cherrybomb
Well-known member
On my Camry,a bolt of the same size,as one from hardware store,used two different size wrenches.What is the reasoning?
Wrench sizes for metric bolts
- Thread starter cherrybomb
- Start date
alex71
Well-known member
There are several different standards for metric bolts. DIN is the most common. JIS is used on many Japanese cars (Probably what you are seeing--smaller heads). There is an ISO standard as well, which has the same head size as DIN for most size, but not all.
JohnDeere1
Banned
If it was a replacement bolt from the hardware you bought the wrong head size but right threads happens to me alot.
I have a batch of 1/4-20 that has half inch heads on them.
I don't think you found anything out of the ordinary.
As said above in a round about way:
Cars aren't hardware.
Cars are engineered for sheer and torque and stress and dispersement of the same. (and also what fits into the robotics the best.)
I don't think you found anything out of the ordinary.
As said above in a round about way:
Cars aren't hardware.
Cars are engineered for sheer and torque and stress and dispersement of the same. (and also what fits into the robotics the best.)
DFB
Well-known member
Ha! I have bunch of 1/4-20 bolts with 3/8" heads on them. 
alex71
Well-known member
True this and to understand standards;
" Standards are so important that everyone should have their own."
lg
no neat sig line
alex71
Well-known member
That would be a heavy hex bolt. The spec starts at 3/8, but it follows the pattern. 1/4 nuts, bolts and hex caps are 7/16 AF. 1/4 heavy hex nuts are 1/2 AF. You've got some kind of unicorn there
DFB
Well-known member
Ya they are full thread and slotted to
dalehsc
ALLIANCE MEMBER
A lot of times it's the engineer's decision(or maybe the accounting dept) what the bolt specs are. Anyone who has experience working on VW's,knows the toolbox is usually empty,by the time you get a major job done. It seems the engineer's wanted to use each & every tool they had in building a vehicle !
as stated it JIS on japanese cars, much prefer the fastener reduced hex size of JIS and quality grade fixing hardware used by japanese automotive engineers. Reduced hex saves wieght and allows beter tool access in confined spaces, good engineering standards by the japanese. sticking with 8 10 12 14 17 & 19mm hex sizes also makes working on Japanese cars easy and organised .
That explains it. I've always wondered what causes this, the problem I run into a lot is with cheap after market accessories, usually kuryakyn if I remember right. Metric and standard do not fit, the only thing that fits is the crappy hex key that come with it. Of course that rounds off if you breath on it.
We figured they were making their own bolts or something, if i remember right even the threads are weird.
We figured they were making their own bolts or something, if i remember right even the threads are weird.
WittHay
Well-known member
Not related to Japanese cars, but i noticed some German equipment came with 19mm hex head sizes and the replacement bolts are 18mm hex head, same size thread.
Never knew much about the names for the different standards in metric, but I found North American metric bolts are slightly different than European bolts which are different than Japanese bolts
Never knew much about the names for the different standards in metric, but I found North American metric bolts are slightly different than European bolts which are different than Japanese bolts
I'd have to go look at Machinery's to be sure, but ISTR that US generally follows the ISO standard, which mostly matches DIN with a few exceptions, and that JIS, as mentioned above, tends to run 1-2mm smaller heads for a given fastener thread.
Sent from my Pixel XL using Tapatalk
Sent from my Pixel XL using Tapatalk
alex71
Well-known member
ISO bolts are slowly dying out. DIN is much more common in the distribution channel. The main producers of ISO bolts were domestic, and now none of them produce metrics anymore, in any volume. You can still buy (wholesale) ISO bolts, but DIN is the de facto standard. The only North American manufacturer of ISO metric bolts is Infasco (Canada), triangle head marking.
If you are buying these in a hardware store and they have any sort of inventory turn at all, you are getting DIN. If they have racks of decades old dusty stock, who knows.
If you are buying from an industrial distributor like me, you will get DIN as well, but you shouldn't have to guess. It should say right on the paperwork/website/etc., what is being sold.
If you are buying these in a hardware store and they have any sort of inventory turn at all, you are getting DIN. If they have racks of decades old dusty stock, who knows.
If you are buying from an industrial distributor like me, you will get DIN as well, but you shouldn't have to guess. It should say right on the paperwork/website/etc., what is being sold.
