Definition of Power Screws and Types of Thread Profiles – Power Screws – Design of Machine

Definition of Power Screws and Types of Thread Profiles – Power Screws – Design of Machine


Hello friends here in this video we will see the Definition of Power Screw with various thread profiles which are there in case of Power screws so let us get started here is the definition part of power screws now as the name suggests it is Power screws means screw which have some Power so here I will write it down that power screws are screws which either receive power or which transmit power so this is the simplest definition of power screws that they are the screws which either receive power or which transmit power now I can say that from this it is very much clear that power screws are different in design then screw fasteners screw fasteners are nothing but those are the screws which are used as a temporary joint like if we have two screws then we are using them as a temporary joint that is called as a screw fastener but power screws since they are transmitting power their design is different from that of screw fasteners next they must have sufficient strength to transmit power here it means that power screws they should be strong enough to transfer the power because they are you mostly used in case of machines where the power transmission is of prime importance so the screw they must have sufficient strength next they should have adequate bearing area to withstand forces means the power screws they AR area should be such that they should be able to resist high amount of forces because they are used in such machineries where always these screws they would be subjected to some kind of axial movement in the horizontal direction or vertical direction so always there are forces acting on such kind of screws so this is the definition part now I will draw some of the commonly used thread profiles in power screws thread profiles of power screws now when I am starting from the thread profile the most commonly used thread profile which we have it is a square threaded screw here the profile is in such a way that it forms a square so I am taking just this section now if I draw the section here this is the thread profile which has square threads and it will look something like this now this is the profile the first one I will say that it is the profile of square threads now square threads are mostly used for power transmission and if I want to indicate some of the common distances if I take any point on this thread and along its axis if I measure the distance on the next thread for the same point this distance would be called as pitch and now here I have this as the height of thread denoted by H and this top surface of the thread is taken as half of pitch that is pitch by two so now this is regarding the square thread after this the second most commonly used profile is of AK matrix here I am drawing the profile of Acme threads this is the cut section and here I will draw the section lines now these are Acme threads now again in case of Acme threads I can show the pitch if I measure the distance that is I take a point on a thread on the next thread if I take the point at the same location and measure this distance it would be called as the pitch and this pitch will remain same throughout denoted by small P next this top surface of the thread it is taken as zero point three seven times of pitch now as we can see from the diagram compared to square thread square thread was having ninety degree angle like this it was in kind at ninety degree but here in case of AK matrix they are inclined at some other angle if I extend these lines so they are at an angle now this angle is called as two beta that is the angle between the thread flanks ACMA threads as I can see here that at the bottom your area is more so this offers additional strength to AK mate rates compared to square threads next the third type of thread profile which we have it is called as but earnest thread Here I am drawing the thread profile for it this is buttress thread profile mostly used in machine vices Here I am drawing the section for the buttress thread now this is the profile of buttress thread so now you’re the thread profile which I have drawn it is called as buttress thread now in case of buttress thread again as I have shown the pitch for square and act methods similarly here we are having the pitch for buttress thread and this top surface it is taken approximately equal to 0.125 times of pitch and here is the height of thread and this angle as I extend this vertical line and this inclined line they will meet at an angle which is inclined at 45 degree so that is the inclination which we are taking for buttress right now as we can see for buttress thread also the area at the bottom that is called as the core of the thread so at the core the area is more so this offers more strength for the thread and buttress thread it is useful for power transmission I will write it down it is for power transmission in both the directions that is if we are using buttress read with the help of that we can transfer the power in forward direction as well as we can transfer the power in the reverse direction so mostly buttressed rates they are used in case of machine vices the where we are clamping the workpiece that is in case of a clamp we are attaching this buttress thread to the machine table and then we when we are rotating the handle with the help of that this thread moves forward or backward so when it is moving forward or backward it has adequate strength to transfer the motion and mostly as I have told it is used in case of clamps or in case of machine vices square threaded screw they are used in case of screw jack in case of universal testing machine and even in case of lathe machine as I talk about Acme threads they are preferably used in case of late machine where we are having the lead screw of the lathe which is continuously rotating and transferring the carriage from one place to another there we are having Acme traits to transfer the motion so in this video we have seen the definition of power screws and the various thread profiles available for power screws

46 thoughts on “Definition of Power Screws and Types of Thread Profiles – Power Screws – Design of Machine

  1. Acme threads can transfer power in both directions…… Buttress thread can transfer only in one direction…….. This is the limitation of buttress thread…….

  2. iso metric trapezoidal thread this profile come under power screw , pls come with complete and correct information , I like the method of teaching

  3. OMG…please correct the statement made about buttress thread. It can transmit power and motion only in one direction.
    Dont spread false knowledge.

  4. I heard about a thread that can unscrew itself if you pull it, I don't even know how it is called, can somebody help me with this thing?

  5. Hlo sir buttres threads are used to transmit power in one direction only because they have 45degree angle between the two teeth.and theese type of threads are used in ratchet type spanners.

  6. I like your video and how you explain the threads. I needed a reminder class. I work in design now but I worked a lot of years as a machinist. Good video.Thanks.

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