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33 votes
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Why exactly does a washer help distribute the stress around a bolt?

I will expand on DKNguyen answer, because to my knowledge also the two reasons are: reduce contact/bearing stresses (having a significant effect on thin finishes live galvanisation) change the joint ...
NMech's user avatar
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27 votes

Why exactly does a washer help distribute the stress around a bolt?

It is for spreading out the stress. But it is also for giving the bolt a bearing surface to turn on. The washer always goes on the side (nut or bolt) that is being turned. It prevents it from marring ...
DKNguyen's user avatar
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17 votes

Why exactly does a washer help distribute the stress around a bolt?

To visualize part of Nmech's answer: in the image, the washer actually greatly increases the contact area of the bolt head. The bolt head looks pretty big: But most of that is the shaft, which ...
Mark Peschel's user avatar
16 votes

Why exactly does a washer help distribute the stress around a bolt?

Except for special applications, most washers are made of dead soft steel, which deforms under the compressive load imposed by a tightened bolt head. As the washer smooshes, it minimizes stress ...
niels nielsen's user avatar
8 votes

Why exactly does a washer help distribute the stress around a bolt?

Another important part of the answer is the symmetry of the stress pattern. The stress caused by a bolt head varies greatly between the points of the bolt head and the straight sides. As a result ...
Jeff Hester's user avatar
7 votes

When are Nyloc nuts indicated instead of cap nuts?

Not all cap nuts are self locking, some are, although they can be a bit weird looking. Nylocs are generally the first choice for general use as they provide good resistance to loosening due to ...
Chris Johns's user avatar
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7 votes
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What's the best way to design a joint with two fasteners?

I think you might have a misconception regarding to how far the pressure from the fasteners extends. One subject you might want to have a look into is "bolt joint stiffness". The most ...
NMech's user avatar
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6 votes
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Fastening a Nut on threaded rod from the middle

Granger Supply makes two different types: The round one is called A Steel Shaft Collar,two piece, Threaded . The second one is called a "CADDY THREADED ROD NUT". They come in a number of ...
JACK's user avatar
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5 votes
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What causes a fastener to lock?

Oxidation, dried lubricant, contaminants, rust - all that acts as a layer of glue binding the elements. As you apply a firm torque, you snap that bond. It takes a considerable time to re-form.
SF.'s user avatar
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5 votes

When are Nyloc nuts indicated instead of cap nuts?

A Nyloc nut is a form of locknut. The purpose is to prevent unintended loosening. A cap nut is not necessarily a locknut. You can get cap nuts that have some form of locknut on the threads; but in ...
JMac's user avatar
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5 votes
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Cleaning Shavings from Tapped Hole

There are a few ways to do this obviously it's easier to clean a through hole than a blind one. Run a clean second or plug tap through the hole. If you keep a tap just for this purpose it also has ...
Chris Johns's user avatar
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5 votes

What type of fastener is this? How does it work?

You are correct, this connection style is called a bayonet. It is secured by pushing the two mating parts together and rotating (usually clockwise) a small amount. There is generally chamfer on the ...
Max Peglar-Willis's user avatar
5 votes

Why can't screws be used for locating parts?

Screws and their holes have a few of problems: Screws are formed, so nowhere near as accurate as a hardened, ground pin. You probably could harden then grind a screw thread but obviously much more ...
DKNguyen's user avatar
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5 votes

Origins of the "threaded fastener pullout formula"

(adding to DKNguyen answer, and giving a slightly different perspective --hopefully). general calculation The calculation is indeed based on a cylinder surface/plane that transfer the force from one ...
NMech's user avatar
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4 votes

M# Screw mm per turn?

Metric bolts use thread pitch in millimeters. Your M3 screw likely uses the standard pitch of 0.5 millimeters. One complete rotation of the screw will advance the screw into the work piece by that ...
fred_dot_u's user avatar
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4 votes
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What does "Lg" mean when defining form of screws

*Figure 1. For McMaster-Carr 'Lg' is the length of the screw." Note that they specify the threaded length separately so Lg will be the distance from the bottom of the head to the tip of the screw.
Transistor's user avatar
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4 votes
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Are concrete screws suitable for repeated removal and reinstallation?

No, they are usually fitted once and left. If you need to remove them then you need to drill new holes. Or you should consider fitting a wooden framework to the concrete and attaching to that so it ...
Solar Mike's user avatar
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4 votes
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Unable to understand minimum length of engagement for bolts

The minimum length of engagement ist the length of engagement that (computationally) will ensure that overtightening the screw will snap the screw, and not strip the threads. The external and internal ...
bukwyrm's user avatar
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3 votes

Dimensioning of beam pressed by screw in assembly

You are on track with your beam calculations, but I doubt you will be happy with the results, just because a 3-D printed part is unlikely to act the way a cast or milled solid plastic part would. You ...
Tiger Guy's user avatar
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3 votes

What causes a fastener to lock?

Under high pressure and high heat metal bonds by a process called diffusion. Where the atoms of the two parts intersperse over time. This and oxidation, slow chemical burning of unintentional ...
kamran's user avatar
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3 votes

Why are Whitworth threads angled at 55°?

In 1841 Sir Joseph Whitworth produced a paper on a universal system of screw threads. He then collected a variety of screws and proposed a universal thread using their average pitch and depth. The ...
Donald Gibson's user avatar
3 votes

M# Screw mm per turn?

A metric thread table is what you want. Table 1. Source: Anzor. So is there a standard rule of thumb, or equation about the distance the end of a screw will travel per rotation? It's not a rule ...
Transistor's user avatar
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3 votes
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Mounting a digital indicator on a plate

You could have a 8mm hole drilled and reamed slightly undersize for a press fit 8mm dowel pin and use a 8mm/8mm swivel clamp which would let you set the angle and height as desired (photo from ...
Spehro Pefhany's user avatar
3 votes
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Why can't screws be used for locating parts?

You seem to have most of it. Take a waterpump on an engine: dowels are used for precise location as the impellor needs to be located with the back of the pump on the engine. Some items use bolts with ...
Solar Mike's user avatar
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3 votes

Why can't screws be used for locating parts?

IMHO, the main reason is that using multiple screws for locating the parts introduces additional stresses on the bolts and makes them susceptible to failure. So especially in high stress environment, ...
NMech's user avatar
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3 votes

Origins of the "threaded fastener pullout formula"

I think you're correct about the cylinder thing. It appears to be a crude equation though since it does not include thread percentage or thread pitch and does not even appear to be assuming a ...
DKNguyen's user avatar
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3 votes
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Looking for a type of the screw with very narrow end

It's called a dog point grub screw and you may be able to find your desired object at McMaster-Carr. The site has a selector panel and one of the entries in the panel includes the ability to specify ...
fred_dot_u's user avatar
  • 7,227
2 votes

What type of fastener is this?

It is a pin with a threaded head. A normal bolt would not work in many chains that go through restricted passages, so the head in this case is designed to sit flush with the surface.
Solar Mike's user avatar
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2 votes

Is there a rule of thumb to construe a screw

In a handbook of mechanical engineering facts you will find tables containing maximum load ratings for different diameters and types of screw fasteners, and required torque values to hold those loads. ...
niels nielsen's user avatar
2 votes

What causes a fastener to lock?

A standard bolt will stretch when tightened. This stretching increases force on the threads of both the bolt and hole and thus increases the force required to overcome static friction and loosen the ...
UseitorLoseit's user avatar

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