Pulley vs Sheave???

I belive these are regional or industry specific differentiations. ie shipyard vs railyard, UK vs US kinda stuff. I am unfamiliar with any technical diffs. and can,as always, be dead wrong.

cr3

For me, a pulley is always used with a rope or cable (round profile), any other type of belting runs on a sheave. No good reasoning to back this up, just the way I've always used it. Bolt or screw, anyone?

A girlfriend used to get upset with me... a screw then bolt.

cr3

When they asked me this at work one, I did a stanza of "Bringing in the Sheaves". They quit asking me.

This is one of those old "bolt vs screw", "string vs twine", "drill or drill bit" questions that is just local usage.

For what it's worth, in some parts of the US, it's pronounced "shiv" like the sharpened toothbrush used by a nasty convict.

One thing about it..... a Pulley or a Sheave..... when you pull on the rope the pulley turns and when the cable follows in or out...... the sheave turns!

don't know about sheaves but pulleys are for belts and not for twine or ropes. Block and tackle is for ropes.

With regards to bolts and screws there is however a very simple answer, screws are not designed to be calculated and or duplicated by design or function. You cannot predict anything about the screw as such other than that it will screw into something. Bolts are however very precisely engineered for one reason only, they can be reproduced without having a sample and thus can be used for engineering and design before manufacture. Bolts are according to a standard which is set and can be relied on. The commonly used term "machine screw" is a misnomer and simply does not exist.

Hope you find the answer for your pulleys and sheaves.

Hurumph...hurumph. I wouldn't put my name to that statement either.

I think I know what you were trying to say....something along the lines of ASME bolt grading or something.

Deutschmeister is that you? Nah. You would of signed it.

Not the one you mentioned, when you are a guest you can be a true guest.

Same as who asked what the guy was on below.

Still think I am right about my bolts and stuff. Just so happens that the misleading errors have been allowed to live on for a long, long time so it all gets abit fuzzy. Originally that is why they were invented and that reason still exists now. Without any set rules for them none of us would be here having a job in engineering methinks.

Regards,

KLB

"screws are not designed to be calculated and or duplicated by design or function" Then what do you call the rod with a helical groove that moves the table on my mill and lathe?

It is obvious that there is no concrete answer --- it is one of those gray areas where effective communication is very important. If the folks you work with understand what you are talking about then whichever term is used is correct.

The same seems to hold true for screw or bolt --- everyone has his own concept, yet there is really nothing (that I have been able to find) that firmly defines or confirms any point of view as the correct one, for these components (pulleys vs sheaves or screws vs bolts) of very common systems.

I have submitted this question to a couple of engineering forums and the outcome is exactly the same as the responses here.

Try it for yourself --- ask this question of many people and you will find the exact interpretations expressed in this thread. If you find something that is a firm definition for either, screws vs bolts, or pulley vs sheave (able to be confirmed as correct) please post it here.

It seems that the consensus (with a few exceptions) is that they are interchangeable depending on the location, specific activity, industry, and designer of the the equipment used.

There IS a clear distinction between a screw and a bolt. Any one who suggests that there is not has a screw loose, and you should bolt.

Yes, I know there is a distinct difference between a screw and a bolt but based on some of the comments made in this thread I can see that there is not a common sense of that difference. In fact a google of the two terms give many definitions of each --

I agree but I'm not going to tell anyone posting here that they are wrong -- If where they work their fellow workers understand them then communication is working for them.

In my mind though there is a clear distinction. Any industrial supply catalog gives a good indicator as to what is called what.

If I am ordering a what is commonly called a 1/4"-20 screw and McMaster Carr has it listed as a "Widget" I am ordering that 1/4-20 Widget. - 1/4-20 being a machine screw with a 7/16" flat -to flat hex head.

For Example Some say:

Some say "a screw has a pointed end and does not use a nut". Not always true

Some say "a bolt does not use a nut but screws into a threaded hole". Not always true

Some say "a screw has a slotted head". -- Not always true

I agree but I'm not going to tell anyone posting here that they are wrong -- If where they work their fellow workers understand them then communication is working for them.

