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Topic: Screw thread

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In the News (Thu 22 Aug 19)

  Screw - Wikipedia, the free encyclopedia
Threaded fasteners are traditionally made by a cutting action such as taps and dies provide, however recent advances in tooling allows them to be made by rolling the blank (a section of rod) between two specially machined dies.
The diameter of a metric screw is the outer diameter of the thread.
The thread angle was 55┬░and a depth and pitch of thread that varied with the diameter of the thread (ie: the bigger the bolt, the coarser the thread).
en.wikipedia.org /wiki/Screw   (4499 words)

 Thread tapping screw - Patent 5061135
The intersection of the radiused thread profile 31 and the cylindrical core 16 of the screw which occurs at 32 does not create a condition where the surface 33 of the core is tangential to the radius 22.
The screw moves axially forward 77 under the influence of the rotation 76 of the helical form of the screw thread generated around a cylindrical bore, and initial "starting" end pressure 78 being exerted in the direction shown.
As the screw moves forward under the above-mentioned influence, there is created a condition of deformation of the nut anchor material in a manner that increases the thread profile depth contact of the mating threads, as a consequence of the thread profile form of the present invention.
www.freepatentsonline.com /5061135.html   (4682 words)

 Historical Background on Screw Threads
One of the first applications of the screw principle was in presses for the extraction of oils from olives and juice from grapes.
The construction of the screw thread depended upon the eye and skill of the craftsman.
Screw threads for fasteners were cut by hand but increasing demands deemed it necessary from them to be factory made.
www.boltscience.com /pages/screw2.htm   (518 words)

Screw thread can be defined as a ridge of uniform section in the form of a helix on the external or internal surface of a cylinder or hole.
External thread (screw): A thread on the external surface of a cylinder.
Threads per inch, n: The reciprocal of the pitch and the value specified to govern the size of the thread form.
www.me.metu.edu.tr /me114/screw_threads.htm   (890 words)

 Screw and Thread Terms
On a straight screw thread, the diameter of an imaginary cylinder, the surface of which would pass through the threads at such points as to make equal the width the threads and the width of the spaces cut by the surface of the cylinder.
The surface of the thread corresponding to the major diameter of the screw and the minor diameter of the nut.
On a single threaded screw the lead and pitch are identical; on a double threaded screw the lead is two times the pitch; on a triple headed screw the lead is three times the pitch, etc.
www.accuratescrew.com /TechTips   (517 words)

This gap is maintained, notwithstanding further screw turns, because the pitch of the screw thread is uniform throughout the screw length.
Screw thread 18 extends substantially the entire length of shaft 12, although it is acceptable for screw thread 18 to stop somewhat short of trailing end 16.
The form of screw thread 18 is conventionally symmetric, forming a substantially isosceles-shaped triangle in cross-section.
www.delphion.com /details?pn=WO09420040A1   (596 words)

 Unified Screw Threads
It is used for producing threads in low strength materials such as cast iron, mild steel, and softer copper alloys, aluminum etc. The coarse thread is also used for rapid assembly or disassembly.
Fine Thread Series, UNF/UNRF: This is used for applications that require a higher tensile strength than the coarse thread series and where a thin wall is required.
The fit of screws threads (class 2A/2B and class 3A/3B), as well as the allowances, max and min.
www.efunda.com /designstandards/screws/screwun.cfm   (305 words)

 Screw Point Chart - by Zero Fasteners
The last thread and a half is slightly cupped by the thread roll-over operation.
A thread cutting screw with a tapping screw thread with blunt tapered point and multi-cutting edges and chip cavities.
A thread cutting screw for wood with a coarse tapping screw thread and a special long sharp point fluted to capture chips.
www.zerofast.com /screw.htm   (655 words)

 Screw Threads   (Site not responding. Last check: 2007-10-12)
The most used screw thread forms are those having symmetrical sides with inclined at equal angles.
Thread Classes are used to specify the amounts of tolerance and allowance.
It is also used for threading into lower tensile strength materials such as cast iron, mild steel and to softer materials as brass and aluminum to prevent stripping of the internal threads.
www.engineering.com /content/ContentDisplay?contentId=41005010   (528 words)

