# Compound Gear for Kenmore Sewing Machine Stitch Selector



## RobinHood (Feb 22, 2022)

Was doing some maintenance on my coveralls (patching holes) when the sewing machine stitch selector failed. This is a 1994 vintage machine, made in Taiwan. And yes, I have to repair it because it is the boss’s machine… (or buy her a new one).

After disassembly of the sewing machine, I found this:




It is actually three pieces - two injection moulded plastic gear halves and the steel hub.

A view from the obverse and a side view.










This compound gear (spur gear together with a bevel gear) was injection moulded as a unit and then pressed onto the steel hub. The hub has knurl marks for better grip. The reason the gear failed was because of a manufacturing defect. You can clearly see the voids on the left hand side of the two halves.






Some measuring and calculating revealed that they are 32 DP gears. I happen to have 6 of the set of 8 32 DP involute cutters (two are missing; one of them being the 26T to 34T one).











I am going to make the gear from two parts: a 20T spur gear pressed onto the hub extension of the 27T bevel gear (this is the cutter that is missing - I’ll use the 25T cutter I have and call it good). The whole thing will then be pressed & locktighted onto the OE steel hub. Going to use aluminum for the material. I will have to make some arbours to hold the individual parts for machining.

Pictures to come once I get to making the gear(s)…


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## DPittman (Feb 22, 2022)

I look forward to seeing the project.  I'm sure you will do a fantastic job.  The only thing that surprises me is that the gears are DP and not metric module.


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## RobinHood (Feb 22, 2022)

They could well be the Module equivalent of DP 32. The OD of the 20T spur gear measures about 0.690 with the dial callipers. 32 DP with 20T calculated comes out to 0.688. I call that close enough.

This gear does not turn constantly. It is only used when selecting one of the 32 available stitch forms on the machine. There is a profile drum with a follower arm that determines the pattern. The gear just changes the position of the follower arm.


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## phaxtris (Feb 22, 2022)

oh this looks tough

just food for thought, by making it from aluminum you might be moving the failure point from that gear to maybe something more difficult to repair


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## deleted_user (Feb 22, 2022)

RobinHood said:


> Was doing some maintenance on my coveralls (patching holes) when the sewing machine stitch selector failed. This is a 1994 vintage machine, made in Taiwan. And yes, I have to repair it because it is the boss’s machine… (or buy her a new one).
> 
> After disassembly of the sewing machine, I found this:
> View attachment 21288
> ...


I like that you can sew.

It is a skill everyone should have. I have a pfaff 360 all mechanical all metal cams and gears, so no breaky...


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## RobinHood (Feb 22, 2022)

phaxtris said:


> just food for thought, by making it from aluminum you might be moving the failure point from that gear to maybe something more difficult to repair



I thought about that as well. I do have some Delrin I could make it out of. The problem with that is how to bond the two gear to each other. Acetal is a tough material to bond. Not much of anything bonds it well reliably that I am aware of.

Aluminum avoids that problem.

If the machine lasts another 28 years after the repair, we should be very happy.


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## RobinHood (Feb 22, 2022)

TorontoBuilder said:


> I like that you can sew.


We had to learn the basics in school as part of home economics. Girls got to go to the shop for both woodworking and metal working basics.


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## DPittman (Feb 22, 2022)

TorontoBuilder said:


> I like that you can sew.
> 
> It is a skill everyone should have. I have a pfaff 360 all mechanical all metal cams and gears, so no breaky...


Ha ha now I know I'm among friends that won't laugh at me....I too sew my coveralls and work jeans.  My wife doesn't seem to care to do that too much. 
I'm at the mother in laws right now and I was just admiring one of her old sewing machines that is all metal and it too is a Pfaff.  Apparently that was a good name but I certainly had never heard of it. 
Even the old basic sewing machines are pretty cool pieces of mechanization.


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## Chicken lights (Feb 22, 2022)

RobinHood said:


> We had to learn the basics in school as part of home economics. Girls got to go to the shop for both woodworking and metal working basics.


Sewing, much less tailoring, is a dying art I feel. I wouldn’t mind knowing more about sewing but it’s a skill not often needed 

Books mention darning socks and nobody does that today, I’d be curious how many years ago this was common


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## RobinHood (Feb 22, 2022)

This was in 70s and early 80s in Europe.


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## PeterT (Feb 22, 2022)

I can't quite tell by the pictures, do you think the set screw pressure is acting to push the hub open & split the assembly? Does this gear engage another plastic gear? Aluminum should be fine I imagine. Metal on plastic is quite common on many RC heli/car applications, application specific of course. The plastic runs smooth & quiet that's for sure. Yes Delrin & UHMW & nylon can be a bugger to bond & not without its machining challenges in certain modes.


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## RobinHood (Feb 22, 2022)

I don’t think so. The two set screws are in the thickest part of the hub (12 mm OD). The ID is a very good sliding fit on a steel shaft. Not much pressure required to lock the gear assembly to the shaft.






Both the bevel and the spur gear engage on other plastic gears.

The only time the gears actually move is during the stitch selection process. If one selects straight stitch, for example, it will remain in that position until that type of stitch is no longer needed - could be a very long time…


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## deleted_user (Feb 22, 2022)

RobinHood said:


> We had to learn the basics in school as part of home economics. Girls got to go to the shop for both woodworking and metal working basics.


Exactly the same at my high school, but my mom had already taught us to cook, sew and do macramé. 

I sew fairly often too...


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## deleted_user (Feb 22, 2022)

DPittman said:


> Ha ha now I know I'm among friends that won't laugh at me....I too sew my coveralls and work jeans.  My wife doesn't seem to care to do that too much.
> I'm at the mother in laws right now and I was just admiring one of her old sewing machines that is all metal and it too is a Pfaff.  Apparently that was a good name but I certainly had never heard of it.
> Even the old basic sewing machines are pretty cool pieces of mechanization.


Pfaff is an awesome old stock brand. I almost bought a leather working business, as part of the negotiations I worked there for a month and got to use some serious sewing machines... most were pfaffs. I used the opportunity to make a new dodger for my father in law's sail boat. 

I really want to buy one with a walking foot to do more leatherworking, but I am stuck hand stitching or doing very light work on my 360.

I have a modern pfaff as well.


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## deleted_user (Feb 22, 2022)

when you can sew you can make nice hats...


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## David_R8 (Feb 22, 2022)

Could that be 3D printed more easily?


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## Tom O (Feb 22, 2022)

Chicken lights said:


> Sewing, much less tailoring, is a dying art I feel. I wouldn’t mind knowing more about sewing but it’s a skill not often needed
> 
> Books mention darning socks and nobody does that today, I’d be curious how many years ago this was common


Dad use to darn his socks using a lightbulb in the 60’s.


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## deleted_user (Feb 22, 2022)

Tom O said:


> Dad use to darn his socks using a lightbulb in the 60’s.


Brilliant.

I darn my very well worn levis when they wear a hole in the ass... because you have to save the most comfortable pairs of jeans... but I have a special function on my sewing machine..


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## 6.5 Fan (Feb 23, 2022)

I need to dig out my late wife's sewing machine and install new zippers in 2 pair of coveralls. A couple of local ladies do this work but i can buy new coveralls cheaper than what they charge for a zipper install. Can't be that hard.......
 For the gears i think aluminum is the way to go.


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## Dusty (Feb 23, 2022)

6.5 Fan said:


> I need to dig out my late wife's sewing machine and install new zippers in 2 pair of coveralls. A couple of local ladies do this work but i can buy new coveralls cheaper than what they charge for a zipper install. Can't be that hard.......
> For the gears i think aluminum is the way to go.



@6.5 Fan, you might consider using Velcro what is usually called hook and pile for a closure.

Might be easier and cheaper to install rather than replacing zippers, just a thought.


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## deleted_user (Feb 23, 2022)

6.5 Fan said:


> I need to dig out my late wife's sewing machine and install new zippers in 2 pair of coveralls. A couple of local ladies do this work but i can buy new coveralls cheaper than what they charge for a zipper install. Can't be that hard.......
> For the gears i think aluminum is the way to go.


zippers are not all that hard.


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## 6.5 Fan (Feb 23, 2022)

Jeez Dusty i would still need to attach the velcro to the coveralls.  The ladies around here seem to think zippers command a high price. The only thing i did much sewing on was a cow.


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## Degen (Feb 24, 2022)

I goning to comment on failure of the part.  In most cases its not manufacturing error but off gassing of the plastics as they age.  A lot of plastics when aging release some of the solvents used in manufacturing and give them desired properties that we desire, depending on the plastics, makes them brittle, shrink or any number of other less desirable properties.

I suspect your failure was going to happen sooner or later, your heavy handed repair of clothing  just hastened that failure (and remind you boss that you saved from the shame of breaking the machine as the  damage was done by the user that used it the most! )

By replacing it the way you plan, that part will last forever, the rest of the parts are still up in the air.


