Mar 7, 2016 at 21:23 o\clock

Simple Machine: Screws

Fast Fact

In 1967, one of the largest screws or bolts was manufactured in Scotland by the Penrith Engineering Works. The length and diameter of these machines was about 24 feet and 4 - St Louis Attractions - feet, respectively. These screws were made from a very strong element called iridium, and oil tankers were connected to each other using such devices.

A screw is one of the six simple machines, with the other five being the lever, wheel and axle, pulley, inclined plane, and wedge. It is one of the most commonly used devices in the world. The screw has an appearance of a thin metal stick with a turning head on top and grooves along its length. Conventionally, it is defined as a mechanical device that has helical-inclined planes and is capable of converting torque to linear force and vice versa.

The inclined planes that form the threads are wound entirely along the screw shaft, and hence, it becomes easier to fix different objects, as driving it down in a rotational form requires less effort than pushing a nail by application of effort in a vertical direction. Also, nails have the tendency of bending when they are used, whereas a screw would never bend as force is evenly spread along the entire shaft. These are a few reasons why using a screw is preferred over a nail, and why the latter is being phased out slowly.


The initial design used was the Archimedes screw, which was developed from Archimedes himself. It was mainly utilized to draw out water from wells, rivers, lakes, etc. This screw had a longer length between its threading and was operated manually. Prominent uses - City Of St Louis - of this device were seen when water was drawn up to the Hanging Gardens of Babylon. The same design was also utilized in the Mediterranean regions for many centuries for irrigation processes, and also to facilitate oil and wine presses. The Archimedes Screw is used even today in numerous mechanical operations. It has a wide application in the form of conveyor screw devices, especially used - los angeles rams tickets - in the food processing industry.

Innovation of the modern screw that is used primarily as a fastener is associated with the development of the lathe machine. In the period before modern devices were mass-produced, cotter pins and pin bolts were widely used as fasteners. Actual development of the modern screw began after Jesse Ramsden, a British instrument manufacturer, perfected a device called 'screw-cutting lathe' in the 1700s. This lathe was further improved and patented in 1798 by David Wilkinson. In the following decades, the importance of threaded fasteners and screws greatly increased in mechanics, which led to the 'standardization of thread forms'. The process of standardization is still ongoing, and has also led to the development of ISO metric screw threads and the Unified Thread Standard. The 'turret lathe' and 'screw machine', which were developed in the 1840s and 1870s, respectively, boosted the mass production of screws. Some important types of such devices that were developed in the course of evolution of modern designs were the Robertson Screw (developed by P. L. Robertson in 1908), and Hex Socket and Phillips-head Screw (developed by Henry F. Phillips).

Working Principle and Explanation

The helical-inclined planes present on the screw are referred to as threads or threading. The structure, space, size, and material of which the screw is made up of determines its strength. This strength is also referred to as the mechanical advantage. The turning head of the screw is a provision or facility where the force from a screwdriver can be applied, and torque can be generated. When force is applied on the screw head, it is transferred to the screw threads, which further begin to advance in the downward direction. The exact opposite motion occurs when one starts removing a screw from the material it is fixed to.

The distance covered by a screw in a straight line in one single rotation is called the lead, while the measurement between two successive inclined planes is called the pitch. The Mechanical Advantage (MA) of this simple machine is controlled by the degree of the lead; less distance covered means more MA, and vice versa. Depending on the orientation of the screws, they are distinguished in two types: right-handed (the helical threads move in a clockwise manner) and left-handed (the threads move in an anti-clockwise manner). The former are most commonly used for numerous application, while the latter are used only for specific purposes (for example, a left-side bicycle pedal and few types of light bulbs). If the pitch is less, greater force is applied by the screw onto the material, in which it is inserted. Also, if the incline of the threads increases, the input force also increases.

