What Causes Clashed Dies?

Coinosaurus · July 30, 2012 5:26AM

I know the book answer. Something doesn't make sense though.

If I have two dies with negative impressions, and they meet w/o a planchet in between, shouldn't the high flat parts of the dies (fields of the coin) simply meet each other w/o imparting any of the negative detail to the opposite die? Obviously there won't be 100% overlap since the flat parts of the dies don't match exactly, but the amount of contact of the flat parts should still be considerable.

In other words, do the dies really get smushed together so much that negative detail is raised above the flat plane of the die surface, and thus imparted to the other die? Seems to me that that amount of deformity would seriously damage a die. Or it could be that the dies are so heated up from repeated striking that they have some "give" to them.

EagleEye · July 30, 2012 6:34AM

Clashed dies happen when the dies are not spaced properly. When the press is started they come together. During a press run, the dies will just miss each other when a planchet is missing.

LanceNewmanOCC · July 30, 2012 6:52AM

.
it is my belief that dies clashed during the die making process as well as during the coin striking process.

only way i can explain for a raised AND recessed clash
.

Unknown · July 30, 2012 6:52AM

This content has been removed.

BillJones · July 30, 2012 7:09AM

<< If I have two dies with negative impressions, and they meet w/o a planchet in between, shouldn't the high flat parts of the dies (fields of the coin) simply meet each other w/o imparting any of the negative detail to the opposite die? >>

Uusally the flat spots or fields on the obverse and reverse dies don't match up as comletely as you might think. Look at the obverse of a Morgan dollar, for example, and compare that with the reverse. The flat areas overlap less than you think.

PerryHall · July 30, 2012 7:17AM

<< 

<< If I have two dies with negative impressions, and they meet w/o a planchet in between, shouldn't the high flat parts of the dies (fields of the coin) simply meet each other w/o imparting any of the negative detail to the opposite die? >>

Uusally the flat spots or fields on the obverse and reverse dies don't match up as comletely as you might think. Look at the obverse of a Morgan dollar, for example, and compare that with the reverse. The flat areas overlap less than you think. >>

The dies are basined to improve the die flow of the metal and hence the fields of the dies are not flat and are slightly convexed.

MrHalfDime · July 30, 2012 7:31AM

"The dies are basined to improve the die flow of the metal and hence the fields of the dies are not flat and are slightly convexed."

What he said. The 'flat' areas of the respective dies, representing the fields, are not really 'flat', nor are they parallel, but are each slightly convex, as PerryHall states. Thus, when they are allowed to strike each other, without a blank planchet between them, the central area of each of the dies will strike first, imparting the clashed image.

BryceM · July 30, 2012 7:44AM

I suspect clashing often happens when the dies aren't alligned well. Dies that are mis-aligned would be more likely to clash in the first place, everything else being equal.

rld14 · July 30, 2012 8:51AM

I have oodles of SLQs with die clashes on them.

I haven't seen one yet from misaligned dies although I am certain that they exist.

howards · July 30, 2012 9:00AM

Most of the detail in clash occurs in those areas where the design (incuse) on one die meets the field (essentially flat, slightly basined as some have pointed out). Where two areas of design clash, you usually won't see any clash marks (except possibly where the design is shallow).

The incuse design elements of one die cause some slight metal flow in the fields of the other die.

Clashed dies article

EagleEye · July 30, 2012 9:08AM

I haven't seen one yet from misaligned dies although I am certain that they exist.

Most misaligned clashed dies are caused prior to the dies being hardened and not while they are hardened and in the press.

I recently published an article in Longacre's Ledger about misaligned die clashes. I pointed out that the famous clash on the 1880 cent was put on the die prior to the die being hubbed - John Dannreuther pointed out to me that because of this is isn't a die clash, but is technically correctly described as pre-die-production damage.

LanceNewmanOCC · July 30, 2012 9:15AM

<< I pointed out that the famous clash on the 1880 cent was put on the die prior to the die being hubbed - John Dannreuther pointed out to me that because of this is isn't a die clash, but is technically correctly described as pre-die-production damage. >>

well done

.

