Tapped or Threaded Holes | tapped hole
Tappedholesaremadeinsheetmetalpartsbyfirststartingwithalasercuthole. Thatholeisthentreatedwithatreadingbittocreatethreadsintheholeforusewithascreworboltwithmatchingthreadstoholdacomponentorattachingthesheetmetalparttoanothercomponent.Thereareanumberofspecificationsyouhavetokeepinmindwhenconsideringtappedholes.IntheAmericansystem,ascrewthreadisdesignatedbytwonumberscalledthescrewsizeandthepitch.Forinstance,#4-40,#8-32,1/4-20.Thefirstnumberreferstothesize(andthereforestrength)ofthescrewshaft;t...
Tapped holes are made in sheet metal parts by first starting with a laser cut hole. That hole is then treated with a treading bit to create threads in the hole for use with a screw or bolt with matching threads to hold a component or attaching the sheet metal part to another component. There are a number of specifications you have to keep in mind when considering tapped holes.
In the American system, a screw thread is designated by two numbers called the screw size and the pitch. For instance, #4-40, #8-32, 1/4-20. The first number refers to the size (and therefore strength) of the screw shaft; the second to the pitch (number of threads per inch) on the screw. So a #4-40 screw has 40 threads per inch, a 1/4-20 has 20 threads per inch. A #4 screw is a smaller diameter (and therefore weaker) than a #6.
Common sizes for threaded screws are 4, 6, 8, 10, ¼”, 5/16” and 3/8”. For each shaft size, there are only 2 common usage thread numbers. For example, #8-24 & #8-32 ...