Milling dome shape

[raytor]

Could someone explain the setup for milling a dome shape using a manual (non CNC) 3 axis mill?
A variety for accessory tooling is on hand as well but no lathe.

[Bill Clark]

form cutter and rotary table.

[Geof]

Originally Posted by raytor Could someone explain the setup for milling a dome shape using a manual (non CNC) 3 axis mill? A variety for accessory tooling is on hand as well but no lathe.

Do you have a rotary table?

Can the head of your machine be set at an angle?

If the answer is yes to both I can make a sketch of a setup that will machine a spherical surface.

[raytor]

Originally Posted by Geof Do you have a rotary table? Can the head of your machine be set at an angle? If the answer is yes to both I can make a sketch of a setup that will machine a spherical surface.

Yes to both - and the rotary table is motorized for continuous rotation.
Please show me the setup - I am driving myself crazy to get it right.
Thanks

[Geof]

The sketch below trys to show my method for generating a spherical surface on a mill with a rotary table. The work is fastened on the table, a single point tool like a fly-cutter is in the spindle and the head of the machine is tilted. The angle of tilt on the head depends on the radius of the cutter; you do not want the cutter to touch the rotary table but you do want the cutter to be touching the surface past the table centerline.

The centerline of the rotary table and the spindle centerline have to be exactly inline normally by adjusting the Y axis. The table rotates continuously with the spindle running and the part is either fed up toward the tool by raising the table if it is a knee mill or by feeding the spindle down.

The combined rotation of the table and cutter with the two centerlines exactly inline automatically generates a spherical surface. If the two centerlines are inline the cutter will touch all the way around and will leave a crosshatched finish on the sphere. If they are not inline the cutter will only cut on one side of the sphere so it is easy to tell when they are in line.

It is not possible to make a complete sphere because you always need a neck to hold the sphere but it is possible to machine down to a very small neck by adjusting the flycutter radius, the angle of the head and the angle the cutter is held.

Where did my picture go?????

[Geof]

Found it!

[raytor]

Many Thanks Geof. That looks like it will do the trick.

R

[Mcgyver]

Geof, kudos to you for a nifty idea. i wouldn't have got it, but seeing it reminds me of a trick I've used to turn a sphere on a lathe without radiusing tackle - take a piece of gauge plate and drill a hole, maybe 3/4 the dia of the sphere. after roughing out the sphere shape just apply the tool steel with the hole free hand and presto, it cuts a perfect sphere (i was cutting wood, should work for soft metals as well).