The most common screw thread form is the one with a symmetrical V-Profile.
The Acme thread form has a stronger thread which allows for use in translational applications such as those involving moving heavy machine loads as found on machine tools.
The maximum diameters of Class 3A (external) threads and the minimum diameters of Class 3B (internal) threads are basic, whether coated (plated) or not--thus no allowance or clearance is available for assembly of components at maximum material condition.
www.efunda.com /designstandards/screws/screws_intro.cfm   (466 words)

 Screw thread - Wikipedia, the free encyclopedia
A screw thread is a helical or tapered structure used to convert between rotational and linear movement or force.
In most applications, the thread pitch of a screw is chosen so that friction is sufficient to prevent linear motion being converted to rotary, that is so the screw does not slip even when linear force is applied so long as no external rotational force is present.
A screw thread may be thought of as an inclined plane wrapped around a cylinder or cone.
en.wikipedia.org /wiki/Screw_thread   (982 words)

 Screw thread Calculations   (Site not responding. Last check: 2007-10-12)
If a screw threaded fastener is to fail it is preferable that the screw fails rather than the internal or external thread strips.
The size of a screwed fastener is first established by calculating the tensile load to be withstood by the screw and selecting a suitable screw to withstand the tensile load with the appropriate factor of safety or preload.
To ensure that the screw fails before the thread strips it is necessary the the shear area is at least 2 times the tensile area.
www.roymech.co.uk /Useful_Tables/Screws/Thread_Calcs.html   (727 words)

 Leland Powell Fasteners - Screw Point Types
Thread Cutting Screws (Type 1, 17, 23, 25, F) Type 1 point: A thread cutting screw with single flute for general use.
Type 17 point: A thread cutting screw for wood with a coarse tapping screw thread and a special long sharp point fluted to capture chips.
Type C point: A thread forming screw with either coarse or fine pitch machine screw thread and blunt tapered point.
www.lelandpowell.com /screw_types.htm   (420 words)

 American Fastener - Thread Terminology
ROLLED THREAD: Threads are cold formed by squeezing the blank between reciprocating serrated dies.
Classes of thread are distinguished from each other by the amounts of tolerance and allowance specified.
External threads or bolts are designated with the suffix "A"; internal or nut threads with "B".
www.americanfastener.com /technical/thread_terminology.asp   (258 words)

 Advanced Thread - The L.S. Starrett Company
Other thread characteristics such as lead, flank angle, taper and roundness variations are confined within these limits with no specific control of their magnitudes.
The differential is considered the size of the thread, with all of its variation in lead, flank angle, taper, and out-of-round, minus the Pitch diameter.
One of the sizes, pitch diameter, is the size of the thread with essentially zero variation in all other thread elements, while the other size, GO functional size, is the size of the thread with the effects of all variations in all other thread elements added to the pitch diameter.
www.starrett.com /pages/pages/77_advanced_thread.cfm   (2583 words)

TYPE C (ASA-C) : A thread forming screw with either coarse or fine pitch machine screw thread and blunt tapered point Eliminates chips and Permits replacement with standard screw In the field.
A thread cutting screw with machine screw thread with blunt tapered point having multi-cutting edges and chip cavities.
Machine screw threads For same general use as type C but where less driving torque is required.
archerscrew.com /page5.html   (340 words)

 Screw comparison guide - screw threads
This pattern uses two threads around the shank for increased driving speed, is commonly used on drywall screws, and sometimes has a high/low design.
The unthreaded portion of the shank is the same diameter as the major diameter of the threaded portion, and the root diameter tapers to the tip.
The thread depth is consistent along the length of the screw, even in the tapered portion, accentuating the pointed appearance.
www.gardensheds.greenhouses.arbors.learnabout.info /screw-threads.htm   (340 words)

 screw thread systems for fasteners   (Site not responding. Last check: 2007-10-12)
In the United States, the convention for describing threads is to give the number of threads per inch, preceded by a gauge number if the bolt is smaller than a quarter-inch in diameter, otherwise by the diameter in fractions of an inch.
The relationship between diameter and number of threads per inch is standardized in a number of series, the most common in the United States being UNC and UNF.
Such a fastener is said to have a right-hand thread; all screw fasteners are assumed to be right-hand unless otherwise specified.
www.sizes.com /tools/thread_screw.htm   (709 words)

