How do you think this was done?

[Brian Leavitt]

A customer brought in this medallion. I have no idea how it was engraved. It's not diamond drag or rotary. Could a fiber have done it? The edges are super clean and smooth. Pretty deep as well.

[Ross Moshinsky]

It's either part of the die and then filled (most likely option) or chemically etched in and enamel filled. I guess it could be engraved with a fiber and then enamel filled but I doubt it.

[Gary Hair]

Cast or chemical etched would be my guess, but definitely not layered. The edges of the letters are slightly rounded and I think a laser would leave them sharper.

[Brian Leavitt]

My first thought was the medallion was cast with the wording on it, but the lady who brought it in said she took it somewhere and had it done. I didn't think about chemical etching. I thought a fiber would leave sharper edges, but I don't own one so I don't know. Must have been etched.

[Kev Williams]

All the sharp corners have the exact same radius. Therefore, it's a safe bet the engraving WAS done by rotary tool-- but maybe not directly...

If the medallion is a one-off, then it was rotary engraved directly.

If it's mass produced, a copper EDM master was engraved and used to burn in the negative master within the casting.

[Bruce Page]

Making a one-off EDM electrode wouldn't be practical. My money's on chemical etching.

[Greg Carmack]

The lettering is stamped into the metal. The metal is then powder coated black and then then the coating is sanded off, leaving it in the lettering.

[John Kleiber]

As a practical matter, why one someone make a stamp for just one?
I've never sanded powder coat down for that purpose, so I am not sure if that would work.
The engraving I would think would have to be deep to avoid marring the lower powdercoat material.
As for the edges, if you eliminate lasering the edge or outline of the character, the edges slop down as opposed to a sharp direct 90 degree drop.

There is no mention of the material, I may of missed it, but that would be interesting to know as well.

[Brian Leavitt]

All the sharp corners have the exact same radius. Therefore, it's a safe bet the engraving WAS done by rotary tool-- but maybe not directly...

If the medallion is a one-off, then it was rotary engraved directly.

If it's mass produced, a copper EDM master was engraved and used to burn in the negative master within the casting.
Rotary was my second thought. But if I zoom way in on the original photo, some of the corners are squared off so I ruled it out.

[Greg Carmack]

They make a stamping press where they can load steel type like a printing press and then press the letters into the metal. It looks like a brass or bronze which is a soft metal.
I've done the sanding process with powder coat and it works great.


As a practical matter, why one someone make a stamp for just one?
I've never sanded powder coat down for that purpose, so I am not sure if that would work.
The engraving I would think would have to be deep to avoid marring the lower powdercoat material.
As for the edges, if you eliminate lasering the edge or outline of the character, the edges slop down as opposed to a sharp direct 90 degree drop.

There is no mention of the material, I may of missed it, but that would be interesting to know as well.

[Kev Williams]

As I stated- They wouldn't make an EDM for just one, someone could just engrave the medallion directly. For many medallions, then go EDM. It's only a couple hundred $ job to do that.

I'm about 90% certain this medallion is a casting, and the lettering incorporated into the casting via EDM. Could be the casting was EDM'd directly, or an insert was burned and inserted into the casting. This makes economic sense because the inserts can be swapped out and different words or graphics can be incorporated into the same medallion.

While it looks like the corners are quite sharp, they're not all that sharp. Not that difficult to sharpen a cutter to produce a .006" wide stroke on the surface of an .010" deep engraving.

That said, why I believe this to be EDM work is the very consistent radius of the edges of the text on the medallion surface. While a similar edge-rounding happens normally with sanding, it's never this consistent. The edge radius of "January 2016" is virtually identical to the "Hydrogen" lettering above it, and of the much larger lettering. It would nearly impossible to produce that much radius on the date engraving simply because the lettering is so small. However, this radius occurs normally during the EDM process because the face of the electrode is burning from beginning to end, and the sharp edges of the electrode slowly erode during the process, and this radius is the result.

349598 349599

Somewhere around here I have a used copper EDM electrode I made that my customer left here to have me duplicate it. It made 2 steel stamps and was too eroded to make a third. If I can locate it I'll put a photo of it up...

[Brian Leavitt]

As I stated- They wouldn't make an EDM for just one, someone could just engrave the medallion directly. For many medallions, then go EDM. It's only a couple hundred $ job to do that.

I'm about 90% certain this medallion is a casting, and the lettering incorporated into the casting via EDM. Could be the casting was EDM'd directly, or an insert was burned and inserted into the casting. This makes economic sense because the inserts can be swapped out and different words or graphics can be incorporated into the same medallion.

While it looks like the corners are quite sharp, they're not all that sharp. Not that difficult to sharpen a cutter to produce a .006" wide stroke on the surface of an .010" deep engraving.

That said, why I believe this to be EDM work is the very consistent radius of the edges of the text on the medallion surface. While a similar edge-rounding happens normally with sanding, it's never this consistent. The edge radius of "January 2016" is virtually identical to the "Hydrogen" lettering above it, and of the much larger lettering. It would nearly impossible to produce that much radius on the date engraving simply because the lettering is so small. However, this radius occurs normally during the EDM process because the face of the electrode is burning from beginning to end, and the sharp edges of the electrode slowly erode during the process, and this radius is the result.

349598 349599

Somewhere around here I have a used copper EDM electrode I made that my customer left here to have me duplicate it. It made 2 steel stamps and was too eroded to make a third. If I can locate it I'll put a photo of it up...
What is EDM?

[John Heavill]

Electric Discharge MachiningThe basic EDM process is really quite simple. An electrical spark is created between an electrode and a workpiece. http://www.xactedm.com/images/edm-capabilities/electric-discharge-machining2.jpgThe spark is visible evidence of the flow of electricity. This electric spark produces intense heat with temperatures reaching 8000 to 12000 degrees Celsius, melting almost anything. The spark is very carefully controlled and localized so that it only affects the surface of the material. The EDM process usually does not affect the heat treat below the surface. With wire EDM the spark always takes place in the dielectric of deionized water. The conductivity of the water is carefully controlled making an excellent environment for the EDM process. The water acts as a coolant and flushes away the eroded metal particles.

[Ross Moshinsky]

I think this is a circumstance where more questions need to be asked. My gut says when you find more information you will find this medal was part of a production run. If they truly brought this one medal to some shop and had that engraved/etched, I would recommend bringing it back to the same shop. I can't imagine being able to do that type of engraving and have it be profitable. How much would you have to charge to setup, engrave/etch, color fill, and clean up to make it profitable? Especially considering the number of characters and the small size of the letters. I'm not sure you can charge enough to make it worth while.

[Kev Williams]

Definitely yes on a production run. I'm betting that medallion blank has been used for possibly hundreds of different applications. That's the beauty of EDM'ing when working with interchangeable mold inserts- a customer can bring me an electrode, simple engraving like this medallion I can have done in less than an hour. Customer takes it to his shop, burns an insert (which would be pre-made usually), possibly 2 hours burn time, install the insert into the cavity, and you're ready to cast medallions. Same basic process for many injection molded parts, just engrave different text or logos on different inserts that pop into a common mold. (eyeglass cases for example)...

[Brian Leavitt]

I was just curious more than anything because she told us the engraving was done separately from the rest of the medallion. I initially told her she should take the blank one she wanted to have done back to the shop that did the other one since we were not going to get remotely close to the look of the completed one, but she said to go ahead and do it anyways. So we just diamond dragged it. She was happy.