cant get angle of thread cut correct

[JasonBModerator @jasonb]

3, 4, 5 is what you want for a triangle though not 30/60, 1,2,3 is a block

[Martin ConnellyParticipant @martinconnelly55370]

A 1:2:3 triangle is a very special triangle with internal angles of 180°, 0° and 0°

Martin

[Anonymous]

Posted by Martin Connelly on 12/05/2016 13:39:04:

A 1:2:3 triangle is a very special triangle with internal angles of 180°, 0° and 0°

It's so special it doesn't exist! In Euclidian geometry if three points are colinear then by definition they do not define a triangle.

Andrew

[Martin ConnellyParticipant @martinconnelly55370]

Seems irony was lost here!

Martin

[Neil WyattModerator @neilwyatt]

Posted by Andrew Johnston on 12/05/2016 14:41:04:

Posted by Martin Connelly on 12/05/2016 13:39:04:

A 1:2:3 triangle is a very special triangle with internal angles of 180°, 0° and 0°

It's so special it doesn't exist! In Euclidian geometry if three points are colinear then by definition they do not define a triangle.

Andrew

I'd challenge that as:

"Three points property: Three points either lie on a line or lie on a circle."

The example given is merely a degenerate triangle, if two of its points were co-incident (e.g. a 2, 2 ,0 triangle) it would be a right degenerate triangle.

Neil

[Anonymous]

Posted by Neil Wyatt on 12/05/2016 15:15:25:

The example given is merely a degenerate triangle, if two of its points were co-incident (e.g. a 2, 2 ,0 triangle) it would be a right degenerate triangle.

Yes, but a degenerate object is not the same as the other objects in a class, and is generally considered to belong to a seperate class. So a degenerate triangle isn't considered to belong to the class 'triangles'.

Getting back to the OP I don't understand how the screwcutting created a buttress thread with the toolbit perpendicular to the work, even if the topslide was set at the wrong angle?

Andrew

[roy entwistleParticipant @royentwistle24699]

1,2, and the sq root of 5 should work ( I think )

Neil    Don't the three points of a triangle always lie on a circle ?

Edited By roy entwistle on 12/05/2016 16:44:29

[maurice bennieParticipant @mauricebennie99556]

3,4,5 triangle is interesting square these and add and you get this ,. 9+16=25 may be others but the maths of 75 years ago is a bit misty now .Enjoying the conversation.

[Martin ConnellyParticipant @martinconnelly55370]

Andrew, the sketch was probably not a good rendition of what was produced. The thread form was asymmetric with one side correct at 30 degrees and the other at 60 degrees due to the incorrect setting of the top slide angle. This would produce a 90 degree thread similar to a buttress thread.

Martin

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