Calling a bolt by its head size

[Wamsutta]

I think it's a bad idea. I see a lot of youtube mechanics doing that.

An M6-1.0 bolt is not a 10mm bolt. It's a 6mm bolt. It may measure 10mm across the width of the hex flats, but it's not a 10mm bolt. And when it comes to SAE, I've always thought of 5/16'' bolts as 5/16'' bolts. I never once thought of them as 1/2'' bolts just because they measure 1/2'' across the flats. Maybe I'm wired differently, but I like the way I do it better.

 

[Wakefield]

most don't know any better
the SAE fine thread 3/8"s "capscrew"? used on most lawnmower blade attachments?
most just know a 9/16" socket or wrench fits its head (there might be a version with 5/8" head but don't remember whether that was bigger shank than 3/8" (was on Toro pro mower)

 

[readhead]

Shank diameter is the size of the bolt.

 

[Don1357]

Shank diameter is the size of the bolt.

A lot of people don't even know what a bolt shank is.

 

[readhead]

That could be disturbing.

 

[readhead]

Here is a handy fact for figuring out how long of a bolt you might need. The height of a nut is equal to the bolt size. 1/2” nut is 1/2” tall and so on. Of course there are specialty nuts that are different but for common nuts it works fine.

 

[ducksface]

I think anyone with any amount of time spent actually doing things can figure it all out.
I'm pretty sure if I was asked to hand someone a diff cover bolt of 7/16ths, I'd know they meant a 1/4-20.

And while you're complaining, I have a complaint:

It's a two inch QUARTER-20 not a QUARTER INCH BOLT when you call it out to the gopher.
If you're going to talk about the lack of knowledge, make sure you're knowledgable. You're bitching about specifics and using a nonspecific as the end all.

Damn guys, you're really showing your ****....

 

[American Locomotive]

If I'm referring to the bolt-head size, I will call it a "10mm bolt". If I'm referring to the shank-size, I will call it an "M6 Bolt". That's the system most my friends, my coworkers and I use. Works well enough for us.

 

[cheechi]

if you work with people who don't care enough to learn, but they want to help with something (especially if you are helping them), call it by whatever you can both communicate.

not everyone needs an engineering degree to turn a wrench. And I have an engineering degree and put a high value in higher education, especially among the trades. Sometimes it's time to change an alternator and other times it's time to plan for the future.

 

[SeisMec]

I've never seen a catalog or been in a hardware store that organized bolts by length and then by shaft size. Always shaft size; then thread count and finally length.

 

[TRWham]

It really doesn’t matter what you call an M6 bolt- you won’t be able to find the 10 mm socket you need to turn it.

 

[2ndGearRubber]

If I'm referring to the bolt-head size, I will call it a "10mm bolt". If I'm referring to the shank-size, I will call it an "M6 Bolt". That's the system most my friends, my coworkers and I use. Works well enough for us.

That's how I do it.

If I'm referring to a fastener to identify it to another person, I'll typically use head size. If the head is the only visible part of the fastener, how can i identify it by shank and pitch?

Now if I need a replacement fastener, I'll specify by shank and pitch. I have 10/12/13/14mm head, m8x1.25 bolts in my "m8 bucket". I don't care in that instance as to head size, it's pitch that matters.




Now, to be fair, most people can't identify pitch by eye, especially at a distance. Yes, many can spit ball 3 or 4 common NC sizes. But can you eyeball m10 x 1.25 or m10x 1.50? Can you do that from the same distance as determining a 17mm or 19mm head? With the same confidence? I sure can't. I can tell a 14 vs a 12 from 6' away. My glasses aren't good enough to call the pitch, unless I'm working with a specific vehicle and know the pitch and shank based on bolt design. As you said, if it's got a 10mm head on it, 99% of the time it's going to be m6x1.

 

[2ndGearRubber]

if you work with people who don't care enough to learn, but they want to help with something (especially if you are helping them), call it by whatever you can both communicate.

not everyone needs an engineering degree to turn a wrench. And I have an engineering degree and put a high value in higher education, especially among the trades. Sometimes it's time to change an alternator and other times it's time to plan for the future.

Big thumbs of there. I struggle with that training people or dealing with new people. I entered the industry struggling with "proper" names for things. Now I've internalized them, and can find it hard to ignore. For instance I've changed over from "12 volts" to "B+" or system voltage, because the latter is actually what I'm looking for. If the battery voltage is 14, and I have 12 at a component, I've got a major drop issue. DMM don't measure voltage, they measure difference in potential, between the two points. It's a math equation.

Most people don't know what a bump-stop is. But if you call it a shock bumper, or the round-ish dog-chew-toy-looking-thing, they get that. All about what works.

 

[larry_g]

Ya want to get people up in arms and arguing then try and define the difference between a bolt and a screw.

To cut to the bottom line FOR ME it is defined in machinerys hand book. A screw is torqued by its head and a bolt is torqued by a nut, Think carriage bolt.

lg
no neat sigline

 

[Lucid Moments]

OP is absolutely correct, and at the same time to many people totally irrelevant. If I am wrenching on a car then what matters to me is what sized wrench I need to use to tighten or loosen said bold. I am not going to get a thread gauge out so that I can always refer to it by its proper nomenclature.

