OT: Aircraft Sparkplug Socket Suggestion

John Garner · Jan 11, 2020

I need a 3/8 inch square drive sparkplug socket to fit aircraft sparkplugs with 7/8 inch hexes. A number of aircraft mechanics have warned me away from several different socket brands that they have been disappointed by, but none have been willing to recommend a best-overall socket . . . Except for one guy who swears by a WWII-era Plomb socket that was passed down by his grandfather. FWIW, the Plomb socket is 3 1/4 inch long and has a 3/4 inch square external hex that allows it to be driven by an open-end wrench.

Thanks in advance.

moonlight machine · Jan 11, 2020

John Garner said:
I need a 3/8 inch square drive sparkplug socket to fit aircraft sparkplugs with 7/8 inch hexes. A number of aircraft mechanics have warned me away from several different socket brands that they have been disappointed by, but none have been willing to recommend a best-overall socket . . . Except for one guy who swears by a WWII-era Plomb socket that was passed down by his grandfather. FWIW, the Plomb socket is 3 1/4 inch long and has a 3/4 inch square external hex that allows it to be driven by an open-end wrench.

Thanks in advance.

Get a 7/8 x 3/8 deep socket, part it off and weld the correct size tube between the socket parts. Job done, it's not rocket science you know.

Garwood · Jan 11, 2020

moonlight machine said:
Get a 7/8 x 3/8 deep socket, part it off and weld the correct size between the socket parts. Job done, it's not rocket science you know.

I used to build transmissions, mostly sticks for pickups, racing and medium duty stuff. I have a vidmar drawer 6" deep and 60" wide filled with sockets I've made like that. Some of them I made the entire thing from scratch, but most were just the end of a socket welded to a tube and another socket welded to the other end.

It can look real good if you put a tiny bit of effort into it.

cvairwerks · Jan 11, 2020

I bit the bullet and bought the Snap On one, S6106K, probably 35 years ago. At $35+ per plug, too much of risk to use something cheap.

awander · Jan 11, 2020

What's a "3/4 inch square external hex"?

John Garner · Jan 11, 2020

Um, an oxymoron? The Plomb socket has an external square rather than the external hex that's on the majority of sparkplug sockets.

awander · Jan 11, 2020

Here's one of those Plomb sockets for a little over $20 including shipping:

PRATT & WHITNEY SOCKET, DEEP, 3/8" DRIVE, 7/8" 6PT, PWA 2254, PLVMB, SKU 12456 | eBay

Bill D · Jan 11, 2020

Then you shove a short piece of rubber tube or hose down into the socket to grab the terminal of the plug so it does not fall off and get lost.
Bill D

Punkinhead · Jan 12, 2020

awander said:
Here's one of those Plomb sockets for a little over $20 including shipping:

PRATT & WHITNEY SOCKET, DEEP, 3/8" DRIVE, 7/8" 6PT, PWA 2254, PLVMB, SKU 12456 | eBay

The pictures don't show, but I assume it also has an internal hex for a ratchet. Otherwise it'd be a pain in the ass to use it with a torque wrench when reinstalling the plugs.

moonlight machine · Jan 12, 2020

Punkinhead said:
The pictures don't show, but I assume it also has an internal hex for a ratchet. Otherwise it'd be a pain in the ass to use it with a torque wrench when reinstalling the plugs.

The internal hex is for the spark plug, the internal square is where the ratchet goes.

cvairwerks · Jan 12, 2020

Bill D said:
Then you shove a short piece of rubber tube or hose down into the socket to grab the terminal of the plug so it does not fall off and get lost.
Bill D

LOL....no room...7/8's wrench flats with the upper plug body being about 11/16's.

S-88 SPARK PLUG - Univair Aircraft Corporation

DDoug · Jan 12, 2020

cvairwerks said:
LOL....no room...7/8's wrench flats with the upper plug body being about 11/16's.

S-88 SPARK PLUG - Univair Aircraft Corporation

Yup, and if it was a problem, I could see a small knurled knob on top
to rotate a nut to engage the HT lead threads, to "catch" the plug.

gbflyer · Jan 12, 2020

Not a professional A&P/IA.

I’ve used both the ATS and Champion magnetic spark plug sockets for 30 years of aircraft ownership and maintenance. I’ve never dropped a plug that was the fault of the tool. I’d be curious why your contacts have such difficulty in a recommendation for you.

