Angle of the Toolpost

[eLuSiVeMiTe]

OBvious now ive though about it. Moves the same distance at 45

Unfortunately we were supposed to learn trigonometry at school...

This is "The Real World," though. If only you'd paid attention At the time you can never imagine a use for certain things you should have learned. Mind you, most the stuff I learned is well and truly forgotten

Aye. Tbh I learnt more out of school than I ever did in school. Pretty useless there In hindsight.
Much like the statement above. When I thought about it again its obvious.

 

[graffian]

I'm guessing that if you set it to 45 degrees it should take off half the amount indicated?

No. sin45&cos45 are sqrt2/2

If your compound is at 30degree, the angle I am talking about is the flank angle of a threaded part.
You set the compound to take a cut; the depth of cut will be: cut*cosθ.
The movement in the x direction would be cut*sinθ.
What that roughly means is a 20 thou cut moves the tool radially 17 thou and axialy 10 thou.

 

[dobbslc]

^^^ I need an exploding brain emoji!
I can only just calculate what needs to be shaved off a diameter!

 

[graffian]

I am not good at explaining things.
Better leave it at that.

 

[eLuSiVeMiTe]

^^^ I need an exploding brain emoji!
I can only just calculate what needs to be shaved off a diameter!

Think of a right angled triangle.
A 40mm b 40mm c 56.57

Travel 40mm diagonally down c and you will have covered less distance across the lathe.
Travel 20mm and your way under half.
Obvious in hindsight. What happens when I don't engage my brain.

I am not good at explaining things.

ok pillaged a pic from google.
Whats theta? well calling angles θ is easier than writing 30degrees all the time, or whatever angle is it.
In the drawing the hypoteneuse is the compound slide traveling.
the adjacent is the tool going deeper into the cut, think they call it Z direction.
the opposite is the tool moving towards the chuck, I guess that's the X direction.

So if you move the tool 20 thou with the top slide:


sinθ:=opposite / hypotentuse.

That means hypoteneuse*sinθ := adjacent.
So 20 thou movement of slide would be .02"*sin 30 = opposite. As Sin30:=1/2 so .02*1/2:=.01"


Cosθ:=adjacent/hypoteneuse.
So hypoteneuse*cosθ. which is .02*.866 which is around .017"


Did I just make it worse?

I should draw a chuck on that picture.

Yes lol.

 

[addjunkie]

Think of a right angled triangle.
A 40mm b 40mm c 56.57

Travel 40mm diagonally down c and you will have covered less distance across the lathe.
Travel 20mm and your way under half.
Obvious in hindsight. What happens when I don't engage my brain.

Yes lol.

Makes sense to me, and Ive spent the day hand cutting a roof. Though I have studied both normal and spherical trigonometry in the past.

All these things are actually explained in any decent lathists book.

 

[eLuSiVeMiTe]

Makes sense to me, and Ive spent the day hand cutting a roof. Though I have studied both normal and spherical trigonometry in the past.

All these things are actually explained in any decent lathists book.

Studied neither but had no need to. When the need arrives I will make the effort.