 

[Old Man Roger]

I guess you could always say, take out the bolts with the 8 mm head. Would that satisfy the engineers? lol Like someone said, you can't see the threads till you take the bolt out, but you can see the head. It saves you from having to tell them what socket they will need too.

 

[Fcvapor05]

The things some people care about...

 

[nbpt100]

I have learned a few things from reading this. One of which is that Youtube mechanics are just a guy with a camera and something to wrench on. Some are professional and it goes down hill from there. From my US perspective, the most common nomenclature is Diameter-thread pitch-length-head type. In Europe it may be different.

For example 1/4-20 x 2.5 SHCS

Sometimes the head type is first.

For example: SHCS 1/4-20 x 2.5

Just my experience from playing engineer and hack small engine mechanic.

I like it when the video tells me the wrench size needed. Knowing the rest is usually irrelevant. If you need to replace the bolts like on a TTY bolt. Then you would need to define the bolt properly so you can get the correct replacement..

And yes, on small engines they often use flanged hex bolts. They use a smaller socket size than the standard SAE bolt heads. For example, a 1/4-20 flanged head bolt uses a 3/8 socket not the more common 7/16. On Toro/Lawnboys walk behind mowers the blade bolt is often an uncommon SAE 7/16-20 UNF which has a 5/8 hex head. The most common blade bolt is 3/8-24 with a 9/16 hex head.

If you are annoyed by the language in a particular Youtube vid why not complain there and you may get the operator to learn something new.

Party on!

 

[dnschmidt]

Does anybody give a **** about any of this? An M6 can have three different head sizes depending upon whether its JIS, DIN or SAE. Use whatever wrench fits.

 

[moron88]

Ya want to get people up in arms and arguing then try and define the difference between a bolt and a screw.

To cut to the bottom line FOR ME it is defined in machinerys hand book. A screw is torqued by its head and a bolt is torqued by a nut, Think carriage bolt.

lg
no neat sigline

from what i can tell, it's actually a pretty easy designation. screws have internal fastening interfaces and bolts have external interfaces. meaning you insert the driver into the screw vs insert the bolt into the wrench/socket/board.

 

[BlakeTheCarGuy]

I don’t know anything about actual sizes of the bolts I just look at the bolt if I see lines it’s SAE and I need to grab my SAE socket or wrenches then I do and if I see numbers it’s metric so I get metric stuff I never knew nothing about the other stuff other than head size.


Sent from my iPhone using Garage Journal

 

[brownsmustang]

I've been in manufacturing maintenance for a titch over 20 years and raised on a farm for the 18 years before that. I have seen and heard and said things that would make most shake their head. I learned quickly that EVERY place of employment has it's own lingo.

 

[darkzero]

When I worked at a shop we did the same although we knew better, at least I did. Called a bolt or nut by the size of the wrench size. It was just easier for the cars we commonly worked on. As said the head size will vary depending on the type of fastener. Outside the shop which I no longer work at I call everything by the thread size.

 

[lardy1]

Work with customers in the residential building arena sometime. You have to learn a new language for each customer.

 

[Negen]

According to my wife the size of the head or the size of the shank isn't so important if the bolt still works is all she cares about.

Sent from my ONEPLUS A6013 using The Garage Journal mobile app

 

[jh87]

If these videos the OP is referencing are automotive how-to videos, it would make sense to call them out by the head size because that’s the relevant information the viewer would need, i.e. what wrench size are they going to need to remove the bolt. If you’re ordering fasteners, you would call them out by the bolts diameter, thread pitch, length, etc. to ensure you got the proper fastener. Head size would be less relevant in this situation as they are standard unless you’re looking for a specialty fastener.

 

[HenryAZ]

And then you are working on an FJ-40, with JIS hardware. You replace a worn out M8 screw with an aftermarket one (from McMaster, e.g.). Now you've got two different wrench sizes (12mm & 13mm) to bolt that cover on.

 

[richfinn]

In England mechanics would refer to an M6×1.0 bolt or nut as a "10 mil" (if it actually had a 10mm head)

I cant see it makes any difference what YT mechanics call it unless you are actually repairing a thread or buying new fasteners

I've been at it for 35 years and understand nuts and bolts pretty good

In a workshop you will always use "slang" terms, that is how the English language works

 

[908Jim]

I'm an engineer, so I get the concern, but I don't necessarily see a problem here. I've designed structural rocket and satellite components, so I appreciate a good bolted joint, but I still do this regularly.

It's a common practice derived from convenience. The mechanic's job is to remove/install the fasteners, so it's just more efficient to refer to them by the size of the tool required. Without a print or assembly drawing of the vehicle, the odds of them getting the thread size of a blind fastener correct are slim anyway.

 

[orangeblood]

According to my wife the size of the head or the size of the shank isn't so important if the bolt still works is all she cares about.

Sent from my ONEPLUS A6013 using The Garage Journal mobile app

OK...this is some funny stuff right here!

