Drilling Copper Slugs

Either core it first with a LASER or use an EDM (electrical discharge machine).

Any good machine shop should have at least one of these availible.

I agree your suggestion of LASER & EDM MACHINES.How about drilling a hole that does not go thru the other side of the material.Example copper shaft with the diameter 100 mm X 700 mm Long.Your making a hole 22 mm dia. X 600 mm Long.What procedure & equipment will be used?

thanks,

Try using a lathe, very slow with lots of lubrication and cooling. You should be able to get a chuck that will fit in the live centre mount (If you havent already got one). Drill from small and increase the hole sizes in regular increments. This will avoid overstraining and overheating the large bit.

Regards

Yes, the right copper cutting fluid and cut angle and rate of cut of the drill will prevent the heat build up and spalling you found.

http://www.google.ca/search?hl=en&safe=off&q=%22machining+copper%22+%2Blubrication&btnG=Search

As a machinist's apprentice I had occasion to drill a lot of 1/2" holes in 1/2" to 3/4" copper plate. You MUST use a specially sharpened bit that looks a lot like a carpenter's wood bit. The central pointed tip extends past the two outer lips with a concave cusp in between. Use plenty of a lubricating water base coolant. If it is a through hole a neatly shaped "button" will be at the end of the twisted spirals cut from the work piece. Stop and remove the spiral waste 'chips' frequently. I assume, of course, you will be using a lathe or drill press suitable for the job.

Never use a standard 60 deg. type drill in copper.

Happy drilling.

If the material can be clamped by a suitable method, then the use of a gundrilling machine may be the best for this application. These machines are usually found in specialized machine-shops, and are the best method for the deep drilling operations that require a length to diameter ratio that is far beyond the feasibility of normal drilling equipment and techniques.

Ing. Robert Forbus

To expand a bit on what others have suggested:

A gun drilling set up, with ability to insert and withdraw the drill in and out of a comparatively deep hole is a necessity for production or large quantity of work. Copper produces a string-like 'chip,' unlike other metals which can be amenable to chip breaker cutting lips. The drill bit and chip has to be withdrawn from the hole frequently to remove the string-like chip.

The cutting lip geometry is critical for successful drilling of copper with a minimum of muss and fuss.

In trying to drill copper to make heat sinks, I have found that the alloy of copper you use is also very important. If you are trying to use alloy 110, you will have a mess everytime. It does not machine or drill well. Try making sure you have alloy 145 copper if you are trying to machine or drill any size of length of this stuff.

You will still need to use cutting/cooling fluid, but you should have better results.

"In trying to drill copper to make heat sinks, I have found that the alloy of copper you use is also very important."

Not only the alloy but the hardness makes a lot of difference as does the drill point geometry for nice tight, round holes with only a slight bur on the exit face of the work piece. You might get better results with the drill geometry profile suggested in my earlier
post(s).

You tend to get a form of friction welding with copper unless you have the right cutting angle and cutting fluid and rate of feed.

Just following the TIP Cutting Carbide-you can ASK THE GunDrill Supplier to Braze another chipbreaker blade. -- If your Copper has to be O.F.H.C.

Stirling's observation is so correct--alloying determines ductility--hence chip lengths--unless CHIPBROKEN-UP.

This was the basis of searching for a whole new range of Copper alloys for easy chip removal.

Highest possible Electrical/Thermal Conductivity is NOT needed in all applications.

Slug Caster can be told that. With the Sky-high Copper Prices now ruling--he'll love that !

All good advice so far, I would just add that 22mm is large enough to use a drill that has coolant holes in it to apply the cutting fluid right at the cutting edge of the drill bit.

We have done this in our shop on a CNC horizontal mill. Using an end mill circle mill a spot deep enough to get the tip of the drill in. Then drill the hole with a coolant fed gun drill. Stone a slight hone on the cutting edge of the drill as an edge to sharp will dig in to copper. Depending on your controller you may have a feature to break chips. Constant coolant through the drill is a must.

Sounds like this could be a good waterjet solution... less scrap and a nicer cut