What is Screw: Definition and 133 Discussions

A screw and a bolt (see Differentiation between bolt and screw below) are similar types of fastener typically made of metal, and characterized by a helical ridge, known as a male thread (external thread). Screws and bolts are used to fasten materials by the engagement of the screw thread with a similar female thread (internal thread) in the matching part.
Screws are often self-threading (also known as self-tapping) where the thread cuts into the material when the screw is turned, creating an internal thread that helps pull fastened materials together and prevent pull-out. There are many screws for a variety of materials; those commonly fastened by screws include wood, sheet metal, and plastic.

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  1. K

    Design of bolts - Influence of higher free length

    Hello all, In a recent discussion, I came across this question of influence of free length (or unthreaded length) in bolts in retaining the clamping force between the elements to be joined. Out of the two proposals in the attached pic., which one will keep the two plates clamped for a longer...
  2. A

    Appliances Replacing banker's lamp shade, the screw is too tight to loosen

    hi guys, My banker's lamp glass shade was broken. I'm trying to replace with a new one but stuck at loosen the screw opposite of bulb fixture. the screw needs to be taken off in order to put the lamp shade on. but i couldn't loose the end screw by hand, with pliers it doesn't grip tight...
  3. P

    Minimum screw thread engagement to support weight?

    Hello All, I know there are rules of thumb and thread engagement calculators online but I am trying to find mathematically what the minimum number of threads acceptable would be. I currently have an eyebolt that will be torqued to a specific value. This eyebolt setup will then need to lift a...
  4. Tanreom

    I How does a screw roll down an inclined plane?

    I was thinking about how various objects would slide down on an inclined plane, and I just couldn't figure this problem out. So let's say I have this screw or cone on its side, on an inclined plane. If friction exists, what would the motion of the screw be as it slides down the inclined plane...
  5. austinmca

    Appliances Removing a Stuck Rusted Screw: Easy Out or Drill?

    How would one go about removing this stuck, rusted screw? Its tip size is 5/8". I tried using an impact driver, but that didn't work. Should I just try to drill through it to break it? For context, I am getting rid of this old sink.
  6. T

    I Playing with Lagrangian and I screw up

    I am sorry for all these questions this morning. Could someone read the attached and tell me where I am going wrong?
  7. abdulbadii

    How to unscrew a screw that has no inner screw pattern?

    How do we unscrew a screw with no inner screw pattern? Just saw one on other place so is not on hand now, it has no engraved pattern at all hopefully its pic, could be brought in
  8. Paul Chen

    Screw dislocation displacement discontinouty

    Consider a screw dislocation, The displacement field is given by And the strain field is derived by My question is that the displacement seems discontinuous across the dislocation surface (y=0, i.e., displacement jump from 0 to b), so why it is still differentiable on the surface and why...
  9. M

    Calculate the torque needed to move a lead screw

    Summary:: Calculate the torque needed to move a load with a lead screw. Torque is needed in order to find the right DC motor and coupling. Hello, I have a design with using a lead screw to move a load (see sketch below). The load will operate in both directions, in order to select the right...
  10. M

    Engineering Torque applied on a vise screw (problem includes friction)

    Hello all, I need some help with a problem at statics, friction applied on threads. A threaded screw is given a ("horizontal") force of 100 N at the end of the handle. As the exercise states, they ask to calculate the force which occurs at the tube as well as the force needed to vise handle to...
  11. T

    What machines are used to manufacture extruder screws for 3D printers?

    Currently I am working on an assignment about making an extruder screw for screw based 3D printer. I am confused that actually what kind of machines those manufactures out there using to manufacture this kind of extruder screws ?
  12. S

    Electrical Screw heads: Phillips/Slotted vs ECX

    (In the USA) recently purchased swtiches and receptacles are held to electric boxes with screws that don't work well with either Phillips or slotted screwdrivers. ( e.g...
  13. titanan

    Can pressing on a screw generate torque?

    Today I and my physics teacher argued about that. I think that in optimal conditions applying force to the top of a screw can turn it and generate torque. ( On a surface) Can you please answer and send an article that mentions that? Because i wasn't able to find one. Thanks already and sorry for...
  14. I

    Considerations for design of lead screw + guide rail set up

    Hi everyone! I'm a mechanical engineering undergraduate and am designing a linear motion system for a school project. I hope to be able to use this system to achieve opposing motion for 2 x 200 kg loads (i.e. move them closer/ further apart simultaneously). Referring to the picture below...
  15. M

    How the action-reaction principle works in the case of a screw fastener and a nut?

