Use It or Lose It: 1966 Singer 331K4

Just when I thought I had counted all of the vintage and antique machines here, I forgot to add the 1966 Singer 331K4 Industrial! This brings the machine count up to 15. Another machine that I absolutely love and don't want to live without.

Although this is a full-on industrial machine, its purpose is not to sew through thick fabrics or leather. The sole purpose of this machine is to sew F-A-S-T!

In fact, it sews SO fast that I only use this baby for sewing mostly straight seams. There's no going slow around curves with this thing.

Other than the fact that this machine was manufactured in Singer's Scotland plant in 1966, I really don't know that much else about it. I had always wanted to try an industrial machine, and found this one advertised locally from a business that was closing and liquidating, and she came home with me for less than half of what they normally sell for. And, like I said, I absolutely love her!

EDITED: I'm adding some more information about this machine for those of you that had questions. First, get the free SINGER Service Manual PDF here from SingerCo: Some of the illustrations are not very clear in this download, but the Service Manual includes all the machine specs plus basic information about threading, needles, and the bobbin winder that came standard with this model.

Next, here's a quick threading guide. It is recommended that a thread stand be used with this machine to help the thread untwist before stitching. I have the original Singer Thread Unwinder No. 225258 stand on my machine, but you could use any stand, as long as it fits on the table.

From what I've seen and read, what looks like a thread spool on top of the machine is actually a thread guide.It is optional to use, but I have found the machine to stitch best when I use it.

And this thread guide MUST be used before continuing on the thread path to the tensioner, thread uptake lever, and on to the needle. Once I had the machine threaded properly it sewed like a dream.

The last bit of information to share is that this machine does not use standard 15X1 sewing machine needles, it uses Singer Industrial Machine Neeldes size 16X87. Just do an internet search to find places that stock the needles.

If you'd like to see some of the other machines in my collection, you can click back to read about these oldies but goodies:
#14. Singer 500A
#13. 1935 Singer 221
#12. c.1960's BERNINA 730 Record
#11. c.1950's Brother


Anonymous said…
I just bought one of these at an is fast you are right!
thanks for posting the service manual link!
That brings me to 6 machines, (and i'm not collecting them!)
Erika Mulvenna said…
Hi there Anonymous, this is an awesome machine! Hope you enjoy it, I don't get to sew on mine enough - and when I do, I love every minute of it. Happy stitching! - Erika
Anonymous said…
Hi. I'm looking @ buying one of these machines used. You mentioned that it's "claim to fame" is sewing fast. My concern is if it will sew through several (3 to 4) layers of outdoor canvas &/or webbing. Think this machine can handle that? Thanks so much! B
Erika Mulvenna said…
Hello Anonymous, I can't answer if this machine will sew through that many layers of thick fabric since I've only ever used it for medium weight fabric. I bought mine used from an alterations shop. In reviews I have read that this machine is rated for medium/heavy work such as upholstery and light leather work. I would suggest testing it out with some sample fabric before you make the purchase. Good luck to you!
tp said…
Hi Miss Sews-it-all,

I am an amatuer in sewing and am planning to get one sewing machine myself to make leather tote bags.

I came across an used Singer 331K4 which is in good condition and the seller is only willing to part for US$650.

Is this a reasonable price?
Please advise. Thank you!

- tp
Erika Mulvenna said…
Hi there tp, there are so many factors that go into pricing a used machine, from the condition of the finish and inside workings to the condition of the table/motor,if the machine has accessories and a manual with it, and if the machine has been recently serviced by a professional technician. My best advice to you is to try and look online to see what similar 331K4's have sold for recently on e-bay or other online venues. Remember, try to see what the actual selling price is as some people will list the machine higher than the actual value. Good luck to you!
Anonymous said…
May i ask how much you paid for yours? Thanks
Erika Mulvenna said…
Hello there Anonymous. I bought my Singer 331K4 years and years ago, I found it in a classified listing on Craigslist in my area. I don't remember the exact price I paid, I think it was advertised for something like $400, but I remember getting it a little cheaper because I paid cash.
Chxherdess said…
Hi, I just bought this model after wishing for a HD machine for years (currently have a Pfaff 130 that my mechanic told me I was going to ruin it with using it through 5 layers of upholstery). Anyway, is it possible to slow it down with a different motor? This is my only machine for upholstery.
Thanks, Melva
Erika Mulvenna said…
Hello Chxherdress, I have seen some VSM bloggers change the gear ratio on an industrial motor to slow down the action on the machine, but I've never done it. My concern with this machine would be that it was manufactured for speed, not for sewing through heavy fabrics. So, I'm not sure how it would work for you. Best of luck!
Unknown said…
I just picked one up a 331K4 in Denver for $125. Runs great. I was wondering if anyone knows how to date the machines with the serial number. Thanks.
Erika Mulvenna said…
Hi there Unknown! Nice find on your 331K4. Yes, you can visit the ISMACS website (International Sewing Machine Collectors) and find a detailed Singer dating chart by serial number.
Anonymous said…
hi I have a singer 331k4 does anyone know where I can get a new brake for the motor it the old singer black 1 horse power kind.
HWP said…
I have a couple of questions I hope you can answer.

