I like SAE. Metric doesn't make sense to me, because I can never remember which way to move the decimal point for a given prefix.

It really makes me mad that my truck, and most modern American cars, use both, though. Not only do I need twice as many tools, it makes it a lot harder to find the right size wrench (there ain't a whole lot of difference, in some cases), which increases the risk of using the wrong size, which increases the risk of damaging the fastener I was trying to loosen.

 

sae bolt and metric bolt

 

Are we talking better standards, i.e. strength? Without digging up my old copy of a standard book, I couldn't say. I can say the finish and anti-corrosion properties of the metric automotive fasteners are generally better in my experience. The fasteners I worked with on jet aircraft engine were SAE Mil Spec pieces...no junk there.

 

What do you think????

Metric all the way. Its so much simpler.

 

metric huh, never mind the head size, there is jap metric, european metric, and british standard metric. all of these have different threads and do not interchange. also we have sae (fine thread) and uss (course thread) and they are slighty different also.

 

I didn't vote in the poll 'cause I don't care which...I just wish it was or the other. One vehicle with both drives (pun intended) me nuts (pun intended again).

Not that I do my own maint. that much anymore...

 

I have ranted and raved about this before and anyone that works on Cat construction eqiupment will agree. They use both standard and metric. Which is fine. But Cat use 16 mm heads instead of usual 17 mm head, and then 18 mm head instead of the usual 19 mm head. And this is all fine and dandy when you can see the bolt or you assume the bolt is standard and it is metric and vice versa. Most of the time you know what they are but when you start tearing in a little deeper then usual you have a fistful of tools with you. And being a mechanic I wish it was all metric. I would have alot more tools and room in my toolbox then. But the Snap On man would not be though.

 

Huh?? Metric bolts are metric bolts. It is possible that you may have run across some different thread pitches which of course do not interchange, but they're still part of the metric standard. Just like SAE bolts, there are fine and coarse thread metric bolts. Some metric bolt sizes may even have very fine or very coarse threads available.

Typically your standard metric bolt sizes used in automotive applications are as follows:

M6x1.0
M8x1.25
M10x1.5
M12x1.75
M14x2.0
M16x2.0

I generally prefer metric fastners because there's a larger variety of grades available and you don't have to keep converting fractions in your head to figure out what the next size socket is...especially when dealing with 32nds and 64ths.

 

Most industrial nuts and bolts tend to stick closer to the metric standards and use the even sized hex sizes instead of the odd ones. My guess as to why automotive applications generally use the odd sizes is because a 13mm head closely approximates 1/2" and is a VERY common size on many cars.

 

I have to go with the SAE and USS size fasteners. When I started out as a mechanic
you kept a 3/8-7/16 and 1/2-9/16 wrenches in your pocket and you were ready for a lot of what the days work brought you. With the metric sizes you need the tool box handy. The only one who gained anything from this is the mfg's. When an engineer had to put a fastner one size larger to provide the safety factor in a given location the spread of 1/16" per size was to much, weight and cost were gained. That fraction of a cent in cost what broke the camels back.

 

[QUOTE=kotzy]I have to go with the SAE and USS size fasteners. When I started out as a mechanic
you kept a 3/8-7/16 and 1/2-9/16 wrenches in your pocket and you were ready for a lot of what the days work brought you. With the metric sizes you need the tool box handy. /QUOTE]

The same can be said about a 10, 13, 15, and 19 mm when working on metric stuff. You still get the odd size fasteners in both standards (for example 11/16 or 17mm)...

 

Talking about odd sizes - I was replacing a steering box on an Astro van the other day and discovered the bolt size was 16mm. None of my metric wrench sets had that size - had to go out and buy it special. Why would GM do that? Once again those GM engineers annoy me!

 

It's almost a pointless question. It's not as if we have any choice in the matter. When working on an American vehicle you have to have a toolbox full of both.

I find working on my German cars easier because everything is Metric instead of a mix.

Have a great day,
Doc

 

16MM= 5/8,

Sears has the wrench for eight dollars, There is a 6pt and a 12pt verison at Sears
http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00 942873000


Set:
http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00 947045000&subcat=Wrenches

 

Once you are above about 13MM you don't have too much trouble finding a SAE size that will fit a Metric bolt. In fact I do LOTS of Metric work and I own VERY few Metric tools above the size of 17MM. I always have an SAE wrench or socket that will fit the bigger fasteners VERY well.

In fact I lived in Germany as a GI in 69 to 71 and being a GI had very few tools, but did lots of car work once everyone learned that I was a car guy. I worked on lots of VW's, BMW's, Mercedes, Fiats and some other brands you probably never heard of, doing all sorts of work and got by pretty well with NO Metric tools at all. The biggest problem was 10MM. At first I had a 3/8" open end that I filed out to 10MM and I still have it. With no more tools than that I overhauled several VW engines and went pretty deep into all sorts of other things.

Then I came up with a 10MM combination that an old German man gave me and then got a set of 3/8" Metric sockets from 10MM to 19MM with the only even sizes being 10, 12 and 14. I thought I had died and gone to Heaven.

Then I came up with a set of Metric Allens and I was REALLY in high cotton.

Once I got back to the states I got some middle quality Metric combinations from 10MM up to about 19MM while my SAE tool collection grew drastically. I did LOTS of work on German cars with no more Metric tools than that. I overhauled MB engines and all sorts of stuff.

German cars don't use very many even sizes. In fact the only even size I can remember seeing on any German car are 10, 12 and 14. Then the Japanese cars started showing me different fasteners including 16 and 18 of which I NEVER see on a German car.

In recent years I have gotten some good combination Metric wrenches, some obstruction Metrics, some offset Metrics, some Metric deep sockets, some Metric socket head sockets and a few odd and end Metrics for special purposes such as a 27MM deep socket for German diesel injectors and a 36MM socket for a few BMW product things. So I now have some quality tools for the Metric stuff.

STILL working on American vehicles is the most frustrating because of the mix between the two.

Have a great day,