The major difference between ISO and DIN in grade 8 or the din equivalent is that for the same size bolt the ISO bolt has a bit higher tensile strength than the DIN. The last place I worked our products were used and sold world wide. I lobbied hard for using DIN so that replacements did not have to come from the US. If DIN was specified the ISO bolts could be used as they were slightly stronger.
alex71
Well-known member
DIN standards cover dimensions and tolerances only. For example, DIN 931 is a metric hex cap screw with partial thread and a coarse (standard) thread form. The material properties are covered in the property classes (8.8, 10.9, 12.9, etc).
While an ISO spec bolt with a larger head may be stronger than its DIN counterpart (due to its larger volume), the material will be the same. What you wrote is a bit misleading.
While an ISO spec bolt with a larger head may be stronger than its DIN counterpart (due to its larger volume), the material will be the same. What you wrote is a bit misleading.
OP
cherrybomb
Well-known member
Thanks for all answers to my question.I had some machine shop experience, back in the day,mostly pipe thread,never really figured metric out.Did recently buy some really good thread guages and I am a study of bolts and hand thread all my assemblies.Seems to be the best way,haste makes waste.
fsae0607
Well-known member
I love my old American iron, but damn if I didn't enjoy working on my wife's former Nissan Altima for this reason.
DFB
Well-known member
Ya I like the bolt/nut sizing when working my Yanmar built John Deere...very standardized. Very seldom do I pull the wrong wrench or nutdriver
californiaHank
Well-known member
- Joined
- Nov 20, 2015
- Messages
- 487
There are few different standards, but they're merging into one dominant one.
ISO (international Organization for Standardization) This is the international standard, and all auto producing countries are voting members of the standardization body. This is the most modern standard, and most manufacturers are moving to use it.
There are also some country-specific national standards:
ANSI (American) - same hex bolt head sizes as the ISO standard
DIN (German) - older versions of the DIN standard had some differences from the current ISO standard, and lots of (mainly German) cars still have hex bolts that match the that standard. This will likely change over time, as manufacturers switch to new designs for parts. It's a slow process. If you're a manufacturer, you don't switch fastener sizes on something complicated like an engine or transmission until you design the next generation of the part. Major engine redesigns don't happen very often - the same basic block is used for many years with only small changes from year to year.
JIS (Japanese) - older versions had some differences from the current ISO standard, but manufacturers are moving to the international specs. Some car companies are moving faster than others.
There are good mechanical engineering reasons for why the ISO standard is better than older standards. These have to do with the amount of thread compression at a given tightening torque for a given head size. (But, I'm not a mechanical engineer and don't have a lot of knowledge in this area.)
If you're replacing fasteners on stuff on an existing vehicle, you generally want to use the exact same size the manufacturer used. Torque specs are different for different head sizes.
Rules of thumb:
ANSI = same as ISO standard
DIN = for some sizes, heads are sometimes larger than ISO spec
JIS = for some sizes, heads are sometimes smaller than ISO spec
Last edited:
The different standards for metric bolts:
https://www.boltdepot.com/fastener-information/bolts/metric-bolt-head-size.aspx
https://www.boltdepot.com/fastener-information/bolts/metric-bolt-head-size.aspx
OP
cherrybomb
Well-known member
So if I understand californiaHank correctly, if all car manufacturers are moving to ISO standards,all car fasteners will be the metric?Wouldn't this been better and a much simpler system if the USA would of done this back in what 1976?Help me History Buffs.
fsae0607
Well-known member
They were in transition... that's why when I used to work on my old '79 Cutlass, both my SAE and metric drawers were empty
Good move.
A really good handle on thread and fastener systems will relieve a lot of frustration and put you in control of the job at hand.
californiaHank
Well-known member
- Joined
- Nov 20, 2015
- Messages
- 487
Part practicality - You can't expect manufacturers to redesign every component on every car and retool every assembly line in a year or two. At least US manufacturers now all use the ISO/ANSI standards. Some German and Japanese manufacturers have been kind of slow converting to the latest metric standards.
Part politics - 'Metrication' in the US started with an Act of Congress in 1975, but Reagan was against it, and plans to convert a lot of stuff in the construction and transportation industries to metric standards got shelved during his time as President. (Canada started 'metrication' around the same time, but they went the whole way, and started using metric units for everything from lumber sizes to temperature measures to speed limits. I think Canada was mostly metric by the early 1980's. There were a few major screwups in Canada around that time, like when someone mixed up pounds and kilograms when fueling a jet, and the plane had to make an unscheduled landing because it ran out of fuel. I was in Canada that year, and that incident was major front page news.)
Last edited: