Compound Gear for Kenmore Sewing Machine Stitch Selector

[deleted_user]

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.

 

[6.5 Fan]

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.

 

[Former Member]

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.

 

[Susquatch]

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.

 

[Former Member]

Exactly.

 

[deleted_user]

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.

 

[RobinHood]

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…

 

[Darren]

awesome work!

 

[DPittman]

BRAVO! Excellent fix and use of skills.

 

[Brent H]

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

 

[YYCHM]

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.

 

[PeterT]

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?

 

[6.5 Fan]

Great work.

 

[YotaBota]

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

 

[RobinHood]

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.

 

[Susquatch]

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.

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!

 

[PeterT]

That's a useful website, thanks for sharing

 

[PeterT]

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.

 

[RobinHood]

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.

 

[RobinHood]

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



And the test run of the available stitches.