Metric fine / coarse

[rickharris]

I have been unable to find a definitive answer to this. Why are there fine and coarse metric threads and where does fine stop and coarse start?

 

[gbritnell]

I can't say I have the right answer but I assume the reason would be the same as SAE bolts. Fine thread bolts are made to be used where there is alot of vibration.
gbritnell

 

[Noitoen]

Normal metric screws have a standard pitch but in applications where you need higher strength applications, the thin thread gives a firmer grip because of the small advance per turn. Since these screws are usually harder their threads are also stronger to support higher strain.

 

[Holescreek]

http://www.misumiusa.com/technical/index.aspx

Click on the link above then scroll down to the technical data. There are PDFs for both fine and coarse metric scrw threads. This site has a wealth of info for free that can be usefull. -MIke

 

[Tin Falcon]

There are advantages disadvantages to both:
Fine threads
used to thread tubing
used on thin material
used when fine advancement per turn desired.

Coarse:
stronger
faster to install /remove
Tin

 

[tel]

There are advantages disadvantages to both:
Fine threads
used to thread tubing
used on thin material
used when fine advancement per turn desired.

Coarse:
stronger
faster to install /remove
Tin

I'd argue that one Tin - you can put a lot more pressure on a fine thread than a coarse, and the larger root diameter of the fine means it will be stronger in shear as well.

 

[bob ward]

For more data than you probably wanted.

http://www.engineeringtoolbox.com/metric-threads-d_777.html

 

[Tin Falcon]

Handbook of bolts and bolted joints
Ok I sit corrected. Coarse thread do have a higher stripping strength. Fine threads have a higher tensile and shear strength. Of course for high strength threads are rolled for male threads and formed with a forming tap for female threads but that is not really part of this thread.
Tin