I will. Here ya go:

Page 1492 of the 26th edition of the Machinists handbook will clearly define the difference between bolt and screw. There is no argument. There is no discussion. If someone in the workplace is making reference to a bolt when they mean screw then they are mis-speaking. Period. The end.

Thank you very much --- feel better now. Somehow that message needs to get out to everyone.

Now that you have made sure everyone understands screws and bolts, (Maybe) the topic will go back to pulleys and sheaves -- What does the Machineries Handbook say about them. Probably not.

Have a nice day sir --- as you so politely put it --- Period. The end.

Funny you asked about the Machinist's HB. I never thought to look. Ha!

Okay, they make no clear distinction. However they do associate sheave more with wire rope (cable).

Period. The end

cr3

A screw is meant to be turned when tightened while a bolt is meant to be stationary (the nut is turned instead). The best example of a bolt is a carriage bolt. Obviously, a hex head bolt can be turned but it does not have a washer face under the head as does a hex head cap screw (like cylinder head screws). That is why washers are typically used with hex head bolts when they are going to be turned to eliminate damage to the part being fastened.

I've always associated sheaves with V-belts, while pulleys have teeth.

BTW I thought I was the only one who sang "Bringing in the Sheaves"!

Gears and sprockets have teeth. Sheaves and pulleys have grooves.

On container handling dockside cranes, the spreader bar (which is the part that actually picks up the shipping containers by latching onto them) is connected to the crane by a sheave beam. This beam typically has two sheaves on each end mounted vertically and oriented perpendicular to the ship. The wire rope from the hoist drums runs through these to raise or lower the spreader bar. Usually there are two wire ropes; one for each side of the spreader bar and these are routed through other sheaves at the back reach of the crane and the end of the boom. The sheaves have a half-circular groove on the rim to carry the wire rope and are sized for the rope.

As to the difference, I always thought that a pulley had a fiber or some other soft type of rope running through it, as in a block and tackle and has a smooth running surface. A chain fall has a toothed chain carry for the pulley, but I have never heard it called a pulley. Maybe called a chain sprocket.

My opinions here, and you know what they say about opinions.

A single sheave does not a pulley make. To have a pulley system you need more than one sheave.

Regards,

Drew

In the recreational boating environment, pulleys are always called sheaves by the pros and pulleys by the uninformed. On said boat they are otherwise the same. Anything with teeth would go by another name.

Not so. You can a have a one part system which is the simplest, with a suspended pulley and a line through it. You pull down, your load goes up.

I agree. Now on the other hand, I would not call that a pulley system. To me a system implies something more complex.

Years ago and probably sometimes still, farmers use a single wheel pully to lift hay bales,among other things, to the top of a barn.

As I understand it a sheave is the shape of the device. A pulley is some thing it can be used for. Time has defined both as the same though.

A pulley being a sheave that is use to change the direction of force.

1. All the definitions I found for both words describe a grooved wheel. No Difference!

2. A search for 'sheave' at McMaster-Carr brings up a list; clicking on any of the entries takes you to a page labeled "...Pulley..."

The etymology of the words may help a definition of original usage.

'Pulley' is probably the diminutive of the Greek 'wheel',i.e. 'little wheel',rather than a cart wheel.

Sheave could be from the Middle English or German for 'wide wheel'

This would support modern usage where 'pulley' is commonly used for small items usually single groove and 'sheave' for large multi groove items.

Now we can argue where the transition from 'pulley' to 'sheave' occurs.

Sheave is a component of a block assembly. They may be "nestled", "U", "Flat" or "V" grooved and usually have sintered or roller bearing. They are ganged between side plates to form blocks. Metal, stone, wood, polymer or composite they are properly called sheave.

Sheaves:

http://www.blockdivision.com/lgsheaves.htm

A "pulley" is correctly defined because of the purpose or action in which it is used. It is employed to correct, deflect or tension a belt, rope or chain. The words "change direction" or "guide"; to avoid abrasion or alignment of larger systems seems vague but easily understood when functionality is defined through use. Although a block does indeed change direction of a rope, be it wire, belt chain or rope; it's primary function denotes it as a "Block of Sheaves" for multi-sheave ganged blocks. When it is included between two points, to correct linear alignment, it becomes a pulley.