 Leland Powell Fasteners - Product Offerings: Lo-Driv Thread Rolling Screw
The screws forming relief feature extends all the way up into the body where the circumference of the threads are at their largest diameter.
When Lo-Driv Screws are driven into drilled or cast holes of the correct size they create strong, tightly mating internal threads.
The screws can not cross thread when driven because they create their own mating threads in the assembly.
www.lelandpowell.com /lo_driv_screws.htm   (261 words)

 MyWord.info thread
A spiral ridge on a rod (screw or bolt).
Screw or bolt can be rotated into or out of an object.
The word "thread" with this meaning is a noun (word that shows name of a thing).
myword.info /sendword.php?thread_1   (150 words)

 screw point types
CUPPED POINT: A special cup section supplied on the end of the threaded member having a depression in the end to reduce the area in contact with the surface which increases its holding and locking power under pressure.
TYPE AB POINT: A thread forming screw combining locating type point of Type A with thread size and pitch of Type B. Normal limitations of Type B apply.
TYPE FZ POINT: A thread cutting screw with a tapping screw thread with blunt tapered point and multi-cutting edges and chip cavities.
www.midstatesbolt.com /screwpoints.htm   (759 words)

 Thread Cutting Screw -
The various slot designs provide true cutting action, cleanly removing the mating metal as it is installed - eliminating a separate tapping operation and generating a perfectly mated thread that contributes to a stronger fastening.
Type 1 thread cutting screws are recommended for steel parts having a thickness less than half of the screw diameter.
The Type 25 thread cutting screw, combining a wide thread cutting shank slot and acute cutting edge with spaced threads for low driving/high stripping torque is ideal for cutting mating threads in thermoset plastic materials.
www.thread-rite.com /metal_fasteners/thread_cutting.htm   (215 words)

 BA screw thread series   (Site not responding. Last check: 2007-10-12)
Like the Whitworth thread, it has a rounded root and crest, but the included angle is 47.5° and the radius was originally 2/11 (0.1818…) times the pitch, but at some later point was changed to 0.18083.
Not only is it based on the meter, but the thread frequency is specified in terms of round numbers in the pitch sequence, with threads per meter allowed to fall where it may.
The British Association thread played a role similar to that of the ASME series in the United States, that is, it filled in sizes below a quarter-inch.
www.sizes.com /tools/thread_BA.htm   (283 words)

 Screw Thread Engineering Software
The user can modify the thread dimensions after the standard thread calculations are done.
One input provides dimensions for the External and Internal threads, Working plug gages, Ring gages, Setting plug gages and Minor diameter gages for the selected thread type and class.
The only typing required by the user is the threads major diameter, number of threads per inch, number of thread starts and the minimum and maximum plating thickness when required.
www.stetfs.com   (613 words)

 Mechanical engineering other topics - ACME Screw Thread Inspection
The 3G designation for both the screw and nut is v.important to the final function.
Aside from the usual thread variables: pitch diameter (which can be measured over pins) and thread pitch the major and minor diameters are also critical.
This provision of a crest and root wear surface is one reason acme threads are chosen.
www.eng-tips.com /viewthread.cfm?qid=73882   (583 words)

 International Screw Machine - Greenfield Distributor
Thread mills allow users to thread high quality, precision holes in the same set up on the same machine, which reduces cost by eliminating offhand tapping and multiple tool set-ups.
Also thread milling allows for 100% of thread height, where tapping usually allows only 65-75 percent.
International Screw Machine Services, LLC recognizes this and in no way is affiliated with Davenport®.
www.internationalscrew.com /pages/Distributor/greenfield_tool_die.htm   (412 words)

 Recoil Screw Thread Inserts , Thread Repair Kits and Tooling
Recoil stainless steel inserts are manufactured in a full range of thread forms and lengths and available in convenient replacement packets, or bulk.
Recoil inserts are the quick and easy method for repairing damaged threads, or creating stronger original threads in alloys and composite materials in original equipment manufacture.
Inserts are available in free running or screw lock style for applications where the thread assembly is subject to vibration.
www.newmantools.com /recoil1.htm   (555 words)

 Elgin Fastener Group - Screw Point Types
Thread Forming Screws (Type C, CA, Tri-Round, Lo-Driv)
Eliminates chips and permits replacement with standard screw in the field.
The locating point works better than Type C where holes between two adjoining pieces of sheet metal may be somewhat misaligned.
www.elginfasteners.com /screw_types.htm   (420 words)

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