As Webster says:
A strong pin, of iron or other material, used to fasten or hold something in place, often having a head at one end and screw thread cut upon the other end.

In climbing, bolts have had a contentious history. A bolt on a climb makes the climb very safe. As you climb, you get to the bolt and clip your carabiner straight into it. There is no messing around with gear and you can place a bolt on an otherwise blank face of rock. However, to place the bolt, one usually has to drill a hole in the rock and then glue the bolt into the rock.

'For bolts' is the safety argument. 'Against bolts' is the idea that you should take only photos, leave only footprints. Bolting a climb changes the character of the rock. Before the introduction of bolts, if someone wanted to do a dangerous climb, they just did it. If they didn't have the balls to do the climb, then the climb would have to wait for someone who did.

The issue of bolting has become a holy war in climbing. If you bolt without consensus, you are likely to find that some groups will have come along and removed or chopped off the bolts.

Personally, I am of the ethic "the only good bolt is a chopped bolt" and "when in doubt run it out."

It is also a 'lovely' device to humanely kill livestock (cattle, horses, and such). The device is a gun of sorts that shoots a retractable rod into the brain of the animal. Its intent is to kill instantly.

A book, titled "Bolt," by Dick Francis, features the device.

Disney Animated Features
<< Meet the Robinsons | The Princess and the Frog >>

Release Date: 21 November 2007

Fans of Chris Sanders, the creative force behind the "quirky" film Lilo & Stitch, were intrigued and excited when word came of his next project for Disney, to be titled American Dog. They were equally devastated and disappointed when Sanders was removed from the project by new Chief Creative Officer John Lasseter and the film was "homogenized" (by their reckoning) and retitled Bolt.

Supposedly, Sanders' concept was just too quirky, and he refused to make the changes Lasseter felt were necessary to finish a quality film. Yet it was precisely that unique Sanders touch which his fans sought, so their disappointment was understandable. Sanders has since left Disney and moved on to Dreamworks; whether this move is ultimately best for both Sanders and Disney remains to be seen.

Despite the controversy, the very basic core of Sanders' story remains, and the historical details of the film's production should in no way diminish the quality of the result on the screen. Bolt is a good, satisfying film not out of place at all in the Disney canon.

Bolt is the canine star of an action-adventure television series. He portrays a dog with superpowers, intent on protecting his human charge, a girl named Penny, from all manner of evil intent, mostly perpetrated by the malevolent Green-Eyed Man.

There's just one problem—Bolt, the actor, thinks it's all real.

The entire production has been carefully—and, no doubt, expensively—staged to hide any evidence of fiction from the dog's perceptions. The director insists on the authenticity created by inducing real emotions in Bolt, rather than filming the results of training. These methods may work on the screen, but it causes problems when a cliffhanger ending to the day's filming leaves Bolt anxious to save Penny, and he escapes.

Improbably, Bolt finds himself 3,000 miles from Hollywood, still believing Penny is in danger, and with no clue that he's nothing more than an actor. He sets off across the country with a selfish alley cat and a worshipful hamster to find Penny and defeat the Green-Eyed Man once and for all.

The plot is admittedly predictable—no adult moviegoer is going to doubt that Bolt will eventually realize that he never had superpowers, while ending up ultimately happier for the knowledge that his beloved Penny is no longer in constant danger. For kids, though, who perhaps have not seen this type of plot numerous times before, the movie addresses these elements well.

As in several recent Disney films, the lead voice actors are celebrities, but their voices are relatively unobtrusive and the characterizations are not designed around the celebrities. This is a change from the way things worked in the seventies, eighties, and nineties, when, say, the part of Baloo in The Jungle Book was written specifically with Phil Harris in mind, or Robin Williams completely changed the way Aladdin's Genie was animated.

John Travolta voices Bolt, and teen sensation Miley Cyrus voices Penny. There's not much more to say about that, except that both actors do fine jobs with their material. The two also duet to sing the soundtrack's lead song, "I Thought I Lost You," co-written by Cyrus.

