# Motorizing a hand-crank leather patcher sewing machine



## polyfractal (Feb 16, 2019)

Hey folks   I do some leather work as another hobby, but don't have an industrial sewing machine (just a little cheapo introductory model).  So I mainly hand-stitch, or pray the little sewing machine can get through the leather without binding.

I recently picked up a "Leather Patcher" machine, also sometimes called cobbler's machines.  Often just referred to as "chinese patcher" online.  These are super cheap and crude manual, hand-crank sewing machines designed to patch boots, bags, etc.  They are knockoffs of old Singer 29k models, and designed to be used by street vendors.  I picked one up and am tuning up the fit and finish (it's a really rough casting, covered in cosmoline, needs deburring/greasing/lapping/etc).

But as a fun practice project, I decided to add a motor to the machine so that it could be operated by foot pedal instead of hand crank.  I don't have a lathe (yet!), so had to mill out a custom v-belt pulley on a rotary table, which mostly worked but isn't something I'd want to do again 

The vbelt is attached to a small pulley adapter that's bolted onto a "hoverboard" hub motor.  These are cheap ($30 new, $15 used) brushless motors that have crazy high torque relative to their price (7-12Nm).  They are designed to direct-drive humans around at low RPM, so they are perfect for something like driving a slow speed leather machine.

All in all, the project was fun and a good practice project.  Learned a lot along the way, and everything even mostly works   Some issues like terrible runout on the motor pulley, but all unimportant given the application, so I'm happy with how it turned out.


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## derf (Feb 16, 2019)

Can you show us how it sews leather?


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## Latinrascalrg1 (Feb 16, 2019)

What ^ he said please!


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## polyfractal (Feb 17, 2019)

Towards the end of the video there's a minute of it "dry sewing" a scrap piece of leather (near 5:24).  That piece was oil tanned, maybe 3-4oz?  Not super heavy by any means.

I'll wind up a bobbin and try out various thickness/multiple pieces today if I get a chance, will report back!


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## danny12 (Feb 17, 2019)

Great videos, I'd like to see more of it sewing as well.


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## polyfractal (Feb 21, 2019)

As requested!  






Some examples sewing through two and four layers of oil-tanned leather (4 layers was  about 7.5mm).  The leather isn't super tough, but not overly supple either.  I unfortunately didn't think to grab some stiff tooling leather at the time, but I don't think it would have an issue getting through that either.


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