View Full Version : Best way to cut holes in copper sphere?

Lee in Texas
01-01-2014, 02:29 AM
It's 5 inches in diameter and I need the 2 holes to centered, to make a Heron steam engine. I haven't tried a lathe or mill. I've heard that copper is too soft. I don't want to damage the sphere. FWIW- I'm ok with sending it off to be done. I need it clean and precise, whether it's done by me or someone else.


01-01-2014, 03:01 AM
You can sharpen a drill with a negative rake and drill it.

01-01-2014, 03:07 AM
A cup chuck would be one way of holding it in either a lathe or a mill.

01-01-2014, 08:45 AM
Fit a dremel in an arm mounted on an arbor held in a collet in your mill, and use it with a small endmill as a trepan.

Charles Lessig
01-01-2014, 10:16 AM
Start by drilling undersized holes.

Drill the first hole. Put the sphere on a flat plate with a rod in the hole. Rest the rod on a block so that it is about
on center vertically. Scribe lines opposite the first hole with a height gage and rotate the sphere on the plate to find the center for the second hole. Drill the second hole.

Pass the rod through both holes and rest the ends on blocks so the rod is parallel the the plate.
Put some modeling clay or wax between the sphere and plate to keep the sphere from rotating.

Set the height gage to about the vertical center of the rod. Locate the halfway distance between the holes with dividers
and mark that place with the height gage. do the same for the other side.

Turn the sphere upside down and set one of the horizontal marks which is the first center to the point of the height gage and hold the sphere in place with wax or clay.

Go to the other side and mark another horizontal line. See it matches the line already there. If not, mark another line
between the two lines . This locates the next center. Drill holes at these centers.

Use a tapered repair reamer to get the undersized holes round and to size.

I think this is the method Heron would have used.

01-01-2014, 11:46 AM
The biggest problem you face is figuring a way to hold the sphere without damaging it. If your lathe is big enough it could be held in the 3 jaw with pads under the jaws, or you could set it in a ring on the mill table and clamp it in place with another ring from the top. Drilling it is no big deal. Just grind neutral or slightly negative rake on your drill and drill it all the way through in one set-up. I have a video on my website that shows how to grind drills to safely use on plastics and brass or copper. If you need a clean hole, it should be reamed after drilling to make it round and to size.


01-01-2014, 12:29 PM
I suggest that you place the sphere on a partly-filled sandbag on the drill press table. Use a step drill for the first hole, while holding the circumference of the sphere with a strap wrench. Chuck a drill of the hole size and drill down through the first hole, still using the strap wrench. Take a bit of care. If you happen to have a spur-point, (wood bit,) of the correct size, use that to just pierce the opposite side of the sphere. Then flip it over and finish with a step drill-much less chance of grabbing.

01-01-2014, 12:42 PM
Get a plastic dog food dish to hold it, screw that to a plank of wood, clamp that to your drill press table, and use a rotary rasp or step drill for the penetration.

Mike Burdick
01-01-2014, 12:52 PM
It's 5 inches in diameter and I need the 2 holes....

Is it hollow, and if so, what is its wall thickness?

If it is hollow and thin walled, then I would rough cut a hole in the sphere with a nibbler - or similar - and solder a machined bushing in it.


01-01-2014, 01:15 PM
If it is thin wall, consider immersing it in a box filled with "Plaster of Paris". Make the box the same size as the sphere so the center of any box face are the centers of the sphere. Drill with a step drill or similar.

01-01-2014, 01:16 PM
Kind of struck me funny how we today consider our techniques to do something that the old greek did 3000 years ago. Not funny that we would use the equipment that we have, but that the basic metal working techniques that our ancestors used are completely unknown today. We can only speculate what tools they had, but they must have been able to solder copper... might well have for the sphere in question. Could have had drills, must have had chisels and punches and certainly would have had hammers and some kind of anvil and a foundry.

I'm reminded of a conversation that was related to me regarding Damascus steel. This was purported to have occurred between Al Pendray, the Florida custom knifemaker, and Professor John Verhoven of Iowa regarding the analysis and duplication of Damascus metal.

The professor was telling Al how they he had analyzed a piece of the 'Damascus steel, duplicated the alloy and melted it in an vacuum induction furnace. He said the billet they produced had none of the properties they were trying to duplicate.

Al paused for a few moments and then asked the professor "Say... do you think those Babylonians had one of them vacuum induction furnace's...?" Al's point, of course, was that it was about the process and not the analysis.



01-01-2014, 02:16 PM
Based on the Antikythera mechanism and other hints I suspect civilization was far more advanced than we can imagine. Looks like we had the tools and the technique to work with electricity on a tiny scale, the ability to machine and create moving astoundingly intricate moving parts... and the knowledge of chemistry required to do some astounding things. Chalice that reacts to the PH of it's content? Greek Fire? Garum? Many other examples exist, others are being found.

I suspect, that when civilization came apart for whatever reason... all the writings were lost. Perhaps because they were stored on non-robust technology. And anything that wasn't "food" or "gold" was melted down as scrap or burned as fuel. Entire ancient machine tools were lost. The storage medium with the information on Greek Fire, and some of the astounding alloys from back then were lost. The information on the chemically sensitive chalice was lost, and so much more.

This is one of the reasons I lament the lack of true robust storage mediums. After this period in civilization passes and the scrappers loot and sack everything... Fragments of our technology will come forward. Pieces of our writings will be found. People will stand in our great crumbled buildings and wonder "how the hell did they do that with such rudimentary technology?"

01-02-2014, 03:43 AM
If only the library at Alexandria hadn't been burned! I wonder where we would be today if we had all that early knowledge.

01-02-2014, 07:08 AM
Get a plastic dog food dish to hold it, screw that to a plank of wood, clamp that to your drill press table, and use a rotary rasp or step drill for the penetration.

Why not use the plastic dog food bowl but use water. Put the sphere into the bowl and clamping it down so the sphere doesn't float when water is added to fill the bowl with water. Place assembly in freezer and freeze the water. It will be an excellent "clamping" mechanism and just set it aside to warm-up to release the sphere.

I've used this freezing procedure on several projects on difficult to mount/hold items and it works great.

01-02-2014, 11:59 AM
I love the plaster of paris cube idea, would make it fast and simple to put the holes in, and as long as the cube was an accurate cube, the holes would be perfect.