    A screw fastener advances into a nut. Assuming there are no frictional forces (or negligible): a) Is the action force tangential to the male helical thread (screw) and the reaction tangential (in opposite direction to action) to the female helical thread (nut) b) or does the action-reaction...
  16. B

    Engineering Velocity Ratio, mechanical advantage, Efficiency of a screw jack

    Hello, I have completed the question below. I am just unsure on whether i am correct or not. I am unsure on Mechanical Advantage. As i have seen a few different equations. Question: Answer: a) Velocity Ratio = $$\frac{\text{Distance Moved By Effort}}{\text{Distance Moved By Load}}$$...
  17. Amitkumarr

    To measure the diameter of a sphere using a screw gauge

    Least count of the screw gauge = Pitch÷No. of divisions on circular scale=1.5÷100 mm =0.015mm According to me,in this case the main scale reading should be taken as 2 mm because it is the one which is visible and circular scale reading should be 76. So, Diameter=2 mm + 0.015×76 mm = 2 mm + 1.14...
  18. V

    Mathematical modeling of a screw compressor

    I am trying to design a compressor in simulink. the mathematical equations has been modeled. but i just need, is there any relation to find the rate of change of volume with respect to time in compressor. Are there any equations or relations to find the rate of change in volume. As its a...
  19. Prialen

    How to choose the right power screw dimensions given the maximum load

    Hi, So I have a uni project and were required to design a jockey wheel and corresponding power screw. We're given a maximum load and have to do the relevant calculations, moment of torque, efficiency etc. My question is I don't understand how to take the given maximum load and find the relevant...
  20. CynicusRex

    Appropriate tightness of bolts between skateboard and trucks

    As you can see in the pictures below the trucks are attached to the skateboard with four screws nuts and bolts, with a 2~3mm piece of rubber between the truck and the board. I've always wondered if tightening the screws bolts harder, decreases or increases the strength of the 7-layered plywood...
  21. S

    Olds Elevator vs Traditional Archimedes Screw

    This device... ... is purportedly superior to the more traditional Archimedes lift where the screw is rotated and the tube is stationary. The video itself does not explain the comparative physics very thoroughly. From the video itself and from the comments section, three broad types of...
  22. R

    Relative velocity between lift and screw

    v=16m/s+4*.659s=18.636m/s (for lift) v0=16m/s-9.81*.659s=9.53m/s my question is that why 16m/s is considered for screw velocity ? it is given for lift .what does it mean 9.53m/s? If you drop something , it gets acceleration and I calculate it 6.45m for screw while falling and why should I...
  23. Justin71

    Torque Calculation for Screw Ball: TL Preload Nut

    Hi I don't understand what Fa mean ? This the weight or no ? And i don't understand too why in the torque TL, we have an additional part with the preload, the internal friction coeff of preload nut ... What is it ? Thanks.
  24. R

    Lift and screw impact velocity

    Homework Statement Consider the elevator and screw in Example 2-17. Assume the velocity of the elevator is 16 mls upward when the screw separates from the ceiling. (a) How far does the elevator rise while the screw is falling? How far does the screw fall? . I have only problem second part of...
  25. Wrichik Basu

    Why does it get harder with time to rotate a screw?

    A couple of forces act on the screw and create the turning effect. But after sometime it gets harder. So, net torque is decreasing, but why is it decreasing? Frictional force comes into action, but friction doesn't depend on surface area. So, frictional force will remain constant. So what...
  26. P

    How to calculate the Torque for a Set screw

    Hi, I am working on a problem where I have to find the tightening torque required for rotating the outer sleeve. The Outer sleeve is rotated by human hand ( One hand operation) hence the sleeve torque feel is determined by the set screw. Problem statement: Please refer the image. O-ring 1 at...
  27. S

    Understand Power Required for Screw Air Compressor

    Could someone help me with getting an understanding of the equations for the power required to compress screw air please.
  28. C

    Establishing equations for a worm screw mechanism

    Hey guys :) So I'm looking to form equations that I can apply a Laplace transformation to. The mechanism specifically is a trailer jack - it converts rotational motion to linear motion. And its high torque provides a mechanical advantage to lifting heaving loads. Can anyone help me form...
  29. carb

    Contact pressure - screw pretension

    Hello, I'd like to calculate the max contact pressure in the below assembly, just before contact loss between the beam and the wall. The beam is clamped to the wall with a pretensioned screw, and sustaining a force at his gravity center. I'm assuming all bodies dimensionnaly stable (no...
  30. R

    Lead Screw diameter for lifting 200Kgs

    Hi I one of my application i am using the lead screw arrangement to lift 200kg weight using handle I used trapezoidal thread and nut. Could anybody suggest the diameter required for lifting the weight of 200kg
  31. sekedarimaji

    Determining Minimum Bolt Size for Display Mounting

    Homework Statement Hello guys, I want to make a mounting for a display which 6 Kg weight. The display will be supported by two hollow square 30x30 with 2 mm thickness and bolted by 2 socket screw in each hollow. Base of the display are made from aluminium sheet 1 mm thick. Homework Equations...
  32. N

    Linear force on lead screw drive

    I have a lead screw drive. The stepper motor puts out 280 oz-in of torque. Its attached to a 1/2 inch dia., .200" pitch, 2 start lead screw. There is a plate that's attached to the screw that moves back and forth along the screw. How much force can that metal plate exert in a linear motion?
  33. voltech444

    Rotary Screw Engines for ORC Systems | Jordan

    I've been reading a lot about rotary screw compressors and using them as expanders in ORC systems. There are about 3-4 companies making these for ORC systems and they seem to be very reliable and efficient. They are much more tough than turbines; they can take dry steam ,wet steam, saturated...
  34. Matterwave

    Fortran [FORTRAN] How did I screw up my code?