1. Is the 331 an newer iteration of the 31-15?

2. Is the 331 a manual oiler or an auto oiler?

3, If it is a manual oiler is it necessary to use a drip pan with the stand?

Thanks for your help.

Erika Mulvenna said…
Hi there HWP. I really can only answer that my machine needs to be oiled manually. I don't know anything about the Singer 31-15, or if this model was an update to it. You might want to try poking around the ISMACS website (International Sewing Machine Collector's Society) to see if you can find any information there.
HAYLEY said…
Erika Mulvenna said…
Hello HAYLEY, and thanks for stopping by my blog! I am unable to offer you any advice regarding the worth or value of your sewing machine, but you can read my article about "How Much is my Old Sewing Machine Worth" right here:

Best of luck to you! - Erika
Unknown said…
I am the guy who got the machine in Denver a couple of years ago.
Someone on another forum was wondering if there was a 31-15 with reverse and several folks suggested the 331K4 was as close as you could get.
I've personally sewn thick layers with the 331k4 machine and it does fine with a large needle and heavy thread.
It is a manual oiler. Mine does have a tray, but I've never noticed oil splatter in it.
Like the 31-15 (I learned to sew on this antique machine 25 years ago), it's a simple, but reliable mule of a machine.
I love mine and got it for a great price ($125 with table and bobbin rewinder, I added a light and spool tower and spent a day tuning up the laminate underside and adjusting the tension).
I've seen similar set ups like mine consistently in the $500 range. Heads alone around $350.
Anonymous said…
I purchased a singer 331k6 at $200 wondering if I can still find the parts when they're needed
HWP said…
I have found SouthStar Supply to be an excellent source. The web site is not the easiest to use, but they do have parts for the 331k. For instance, I just checked for a hook for that machine and they have it. I'm sure they'll have feet, needle plates, and dogs as well. They sell a very broad range of feet for industrials and their prices are very modest.

You do have to make a minimum purchase (I think it's $25.00). They also offer outstanding customer service. When you place an order they request your phone number in case there are problems with the order. They really do call if they need to.

I have no affiliation with the company--I'm just a very happy customer who has dealt with them on several occasions needing parts for a 31-15 and a 20u33.

Erika Mulvenna said…
Thanks so much HWP for the information on where to source parts, and to Unknown in Denver for your comments about the 331K4. Happy stitching! - Erika
Unknown said…
Hi miss sew it all nice to see your blog, just wanted to know if 331k4 is better than 31k15 in terms of sewing thick fabric with heavy thread, also what is the thickest thread it can take, thanks
Erika Mulvenna said…
Hello balsagar Kotkar, I only use this machine with regular weight all-purpose sewing thread and medium weight cotton fabrics. I've never sewn thick fabrics with it or used a thick thread. I've also never used a 31k15 machine before, so I'm really not able to give any feedback on which may sew better, or how a 331K4 might sew with thick fabrics and heavy threads.

I've never had any issues sewing with the regular weight threads and medium weight cottons, and this machine does sew fast. Without modifying the motor/pulley system, this machine does not like to sew slowly at all. Best of luck to you! - Erika
Anonymous said…
I really hope you can help. I have just bought an industrial sewing machine. It's an oldie but sews like a dream. It gallops along like a racehorse. I have been trying to find the manual for it. No luck so far, this is where I desperately need your help. My machine is a
Singer 31K5. I did say an oldie. I love it. Please say you have the manual I need, or know where to get it. I tried Singer, they didn't even know what I was talking about. Please, please, please
Many thanks
Erika Mulvenna said…
Hello Anonymous, and thanks for visiting Miss Sews-it-all! Your old Singer sounds pretty cool, I've never heard of a 31K5 before. If you are looking for more information, I would suggest visiting some of the VSM groups and forums online, like the ISMACS site or the Needle Bar. Best - Erika
Anonymous said…
Hi my name is george i live in the UK, i have just retired after working in the upholstery side of the aviation sector, I have just purchased a Singer 331K4 with the intention of starting a hobby in the sewing of various covers for friends and family, i picked this machine because i think Singers are still great machines i know this is an old one but with a little love and care it will be fine, so my questions are.

