Spark plug hex sizes: common applications?

[gamp945]

Hi all,

Kind of a noob question maybe? I know that 5/8" (16mm) and 13/16" are the two most common spark plug hex sizes, but there are also others.

My question is: what applications are the "other" hex sizes commonly found on? For example, 18mm and 3/4".

Surprisingly, a google search yielded no useful information on this topic!

This question was brought to mind when I was browsing spark plug socket sets and wondering if I needed anything other than 5/8" and 13/16" for my homeowner/hobbyist usage. Craftsman apparently thinks I need 18mm and 3/4", but I don't know what equipment these sizes are used on.

Thanks for reading

 

[wayne55]

On some of my lawn mowers or other small engines, the 3/4 is used.

 

[bmwpowere36m3]

Depends on what you work on and COO. Their certainly out there. My older Kawasaki bike uses 18mm plugs.

 

[T45]

14mm is on european cars and some motorcycles

 

[M6erfan]

Below are just a few examples...

18mm hex, KTM motorcycles
3/4", Small engines/Lawnmowers
14mm & 18mm bi-hex (12 point), Modern BMW's/Mini's

 

[HAP]

9/16" on the Ford 5.4

 

[gungatim]

most small engines use 3/4", 18mm I've mainly encountered on motorcycles, IIRC BMW chrome heads, and my old Yamaha...

 

[Show7d3]

Small engines such as B&S and Kohler OHV, and some chain saws and trimmers use 5/8". Others can be 3/4 or 13/16. I'd say get various sizes of sockets and you'll be covered.

 

[shockwave]

14mm 6point on some newer Asian vehicles
5/8 is the most common 13/16 on older vehicles
9/16 on newer fords (with carb cleaner or penatrant) very easy to break in the head
18mm motorcycle
11/16 older Bmw m series had these

 

[bubinga]

sometimes you need a deep 5/8" (16mm) Nissian 4 cyl comes to mind.
the one HF sells is decent.

 

[Superbec]

You basicly need all 14,16,18,21 mm in both 6 and 12 point. and whatever standard one you may need.



If you don't have any I would look for a complete set , also get the ones with the magnetic ring not the stupid rubber plug !

A few locking extensions and cardans will probably come in handy

Nothing is more frustrating than having a bunch of keys but the one that works

 

[M6erfan]

11/16 older Bmw m series had these

Forgot about that one, I have it, for BMW S38/S14 motors. Not too common lol

 

[sberry]

Some old engines had big ones, 7/8 too but they are pretty rare today.

 

[dnschmidt]

What people are calling 9/16" on Fords is actually 14mm. If you've ever noticed that the 9/16" fits a little sloppy, not much just a little, it's because 14mm is slightly smaller than 9/16". Also some 14mm plugs are 12 point and obviously require a 12 point socket.

 

[Cope]

Some old engines had big ones, 7/8 too but they are pretty rare today.

Back in the day that was called a commercial spark plug. Same one was used on my Cushman scooter.

 

[MJD1]

IH tractors used a 7/8" hex, other manufacturers did also.

 

[Schurkey]

I bought an 18mm spark plug socket for my Honda motorcycle. Either it never did fit well, and I didn't notice, or NGK has changed their hex size. 18mm is just a bit too large; although I use it anyway as I don't have anything that fits better.

 

[bob15]

IH tractors used a 7/8" hex, other manufacturers did also.

Deere 2 cylinder's are also 7/8" hex

 

[WildwoodChuck]

Carlyle (NAPA)

3/8" drive

CHT SSP3818 9/16"
CHT SSP3820 5/8"
CHT SSP3824 3/4"
CHT SSP3826 13/16"
CHT SSP3828 7/8"
CHT SSP3818M 18mm

They also have 5/8" & 13/16" with universal joints, their other brand evercraft offers 9/16", 5/8", 13/16" & 3/4" with universal joints some extended special use sockets and some 1/2" drive ones.