Learning to TIG Weld

Like any good tinkerer I have always wanted to learn to weld and I recently got the chance to give TIG welding a try. My instructor operating under the premise “its all good as long as you don’t kill yourself” supervised me welding a stainless steel box together that I had earlier sheared the pieces for.

Assuming this was more that enough practice for me, he left me to weld some sprockets onto my motor shafts.

Before continuing, though, I have to explain why I am welding sprockets to motor shafts instead of keying, grinding the shafts down or press fitting as I have been asked by others.

These are the sprockets in question and this is the motor. The shafts for the motor are stainless steel and perfectly round. With a 5mm shaft they are to small to press fit for the 1/4 diameter sprockets. The 2 set screws were also very loose in their treads so I did not have much faith in their reliability to hold on to the shaft that was substantially smaller even if I ground down the shaft to a “D”. Lastly the shaft for the sprocket was very thin so keying the shaft and cutting a segment out of the sprocket also did not seem like a viable option.

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So I settled on welding them together. Yes I know this is permanent and yes I am fine with that.

Continuing…Using the set screws to hold the sprocket in place while I welding the sprocket to the shaft (sorry no welding pictures) I clamped the grounding clamp around the ring of teeth. My plan was to jump the arc on the shaft poking through the center and then the electricity would travel through the shaft onto the sprocket (fusing) and out the ground clamp.

It worked great for the first motor.

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The second motor not so much.

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What happened was that the arc jumped onto the sprocket bypassing the shaft entirely and then decided that only one of the teeth would provide a viable ground so all of the electricity traveled through one tooth and it melted instantly. Poof.

Lesson learned.

But all was not lost. I was able to grind the glob of melted steel down with a Dremel and then guess what it works! Because the chain wraps most of the way around the sprocket at any given time, losing one tooth does not change the position of the #25 roller chain. As of now the go cart is running great even with 1 tooth missing – something to change in the future though.

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