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## Susquatch (Feb 24, 2022)

Degen said:


> In most cases its not manufacturing error but off gassing of the plastics as they age. A lot of plastics when aging release some of the solvents used in manufacturing and give them desired properties that we desire, depending on the plastics, makes them brittle, shrink or any number of other less desirable properties.



I believe that you are correct about that possibility. 

They are called plasticizers. It's the same as the waxy fog film you see on the inside of the windshields on many new imported vehicles. These plasticizers volatolize over the life of the product at a logarithmic rate similar to what happens with radioactive substances. Typically, as a result, the plastics become more and more brittle over time.


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## Degen (Feb 24, 2022)

Exactly.


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## deleted_user (Feb 24, 2022)

Susquatch said:


> I believe that you are correct about that possibility.
> 
> They are called plasticizers. It's the same as the waxy fog film you see on the inside of the windshields on many new imported vehicles. These plasticizers volatolize over the life of the product at a logarithmic rate similar to what happens with radioactive substances. Typically, as a result, the plastics become more and more brittle over time.


Yep... 

I have an old pair of hockey skates, I haven't worn in 15 years,... took em out of storage and loads of plasticizer had migrated to the surface as a thick white waxy film.


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## RobinHood (Feb 25, 2022)

So after a bit of turning, dividing and glueing, the new part is ready for installing back into the machine.

20T spur gear done. 27T bevel gear blank with spur gear mounting boss. I did the shaft collar bore after the teeth were cut and before I parted it off the machining stock.





Setting up the DH for the 45* bevel cut.





Almost done - I did another 10 thou pass after this.





All the parts ready for assembly.





Assembled with locktite.










I’ll let the glue cure overnight, clean the sewing machine and lube the components and return it into service tomorrow.

Should be good for another 30 years or so…


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## Darren (Feb 25, 2022)

awesome work!


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## DPittman (Feb 25, 2022)

BRAVO! Excellent fix and use of skills.


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## Brent H (Feb 25, 2022)

Nicely done Rudy!!!  Looks great and well constructed!


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## YYCHM (Feb 25, 2022)

DPittman said:


> BRAVO! Excellent fix and use of skills.



And equipment  The right tools and machines help.  But Ya, I'm always in awe of Rudy's work...  The beveled gear was what I was interested in seeing made.


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## PeterT (Feb 25, 2022)

Good job. I was wondering how you were going to set up for the bevel gear. I forgot you have a horizontal attachment.
I always ask this question on funky gear forms - do you have a measurement technique to confirm pitch diameter in-situ, or is it entirely dependent on accurate DOC from the blank?


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## 6.5 Fan (Feb 26, 2022)

Great work.


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## YotaBota (Feb 26, 2022)

Gotta luv it when a plan comes together.
Concur with all above.


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## RobinHood (Feb 26, 2022)

Yes, it does help when the right equipment is on hand.

For the spur gear, I used this gear calculator. 









						Gear Measurement over Pins Calculator | Evolvent Design
					

Make sure your gear is the right size by checking its dimension over pins or wires. This measurement over pins calculator works on module and diametric pitch gears of all sizes




					evolventdesign.com
				




It has a section for measurement over the wires. Before I did that though, I just used the DOC engraved on the actual cutter. The over-the-wire measurement just confirmed it - it was within 1 thou.

Now I knew that I can trust the DOC as published and used it as a baseline for the bevel gear. Knowing that I am also not using the correct cutter of the series (because I don’t have it) and that the cutter I have seemed to sit lower in the OE gear, I just eyeballed the final depth of the bevel gear. Since I have the mating gear, it was not such a hard guess to get it right. So basically, I knew the min depth and went from there.


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## Susquatch (Feb 26, 2022)

RobinHood said:


> Yes, it does help when the right equipment is on hand.
> 
> For the spur gear, I used this gear calculator.
> 
> ...



I can't wait to hear how the install and test run goes @RobinHood. I'd still be looking for that part on ebay so kudos to you for taking that project on and my admiration for how it turned out. Very very very cool!


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## PeterT (Feb 26, 2022)

That's a useful website, thanks for sharing


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## PeterT (Feb 26, 2022)

I see they offer cutters too. I just had to look. Prices=ouch. This is why one should always grab things like this at garage sales & whatnot.


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## RobinHood (Feb 26, 2022)

Didn’t even see that they sell cutters... Paying that kind of $$s for a quality cutter is one thing, but if they are just rebranding the off-shore stuff for that price may as well cut out the middle man and buy direct.


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## RobinHood (Feb 26, 2022)

No left over parts - that in my book is always a good install…






And the test run of the available stitches.


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## Susquatch (Feb 26, 2022)

RobinHood said:


> No left over parts - that in my book is always a good install…
> 
> View attachment 21421
> 
> ...



