Screw Thread failure

Don't remember text book formula but common sense says its should be

Shear strength of material x number of threads in use x 3.14 x thread mean dia x sectional area of one thread at mean dia,

Hi Rakesh,

thanks for the reply. but the units do not match.

area=Shear strength of material x number of threads in use x 3.14 x thread mean dia x sectional area of one thread at mean dia,=(pounds/sq inch)*no of threads*3.14*inch*(sq inch)=pound*inch

Can u please clarify this.

Hi

Formula given is not for the area but for the bolt or nut failure strength

You can take any one system of unit.For example

Bolt failure strength=KG

Area = mm²

shear strength =Kg/mm²

Dia = mm

Thanks

I believe Rakesh meant to say strength x number of threads x 3.14 x thread mean dia. x thickness of one thread at mean dia. That would give units of #/in² x in X in which boils down to #.

Yes correct, I was wrong with my 1st post.

Hi,

Sorry friend there was some mistake it should be like this

Shear strength of material x number of threads in use x 3.14 x thread mean dia x width of one thread at mean dia,

Or

Shear strength of material x number of threads in use x sectional area of one thread at mean dia,

You need to narrow the field a little... What material, application, etc., etc.

Check this site to see if you cant answer your own question, if not please provide some specifics and you will no doubt get some terrific answers

http://www.engineersedge.com/thread_strength/thread_bolt_stress.htm

Imagine someone asking, how high does a rocket fly? How far does a bulklet go? How deep does an oil rig drill?

check the site www.boltscience.com also try a very good site

www.roymech.co.uk this has all the calculations and links

I've just typed 'thread stripping calculation' into google and found a couple of usefull sites such as:

External Thread: http://www.tribology-abc.com/calculators/e3_6e.htm

Tapped hole: http://www.tribology-abc.com/calculators/e3_6f.htm

http://www.engineersedge.com/thread_strength/thread_bolt_stress_area_iso.htm

Excel Calc sheet to download: http://www.excelcalcs.com/repository/machines/bolts-and-threads/thread-stripping.xls/

Note: I have not downloaded this sheet so take no responsibility if anything occurs during or after download. It looks like a genuine site though but I suggest you virus check anything you have downloaded before opening.

Kev Brown

Excelcalcs is a terrific site. They offer a free download (donations appreciated) that places the formulas on the spreadsheet along with the results. It makes debugging and sharing a lot easier.

They also have a depository of spreadsheets from other users. As you said, I cannot guarentee the safety of them, but have never had a problem.

Just a satisfied user, not connected in any way.