Author Topic: Spark plug  (Read 374 times)

Offline Doc

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Spark plug
« on: August 26, 2018, 01:30:52 PM »
Decided to make a few spark plugs. Making 8-48 plugs. Might set up the NC mill to turn the insulators again it worked so well the last time. I would quit breaking them I wouldn't need to make any more. They are a bit fragile and I've broke more than I'd like to admit to. Anyway decided to make some this morning had a couple insulators from the last run so I'll make a couple and then maybe set up the NC and whip out a couple dozen again.
George

Offline philf

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Re: Spark plug
« Reply #1 on: August 26, 2018, 03:08:47 PM »
Doc,

Do you use machinable ceramic for the insulators?

If so, how are they fixed to the metal body?

Phil.
Phil Fern
Location: Marple, Cheshire

Offline Doc

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Re: Spark plug
« Reply #2 on: August 26, 2018, 03:39:38 PM »
No I have been using Corian material I take a Corian cutting board and cut it up and use it. The Corian material has held up amazingly well have not had any fail and I have run some of my engines with them for a fairly long time.
  To hold the insulators in I swage them making a swaging tool to do it is quite simple basically a hole the insulator fits through and either a chamfer or an inverted radius around the hole. Just press it down on top and it will swage the material down around a collar on the insulators.
George

Offline philf

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Re: Spark plug
« Reply #3 on: August 26, 2018, 04:13:54 PM »
Hi Doc,

I'm surprised that Corian survives as it is only rated to 212 F.

I would have thought you'd have to use PEEK or Vespel. PEEK starts to soften at 289 F. Vespel is good to about 300 C (nearly 600 F).

At work we used Vespel tips to press solder tape on copper substrates to stop the solder balling up as it melted at about 260 C. They worked about 1,500 times an hour, 20 hours a day, 7 days a week. The tips lasted for weeks before we had to skim a few thou off the surface. A super material but very expensive.

I have lots of bits of machinable ceramic but have never found a use for it at home and I don't like the thought of covering my lathe in the dust.

Phil.
Phil Fern
Location: Marple, Cheshire