The ratio of the screw circumference to the distance covered by it at the time of every rotation is called the Ideal Mechanical Advantage (IMA). This ratio is represented as:

IMA = Screw Head Circumference/Distance Covered by the Screw Shaft

If circumference of the head is 2, where is the radius of the head surface, and is the distance advanced by the screw on one rotation, the IMA can be represented as:

IMA = 2/

The Actual Mechanical Advantage (AMA) is the ratio of the force applied during turning of the screw head to the force exerted by the device on the material, in which it is to be inserted. Thus, this type of mechanical advantage can be represented as:

AMA = Input Force/Output Force

One amazing advantage of the screw over the nail is that it can get automatically locked in the material, where it is inserted. This is caused due to the extra friction produced by the inclined planes, when it rotates and gets fixed in the interior portion.

The following pictures illustrate the various types of screws that are used currently.

Applications in Modern Era

Though the latest designs were developed in a very short period of time, the ability of screws to transfer torque has made it a very effective tool. It has also replaced rivets and fastening pins in the mechanical industry due to its ease of operation and utility. This type of simple machine is used in machinery, where power is transferred from one part to another.

A very good application of this device is regarding micrometer gauges, which are used in mathematics and physics for precise measurement. Conveyor belts, propellers, drillers, helicopter blades, etc., are a few prominent examples, where the use of screws can be seen in our everyday lives. The concept of screws is also used in an architectural sense, like building spiral staircases; the motion of a person climbing them is same as that of a normal screw.

This simple machine can handle about five times the holding strength, as compared to the same strength of a nail. The screw is still undergoing many changes and is evolving continuously. Due to its basic principle of physics, it is considered a member of the six simple machines, and has become an indispensable part of modern mechanics.

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Mar 7, 2016 at 18:49 o\clock

How to Tell People Things They Don't Want to Hear

Whenever we face a communication dilemma, whether we must tell our aging parents that they can no longer live independently or tell our best friend that her clothes do not suit her, we agonize over what to do. How do we tell people things they do not wish to hear?

These kind of communication dilemmas slip up on us all the time. We go our merry way, and as if they were waiting in the bushes to ambush us, there they are. We are caught off guard. Whenever Im asked to speak about my book, Managing Sticky Situations at Work (, Im asked, What is the most common situation you find? After some thought, I realized that its these kind of communication dilemmas. We all commonly find ourselves in a position where we have to tell someone something they dont want to hear.

At work, you may have to tell an employee that his job has been eliminated. Or, you might have to explain to a board of directors that profits fell this year. The list is endless. How we respond to these communication dilemmas put us either in the category of confident communicator who can say it just right or in the category of communication imbeciles who fail at these tests. If you think yourself inept at these tough communication tests, you are not alone.

The Say It Just Right Model gives us some guidance. We need to pay attention to the Three Cs: Change is within you, Show Curiosity and Compassion. We need to make sure we think through the communication before it happensin other words, dont react. The Decision Points help us there. In addition, let me share a few more basic tips:

Think before you speak. This axiom may seem obvious. But how often do you find yourself blurting something out and then wishing you had not done so. Often we prefer not to think about these communication dilemmas. In fact, we put them out of our minds because they distress us. For that reason when the time comes to fire someone or to report bad financial news to your boss, you wing - St. Louis - it and hope for the best.

Put yourself in the other persons shoes. We think we understand how other people are thinking and feeling, but that is one thing we can never fully understand. We have to really work at trying to put ourselves in the other persons shoes. Often in workshops when people share their frustrations with their bosses or their co-workers, I ask them, What do you think is going on with that person? They shrug off that question with responses like, They are just crazy. Or They dont care about anyone but themselves. In reality, we have not really given that question much thought. If you really dont know what is going on with the other person, ask him. What a novel thought? If youve not broken down all trust with that person, he will tell you. And above all, do not assume that he is feeling something unless he tells you either verbally or nonverbally.


Do not say: Im sure youre feeling lost and alone, knowing you have to search for another job.

Do say: I know this news comes as a blow to you. I sense your need to take it all in. But, before you leave, tell me what I can do to help you.

Do not jump in with all your pre-fabricated solutions too soon. People need to take in what youve just dished out. Give them a chance to absorb what youve said. Ask them what they want to do.