 

[Citation]

I'm an engineer, so I get the concern, but I don't necessarily see a problem here. I've designed structural rocket and satellite components, so I appreciate a good bolted joint, but I still do this regularly.

It's a common practice derived from convenience. The mechanic's job is to remove/install the fasteners, so it's just more efficient to refer to them by the size of the tool required. Without a print or assembly drawing of the vehicle, the odds of them getting the thread size of a blind fastener correct are slim anyway.

Same here. In CAD it's easy to see a bolt is a 4-40 x 0.75" etc. In these cases the head is often either an afterthought or selected due to access concerns (do I use a phillips, SHCS, Panhead etc). In some cases I can easily switch between socket head, traditional hex or philips. That change many have no impact on the joint I'm trying to make but it does impact someone who has to take things apart later. When it's time to remove that water pump pulley, well I don't actually know what the diameter or length. It doesn't really matter as I'm not deciding which faster to use, only what tool I need to work with it. What I need to know is I need a 10mm socket to remove it thus it's a "10mm bolt". The shank size will mater if I need to torque the fastener down and I don't have a book to tell me (or if the book is wrong). Else, yeah, the critical information is which tool do I need to use.

 

[sz0k30]

And when it comes to SAE, I've always thought of 5/16'' bolts as 5/16'' bolts. I never once thought of them as 1/2'' bolts just because they measure 1/2'' across the flats. Maybe I'm wired differently, but I like the way I do it better.

That's because you are doing it the correct way!

 

[Spacey_G]

from what i can tell, it's actually a pretty easy designation. screws have internal fastening interfaces and bolts have external interfaces. meaning you insert the driver into the screw vs insert the bolt into the wrench/socket/board.

That's incorrect. The difference is in application. A bolt passes through both parts and threads into a nut. A screw passes through one part and threads into a tapped hole in the other.

The exact same fastener could be a bolt or a screw depending on how it's used.

 

[Citation]

That's incorrect. The difference is in application. A bolt passes through both parts and threads into a nut. A screw passes through one part and threads into a tapped hole in the other.

The exact same fastener could be a bolt or a screw depending on how it's used.

Is it a strut or a shock? Gearbox or transmission? AWD or 4WD?

This is the problem when a technical definition (or lack their of) is used by many people. That definition seems to me to describe the joint vs the fastener used. I wouldn't think of the head bolts on my car's engine as head screws even though, by that definition, they are.

 

[fartymarty]

I wouldn't link of the head bolts on my car's engine as head screws even though, by that definition, they are.

The definition as far as bolt vs screw in Machinery's Handbook is fine ...for Machinery's Handbook.
For me, if it has a hex head or a carriage head it's a bolt as long as it has machine threads. If it has any other type of head it's a screw. Hex heads with sheet metal type threads are screws. Of course the exception to the rule are lag bolts. Confusing and yet It makes sense to me.

 

[larry_g]

The definition as far as bolt vs screw in Machinery's Handbook is fine ...for Machinery's Handbook.
For me, if it has a hex head or a carriage head it's a bolt as long as it has machine threads. If it has any other type of head it's a screw. Hex heads with sheet metal type threads are screws. Of course the exception to the rule are lag bolts. Confusing and yet It makes sense to me.

This lends credence to the old saying, "Standards are so important, everyone should have their own."

lg
no neat sig line

 

[VolvoRyan]

Pedantry. Not Practical. I agree with the principle here, but not its use.

For how-tos and tutorials and even service literature, wrench size is what matters. There are TONS of specialty fasteners on an automobile. What tool you use is the pertinent information. The diameter and pitch of the fastener is utterly useless most of the time.

For example, Volvo's repair information has wrench/tool sizes so that you can grab the right tool to do the job in a timely manner. When torques matter, the value is given.

I've had the screw/bolt debate, and it's a fun one! A little part of my cries every time a screw is called a bolt.

-Ryan

 

[BillK]

If I'm referring to the bolt-head size, I will call it a "10mm bolt". If I'm referring to the shank-size, I will call it an "M6 Bolt". That's the system most my friends, my coworkers and I use. Works well enough for us.

But that is not really correct. What do you call a 3/8 x 16 bolt that has a 9/16" hex head ? Certainly not a 9/16 bolt.

If you look in any catalog like McMaster Carr or even the bolt bins at Home Depot the bolts and screws are listed by the size of the threads. Not the hex size.

 

[M6erfan]

I always use the thread diameter and length...

M6 x 20
M5 x 12
M8 x 45

etc...

95% of what I work with is metric and "standard' course thread. If it's a rare pitch, I'll call that out too. My fastener bins are labeled accordingly so even if someone doest understand what I said, it's labeled clearly on the bin, so easily picked.

 

[American Locomotive]

But that is not really correct. What do you call a 3/8 x 16 bolt that has a 9/16" hex head ? Certainly not a 9/16 bolt.

If you look in any catalog like McMaster Carr or even the bolt bins at Home Depot the bolts and screws are listed by the size of the threads. Not the hex size.

Nothing I work on frequently has SAE fasteners. If I do, it usually works like this:

- If the bolt is installed in something, it's whatever size the head is
- If the bolt is free laying around, it's whatever the shank size is.