Wife says that you are a very talented man. Coming from her that is one hell of a compliment. She is a seamstress.


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## RobinHood (Feb 26, 2022)

Please thank her for that compliment.


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## Chicken lights (Feb 26, 2022)

Susquatch said:


> Wife says that you are a very talented man. Coming from her that is one hell of a compliment. She is a seamstress.


I forgot about that until now.....

I have fabric that is one sided colour I’d like to sew together to make a curtain, so each side is the same colour 

But I don’t have extra material on the width for a fancy tuck and hem, only on the height do I have room to play 

The material won’t fray so that’s not an issue 

I’m next to clueless on sewing so don’t know my options


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## YYCHM (Feb 26, 2022)

Chicken lights said:


> I forgot about that until now.....
> 
> I have fabric that is one sided colour I’d like to sew together to make a curtain, so each side is the same colour
> 
> ...



Paper Stapler..... my sewing machine of choice


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## deleted_user (Feb 26, 2022)

YYCHM said:


> Paper Stapler..... my sewing machine of choice


been there, done that


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## Susquatch (Feb 27, 2022)

Chicken lights said:


> I forgot about that until now.....
> 
> I have fabric that is one sided colour I’d like to sew together to make a curtain, so each side is the same colour
> 
> ...



Wife says:

1. Sew it all the way around and turn it inside out. Just need a 1/4 inch or so on the sides. 

2. Cut some off the top/bottom and make an edge out of it for the sides. 

3. Buy a different material for the side edging that matches. 

4. Add seam binding on the edges. 

5. Bring it here next time you are in Chatham and she will do it for you.


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## Chicken lights (Feb 27, 2022)

Susquatch said:


> Wife says:
> 
> 1. Sew it all the way around and turn it inside out. Just need a 1/4 inch or so on the sides.
> 
> ...





Interesting, that she had that many solutions, for something that had me pondering 

Old is on the right, first prototype is on the left. It’s always fascinating getting a peep into someone else’s hobby specialty. Please tell the “wife” I said thank you and that she’s too good for you, sir


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## Susquatch (Feb 27, 2022)

Chicken lights said:


> View attachment 21429Interesting, that she had that many solutions, for something that had me pondering
> 
> Old is on the right, first prototype is on the left. It’s always fascinating getting a peep into someone else’s hobby specialty. Please tell the “wife” I said thank you and that she’s too good for you, sir



Will do. And yes, she is. 

I'm like you. But I would have had at least one solution. Spray both sides with flexible contact cement and glue them together, then cut or stitch and cut along the edge.


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## historicalarms (Feb 27, 2022)

Hey Chicken, next trip by here bring your sewing projects with you, that room beside my gun room is a dedicated sewing room that is run by a woman that has made bride & graduation dresses for 40 yrs...if nothing else she will certainly give you the directions you need to complete your stuff at home.


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## Susquatch (Feb 27, 2022)

historicalarms said:


> Hey Chicken, next trip by here bring your sewing projects with you, that room beside my gun room is a dedicated sewing room that is run by a woman that has made bride & graduation dresses for 40 yrs...if nothing else she will certainly give you the directions you need to complete your stuff at home.



My girl does wedding parties, bridal gowns, custom dresses, furniture upholstery, suits and pants, draperies, etc etc. too! 

I hope our ladies never meet. It will either be a giant cat fight or both of us will get killed.

Reminds me of a true story. My wife sewed long before we met. After we met, her dad invited me to an ethic party. I had no clothes to wear to such a big deal. So she made me a suit. I put it on and everything fit perfect except the crotch which was down to my knees. My mom took one look at it and said.  "Oh oh, you've been lying again haven't you! She is going to be really disappointed on your wedding night....."


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## Chicken lights (Feb 27, 2022)

historicalarms said:


> Hey Chicken, next trip by here bring your sewing projects with you, that room beside my gun room is a dedicated sewing room that is run by a woman that has made bride & graduation dresses for 40 yrs...if nothing else she will certainly give you the directions you need to complete your stuff at home.


Yessir. I actually had the fabric with me, last trip, but it was still on the roll. 

Sounds like a bunch of the guys and their wives sew, it “probably” can’t be that hard to figure out 

I think I just shot myself in the foot saying that


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## j_daw_g (Mar 17, 2022)

Out of curiosity, is there any chance that you could share the model number of the machine? I'm about to lose my vintage Kenmore to an identical fate.


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## RobinHood (Mar 17, 2022)

Sure no problems. Here is the data plate with model number and a front view.


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