The film, like Chicken Little and Meet the Robinsons, was released in Disney Digital 3D in select theaters, but, as in the earlier films, the 3D effect is largely unnecessary. The film was also released with a 3D short, featuring Mater from Disney-Pixar's Cars in "Tokyo Mater", one of "Mater's Tall Tales".

With humor, action, adventure, and heart, Bolt is a very good film, despite its tumultuous history. Its simplistic story and predictable plot, though, means it's not likely to ever be counted among the company's finest.

Information for the Disney Animated Features series of nodes comes from the IMDb (, Frank's Disney Page (, and the dark recesses of my own memory.

         NUT             HEAD
          |      SHANK     |
  THREAD  |        |       |
    |    __        |      ___
    |   |__|     ________|__ |
  //////|  |/////        |   |
  //////|__|/////________|__ |
        |__|             |___|
         |      |________|
                 GRIP LENGTH


Bolts and screws fall under the umbrella term "fasteners." The two are often confused because a fastener can be both a bolt and screw at the same time.

Fasteners are broadly identified by function, shape, and relationship to fastened material. Machinery's Handbook defines a bolt as a threaded fastener that holds together unthreaded components using a nut; a screw, by contrast, either is applied to a threaded opening or creates its own threads during application (like a wood screw or self-tapping screw).

A bolt can also be a screw if it is inserted into a threaded opening and secured with a nut.

Un-threaded bolts acted as door hinges and locking mechanisms in Ancient Rome. They were notched to accept wedges, which were hammered into place.

Screw threads probably originated around 400 BC, when Archytas of Tarentum, a contemporary of Plato, used screw threads suspended in an unthreaded shaft to raise water. This device--the water screw--is also known as Archimedes' screw, because Archimedes more famously used it for the same purpose a century and a half later. Water screws also worked in Ancient Egypt to pump bilge from ships and allegedly in Assyria's Hanging Gardens of Babylon. Threaded wood shafts aided in the pressing of grapes in all three locations.

Metal bolts appeared in fifteenth century Europe. Their threads were cut by hand in a process that was most assuredly grueling; an early application was in Gutenberg's printing presses. Luc Besson devised thread-cutting machines in France in 1568 before developing ridged plates for use with lathes--a development currently in use. As was his way, da Vinci conceptualized a number of screw-cutting machines. J and W Wyatt achieved the mass manufacture of bolts in Britain in 1760.

Early bolts featured non-standard, square heads; hex-shaped bolt heads, smaller in area and approachable from more angles, evolved as a direct consequence of shrinking machinery. James Nasmyth introduced the mass-manufacture of hex heads in 1830; hex nuts would appear fifty years later, owing to a greater ability to produce and accurately machine mild steel.

The non-standardization of bolt threads occupies a shocking span of human history. It was in 1841 that Joseph Whitworth proposed a standard 55-degree thread pitch and standard number of threads-per-inch correspondent with shaft diameter (he had analyzed screws from all over Britain). Two decades later, William Sellers would engender the American Coarse and Fine Series; American threads (pitched 60 degrees) feature more pointed ridges and valleys than Whitworth's threads, which makes them easier to manufacture.

Between nations, non-standardization of bolt threads persisted through World War II (two). It was a particularly nasty specter for the Allies. Today's ISO thread metrics are prefaced by standards agreed upon by Canada, the US, and Britain in 1948, for all nations using Imperial measurements.

The last eight decades have witnessed a number of small changes to worldwide bolt and nut metrics, none of which are detailed here.



Types & Applications


The types of bolt in the world are myriad. This list is abbreviated to include the most common/important.