1. Do you know where i can purchase these parts
take up lever guard part number 139766 plus 2 screws part number335
arm spool pin part number 53229 2 off

2. is there a chat room or a forum that i could join so that i could help with these problems.
Many thanks
Erika Mulvenna said…
Hello George, and thanks for stopping by my blog! I'm not sure where to purchase replacement parts for this model. I haven't run across anyone else with this machine before. Did you try some of the VSM public groups here on Facebook? Someone there may have an answer for you! - Erika
Unknown said…
I was just gifted a 331k4 with the stand. Do you know what the knee lever does?
Erika Mulvenna said…
Hello Unknown, the knee lever lifts up the presser foot on this machine, you have your hands free to keep them on your project.
Unknown said…
Hi Miss Sews- it-all
I wondered if I could change my Singer 331k4 using system by adding motor to operate it because my machine is too old and works only on feet.. and if it ,so what kind of motors could operate this machine?
By the machine was a gift from my mother after my wedding(she died 2 years ago)..and l love it so much.If you have any answer to my question about the way that I can make this machine works electrically..please reply.
Thank you
Erika Mulvenna said…
Hi Unknown, interesting question about updating your 331K4 with a different motor. I really don't know how that would work! I know you can update older industrials with electronic step motors, maybe you can get in touch with an industrial sewing machine store and ask? Best of luck to you! - Erika
Unknown said…
Hello I use this machine a lot and your right about corners takes some control
Toolmaster said…
The link to service manual seems to no longer work. Is there a new or alternative link? I just bought one of these and the information is really important to have.
Erika Mulvenna said…
Hello Toolmaster, thanks for the heads-up about the link. I have updated the link to bring you to the download page at Singer Sewing Company's official website.
MP said…
Bonjour j'ai une 33ik4.par contre je voulais savoir où je peux trouver précisément le numéro de série de la machine svp ? Existe t-il des astuces pour coudre des tissus extensibles stretch sans que cela saute des points ? Pouvez vous me dire les références d'aiguilles idéales ? Merci d'avance !
Erika Mulvenna said…
Hi MP, I see you have lots of questions about sewing stretchy fabrics or knits with this machine. I've only sewn stable woven cottons with this machine, and wouldn't know if it is suited to sewing knits. The serial number might be underneath the machine, I'm not sure. I no longer have this machine in my collection. Thanks so much for stopping by my blog. Cheers!
Martha Williams said…
I as of late discovered numerous helpful data in your site particularly this website page. Among the heaps of remarks on your articles. Much obliged for sharing.
Erika Mulvenna said…
Thank you Martha, I'm so glad you found some useful information here! Cheers - Erika
mkapp2011 said…
Hello! I am wondering what belt you use for the machine.thanks! Michelle
Erika Mulvenna said…
Hi mkapp2011, I used a black "V" belt for this machine, so sorry I don't remember where I purchased the belt from. Cheers - Erika
Erika Mulvenna said…
Thanks Busy, that is so cool!!!
David Nash said…
Hello, I'm the man who sells purses, bags and wallets on The Quayside Market in Newcastle upon Tyne and I've used my 331K4 every day for nearly forty years !
I don't sew fast but I DO sew thick and often stepping up and down different levels !
It can do this flawlessly but sometimes it goes completely wrong and I could go mad trying to get it back into sync !
More often than not it's the top tension !
I use a 40 weight thread and some pretty big needles too !
Rachel said…
I purchased this model and was wondering if you had the final pictures of how it is threaded, all the way to the needle, and how you did your Bobbin. I had to take the bobbin out and now I can't get the top threas to catch the bobbin thread.
Erika Mulvenna said…
Hey Rachel, I no longer have this machine or any other pics other than what's here. I can suggest looking at that downloadable PDF manual linked in the post for instructions, that really helped me out with threading. Best of luck to you! Cheers - Erika

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