Introduction: The Vandals Broke the Handle - Gearhart Knitting Machine Repair With Lasers
Using a CNC laser to repair a 1908 Gearheart knitting machine.
I bought an old Gearhart Knitting machine for $100 that says 1908 on the casting and 1914 on the instructions. This thing is the coolest machine I own. It inspires me to observe how things were so carefully and skillfully designed and built. Now-a-days it seems like we don't have that kind of time or care or time to care. The history of these little sock knitters is extraordinary especially because they helped the US win WWI! Before its invention people knit socks by hand - a pair in few days. A skilled operator can make a pair on this in about 40 minutes. WWI fighters were suffering from trench foot caused by having wet feet continuously, literally loosing life and limb. Women stateside were given machines for free if they knitted a number of socks for the troops thus reducing trench foot, gangrene and helped significantly with the war effort. Supposedly they made some 200,000 of these knitters.
I got a good deal but it had a broken crank. I had to repair the crank to make it work. I decided to try casting the broken bevel gear crank but I was missing parts so I had to cast two halves and hot knife weld them together. I cast them in jeweler's wax planning to use lost wax casting. The prospect of casting was too much work so I abandoned that path.
Next I thought of how to make a bevel gear out of thin slices of metal and bolt them together. I could get the steel laser cut and bolt everything together.
I drew up the gears in 2D and made two different tooth lengths in 16 gauge stainless to be stacked to create a approximate bevel. I put 1/4" 20 tap drill sized holes in the parts so I could just tap the stack while clamped in a vice and the whole thing would bolt together. It worked like a charm even though I broke a tap and had to make some new holes.
I prototyped the gear stack on my little CNC laser out of "book binder cardboard.
I had another project for some 15mm wrenches built into bottle openers for a local bike shop so I took the opportunity to throw the parts on the same laser order.
Here is the solution and the finished product - knitting again after maybe 100 years.
I do product design for hire and this kind of stuff for fun. I was also one of the designers of The Jiggernaut which has another instructable on this site. Thanks for checking out my project.