Ball Valve Grinding

[intelsingh]

Does anyone have any ideas about grinding big sized ball valves? Any particular machine which does that?

[Geof]

Are ypu wanting to grind to a specific size or do you just want to grind a nice round ball with a very good surface?

[intelsingh]

Dear Geof,
This would be precision ground to a particular size. The ball valve would be coated with tungsten carbide and would have to be ground within the specified tolerances.

[Geof]

I have no idea if a dedicated grinder exists that can do what you want however consider this.

If you take sphere and hold a hollow cylinder, a tube I guess, against it the cylinder ID contacts the sphere all the way around and the axis of the cylinder and axis of the sphere intersect..

If you take a sphere and mount it between centers so it can be rotated and also mount the cylinder so it can be rotated; i.e. put the sphere on a fourth axis with a tailstock on a mill and the cylinder in the spindle you can lap the tube to the sphere using grinding paste. I know it works because I used this procedure some 50 years ago when I was an apprentice and was making some firefighting equipment that had an internal ball valve.

Now consider this: A cup wheel on a grinder is a cylinder so just set the sphere up on the grinder the same way and grind the sphere to the final size.

Of course this is not possible with a full sphere but ball valves have a hole through them for the fluid to pass and another hole, which may or may not go all the way through for the operating shaft. Even if the operating shaft hole did not go all the way through you could still have a flat spot on the opposite side of the sphere with a center hole.

Incidentally it is very easy to know when the sphere and cylinder axes intersect because the surface finish gets a fine cross-hatched appearence, if they are not aligned the finish just has swirls in one direction.

[intelsingh]

Dear Geof,

It can be done with a cup wheel. But it can spoil the slides of a conventional milling machine as i would be grinding tungsten carbide.
A machine in which a straight diamond grinding wheel can be used. You can check videos at Watsongrinding.com.

Theres also a CNC machine by Saporiti, but thats expensive.

Any ideas on how this can be achieved? Or does anyone know any custom made machine for such an application, to grind ball valves of various sizes.