Can Nylon/Plastic gears be recut in steel?

July 1, 2009 10:46 AM

Sewing Gear Filter: I have a number of sewing machines that have nylon or plastic composite gears that have broken. Some of them I can have replaced, some of them are no longer made. I am wondering about DIY bionic sewing machine parts.

My machines have gears similar to these. Some of them are beveled drive gears as well.

I have some access to machine shop equipment and think I could probably make the gears myself with a little patience and a couple of books, but was wondering:

If the gears were originally nylon or plastic are there reasons that go beyond cost, noise, maintenance, and weight? As far as I know it is just a function of them being cheaper to manufacture, quieter in general, and requiring less lubrication.

If I grind or cast the same shape gear out of steel am I going to ruin the other components? It doesn't seem like I would, but I thought maybe they made the gears more flexible/fragile so that they break before bending other parts.

Are there any book or tips you know of for this kind of thing? They need not be specifically sewing related, but not having a degree or experience in engineering they need to be approachable.

I have tried to get answers from antique car repair shops, but none of them want to take on small work like this. I have tried google and dealerships, but most of the information seems to be proprietary - which is fine but a few of the pieces are so old that they are no longer manufactured.

Thoughts or ideas? These machines are so good I am willing to put work or money into them.

posted by Tchad to sports, hobbies, & recreation (10 comments total)

Have you looked in McMaster-Carr for the gears? I'd imagine that many of them are standard parts instead of custom made.
posted by exogenous at 11:10 AM on July 1

You should be able to find a machinist who can look at the broken gears and either make a metal equivalent or tell you the relevant numbers so you can look for a pre-made replacement. That said, having a one-off gear machined can easily cost several hundred dollars. Shop time ain't cheap.
posted by indyz at 11:11 AM on July 1

While all-plastic geartrains suck, I've read that even back in the good ol' days manufacturers would include one or two plastic gears as a sort of mechanical "fuse" - if something got jammed the plastic gear would break before anything more important gave out. So maybe you shouldn't replace all the plastic gears with metal ones.
posted by Quietgal at 11:51 AM on July 1

Other sources of gears: Stock Drive Products; W. M. Berg Co.
posted by jet_silver at 12:48 PM on July 1

I would go with aluminum or brass over steel just to make your life easier if you're doing this yourself.

I'm trying to get an old mill that was put away wet back into trim and, while looking for something else the other day, found a web site where a guy did exactly what you describe for a plastic gear from an old camera.
posted by Kid Charlemagne at 1:53 PM on July 1

Why not look on Craigslist for other sewing machines you can plunder?

I'd worry about the fact that often plastic gears are not made to the same rigid spec as metal gears, so if you try and re-create a plastic gear in brass, it's possible it is not going to work perfectly. Plastic gears also absorb vibration, and since they require no lubrication the machine may not be set up for you to lubricate new metal gears. I imagine that metal gears may be harder for your sewing machine engine to drive; it may not be enough to matter, but if it is, you will stress your motor.
posted by oneirodynia at 6:55 PM on July 1

I can't help on the gear replacement, but I would be astounded if the parts were no longer available. I've had a machine from the 60s and another from the early 40s repaired and they had no problem getting parts for them. If it has plastic workings it can't be much older than the 1960s or so (and odds are is from the 70s or later) I asked the repair guy at the shop where I get my machines serviced, he said parts are still made for pretty much every major brand of machine sold in the US for at least the last forty years, and you can still get parts for the really big names (singer, sears, etc) going back to foot-pedal models.


also, like oneirodynia said, I'd be concerned about the motor. I've had and used a bunch of machines in my life, and the motors older metal construction models seemed way more powerful. I'm sure some of it is improvements in sound and vibration dampening, but not all- my machine from the 60s could blast through leather as good as a low end industrial. No way would my modern fancy machine do that.
posted by Kellydamnit at 11:30 PM on July 1

Wow. Thanks guys.

Reading through the responses I realized I am not making the machines bionic as much as Frankenstein.

The gear catalog references are something I have NEVER come across. I can imagine why a repair shop would not want to tell me about them.

I am not so concerned with the motor situation because I am also changing out the motors to industrial motors and mounting the machines on tables I have built.

As far as the availability of parts go, there are a few things at play:

-Two of the machines are early 1970's Pfaff 1222 electronic machines the boards went bad on. They would make good production machines for shirts and medium weight delicates. I don't need the electronic capabilities (automatic threading, foot pedal control, and take-up lever upright stop), so I plan on reworking them into regular mechanicals. The boards are no longer available and I don't want to keep replacing 35 year old salvaged circuit boards. I thought while I was at it I would just rework the gears as well.

-One of the machines is a 1967 Bernina that is all-metal except one damn gear that has snapped twice. Otherwise, it is probably the most perfect machine I have sewn on. So that will be my first experiment. It is compact and would make a good "portable industrial" built into a wheeled folding table for on-site jobs where I need power and speed.

-The brands are known for their engineering perfection - especially the Bernina, so it seems like the plastic gear was more of a weight, oiling, and sound issue than a price issue.

-I don't mind oiling metal gears, so removing the top once every three weeks to oil and clean it is not a problem. These are machines that will be getting a lot of use.

-Sound is not a consideration. They are being used in a small design studio, not a home, so I can deal with a little hum.

-Personally, if it can be done, I like to lessen any and all plastic in the world. It needs to be replaced more frequently and I like lifetime fixes, not 5-10 year ones if I can have them.

At the end of the day I have my "core" industrial machines - 2 Singers from 1911 and a Pfaff from 1936. For those there are parts aplenty. If I can add some functionality to the workroom by adapting sturdy machines that have a handful more stitches all the better.

It is an experiment on reuse and mechanics for me. Because I am around them and use them everyday, I am also planning on tricking them out with new paint jobs and chrome, just for the fun of it. So some of this is playing around with what may or may not be mechanically possible as well.

Thanks again! Such good leads and concerns. Love love love Metafilter.
posted by Tchad at 9:25 AM on July 2

If you're thinking of looking locally: I had a small screw snap on my vintage car once and couldn't find a replacement with the same length, gauge, and threading for the life of me. By chance, I walked into an old watch repair shop and the guy had the tools there to make tiny, precise metal watch parts from scratch. Quintessential gruff old man in a cluttered, musty shop with a pooch sleeping in the corner. Would only accept a fiver for hand-turning a screw for me.
posted by sub-culture at 9:58 AM on July 2

-The brands are known for their engineering perfection - especially the Bernina, so it seems like the plastic gear was more of a weight, oiling, and sound issue than a price issue.

This sounds very much like the situation Quietgal was talking about. Being that well engineered, there's a reason that there is one plastic gear among the metal. If you value this machine, I would not recreate this gear in metal for the very reason she mentions: the plastic gear protects other components.
posted by oneirodynia at 5:56 PM on July 2