 

Anybody have advice, or know of a solid parts source for the Necchi 840?

 

[solowiej]

Just to leave this info here: I needed a bobbin case for my 840-100. Many claimed the same style  and measurements, but the one that finally fit just right is called:

Cutex Bobbin Case #173058 for Singer 206W, 306W, 319 Sewing Machines

So #173058 is the winning number for smaller 335 machines (not the 335G with larger bobbin)

It's also worth noting that the larger 335G bobbin hook set does install nicely to the 335 machines with no other parts changing. If you need to shop for the right bobbin case, it may make sense to replace the whole set and take the upgrade. There are plenty of inexpensive hook sets for both models. The higher end original Italian-made ones appear to be these:

Large Bobbin for 335G model and clones: CERLIANI 130.00.335

Standard Bobbin for 335 model and clones: CERLIANI 130.03.017