Teflon as spark plug insulator

minh-thanh · Sep 7, 2022

TSutrina said:
Gave some thinking of making a ceramic spark plug insulator. Skip firing and sealing. Dry out the green clay it will shrink. steel expands greater then the clay, but the clay before sintering may slump on the OD of the clay. The electrode will push the clay out so the sintered ID of the insulator will be bigger. In use the temperature will be lower then sintering so there will be a gap on the ID of the insulator to the electrode. On the OD of the insulator the steel cold if slumping occurred will compress the insulator and when hot that pressure will reduce and could turn to a gap. Ceramic is strong in compression. Thus the steel of the spark plug is unlikely to break the ceramic.
How to make the spark plug. If you can the use of a pottery kiln that is the easiest. Search for a place that teaches pottery even a school and get your plugs put into a firing and glazing firing. Else you can look up how to pit, sawdust, barrel fire clay. These methods are thousands of years old and you can learn how they sealed the porosity. A pit built like a rocket stove with a fan flowing in are is much hotter for the final step up. Note this is how they smelt steel for hundreds of years. So you get to glazing temperatures. There is also a very fast DIY glazing approach on the web. The problem is that the faster you heat up the ceramic or clay the more likely that it will crack. And a spark plug is not the ideal shape for thermal shock.

Yes, I was intending to make ceramic insulators
( I have "some" experience in firing ceramic and granite bricks ) , I have to make a kiln / smelting furnace before I can try to make it .

lee9966 · Sep 7, 2022

I am gratified to have all these responses! I have used corian in one Tiny IC Twin I designed. Running it for a minute was fine, tuning for highest RPM took longer and the corian started deteriorating. Mostly it is the result of bad design. I did hit 10,400 RPM and was surprised nothing failed mechanically.

I have a digital controlled kiln for hardening/tempering knife blades , and would like to get more details about making a ceramic insulator.

minh-thanh · Sep 8, 2022

lee9966 said:
I have a digital controlled kiln for hardening/tempering knife blades , and would like to get more details about making a ceramic insulator.

Hi !
I have not made ceramic insulator yet
But If you are interested, I will tell you a little bit about my experience in firing ceramic/granite tiles - what I can remember , if ceramic insulator it doesn't have glazing so it seems much simpler .

minh-thanh · Sep 9, 2022

Hi All !

The chart above is standard for tiles kilns
The chart below is my recommendation - It has a period of time to increase the temperature - if the kiln does not have a linear heating element over time.
With a tiles kiln, the drying part is part of the connection of the kiln so let's include it in the insulation firing process - it's just the process of removing moisture in the material - the temperature is about 100 to 150 degrees Celsius
The stage direct and indirect cooling we don't need because when we finish heating it we just let it cool in the oven, so we only have Stage 1, 2 and 3.
Stage 2 in the brick kiln has 2 parts: Because we only burn the insulating porcelain - no glaze, we gather it into 1 stage.

Red is the set temperature
Orange is the temperature of the material

Let me know you're interested, please leave a comment