BryceM · July 30, 2012 9:41AM

Interesting!

Nysoto · July 30, 2012 10:47AM

With the screw press, the operators would get in a rhythm and if the feeding mechanism ran out of blanks, the dies would clash (just speculating). Early dies could clash anywhere on the die including the periphery, so basining does not explain all cases. The early dies were not hardened without variation, one would be slighty less hard than the opposing and it would take the impression, as early clashed dies sometimes only show clashing on one die. Some dies did develop die breaks from clashing. The tempering operation after hardening does make the die less brittle at the expense of making it a little softer.

EagleEye · July 31, 2012 12:49AM

With the screw press, the operators would get in a rhythm and if the feeding mechanism ran out of blanks, the dies would clash (just speculating)

Even a screw press has a stop on it to prevent the dies from coming together. Incorrect spacing is the key to die clashes, not missing planchets.

MrHalfDime · July 31, 2012 1:07AM

"Even a screw press has a stop on it to prevent the dies from coming together."

Can you point to a specific reference which would verify your statement? Many of us in the JRCS have endeavored to study the early minting process in detail, using the hand screw press, and having this information would prove most useful in our studies. There are no photographs of the early hand screw presses used at the first United States Mint, and only anecdotal information seems to remain. Any information you could supply would be appreciated.

EagleEye · July 31, 2012 2:05AM

It stands to reason, that the anvil die should not be the sole object that stops the hammer die from advancing downward. Just going from logic, not any mint record, it seems that the die setting would be very important. Too close and the dies clash. Too far and you don't get a good strike. Without a stop on the screw press you could not set the dies to the proper distance apart and could not control the standardization of the coins produced. The result would be a very quick turnover of dies and either coins with huge wire rims or weak strikes.

The Mini-Mint at the ANA uses a small screw press to strike pewter pieces. It has a stop on it. If you swing it without a planchet it just goes down to the set distance and returns without clashing the dies.

dcarr · July 31, 2012 5:13AM

<< Clashed dies happen when the dies are not spaced properly. When the press is started they come together. During a press run, the dies will just miss each other when a planchet is missing. >>

Actually, that is not correct for "modern" (circa 1836 & newer) mechanical coin presses (of the type typically known as "knuckle joint" presses, like my Denver Mint surplus 1986-vintage Grabener).

The lower die is basically stationary (except when used to eject a struck coin from the collar).

The upper die is mounted on the end of a ramrod (or "piston"). Striking force is adjusted by lengthening or shortening this piston. The entirety of the stamping force is carried by the vertical frame rails which span the upper and lower die mountings. There is no such thing as steel that doesn't stretch a little bit. Even the hardest (and most brittle) steel will stretch some. But, in addition, brittle steel is actually very bad to use for frame rails because once a crack starts in a frame rail, the coin press is shot. So the frame rails are engineered to stretch (but not permanently deform). And because of this, to get a full impression when stamping a coin, if there is no resistance to the downward motion of the upper die, the face of the upper die will routinely pass below the level of the lower die face. When I was stamping fantasy "1970" and "1975" Ike dollars, almost all of them were over-struck on existing Ike dollars. But I did try stamping on a legally-monetized US Mint copper-nickel clad Ike dollar blank planchet (type-2). To get an impression equivalent to a US Mint Ike dollar, the coin press setting required that the upper die pass almost 2mm below the level of the lower die when nothing impeded the path. So clashed dies will routinely occur when there is no planchet between them. Clashed dies are the number one cause of die failure. A die clash can result in minor damage (such as minimal design transfer), or severe damage such as major cracking. At the end of producing my "1964-D" Peace Dollar over-strikes, I clashed the dies intentionally. I was able to get the entire date area to break off as a large cud.

