# Why is it?



## CowboyRam (Dec 13, 2015)

I have set of metric wrenches that go from 15 to 17, and skip 16. Also have some sockets that go from 17 to 19. I just does not make any sense to me to. Today I was taking a part of my baler and need an 18 metric socket, and of course I did not have one; my set skipped that one, so I had to use my 18 metric wrench. Just would have been just a bit faster with a socket. OK end of rant.


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## deadmoose (Oct 30, 2011)

As for the 16, just use 5/8. Iirc. 18 is just uncommon.


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## endrow (Dec 15, 2011)

Some of the later model John Deere equipment. Will require you to own an 18 millimeter socket and wrench


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## Farmerbrown2 (Sep 25, 2018)

New Holland 411 Discbine had some of those oddball sizes. It seams to me that the harder the bolt it makes the wrench size change in metric . My kid and I where mounting a sprayer on a neighbors NH TC18 tractor last week had to call dealer to figure out what size bolts fit in bell housing I hate the metric system.


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## Farmerbrown2 (Sep 25, 2018)

The metric system just sucks there I said it .


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## paoutdoorsman (Apr 23, 2016)

endrow said:


> Some of the later model John Deere equipment. Will require you to own an 18 millimeter socket and wrench


Yep, I've been working on a lot of 2011-2015 Deere Gators and compact tractors lately, and my 18mm gets used a lot. None of my wrench or socket sets skipped it though. My Gearwrench ratcheting wrench set skipped 15 though, and it irks me everytime I could use it.


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## bbos2 (Mar 20, 2015)

paoutdoorsman said:


> Yep, I've been working on a lot of 2011-2015 Deere Gators and compact tractors lately, and my 18mm gets used a lot. None of my wrench or socket sets skipped it though. My Gearwrench ratcheting wrench set skipped 15 though, and it irks me everytime I could use it.


I think 15mm is a bad one to skip . our combine seems to use it constantly . I thought the moco had a lot of 18?? Manufacturers must have deals with tool companies, seems like every time I work on a project it's a different fastener. Tool collection keeps growing


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## Thorim (Jan 19, 2015)

bbos2 said:


> I think 15mm is a bad one to skip . our combine seems to use it constantly . I thought the moco had a lot of 18?? Manufacturers must have deals with tool companies, seems like every time I work on a project it's a different fastener. Tool collection keeps growing


It's a conspiracy I tell you, a conspiracy, pounds desk just barely missing keyboard lol


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## mlappin (Jun 25, 2009)

Metric system isn't that odd once you get used to it, spent years working on dirt bikes and ATV's, all metric. Just sucks owning two separate sets of wrenches, allen wrenches, sockets, taps and dies.


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## paoutdoorsman (Apr 23, 2016)

bbos2 said:


> I think 15mm is a bad one to skip.


That was a fat finger on my part bbos2. Meant to say 16mm. 15mm would be much worse...


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## somedevildawg (Jun 20, 2011)

Just find a set of wrenches and sockets in 1/16 increments.....good luck finding them tho


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## Coondle (Aug 28, 2013)

I too once lamented the metric system but have become converted.Many metric sizes have a close approximation to SAE or A/F, but 16 mm is almost exactly 5/8.

Many think 9/16 and 14 mm are the same; not so the 14 mm is slightly smaller than 9/16. Further 1/2 inch and 13 mm while often interchangeable the 13 mm is slightly larger. (1/2 inch converts to 12.6 mm).

Usually an 11/16 socket or ring spanner will fit on 18 mm but it is a tight fit being 1 1/2 one hundredths of an inch larger than 11/16. A tight specified open end spanner may not fit however.

Interesting interrelationships of units in the metric system.

The length of one metre although now having an atomic specification was originally the length of pendulum that had a period of one second.

A volume of pure water (at sea level at i think 20*C) measuring one metre by one metre by ne metre weighs exactly 1000 kilograms, so one litre of water = 1 kilogram.

The system is here to stay and is increasing in use in engineering possibly because the ISO (International Standards Organisation) for metric screws were established in 1947 and offer only two thread sizes for each diameter. As manufacturers retool the trend is to retool in metric because so much of the world is operating on that system. The international language is increasingly English and measurement is increasingly in MKSA (metre, kilogram , ampere, second), except in aviation as yet.

The USA uses the metric system in its currency, Australia converted in 1966, to metric speedos/odometers in vehicles and metric weights and measures in the 1970's. Even the UK has converted to metric currency, metric speedometers and odometers in vehicles.

The system is simple, sensible and easy to use once you become used to it.


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## slowzuki (Mar 8, 2011)

I can answer why some metric wrench sets are different. There are JIS, ISO and DIN metric standards for bolts. From wrenching on metric japanese vehicles all my life it works great if everything is all on one standard. JIS for 99% of car work you need an 8, 10, 12, 14, 17, 19, 21 and thats it.

First time working on a domestic with metric bolts I had no idea what was going on with the additional 11,13,15,16,18 etc sizes and none of my taps worked as the threads are coarser pitch.

Well I'm pretty well prepared now in every system and we got rid of the only car with had with Whitworth bolt sizes. I've got all my SAE sockets and wrenches in 1/16 increments, much of the range in 1/32 increments. It comes in handy with rusty fasteners, just switch to the other units and pound the nearest smaller size on.


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## r82230 (Mar 1, 2016)

slowzuki said:


> Well I'm pretty well prepared now in every system and we got rid of the only car with had with Whitworth bolt sizes. I've got all my SAE sockets and wrenches in 1/16 increments, much of the range in 1/32 increments. It comes in handy with rusty fasteners, just switch to the other units and pound the nearest smaller size on.


I am prepared to, with a metric blue tool & vise-grip, that work on English or Jap stuff :lol:, oops, better say 'adjustable pliers', before some gets me a kick somewhere. I too remember the different metrics, when working on a Jap bike or an English one, back in the day.

Larry


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