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Thread Manufacturing                           ME 312 Manufacturing TechnologyVikrant Sharma, Mechanical Engineering Depar...
IntroductionScrew threads probably are the most important of all the machine elements.The general applications of various ...
Thread termsMajor diameter. The outside diameter and the largest diameter of the thread.Minor diameter. The inside diamete...
Classification Of Screw ThreadsAccording to location : external screw thread (on bolts etc.) internal screw thread (in n...
According to standard :     BSW (British Standard Whitworth); thread – size is designated by TPI (threads per      inch)...
Vikrant Sharma, FET.MITS   ME 312 Manufacturing Technology
Methods of screw thread productionVikrant Sharma, FET.MITS             ME 312 Manufacturing Technology
Production of screw thread by machiningThread cutting by hand operated tools :Usually small threads in few pieces of relat...
For producing external threads, the hand operated dies are commonly use,  which are coaxially rotated around the premachin...
Split die : the die is made in two pieces, one fixed and one movable  (adjustable) within the cavity of the handle or wren...
Internal screw threads of usually small size are cut manually, if needed, in   plates, blocks, machine parts etc. by using...
Machining screw threads in machine toolsThreads of fasteners in large quantity and precision threads in batches or lots  a...
Diagrammatic representation of screw cutting on a lathe.Vikrant Sharma, FET.MITS                                       ME ...
Thread chasing:Thread chasing is the process of cutting a thread on a lathe with a chasing  tool that comprises several si...
Vikrant Sharma, FET.MITS   ME 312 Manufacturing Technology
Thread milling:Thread milling is a machining process used for cutting screw threads with a  single-form or multiple form m...
Milling external and internal tapered threads.Vikrant Sharma, FET.MITS                                             ME 312 ...
Machining threads in semiautomatic lathes: Both external and internal threads are cut, for batch or small lot production, ...
Vikrant Sharma, FET.MITS   ME 312 Manufacturing Technology
Production of screw threads by thread rollingIn production of screw threads, compared to machining thread rolling, is gen...
Thread rolling is accomplished by shifting work material by plastic  deformation, instead of cutting or separation, with t...
Thread rolling between two flat dies:The basic principle is schematically shown in Fig. below .Flat dies; one fixed  and t...
Vikrant Sharma, FET.MITS   ME 312 Manufacturing Technology
Thread rolling between a pair of circular dies:Circular die sets occupy less space and are simpler in design, construction...
Vikrant Sharma, FET.MITSME 312 Manufacturing Technology
Thread rolling by sector dies:It is the simplest and fastest way of thread rolling enabling easy auto-feed of    the blank...
Thread grindingIn production of screw threads, grinding is employed for two purposes; Finishing the threads after machini...
Center-type thread grinding: Vikrant Sharma, FET.MITS      ME 312 Manufacturing Technology
Centerless thread grinding: Vikrant Sharma, FET.MITS     ME 312 Manufacturing Technology
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3.thread manufacturing

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Transcript of "3.thread manufacturing"