"Tensioner", "Guide" and "Pulley" are synonymous; rather than pulley and sheave, which are not.

Pulley:

http://www.randmachineco.com/cableguides.htm

Screw

A screw is a shaft with a helical groove or thread formed on its surface and provision at one end to turn the screw. Its main uses are as a threaded fastener used to hold objects together and as a simple machine used to translate torque into linear force.

Bolt

A bolt passes through a hole of larger diameter than its thread and is held in place by a nut or similar device. Bolts are not designed to be turned. What is often referred to as a bolt is in fact a 'cap screw', which is designed to be turned (or screwed). Cap screws may or may not be used with nuts. The distinction is subtle, but significant in the design of the fastener. If threaded all the way to the back of the head, a cap screw becomes a 'machine screw'.

How about a bolt for a door it don't have threads on it. You have to turn it to unlock it. You know to get the tang out of the groove before you slide it out.

Sorry to disagree. when a bolt has thread all the way up to the head, it becomes a setting bolt, not a machine screw. The term machine screw was brought into the equasion when some bolts had screw driver heads so people thought of them as screws.

Setting bolts have thread all the way up so you can use them to "set" a certain adjustment rather than fix two loose parts.

I still maintain that the primary difference between screws and bolts is their design and pre-determined shape, i.e. you can manufacture a nut for a bolt but not for a screw as you can manufacture a bolt hole with thread for a bolt but not for a screw, screws tap their own thread.

Sorry, but a 10-32 machine screw takes a 10-32 nut and the nut can be of many different types. As with 1/4-20, 1/4-28 and on and on. I could be mistaken, but if I am I just wasted money on 1000 ea. 10-32 nyloks.

Don't think I've ever heard of a 10-32 Bolt.

What is we talkin' about?

I fergot!

One of these ... here

We started with "Pulleys vs Sheaves" wonder what tack it will take next.

Technically, the errors and omissions policy of the Schlumberger's web site designer would be liable for improper wording; if a finite definition of usage based terminology, were employed.

Maybe Schlumberger; their self insured business model structure and their suppliers don't want the words defined separately, as vendors who willingly allow their equipment to be used against labeled policy may be forced to expose themselves to risk? (Luckily, there are expensive insurance policies, (which few can afford); for such errors and omissions).

So the Golden Rule applies? He who has the gold, cooks the books and defines or chooses not to define the English language rules the day?

Despite the known use of wording, it may only be enforced emphatically, in order to eliminate competition or defer liability? The privilege to denominate such wording is reserved for whomever requires specific expression to avoid liability, at ones own discretion?

Here's a specific example of where it counts:

I assure you, "pre-fabricated" and "modular" do not meet the same definition, as the specified use of these terms denotes insurance and regulatory language, in order to prevent misunderstandings from occurring, in spite of States Rights and Insurance regulations, from state to state.

Why?

"Modular" buildings, here in the US, are required DOT cert. and insurance to cross state lines on Federal highways. They must be constructed to withstand Federal standards, in case of an accident. They must exceed 80 mph winds and braking without ending up all over the highway.

Can anyone apply for this important certification? No.

Are they used incorrectly by most people? You betcha!

Does anyone realize this definitive language specific contract structure exists? Few.

Does it restrict me from manufacturing a high quality, partially assembled building system and delivering it across state lines, (even if it exceeds the requirements)? Absolutely.

Similarly to the terminology for the SAE standard bolts, mentioned above. How would you Patent a device of method of compliance without finite terminology? How would you secure ISO certification with such variation and vague intention?

The meaning should be finite and without exception, in order to provide concrete language to limit erroneous mis-understanding by insurers who may not underwrite liability in the state being traveled through and the end user; so the definition becomes of significant value.

Shall we fight it out in court over every single patent allowed to be filed so vaguely? Should patent rights be upheld based upon wealth or threat, instead of accurate and purposeful language? Ask the accountants what that costs them.

Kleenex, Velcro; we all know the difference between a brand name and social miscommunication, (and obvious irresponsibility). It matters greatly when you specify one thing and provide another.