Hex bolts are standard in most applications, particularly structural. Variations on the hex bolt are also myriad, ranging from slotted heads to built-in washers to coarse threads for tapping into wood (as lag bolts).
Carriage bolts present a pleasing, featureless, domed head. The squared section just underneath digs into wood (often framing lumber), securing the bolt for the application of the nut.
U-bolts feature two threaded ends and are often paired with a bar, for securing pipe. The similar (though inferior) J-bolt is often used for the same purpose.
Shoulder bolts feature a free-spinning sleeve before the threaded section, allowing for the creation of a pivot joint.
Sex bolts are hollow, with a female (or internal) thread. They are paired with mating screws and are used wherever it is advisable to have a bolt head at both ends.
Eye bolts feature a looped head, to attach a chain or hook. The loop can be open or closed.

Note that "type" and "drive"--the means by which a fastener may be tightened--represent separate worlds unto themselves. Different types of drive are more applicable to screws; bolts are generally not driven, for reasons outlined at the beginning of this write-up.



Grades & Materials


As of October 2014, there exist 37 grades of bolt, divided between standards devised by SAE, ASTM, and ISO. All three organizations use the same metrics: proof load, yield strength, and tensile strength--respectively, the load the bolt can bear without deforming, the load at which the bolt deforms, and the load the bolt can bear while stretched.

Chances are very good that you have observed SAE markings on a bolt head:


     |              \|/ 
/ \ /|\
SAE Grade 5     SAE Grade 7


More "legs" denote a stronger bolt, typically of alloy steel. Regardless of classification system, bolts with no markings can be presumed to be of low or median steel.

Bolts manufactured to ISO and ASTM standards bear those organizations' alphanumeric codes. Stainless bolts display specific grades, usually (again) SAE markings such as 304 or 316.

Bolts made of non-metals like nylon are common in applications requiring electrical isolation.





The goal, if such a word be used, is to pre-load the bolt evenly. 

"Clamp force" refers to the amount of force exerted by the bolt head and nut, as the bolt stretches. It is directly proportional to the amount of applied torque. Tightening is usually limited by friction.

Whether one tightens the head or nut matters only if the materials bolted together are dissimilar, in which case tightening whichever side faces the softer material will allow for more load. It is important (and safe) to use an appropriately-sized wrench; adjustable and open wrenches should be turned in the direction the handle is cocked, so as to (in the case of the adjustable wrench) place the load on the solid jaw rather than the adjustable one. Teflon tape, grease, etc. reduce friction. Washers distribute force on the faces of bolted materials.

"Galling" is the seizing and tearing-free of threads inside the nut, usually a consequence of overtightening or unevenly pre-loading (a good way to do this is to put the bolts on your tire in the wrong order). Removing a galled nut is sometimes possible with the application of penetrating oil and much tapping/suffering; frequently it is impossible (or impractical, if the bolt is small enough to be twisted apart by hand). It is important to tighten bolts smoothly.

Combining a nut and bolt of dissimilar metals results in corrosion and seizing.





Nord-Lock Bolt Securing Systems. "The history of the bolt.", 9/27/14

Santa Rosa College. "The Nuts and Bolts Behind Engineering." (.pdf), 9/27/14

eHow. "The History of Hex Head Nuts and Bolts.", 9/27/14

ThomasNet. "The Evolution of Bolt Manufacturing.", 9/27/14

Bolt Depot. "Fastener Type Chart" and "How Fasteners are Identified.", 10/4/14

Engineer's Edge. "Hex Bolt Identification Guide.", 10/4/14

Wikipedia. "Bolt.", 10/4/14

Bolt Science. "Tightening the Nut or the Bolt?", 10/9/14

Bolt (?), n. [AS. bolt; akin to Icel. bolti, Dan. bolt, D. bout, OHG. bolz, G. bolz, bolzen; of uncertain origin.]


A shaft or missile intended to be shot from a crossbow or catapult, esp. a short, stout, blunt-headed arrow; a quarrel; an arrow, or that which resembles an arrow; a dart.

Look that the crossbowmen lack not bolts. Sir W. Scott.

A fool's bolt is soon shot. Shak.


