Caption this!!

[Russ]

....and not the old Landy favourite , the Whitworth

 

The form of a Whitworth thread is based on a fundamental triangle with an angle of 55° at each peak and valley. The sides are at a flank angle of Θ = 27.5° to the perpendicular to the axis. Thus, if the thread pitch is p, the height of the fundamental triangle is H = p/2 tan Θ = 0.96049106 p. However, the top and bottom ¹⁄₆ of each of these triangles is cut off, so the actual depth of thread (the difference between major and minor diameters) is ²⁄₃ of that value, or h = p/3 tan Θ = 0.64032738 p. The peaks are further reduced by rounding them with a 2x(90°-Θ) = 180°−55° = 125° circular arc. This arc has a height of e = H sin Θ/12 = 0.073917569 p (leaving a straight flank depth of h−2e = 0.49249224 p) and a radius of r = e/(1−sin Θ) = 0.13732908 p.

 

I've thrown out every Imperial tool I've ever accidently bought, Whitworth is another level of hatred altogether!

[tazzieman]

I've thrown out every Imperial tool I've ever accidently bought, Whitworth is another level of hatred altogether!

When I rebuilt the old Landy I changed to the post WW2 and non USA bolts.

Mind you there are some ancient 1930s parts that remain on that car.

The clutch pressure plate heads were a bear to remove and I had to borrow a socket set from old mate who collects old English motorcycles..

[Pauly]

When I rebuilt the old Landy I changed to the post WW2 and non USA bolts.

Mind you there are some ancient 1930s parts that remain on that car.

The clutch pressure plate heads were a bear to remove and I had to borrow a socket set from old mate who collects old English motorcycles..

 

I would have thrown it in the scrap metal bin if it had those threads on it. 

[Uncle]

LOL after 37 years of either getting my Dad a bolt or looking for one myself I trust my gut on thread pitch

[tazzieman]

Just joshing Uncle 

[Uncle]

I know mate!

[Airhead]

 

The relationship between the height H and the pitch P is described by the following equation:

 or

In an external (male) thread (e.g., on a bolt), the major diameter D_maj and the minor diameter D_min define maximum dimensions of the thread. This means that the external thread must end flat at D_maj, but can be rounded out below the minor diameter D_min. Conversely, in an internal (female) thread (e.g., in a nut), the major and minor diameters are minimum dimensions, therefore the thread profile must end flat at D_min but may be rounded out beyond D_maj.

The minor diameter D_min and effective pitch diameter D_p are derived from the major diameter and pitch as

 

 

....and not the old Landy favourite , the Whitworth

 

The form of a Whitworth thread is based on a fundamental triangle with an angle of 55° at each peak and valley. The sides are at a flank angle of Θ = 27.5° to the perpendicular to the axis. Thus, if the thread pitch is p, the height of the fundamental triangle is H = p/2 tan Θ = 0.96049106 p. However, the top and bottom ¹⁄₆ of each of these triangles is cut off, so the actual depth of thread (the difference between major and minor diameters) is ²⁄₃ of that value, or h = p/3 tan Θ = 0.64032738 p. The peaks are further reduced by rounding them with a 2x(90°-Θ) = 180°−55° = 125° circular arc. This arc has a height of e = H sin Θ/12 = 0.073917569 p (leaving a straight flank depth of h−2e = 0.49249224 p) and a radius of r = e/(1−sin Θ) = 0.13732908 p.

That's easy for you to say!