33

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 tightening characteristics (see joint diagram). reduce contact stresses on surfaces. The basic idea is that since contact stress is defined as: $$\sigma = \...


27

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 up the work surface and also changes the tightening characteristics. I don't know the specifics of that though but that's what I was told by a toolmaker. Always ...


20

My first thought is that it might be intended to be a wing nut driver of some sort, but those are usually hollow cylinders with slots for the wings. Ah ... sure enough, it's described as such in this Ebay ad:


16

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 concentrations caused by bumps under the bolt head and surface flaws in the part the bolt is running through.


15

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 obviously does not spread out load on the material. So the actual contact area looks like this: Comparatively, the bolt head on the washer looks like this: That's a ...


11

As Dave Tweed points out, the ratio of torque to tension is lower the lower the lead angle is. Since the important measure of bolt tightness is generally the tension in the bolt, we want to achieve that minimum pretension with the least effort possible. Assuming we have to maintain a certain shear area of the thread (so the the threads are stronger than the ...


9

For any given size of fastener and given thread pitch, a single-start thread gives you the greatest mechanical advantage in terms of the torque required to achieve a given tension. Aside from acme threads that are often used on leadscrews for mechanical motion (e.g., CNC machinery), the only other place I have seen multiple-start screws is on self-tapping ...


8

When dealing with pressure vessels, you should not rely on rules of thumb. You should rely instead on the ASME Boiler and Pressure Vessel Code or whatever code is required by your local enforcement or regulatory body. There are far too many variables for a one-size-fits-all answer. The design pressure/temperature, materials of construction, flange ...


7

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 vibration or flexing of the joint and will stay in position on a thread even when not under tension (unlike spring washers). Unlike locking adhesives they can be ...


7

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 popular is the "Rotscher’s pressure-cone method". Essentially there is a pressure cone which radiates outwards with an pressure cone angle a. According to ...


6

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.


6

Granger Supply makes two different types: The round one is called A Steel Shaft Collar, Clamp, Threaded . The second one is called a "CADDY THREADED ROD NUT". They come in a number of sizes.


6

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 local stresses, which are what you really care about because those are what the materials have to withstand, can be much higher than the average stress. A washer's ...


5

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 the benefit of keeping one 'fresh' tap which clean clean up any burrs of defects from worn taps when initially cutting the thread. Flush the hole with cutting ...


5

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 general this is not a standard feature of all cap nuts.


5

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 male side (shown at the tip of your arrow in the second picture) which allows the two parts to locate easily and when rotated, this chamfer pulls the two parts ...


5

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 expensive. Probably only used on things like micrometers. The tapping operation itself removes a fair amount of material. Second only to the drilling operation. ...


4

I've always referred to this style of female fastener as a "T-Nut"


4

It can also be used for fastening the 'eye' of hook and eye fasteners into wooden frames.


4

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 matrial and debris between the two parts, cause a strong bond that many times cuase the fastener to break before it can be removed.


4

*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.


4

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 amount. According to the Bolt Depot chart, there is only one standard pitch for M3 screws, although other sizes will have standard, fine, super fine pitches ...


4

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 can be easily removed and refitted, without disturbing the concrete fixings.


3

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 result was the 'Whitworth thread' with the depth and pitch of constant proportion, giving the 'V' thread a mean angle of 55 degrees and the number of threads per ...


3

I have always used the rule of thumb that the bolt has to be engaged at least one bolt diameter. This partly comes from looking at structural nuts. Structural nuts develop the full strength of the bolt in tension. These nuts typically engage about one bolt diameter.


3

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 bolt. If we exclude other materials and chemical changes to the surfaces then that snap that you experience is the moment you overcome that static friction ...


3

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 would be well served to just buy aluminum bar stock and cut it with a hack saw. As to the screw force produced, I doubt you will be happy with that either. ...


3

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 of thumb - it's defined by the pitch. Conversely, how many turns it will take to travel a specific distance? Turns required = distance / pitch. Say I have ...


3

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 McMaster).


3

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 threads and a shank to give a controlled location. Other parts such as wheels use a concentric flange on the hub with a matching hole on the wheel so that the ...


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