Lightning; a thunderbolt.


A strong pin, of iron or other material, used to fasten or hold something in place, often having a head at one end and screw thread cut upon the other end.


A sliding catch, or fastening, as for a door or gate; the portion of a lock which is shot or withdrawn by the action of the key.


An iron to fasten the legs of a prisoner; a shackle; a fetter.


Away with him to prison! lay bolts enough upon him. Shak.


A compact package or roll of cloth, as of canvas or silk, often containing about forty yards.


A bundle, as of oziers.

Bolt auger, an auger of large size; an auger to make holes for the bolts used by shipwrights. -- Bolt and nut, a metallic pin with a head formed upon one end, and a movable piece (the nut) screwed upon a thread cut upon the other end. See B, C, and D, in illust. above.

See Tap bolt, Screw bolt, and Stud bolt.


© Webster 1913.

Bolt, v. t. [imp. & p. p. Bolted; p. pr. & vb. n. Bolting.]


To shoot; to discharge or drive forth.


To utter precipitately; to blurt or throw out.

I hate when Vice can bolt her arguments. Milton.


To swallow without chewing; as, to bolt food.

4. U. S. Politics

To refuse to support, as a nomination made by a party to which one has belonged or by a caucus in which one has taken part.

5. Sporting

To cause to start or spring forth; to dislodge, as conies, rabbits, etc.


To fasten or secure with, or as with, a bolt or bolts, as a door, a timber, fetters; to shackle; to restrain.

Let tenfold iron bolt my door. Langhorn.

Which shackles accidents and bolts up change. Shak.


© Webster 1913.

Bolt (?), v. i.


To start forth like a bolt or arrow; to spring abruptly; to come or go suddenly; to dart; as, to bolt out of the room.

This Puck seems but a dreaming dolt, . . . And oft out of a bush doth bolt. Drayton.


To strike or fall suddenly like a bolt.

His cloudless thunder bolted on their heads. Milton.


To spring suddenly aside, or out of the regular path; as, the horse bolted.

4. U.S. Politics

To refuse to support a nomination made by a party or a caucus with which one has been connected; to break away from a party.


© Webster 1913.

Bolt, adv.

In the manner of a bolt; suddenly; straight; unbendingly.

[He] came bolt up against the heavy dragoon. Thackeray.

Bolt upright. (a) Perfectly upright; perpendicular; straight up; unbendingly erect. Addison. (b) On the back at full length. [Obs.]



© Webster 1913.

Bolt, n. [From Bolt, v. i.]


A sudden spring or start; a sudden spring aside; as, the horse made a bolt.


A sudden flight, as to escape creditors.

This gentleman was so hopelessly involved that he contemplated a bolt to America -- or anywhere. Compton Reade.

3. U. S. Politics

A refusal to support a nomination made by the party with which one has been connected; a breaking away from one's party.


© Webster 1913.

Bolt, v. t. [imp. & p. p. Bolted; p. pr. & vb. n. Bolting.] [OE. bolten, boulten, OF. buleter, F. bluter, fr. Ll. buletare, buratare, cf. F. bure coarse woolen stuff; fr. L. burrus red. See Borrel, and cf. Bultel.]


To sift or separate the coarser from the finer particles of, as bran from flour, by means of a bolter; to separate, assort, refine, or purify by other means.

He now had bolted all the flour. Spenser.

Ill schooled in bolted language. Shak.


To separate, as if by sifting or bolting; -- with out.

Time and nature will bolt out the truth of things. L'Estrange.

3. Law

To discuss or argue privately, and for practice, as cases at law.


To bolt to the bran, to examine thoroughly, so as to separate or discover everything important.


This bolts the matter fairly to the bran. Harte.

The report of the committee was examined and sifted and bolted to the bran. Burke.


© Webster 1913.

Bolt, n.

A sieve, esp. a long fine sieve used in milling for bolting flour and meal; a bolter.

B. Jonson.


© Webster 1913.

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