Example:

ATS MAGNETIC SPARK PLUG SOCKET from Aircraft Tool Supply

John Garner · Jan 12, 2020

gbflyer --

The socket-design shortcomings that I've been told about are 1) socket OD large enough to interfere with cooling fins on some cylinder heads, 2) socket ID too small to clear RF shield on some spark plugs, 3) socket opening too shallow to fully engage sparkplug hex on some spark plugs, and 4) socket drive recess has only one shallow retention dimple that doesn't hold the socket on the driver very well. I don't remember which is which, but these shortcomings are associated with sockets from Bonney, Champion, Cruz (sp?), and Giller.

I had the single-shallow-dimple situation on a 1/2 inch drive Thorsen (which, I believe, stamped the Giller name on tools sold to the U S Government) aircraft sparkplug socket 40-some years ago. But my only use of that particular socket was in changing sparkplugs on a four-cylinder flathead engine, it was simple to hold the socket onto the ratchet.

All that said, the ATS socket looks pretty good. Thanks for pointing me in that direction.

John

John Garner · Jan 12, 2020

awander --

Thanks for that tip. I may have a new old socket in my collection.

John

gbflyer · Jan 13, 2020

John Garner said:
gbflyer --

The socket-design shortcomings that I've been told about are 1) socket OD large enough to interfere with cooling fins on some cylinder heads, 2) socket ID too small to clear RF shield on some spark plugs, 3) socket opening too shallow to fully engage sparkplug hex on some spark plugs, and 4) socket drive recess has only one shallow retention dimple that doesn't hold the socket on the driver very well. I don't remember which is which, but these shortcomings are associated with sockets from Bonney, Champion, Cruz (sp?), and Giller.

I had the single-shallow-dimple situation on a 1/2 inch drive Thorsen (which, I believe, stamped the Giller name on tools sold to the U S Government) aircraft sparkplug socket 40-some years ago. But my only use of that particular socket was in changing sparkplugs on a four-cylinder flathead engine, it was simple to hold the socket onto the ratchet.

All that said, the ATS socket looks pretty good. Thanks for pointing me in that direction.

John

Thanks. Wow, I’ve been lucky I guess, but I’ve just never had any of that in terms of interference or not reaching the hex with Champ or ATS. I’ve never had an oddball engine though. It’s been C90, O290, O320, O470, IO520, and O540 experience for me. Might be an issue somewhere else.

No problem on the link. Happy to help. Hope you find one that works for you.

gbflyer · Jan 13, 2020

Polled a couple of other friends and the Snap On S6106K came up again.

steve45 · Jan 13, 2020

John Garner said:
But my only use of that particular socket was in changing sparkplugs on a four-cylinder flathead engine, it was simple to hold the socket onto the ratchet.

John

Where did you find a four-cylinder flathead airplane engine?

I've never had a problem with an ordinary 7/8" deep socket (Proto, Challenger, etc.) on Continentals & Lycomings.

There are locking socket extensions that grip a socket better than the older extensions. You can get those at auto parts stores and Harbor Freight.

John Garner · Jan 13, 2020

steve45 --

The flathead four bangers were liquid-cooled ndustrial engines, not aircraft engines. Nevertheless their sparkplugs had 7/8 inch hexes.

My aircraft sparkplug socket came from a discount store in 1974 or thereabouts. It was blister-packed as a Herbrand 1/2 inch drive deep socket, priced at $1.49 (IIRC).

Interestingly, the socket I got was branded Thorsen, while some of the other hang-cards contained Bonney-branded sockets that appeared to be absolutely identical to the Thorsen-branded sockets.

I suspect that Triangle Tool-- the owner of both Bonney and Herbrand brands -- was the actual manufacturer, making the aircraft sparkplug sockets as specials . . . Packaging and selling "overruns" under their economical Herbrand brand. I also suspect there may have been a government contract involved, because I saw visually-identical sockets marked as Bonney and Giller in Air Force civil-engineering "power production" tool boxes in the late 1970s.

John

OT: Aircraft Sparkplug Socket Suggestion

Titanium

Diamond

Diamond

Cast Iron

Stainless

Titanium

Stainless

Diamond

Cast Iron

Diamond

Cast Iron

Diamond

Plastic

Titanium

Titanium

Plastic

Plastic

Stainless

Titanium

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