Guineafowl
Member
- Messages
- 764
- Location
- Inverness
Settle an argument for me...
My mate insists that setting the compound slide to 45deg, and feeding in using that, results in 1/2 the indicated depth of cut being taken, but I don’t think the geometry works like that.
Here, I’ve constructed a right-angle triangle with the adjacent side labelled ‘f’ for feed, and the hypotenuse labelled ‘c’ for compound slide advance.
Trig tells me that f=c.cos(theta)
If I wanted to set 2 thou for every 1 thou of feed, ie 2:1 ratio of c:f, the angle required is cos-1 (1/2), which is 60deg.
Since my compound slide is set to 90deg for straight in feed, rather than the 0deg implied by the triangle, I have to take 90-60=30deg on the compound slide dial, for a 2:1 reduction in feed. Not 45deg.
I think his confusion is that 45deg will give a 1:1 ratio of f to the unlabelled side, but what we’re interested in is the ratio of c:f.
My mate insists that setting the compound slide to 45deg, and feeding in using that, results in 1/2 the indicated depth of cut being taken, but I don’t think the geometry works like that.
Here, I’ve constructed a right-angle triangle with the adjacent side labelled ‘f’ for feed, and the hypotenuse labelled ‘c’ for compound slide advance.
Trig tells me that f=c.cos(theta)
If I wanted to set 2 thou for every 1 thou of feed, ie 2:1 ratio of c:f, the angle required is cos-1 (1/2), which is 60deg.
Since my compound slide is set to 90deg for straight in feed, rather than the 0deg implied by the triangle, I have to take 90-60=30deg on the compound slide dial, for a 2:1 reduction in feed. Not 45deg.
I think his confusion is that 45deg will give a 1:1 ratio of f to the unlabelled side, but what we’re interested in is the ratio of c:f.