Not a lot new

[John Stevenson]

From some recent posts and some private emails concerning links that I and others have ut on it becoming more obvious that there isn't a lot of original material left to be found.

The recent threads on taper turning, ball turning, hexagon chuck jaws and large radius turning all lead back to solutions devised years ago by this versatile and very busy guy called Anon.

Now Anon was a busy guy, that busy he didn't have time to sign most of his work but fortunatly it did get recorded.

Looking thru the resurfaced post on vintage farm plans thaat's currently running I found this on taper turning.

http://www.vintageprojects.com/machineshop/offsettaperturning.pdf

No idea how old as the date isn't on the article but guessing pre war or just post war.

I also came across the old trick of ball turning with a flycutter in the mill and a dividing head.
I have often seen this and if I get chance later next week I'm going to set one of these up and get some pics as the diagram doesn't really make it clear.
Here's a sketch from another book of the same method.



John S.

[Your Old Dog]

Not a lot new except us new "wannabes" ! I hadn't seen that one John and it may save me some time. I do believe I can do dat !

edited: I was making referance to the 4jaw setup.

Ray........

[This message has been edited by Your Old Dog (edited 04-10-2005).]

[Daminer]

John;

The retired machinist/toolmaker I mentor with at the H. S. Showed me that trick using a spin index held in the mill vise.....Once the students found they could make thier own gear-shift knobs, etc., they went to work with a little more interest than usual.....

You have to calculate the angle by measuring the shaft into the ball versus the diameter, a basic trig problem that made em' groan.....

We use standard brazed boring bars and run the mill in reverse, works great.....

Jim

[alwynoak]

john
nice picture, but it does,nt tell you what angle A is, looks about 45degs but this will only make hemisphere,and not a ball,looking at the pic and the dotted lines you would think,or most people would think they could make a ball,sorry only half a ball,at that angle.

[John Stevenson]

Alwynoak,
This is why I want to do it and get some photos.
It's one of those jobs that the more you stare at it the less you understand it

The picure came out of an old engineering book and I scanned it in ages ago.
There was a formula on the same page to calculate the angle A based on B and R but that wasn't on the photo.
Now I'm struggling to find the damn book.

As a quick explanation if you take the circular path that the cutter is taking and where the tool is now call this X the opposite side we will call Y and that's at the base of the ball.
Now imagine we don't touch the flycutter but we rotate the dividing head 180 degrees.
That point Y will now be under the centre line, still at the base of the ball.
Point X will now be the very topmost point of the ball.
By the time the dividing head has rotated once the tool will have traversed every part of the ball above the shank and it will have cut a sphere except for the shank.

Now to try and dig that book out and hopefully late Tuesday or Wednesday when the mill is free again I can get this setup.

John s.

[Tony]

very clever, very clever.
i'm always amazed at how ingenious people can get.

the formulas shouldnt be too hard... looks like the shank diameter is a function of angle A.. if A is 0 degrees, you'll cut your shank on the last revolution.. if A is 90 then your ball diameter and your shank diameter will be the same.. so i'd guess:

new diameter = B * sin(A)

this is assuming one starts with a straight cylinder. if you start with a workpiece like the drawing shows, you'll have to do the math backwards.. ie B = diameter you want / sin(A)

diameter of ball will be twice the distance you set your flycutter off center (workpiece axis = center, not flycutter center).

now a good question is: how fast do you have to turn that rotary table before you're climb milling?

-tony

[CCWKen]

I believe angle "A" must be 45 degrees.