If you are saying to your elderly parents that they can no longer live independently, dont say: Ive looked into the - City Of St Louis - assisted living facility nearby. Lets go tour it.

Instead say: What options would you like to explore?

Be prepared to offer support but do not waiver on your initial request. In other words, if you are telling someone something they dont want to hear, do not back peddle.


If you are telling your best friend that her clothes do not suit, do not say, I didnt really mean you should change your wardrobe, I just wanted you to know that you could look really good in more professional clothes. But I love what you wear.

Instead say: When we all reach a certain age, we must re-evaluate our clothes choices. If youd wear turtlenecks instead of low-cut blouses, youd look younger and it would better fit your image. How might I help you select something for that important interview?

Being able to say it just right, when you must tell people something they dont want to hear, takes practice and preparation. Communication is one of the hardest things we do and yet we give it very little thought. Its time to think about what you say and strive to say it in the best way.

Author's Bio:

Dr. Joan Curtis is a nationally known communications coach, certified by the International Coaches Federation. She has over 20 years experience as a trainer and educator. She has taught communication skills and presentation skills to leadership groups throughout the country

She is the author of two books: Managing Sticky Situations at Work: Communication Secrets for Success in the Workplace, which introduces the Say It Just Right Model of communication, and Strategic Interviewing: Skills and Tactics for Savvy Executives, which introduces the - moving to st louis - proprietary POINT process. She is under contract for her third book, The New Handshake: Sales Meets Social Media.

Her web sites include: and

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Mar 3, 2016 at 04:25 o\clock

What Are Ways To Increase Breast Size Without Having Surgery?

Size of bust is important for a woman, they give her confidence and attractive looks, if you have smaller busts there are ways to increase breast size without surgery and at convenience of your home. Herbs have been used since ages not only for curing disorders and diseases but also for improving looks and appearance of human beings. These are natural medicines which are safe and suitable for men and women alike. The role of breast size in improving looks of a woman can be measured by the fact that large number of women opt to go for surgical operations to make their chest area look fuller, bigger and firmer.

Although results of these are not guaranteed as surgery is not a natural method and most of the time body is unable to maintain the results for a long time. This not only wastes the entire effort but also casts serious side effects. Whereas herbs affect the body naturally and push it to improve size and fullness of chest area on its own therefore results obtained by herbs last forever and are perfectly safe. Use of herbs is dependable, safe and most popular way today to increase size of breast without having surgery.

You do not have to bother yourself in finding and understanding herbs which are necessary for natural bust enlargement. All of these herbs are available in their purest form and in right doses in the form of Big -36 capsules and Big B-36 oil. Consuming these capsules and massaging your chest area with oil make your bust-line fuller, firmer and bigger in couple of weeks. Using these two in combination, works as the best way to increase breast size without having surgery safely and quickly. Breast of a woman comprise of ducts, glands and fatty tissues, these do not contain any muscles, Big B-36 capsules and Big B-36 oil affect fatty tissues and adipose tissues to improve size, fullness and firmness of bust.

The effect of herbs used in capsules promotes growth of fatty tissues in a woman's breast to make them bigger and fuller. Herbal ingredients of Big B-36 capsules also promote growth in size of adipose tissues, these tissues are suspended in connective fiber which joins chest muscle to the underside of the breast, when adipose tissues grow they strengthen connective fiber and lift the bust upwards to make it firmer and provide deep cleavage to a woman. With these benefits you will not only gain increased breast size without having surgery but will also gain exotic looks.

Massage with Big B-36 oil is recommended to make results obtained from Big B-36 capsules long-lasting. Massage promotes higher blood flow, when there is more blood flow towards chest region the tissues get optimum nourishment and fatty tissues grow in number. Higher blood flow also keep skin of breast nourished to prevent formation of lines, wrinkles and keep skin supple and soft. Consuming Big B-36 capsules and regular massage with Big B-36 oil in combination work as most effective ways to increase breast size without having surgery and gain fuller, firmer and well-shaped breasts safely and in short duration.

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