How about the guys who re-fitted the roof of the tunnel in Boston with "lag-bolts"?

Excuse me, I meant "Multi-part Epoxy activated, impact actuated, rotary mixed, Grade 8 Steel, SAE .75 in. x 5.5 in., fine thread shank bolt, embedded fastening system; manufactured by "____________"; known as "_____________".

What happens when one mistakenly uses split-lead shield inserts and low quality "tin-filled", grade zero "Lag Bolts", without washers; instead?

Or ignore manufacturers instructions during installation and uses worn bits to over-bore every hole? How would any of you reading this feel about being threatened with your job, or forced to continually be the hard line, for standing up for clarification of terms or suggesting we follow safe procedure?

Finite terminology and proper definition makes a great deal of difference, especially when death can occur rigging. I imagine the terms had separate meaning, until someone within industry seen fit to blend the words, at their exclusive gain.

Do you realize every single chain hoist used for every single concert or theatrical event you witness has a label clearly stating the device MUST NEVER be used for lifting persons or suspending loads over the heads of people?

Architect, Engineer, Designer, Stinky Pete; what's the difference?

They perform at the same incompetent level, when they go to work and prescribe or are forced to use a lifting device when it is explicitly restricted, rated or insured for the very use it is supplied for. It doesn't take a degree to figure out which guy you want to be when they assign fault and send someone to prison for using the "pulley" incorrectly, does it?

I wonder how Stinky Pete feels about this?

Dude...are you ok? It's just a link to a definiton of a pulley/sheave. It is one of any thousand compartive definitions I could have extracted. I just happen to do business with SLB and so.....

But really...did you have to beat up on Stinky Pete like that?

WOW!...... that was a diatribe of unexpected vindiction!

It's all true, as best I can tell. But unexpected all the same.

CR3

When I went to chain hoist school (don't laugh) I never saw nor heard any such statements, nor have I seen it on any of the chain hoists fro the 120 or so lighting jobs I performed.

Not to be argumentative mind you, just my experience.

cr3

When devising, implementing or enforcing standards, the language and terminology becomes extremely important. In fact it becomes a work of passion; in order to be of any quality. Try translating and conveying your exact intentions, to Chinese or Cyrillic, when vague or seemingly unimportant wording is "thought" to be adequate or unimportant. (The few people who chimed in here do not, by any means form a consensus which would be adequate for International acceptance).

Here is a site discussing a group of professionals who are addressing the International Standards and Protocols for the the very terms we have been discussing:

http://www.alia.com.au/standards/standard.htm

It just so happens I've asked the gentleman who is responsible for devising the standards for the rigging, chain hoist and overhead lifting regulations about his interpretation. (In fact I asked his opinion on the matter, just prior to writing the last post).

He brought to my attention his recent work, which included removing the WARNING stickers from EVERY entertainment hoist, currently used for overhead lifting in entertainment; at a manufacturers level. (Maybe they removed the stickers at your school, like they do at all the rental shops I have worked, before you showed up for class? Nothing like a paradox to ruin the class, right off the bat, ehh?)

(Did I strike a personal chord... GUEST? Maybe you'll be polite and allow everyone the courtesy of knowing your name, if you want to slander me on the forum, won't you?)

The Rigger mentioned above, agreed that too many people refuse to realize the immediate importance, clarification of accepted language requires. Most would rather criticize or allow ambiguity, rather than help refine the mountain of documents which involve diligent technical editing, before publication of standards. He sited a well known dictionary, which mixed the words so completely, it was impossible to translate clearly.

We also discussed writing the linked dictionaries, you all so diligently credited, in order to abridge the definitions by acknowledging and deliminating regional or SLANG interpretations. This may someday help remove the source of the confusion we have discussed here, for future litigation and so we can confine our terminology to "best practices and procedures".

Thank you C Rummel3 for bringing this technical dilemma to discussion.

Should anyone who reads this post, from any of the various disciplines, have qualified professional opinion and time to edit the International standards under review; please feel free to assist in this daunting task at www.esta.org. (Clothesline "Pully" manufacturers need not concern themselves, please).