  1. 1. Thread Manufacturing ME 312 Manufacturing TechnologyVikrant Sharma, Mechanical Engineering Department. FET. MITS
  2. 2. IntroductionScrew threads probably are the most important of all the machine elements.The general applications of various objects having screw threads are :fastening : screws, nut-bolts and studs having screw threads are used for temporarily fixing one part on to another part.clamping : strongly holding an object by a threaded rod, e.g., in c-clamps, vices, tailstock on lathe bed etc.controlled linear movement : e.g., travel of slides (tailstock barrel, compound slide, cross slide etc.) and work tables in milling machine, shaping machine, cnc machine tools and so on.transmission of motion and power : e.g., lead screws of machine tools.precision measurement of length : e.g., the threaded spindle of micrometers and so on.exerting heavy force : e.g., mechanical presses Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  3. 3. Thread termsMajor diameter. The outside diameter and the largest diameter of the thread.Minor diameter. The inside diameter of the screw and the base of the thread. It is also called the root diameter.Pitch. The distance from one point on a thread to the same point on the adjacent thread.Pitch diameter. The diameter of an imaginary cylinder whose surface would pass through the threads at such points as to make the width of the thread cut equal to the width of the spaces cut by the imaginary cylinder.Crest. The top surface joining the flanks of the threads.Root. The bottom surface joining the flanks of the thread.Flank. The slanted surface joining the crest and the root; the surface that is in contact with the nut.Lead. The amount by which the nut advances along the screw with one turn if the screw is held stationary.For single-pitch threads, the lead is equal to the pitch;for double-pitch threads the lead is double the pitch;and for triple-pitch threads, the lead is three times the pitch. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  4. 4. Classification Of Screw ThreadsAccording to location : external screw thread (on bolts etc.) internal screw thread (in nuts etc.)According to configuration : straight (helical) – most common, e.g., bolts, studs etc. taper (helical), e.g., in drill chuck radial (scroll) as in self centering chuck According to the direction of the helix : right hand (common) left hand (occasionally) According to form : vee thread (600 or 550 angle) – most common acme thread (290) square thread (generally in power screws) buttress thread (45o) semicircular (groove section) thread being used in recirculating type bolts, screws. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  5. 5. According to standard : BSW (British Standard Whitworth); thread – size is designated by TPI (threads per inch) metric thread; thread size is specified by pitch or lead (in mm)According to number of start : single start – most common multi-start (2 to 4)According to segmentation : full threads (common) half turns as in half nuts sector thread – e.g., in the jaws of lathe chucks. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  6. 6. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  7. 7. Methods of screw thread productionVikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  8. 8. Production of screw thread by machiningThread cutting by hand operated tools :Usually small threads in few pieces of relatively soft ductile materials, if required, are made manually in fitting, repair or maintenance shops.External screw threadsInternal screw threads Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  9. 9. For producing external threads, the hand operated dies are commonly use, which are coaxially rotated around the premachined rod like blank with the help of handle or die stock.Solid die : used for making threads of usually small pitch and diameter in one pass.Spring die : the die ring is provided with a slit, the width of which is adjustable by a screw to enable elastically slight reduction in the bore and thus cut the thread in number of passes with lesser force on hands. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  10. 10. Split die : the die is made in two pieces, one fixed and one movable (adjustable) within the cavity of the handle or wrench to enable cut relatively larger threads or fine threads on harder blanks easily in number of passes, the die pieces can be replaced by another pair for cutting different threads within small range of variation in size and pitch.Pipe die : pipe threads of large diameter but smaller pitch are cut by manually rotating the large wrench (stock) in which the die is fitted through a guide bush Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  11. 11. Internal screw threads of usually small size are cut manually, if needed, in plates, blocks, machine parts etc. by using taps which look and behave like a screw but made of tool steel or HSS and have sharp cutting edges produced by axial grooving over the threads.Three taps namely, taper tap, plug tap and bottoming tap are used consecutively after drilling a tap size hole through which the taps are axially pushed helically with the help of a handle or wrench. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  12. 12. Machining screw threads in machine toolsThreads of fasteners in large quantity and precision threads in batches or lots are produced in different machine tools mainly lathes, by various cutting tools made of HSS or often cemented carbide tools.Cutting threads on the lathe:For cutting an accurate screw thread on the lathe machine, it is necessary to control the relation between the feed movement of the cutting tool and the turns of the WP. This is done by means of the lead screw, which is driven by a train of gears from the spindle. Modern lathes are fitted with change gears boxes, by means of which any thread pitches can be cut without working out and setting up the change gears. However, there are some machines on which change gears must be fitted for screw cutting. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  13. 13. Diagrammatic representation of screw cutting on a lathe.Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  14. 14. Thread chasing:Thread chasing is the process of cutting a thread on a lathe with a chasing tool that comprises several single-point tools banked together in a single tool called a chaser. Chasing is used for the production of threads that are too large in diameter for a die head.Thread chasing reduces the threading time by 50% compared to single-point threading. However, thread chasing is a relatively slow method of cutting a thread, as a small depth of cut is used per pass. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  15. 15. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  16. 16. Thread milling:Thread milling is a machining process used for cutting screw threads with a single-form or multiple form milling cutter. Thread milling makes smoother and more accurate threads than a tap or a die. It is more efficient than using a single-cutting-point tool in a lathe. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  17. 17. Milling external and internal tapered threads.Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  18. 18. Machining threads in semiautomatic lathes: Both external and internal threads are cut, for batch or small lot production, in capstan and turret lathes using different types of thread cutting tools; External threads in capstan lathe by self opening die and single or multipoint chaser in turret lathe Internal threads of varying size by collapsible tap. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  19. 19. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  20. 20. Production of screw threads by thread rollingIn production of screw threads, compared to machining thread rolling, is generally cold working process. provides higher strength to the threads. does not cause any material loss. does not require that high accuracy and finish of the blank. requires simpler machines and tools. applicable for threads of smaller diameter, shorter length and finer pitch. enables much faster production of small products like screws, bolts, studs etc. cannot provide that high accuracy. is applicable for relatively softer metals. is used mostly for making external screw threads. needs separate dies for different threads. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  21. 21. Thread rolling is accomplished by shifting work material by plastic deformation, instead of cutting or separation, with the help of a pair of dies having same threads desired.Different types of dies and methods are used for thread rolling which include, Thread rolling between two flat dies Thread rolling between a pair of circular dies Thread rolling by sector dies Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  22. 22. Thread rolling between two flat dies:The basic principle is schematically shown in Fig. below .Flat dies; one fixed and the other moving parallel. All the flat dies are made of hardened cold die steel and provided with linear parallel threads like grooves of geometry as that of the desired thread. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  23. 23. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  24. 24. Thread rolling between a pair of circular dies:Circular die sets occupy less space and are simpler in design, construction, operation and maintenance.The two identical circular dies with parallel axis are rotated in the same direction and speed. One stays fixed in a position the other is moved radially desirably depending upon the thread depth. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  25. 25. Vikrant Sharma, FET.MITSME 312 Manufacturing Technology
  26. 26. Thread rolling by sector dies:It is the simplest and fastest way of thread rolling enabling easy auto-feed of the blanks. Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  27. 27. Thread grindingIn production of screw threads, grinding is employed for two purposes; Finishing the threads after machining or even rolling when High dimensional and form accuracy as well as surface finish are required, e.g., screw threads of precision machines and measuring instruments The threaded parts are essentially hardened and cannot be machined or rolled further, e.g., leadscrews of machine tools, press – screws etc. Directly originating (cutting) and simultaneously finishing threads in any hard or soft preformed blanks. This is employed generally for finer threads of small pitch on large and rigid blanks Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  28. 28. Center-type thread grinding: Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology
  29. 29. Centerless thread grinding: Vikrant Sharma, FET.MITS ME 312 Manufacturing Technology

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