This picture shows the frame rails (in motion) while a coin is being struck:

Zoins · July 31, 2012 5:19AM

<< 

<< Clashed dies happen when the dies are not spaced properly. When the press is started they come together. During a press run, the dies will just miss each other when a planchet is missing. >>

Actually, that is not correct for "modern" (circa 1836 & newer) mechanical coin presses (of the type typically known as "knuckle joint" presses, like my Denver Mint surplus 1986-vintage Grabener).

The lower die is basically stationary (except when used to eject a struck coin from the collar).

The upper die is mounted on the end of a ramrod (or "piston"). Striking force is adjusted by lengthening or shortening this piston. The entirety of the stamping force is carried by the vertical frame rails which span the upper and lower die mountings. There is no such thing as steel that doesn't stretch a little bit. Even the hardest (and most brittle) steel will stretch some. But, in addition, brittle steel is actually very bad to use for frame rails because once a crack starts in a frame rail, the coin press is shot. So the frame rails are engineered to stretch (but not permanently deform). And because of this, to get a full impression when stamping a coin, if there is no resistance to the downward motion of the upper die, the face of the upper die will routinely pass below the level of the lower die face. When I was stamping fantasy "1970" and "1975" Ike dollars, almost all of them were over-struck on existing Ike dollars. But I did try stamping on a legally-monetized US Mint copper-nickel clad Ike dollar blank planchet (type-2). To get an impression equivalent to a US Mint Ike dollar, the coin press setting required that the upper die pass almost 2mm below the level of the lower die when nothing impeded the path. So clashed dies will routinely occur when there is no planchet between them. Clashed dies are the number one cause of die failure. A die clash can result in minor damage (such as minimal design transfer), or severe damage such as major cracking. At the end of producing my "1964-D" Peace Dollar over-strikes, I clashed the dies intentionally. I was able to get the entire date area to break off as a large cud.

This picture shows the frame rails (in motion) while a coin is being struck:

<snip> >>

Thanks for a great and informative answer Daniel.

dcarr · July 31, 2012 5:23AM

<< It stands to reason, that the anvil die should not be the sole object that stops the hammer die from advancing downward. Just going from logic, not any mint record, it seems that the die setting would be very important. Too close and the dies clash. Too far and you don't get a good strike. Without a stop on the screw press you could not set the dies to the proper distance apart and could not control the standardization of the coins produced. The result would be a very quick turnover of dies and either coins with huge wire rims or weak strikes.

The Mini-Mint at the ANA uses a small screw press to strike pewter pieces. It has a stop on it. If you swing it without a planchet it just goes down to the set distance and returns without clashing the dies. >>

In a modern knuckle-joint press, the "sole" item that really limits the downward motion of the upper die is the crank. Think of the upper die as a piston in a car engine. The piston is connected to the crank via a connecting rod. The stroke of the crank is what limits the downward motion of the upper die. If something gets in the way of the upper die, then the frame rails stretch (to a point). Ultimately, at some level of force, something will give. A die might buckle. Or the coin press might have a mechanism to instantly disengage (disconnect the crank from the flywheel).

Old screw presses could not generate enough stamping force to cause huge wire rims (also known as "finning") on larger-diameter coins. Consistent strikes could be generated by getting a "feel" for the needed velocity imparted to the screw's rotating weights.

EagleEye · July 31, 2012 5:23AM

Thanks for adding that, Daniel.

Nysoto · July 31, 2012 5:55AM

<< With the screw press, the operators would get in a rhythm and if the feeding mechanism ran out of blanks, the dies would clash (just speculating) >>

<< Even a screw press has a stop on it to prevent the dies from coming together. Incorrect spacing is the key to die clashes, not missing planchets. >>

There are numerous examples of pre-1836 dies clashing multiple times in various die stages, with the clash marks lapped off by the engraver and then clashing again (1812 O.107 .50c). Some die pairings clashed as many as nine times (1807 JR-1 10c). If EagleEye's theory is correct, the "stop" would have to come out of adjustment multiple times during various stages of some die pairings, combined with a missing planchet at those times.

What Causes Clashed Dies?

Comments

Leave a Comment