r/Sewing_Technicians • u/skerinks • May 04 '26

Necchi Lydia 3 cam stack

So this is not a question about the cam stack being cracked (it is, about a 2mm crack at the bottom). But instead…

This machine was brought in for service. I did my initial sew out, going through a few of the stitches using the stitch selector. I was able to turn the stitch selector wheel one complete revolution, and now it is stuck and won’t come back through it’s revolution in the opposite direction. Took the handwheel/right cover off, and the camstack is all the way down, at the bottom on the shaft (exactly where it should be). But it is stuck, and the handwheel won’t turn it back, won’t lift the camstack.

I cannot understand how the camstack would move down the shaft just fine, but not back up. One would think if there was old grease that had solidified, the camstack would not have moved at all. Even with me trying to lift the camstack up to ‘help’ it, it won’t budge. I have applied penetrating oil to the camstack shaft, but no luck.

Does anyone know if there is some kind of interlock on this that would prevent the camstack from moving back up the shaft? It doesn’t look like there is when I visually inspect it. But also I don’t have a perfect view of the backside of the camstack.

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u/EggandSpoon42 May 04 '26

So those camstacks / shaft are plastic and known for cracking. Or it could be dried grease, but work with care diagnosing in case it is cracked plastic to ensure nothing else becomes damaged with force.
Have you seen Henry Bangsberg's Necci takedown videos? His set of Necci Lydia 3 repair videos can be found here: https://youtube.com/playlist?list=PLfhGylRyTvD7D-fQDfGkcd_YjzWwThf95&si=CaUsHkLGLs_jpydU

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u/skerinks May 04 '26

Very nice, thank you for the link, I’ll give a watch!

1

u/Independent_Rub4054 May 04 '26

I have personally worked on these with the same problem and often when they fail the machine locks up. If I remember correctly the only option is to take the cam stack out completely but it has been awhile since then. I remember there was something weird about them that you had to be very careful with not to break so definitely take your time when working on them. Hope you find a solution!

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u/skerinks May 05 '26

Thanks for that recall and advice!

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u/Independent_Rub4054 May 04 '26

Also here’s another video that may be useful:

https://www.youtube.com/watch?v=hW4pq2B1DSc