Maybe we can try to agree linguistically and metaphorically, if not entirely in a physical sense? Just because we have been using ancient terminology for the past several hundred years, doesn't mean we can't re-define the terms for clarity, does it?

It seems the very thought of such derisive thinking equates medication abuse, by some. One shouldn't be cajoled to apologize or insulted for geometric associative thinking; you poor linear, one-track minded hucksters.

P.S. I agree the sprocket should be mentioned in the definition for clarity. Please pardon my omission;)

Ironically, the Jetson's cartoon exasperated this same dilemma when "Spacely Sprocket Corporation fought it out legally with the competing Cogswell COG company. 'It's a cog."; "No, it's a sprocket!"

Hammering out these details and re-educating scientists and engineers about the legitimate role of finite terminology is of critical importance.

Moto

Everything you said is completely true whether it is nuts, bolts, rebar, sheaves, pulleys, or steel beam and cement/concrete. Specifity is extremely important when dealing with any structure or machinery --- both legally and ethically -- don't be distracted by the belitteling of others here --- you are very correct.

Thanks to everyone for input on this.

It seems that the consensus (with a few exceptions) is that they are interchangeable depending on the location, specific activity, industry, and designer of the the equipment used.

My specialty is automated conveyor systems designed and produced by Siemens Dematic. There are drive pulleys that are 12" dia and up to 40" long driving a flat belt.

End pulleys that look like 6" rollers.

We also have large turn conveyors driven by round belts and every driven (Pulley/Sheave) is designated a sheave.

So it really comes down to call 'em whatever you want as long as your meaning is clear to the folks whom you are talking.

Thank You All

ietech

This is the wiki explanation, of course wiki is not always correct.

http://en.wikipedia.org/wiki/Pulley

The accepted practice of applying this nomenclature tends to be:

A wheel with a grooved periphery designed to engage a "Vee" belt is called a "sheave."

A wheel with a flat or slightly crowned periphery for engaging a flat belt is called a "pulley."

And lastly, a wheel whose periphery is scored with machined or cast axial grooves for engaging a gearbelt (or "timing belt" is called a "sprocket."

And now that I am finished "screwing" with this topic I am "bolting" to the next subject!

Regards,

Ing. Robert Forbus

"The accepted practice of applying this nomenclature tends to be:

A wheel with a grooved periphery designed to engage a "Vee" belt is called a "sheave."

A wheel with a flat or slightly crowned periphery for engaging a flat belt is called a "pulley."

And lastly, a wheel whose periphery is scored with machined or cast axial grooves for engaging a gearbelt (or "timing belt" is called a "sprocket."

And now that I am finished "screwing" with this topic I am "bolting" to the next subject!

Regards,

Ing. Robert Forbus"

I was taught the same thing during my machine design courses in college.

-A sheave has a v-shaped profile and is meant to drove a v-belt

-A pulley has a flat or slightly beveled profile and is meant to drive a flat belt

In the HVAC industry, fan wheels and motors utilize sheaves (actually one sheave is called the sheave and the other is called the drive, referring to driven and driving applications respectively) a v-belt or multiple v-belts (depending on the application) transfer the power between the two

It has been over 2 1/2 years since my last check, so I tried again. From McMaster Carr:

I have had a difficult time getting the definitive answer on this issue. It is different with every vendor and every discussion board. It is important to make the descision for inventory sake, so we have gone with the definition that a sheave is a part of the pulley assembly. The sheave is the wheel that touches the rope, chain, belt, etc. The pulley is an assembly that consists of one or more of the following; sheave(s), bushing(s), block, tackle, rope, belt(s), chain, etc. My definition is based from manufacturer's such as Browning (Emerson-EPT) who defines all their wheel elements as sheaves. It makes sense to me that a pulley is intended for work, which, on its own, the sheave cannot achieve.

We had to do the same thing with bolt vs. screw. Our definition; a bolt is a threaded fastener that follows a engineered standard for thread size and pitch that is intended to match up with another threaded device, such as a nut or pre-tapped hole. This has worked out well for us.

Right or wrong, that's how we are tracking these items and it makes it easy for the end-user to query on parts.

http://www.esta.org/tsp/news/newsdetails.php?newsID=245