    Hi guys, there's a bug in my code which I've been trying to get rid of for the last 2 weeks. I'm completely out of ideas now on what it is so I have to turn to you guys for help. The code is here: module helectron use params use parallel !* electron density parameters integer ...
  35. N

    Bending moment and shear force for screw

    Can someone help me with determining the free body force diagram, and hopefully I can go on from there. Homework Equations M = F.dI found T = 500N The answers are shear force = -62.5N , Moment = 64.4 Nm , Tension = 500N
  36. George Zucas

    What is the optimal profile for a self reversing screw?

    Hello everyone, I am trying to design a self reversing screw. What I am doing is, I am sketching a rectangle and using extruded cut option in Solidworks, cut it along a helical curve. One more and this time in the opposite direction. It comes out nicely. Now what I don't know is, should I use a...
  37. elementHTTP

    Mass flow rate, conveyor screw calculations and books

    I am interested in mass flow rate in conveyor screw transportation http://www.colormaxsystems.com/wp-content/uploads/2013/11/5-screws-300x222.jpg any recommended book,engineering guides ?
  38. M

    Proper Screw Threading Design

    Hi, My question regards a plastic bottle that I'm designing. For the threading that fits the two parts together, will and Acme thread work? This is how I've designed my part, but I can change the thread profile if need be. Also, is there anything that I need to know regarding the pitch? I have...
  39. A

    Torque on lead screw based on psi

    So in a cnc machine, the screw that drives the x,y,z axiis are called "lead screws". I am constructing a machine that displences fluid at percise volumes. It will be essencially a seringe with one way valves coming in and going out. To open the "check valve" it requires at least 1.5 psi. If I am...
  40. O

    How Much Torque is Needed to Lift a 1000 lb Load with a Power Screw?

    Homework Statement A power screw with a pitch of 1 mm is directly coupled to a stepper motor rotating at 60 rpm. If the efficiency of the power screw is 35%, what is the stepper motor torque required to raise a 4450 N (1000 lb) load? Homework Equations P=τ*ω τ=F*r The Attempt at...
  41. G

    Torque on the Drive Shaft of a Screw Conveyor

    My work has a drive shaft that has been breaking on a U-trough screw conveyor. I am looking for some helpful equations to find the torque on the shaft so I can accurately model and optimize the shaft in SolidWorks.
  42. L

    Screw theory and Chasles' theorem

    I am currently working on my masters and happened to stumble upon screw theory, of which I have no previous experience with. Fundemental to screw theory is Chasles' theorem or Mozzi's theorem that states that any rigid body motion can be produced by a translation along a line and rotation about...
  43. I

    Lead Screw model in Creo and calculations

    Hi I'm trying to make a lead screw in Creo which would be used to move a 400lb load linearly along the ground. This would be turned manually using a lever as shown in the pic (not the complete model). I have used a lead screw with a major diameter of 1 1/4 and determined the torque to move...
  44. K

    Zero Errors in Vernier Calipers and Micrometer Screw Gauge

    Hi, I have a question to ask. On my notes that my teacher gave me, he said that there are some errors in the notes. He had not responded to me which are the errors yet but he said about zero errors in vernier calipers and micrometer screw gauge. The question is: On my notes, it says that...
  45. S

    Designing a Twin Screw Pump - Why the Pressure Loss?

    I'm having to design a screw pump and I'm a bit confused about things, I've never really seen a screw pump before. I've decided upon a twin screw - screw pump and my first question is why do most examples have an outlet at a higher level than the input, surely that just leads to a pressure loss...
  46. M

    Final year project on archemedes screw

    hey guys! i want to work on archemedian screw/its applications as my final year engineering project. can u help me to make it more engineering affiliated ? i got this idea from a site related to school level science project...i really want to do this. please suggest ideas! thanks in advance.:smile:
  47. N

    What is the Shear Modulus of This Screw?

    I have a screw that is used in our plant that is rated to break at 39 ft/lbs of torque. The diameter of the shaft is .130 inches. What is the shear modulus of the material that is being used. Thanks
  48. G

    What is the Total Work Required to Drive a Screw Completely into Wood?

    Homework Statement It takes 25 turns to drive a screw completely into a block of wood. Because the friction force between the wood and the screw is proportional to the contact area between the wood and the screw, the torque required for turning the screw increases linearly with the depth...
  49. Z

    What Defines the Power of a Screw?

    I'm in a class that is talking about screws (common everyday type of screws). The question came up with regarding exactly defines the power of a screw? We're sure that the smaller the space is in between the thread contributes to more clamping power. For the other factor, we're thinking that...
  50. D

    Bolt screw shear strength calculations

    Hi guys, I have an electric motor that comes with a flange to be bolted on a plate horizontally so that the 4 screws carry the weight of the motor and the momentum it creates on them. Could you direct me to how to calculate if the given screws and nuts stand up to the load? Perhaps an example...