Mind The Gap

One day I had an idea, went into the garage and built it. The End.

Not sure what more I can say about this post. I thought it would be cool to make more of an unconventional themed oil filled candle. I figured a spark plug lends itself well to a flame theme so I went for it. A day in the shop landed me a double scaled spark plug candle.

The entire plug was made from a single piece of 6061 aluminium and done to scale. The specs are as follows. Overall height 7.750”, spark plug maximum diameter 1.460”, oil chamber volume .68 cubic inches, 100% cotton wick, 99% pure paraffin(e) lamp oil, burn time approximately 2 hours.

So here we go…

Project planning began by recreating a spark plug scaled 2:1 in a CAD program. This is what I referenced to for all the machining dimensions.

 

The actual hands on portion of the project started off with a 6.5 inch section of 1.500″ 6061 aluminum.

Using various cutters I was able to build the first have to my CAD specs. It is starting to look fairly authentic.

Onto the milling machine where the wrench hex was milled into the plug.

The first half worked out as planned, here’s hoping I don’t screw up the second half.

The threaded section was spun down to spec before the threading began.

A 2:1 scale of the threads turned out to be approximately 10 tpi. I re-geared the lathe for the proper pitch and set up the threading tooling before cutting.

Time to drill out the oil chamber using a 9/16 inch drill bit to a depth of 2.800 inches.

With the chamber drilled I machined in a shoulder to allow for the wick holder to rest on.

The completed spark plug worked out great. Next step was to machine a mounting base, a wick holder and a ground electrode.

With the wick holder complete I gave the spark plug a test drive. Turns out it actually works!

To make the plug look more authentic a ground electrode was required. I came up with a few ideas before settling on using a .250″ stainless steel round bar. I trimmed .400″ of the round stock down to .120″.

Next step was to get some heat into the round bar in order to give it a 90 degree bend in the vise.

With the bend complete all that was required was trimming up of the electrode length to spec.

In order to fit the ground electrode into the plug a .125″ hole was drilled to allow the stainless pin to rest into.

Here are all the fabricated components including the base. I opted to keep the base super simple in order to not distract from the spark plug.

And so this brings us to the part of the show which displays some of the completed shots.

Very happy with how the hex turned out, as well as the rest of the machining.

A few notes on the electrode. The spark plug gap is NOT to spec. It would not work out without smothering the flame therefore I opted for a visual pleasing gap which is a bit larger. Second thing to note is that different wicks and different oils burn differently. Some give off more carbon the others. In my case the flame has no visible black carbon however the bit that is present gets deposited on the stainless electrode. I like to think of it as a clean burning eco friendly oil candle. Third thing I decided on was to leave the finish of the electrode rough. I had contemplated polishing it but I thought the rough look gave the candle a bit more character.