aka9950202
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What do they call in here in Australia ? When I asked about corian they did not know what I was talking about .
Cheers,
Andrew in Melbourne
Corian for spark plugs
- Thread starter Metal Butcher
- Start date
Help Support Home Model Engine Machinist Forum:
Cheers,
Andrew in Melbourne
Cogsy
Well-Known Member
Possibly just something generic like 'acrylic counter top' but here in Perth I've seen local counter top suppliers websites with the name 'Corian' on them. I didn't find much on Google when I searched 'Corian Perth' but instead I just searched for counter top businesses and browsed their websites.
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Steve, those are looking good.
Plugs looks fine. What about heath resistance .
Corian is made from acrylic and alumina and is heat resistant to 100°C (per Wikipedia). On the one hand, numerous people have successfully made spark-plugs with on, but on the other hand it does not sound like an ideal material to me. I have not (yet) tried to make any spark-plugs, but I would be more inclined to use teflon, which in my experience machines well with sharp HSS tools.
The ideal material would probably be machinable ceramic, but hold onto your hat when you look at the price!
The ideal material would probably be machinable ceramic, but hold onto your hat when you look at the price!
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I have a local guy who does SLA printing. He is doing some patterns for my Gardner. He says he can hold tolerances in microns. Would anyone be interested in printed spark plug insulators.
Nothing in our price range is ideal but it's the best cheap material out there. As an insulator it will out perform most materials we use in this hobby. I have the same plugs in the peewee that were put in in 2010 and I run it more than any other engine I own.
Can't disagree with that. Care must be taken when you machine them but also when you press the insulator into the base. I have cracked a few during that step also. Once they are done, you cant beat them.
Fish spine beads are used by some guys as insulator. Stuff is alumina. Don't know about prices. Beads are made in different sizes.
The beads are over a buck a piece and are too short to make an insulator. The rods I saw were 27 bucks a foot and machinable but the forum I looked there was a guy who was blowing up diamond inserts trying to machine the stuff. Being ceramic I would think they are unable to be modified. Do you have any photos of the plugs made from this stuff Kimmo?
There's this chap Graham Meek on modelengeneeringwebsite who's done these plugs. He made the ptfe insulator with the bead on the head of the plug. There's drawing on site too.
Found it!
http://modelengineeringwebsite.com/Miniature_spark_plugs.html
I see how it worked for him. Wouldn't work for me as the available sizes are not quite right. This latest plug i'm making only has .078 hole in the base.
http://modelengineeringwebsite.com/Miniature_spark_plugs.html
I see how it worked for him. Wouldn't work for me as the available sizes are not quite right. This latest plug i'm making only has .078 hole in the base.
OK. I'ts good to have few option. I think they all works fine, corian, beads and ptfe. Ptfe's possible chemical decomposition worries some guys, don't believe it's a big issue with these engines.
Some other possibilities: Soapstone (samples often available from countertop manufacturers), hexagonal boron nitride (nice and white, machines like graphite, good to 950C), Macor (machinable ceramic).
I suspect that the first time I want to make a spark plug, I will use HBN.
I suspect that the first time I want to make a spark plug, I will use HBN.
Where do you buy HBN rod?
Goodfellow chemical: http://www.goodfellow.com/E/Boron-Nitride-Rod.html -- but their price is way over the top; I've had access to some scraps from laboratory work. I wouldn't make a plug out of HBN from Goodfellow.
There's a possibility of getting reasonable prices from vendors on alibaba. But you have to ask for a quote.
Ebay currently has some NOS steatite rods on sale -- 1/2 inch diameter by 8 inches long for $14.o0 with free shipping. Steatite is purified soapstone. It is reputed to be machinable, but I've never tried it.
There's a possibility of getting reasonable prices from vendors on alibaba. But you have to ask for a quote.
Ebay currently has some NOS steatite rods on sale -- 1/2 inch diameter by 8 inches long for $14.o0 with free shipping. Steatite is purified soapstone. It is reputed to be machinable, but I've never tried it.
One can also purchase 1/4inch diameter x 5 inch long white soapstone rods for $4.50 per pack of 10. That is also possible source material for small spark plugs.
http://www.safetyequipmentdirect.com/radnorr-1-4-x-5-round-no-1-select-soapstone-10-per-card.html
http://www.safetyequipmentdirect.com/radnorr-1-4-x-5-round-no-1-select-soapstone-10-per-card.html
Your right about the price being over the top. At 100 bucks an inch i'll stick with the Corian.
