rnzo

Thanks Pastor Bob, indeed I have posted some questions already and got answers that helped me tremendously. I plan to document the 840 "renovation" in a post, as it may help others to revive these (and it would be a shame not to) ! Lorenzo

And sure enough the pulley is so close to the body of the motor that inserting some cardboard (for some protection) and sliding a flat head screwdriver, and then gently turning the screwdriver is an easy way to free the pulley from the shaft! Thanks again Bob, now I just have to be patient till I receive my 45mm pulleys and 15mm aluminum tube!

Thanks a lot Bob, very much appreciated! The second approach (use belt in the pulley) reminded me of these rubber gizmos from my youth that we used to get better grip to open jam jars... I went with this approach as with pliers I was concerned of leaving marks on the pulley. And indeed, it seems obvious *after* reading your suggestion, that as the V belt can transfer so efficiently torque to the sewing machine shaft, it can be used to get a good grip on the pulley. Took me 5 mins, mostly finding the right body position so I could apply enough torque, and to remove the nut. I'm now off to order a gear puller (which will also help to remove say balance wheels if i need to do this in the future) to get the pulley out. Thanks again and wishing everyone a happy Sunday! Lorenzo

Hi all, I'm almost done renovating a Necchi 840 (which is a clone of a Pfaff 335), and I am at the stage of installing the servo motor. I bought a Jack 563a servo motor (which is probably a bit overpowered), and the minimum speed is 200 rpm, which for me is still too fast. I've been thinking of using a smaller pulley (like 45mm which is quite common or 40mm which is a bit more unusual) on the servo. I'm aware of the 13mm shaft considerations (I'm planning to use a 15mm shaft pulley with some inner tubing to adapt to the 13mmm shaft, I think this was mentioned by Uwe on this forum). My hope is that the 40-45mm pulley would slow the servo enough for my purposes, without having to build a full reducer with pulleys, bearings and an extra belt. However, I'm facing a fundamental problem: how do I unscrew/remove the nut that secures the pulley to the shaft ? It find it super tight and can't really get a good grip on the pulley. I tried to heat the nut with a heat gun, hoping it would expand with the heat and ease a bit, but was not successful (or maybe I need to try for a longer time). Or maybe it's time to hit the gym on a more regular basis? Any suggestion or tip would be very welcome (I read the tip about using a gear puller to get the pulley out, but I'm not yet at this stage!), Lorenzo PS: The Necchi 840 was sold for parts, and I have been cleaning, renovating and fixing it. Sadly, the top shaft that supports the balance wheel is slightly bent near the balance wheel. This is not too bad as I don't intend to run it over say 150spm, but because of this deflection I don't really consider changing the balance wheel for a larger one, thus I am looking at the servo pulley or a speed reducer.

Hi everyone, Thanks for accepting to the forums. I have been lurking for a long time on these forums in the sewing machines section. I have been mostly renovating and using domestic (I know...) sewing machines, in particular the old Necchi BU/Mira/Supernova types. I bought for very cheap (as it was sold for parts) my first industrial machine head, again a Necchi, this is a Necchi 840, which is a clone of the Pfaff 335. This one was my first walking foot, and I spent very significant time renovating it, replacing some broken parts (or more precisely: buying some Pfaff 335 clone parts from Asia and then trying to make it work in the Necchi, as sometimes the dimensions were slightly different). Along this journey, I came to learn many things about how seeing machines were working, that it made this experience very worthwhile. As probably you'd have guessed, for me this is a hobby, and I'm mostly into sewing light/medium fabric (pu leather, supple leather, cordura and other synthetic or canvas fabrics) to make bags, in particular messenger style bags to carry camera and photography gear. Lorenzo