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Machining replacement tips for Harbor Freight spot welder

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Picture of Machining replacement tips for Harbor Freight spot welder
The contact points of our Harbor Freight spot welder had gotten too pitted and damaged to work.  I had no luck getting replacement parts from anywhere, so I made a replacement set.  I used TechShop San Jose's lathe to make the parts. 
 
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Step 1: Load copper rod into lathe with collet closer

Picture of Load copper rod into lathe with collet closer
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I bought a nice copper rod from McMaster-Carr - it wasn't cheap, but it was less costly than a new spot welder.  The piece was 3/4" in diameter, so I used a 3/4" collet to hold the rod. 

Step 2: Cut thread side to 8mm

The threaded part of the tongs that the tips screw into are 8mm, so the plan is to cut the copper shaft to 8mm. 

Step 3: Cut angled tip

Using a triangular cutter, I shaped the front of the part to resemble the bad one I had taken off. 

There is no need to part the piece, as it will pop off when you get mostly done shaping.


Step 4: Thread the back side

Picture of Thread the back side
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I used a die to thread the back side.  Shiny!


Step 5: All done!

Install the tips and weld!  The originals had flats to use a wrench to install them, but a pair of pliers or vice grips works fine.


mackamitsu11 months ago
you can file a pair of flats on the tip to use a wrench if you want.
klee27x1 year ago
I'm curious. Do you buy taps individually, where and when you need them for specific tasks? Or did you buy a complete set of them up front? Or do you find there are a few key sizes that are your go-to's that cover most of your needs? If yes to the latter, which are your most frequently used taps?
BradMartinson (author)  klee27x1 year ago
I have usually invested in full sets of taps over the years - a nice combo metric & SAE set has kept me company for about a decade now. Craftsman brand, as I recall.

However, for this project, I was able to use the ones at TechShop San Jose to do the job -- they have a complete set available for member use.
Great job!
Great job!