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Machine Doubling Versus Hub Doubling.

 
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Pillar of the Community
United States
7629 Posts
 Posted 08/12/2009  11:50 am Show Profile   Bookmark this topic Add coppercoins to your friends list Get a Link to this Message
First thing first. The title is what it is because hub doubling is the technical term for the thing that causes doubled dies. The following statement puts it into context. "Every doubled die is an example of hub doubling."

Machine Doubling happens on the press explicitly, meaning that the doubling is CAUSED by some malfunction in the press.

Hub doubling is caused at the hubbing press during die manufacture, and has nothing to do with the actual striking of the coins.

So...what's the big difference? Two very basic things differentiate the two. First, hub doubling is on the die itself. It is part of the design (not intentionally) that the die impresses into every coin it strikes. The dies are carefully inspected before being placed into service. Technicians are trained to spot and reject hub doubling - but it does slip once in a while as is evidenced by the cataloging systems that list thousands of different doubled dies.

Machine Doubling, on the other hand, is the result of parts coming loose during the striking process. It all depends on the adjustment and proper operating order of a machine, which can malfunction at any time, and can mint thousands of examples of its malfunction before being discovered. Not only this, but it can happen on ANY die hung on the press, because the design on the die makes no difference as to whether it is securely fastened to the machine. So yes, doubled dies can (and sometimes do) also have Machine Doubling.

Back to the subject. I said two things differentiate the two. The first is their nature of manufacture. The second is the characteristics we use to detect which is which. Anyone with some experience spotting the two can with 100% accuracy identify both....EASILY. It's not rocket science. It's actually very simple.

I have created a diagram which illustrates the following points in a visual form to aid in understanding what I am about to type. I will post the diagram after completing the description so you can use it to refer back to this post.

Machine Doubling
1. Always cuts away at the normal thickness of the devices affected. This in effect makes the device that stands out in relief thinner than it should be.
2. Has a step-down appearance to the 'doubling' which lacks character, boldness, and thickness.
3. Never shows 'notching' at the corners of the devices because the original die used to create them does not have this notching.

Hub Doubling
1. Always has extra thickness to some degree - in other words, the doubling never robs from the normal devices to cause the doubling.
2. In many cases 'notching' shows at the corners of the devices where the overlap in hubbing occurred. Just look at the picture, find 'notching', and this statement will be very clear.
3. Hub doubling actually creates a secondary 'set' of devices, which is apparent when looking at the doubling. It has relief - character. Machine Doubling only flattens parts of the only set of devices that exist, because there was no doubling in the die that created the coin.

So...look at the images, refer back to this, and look at the images again. Once you get a hang of what this thread shows you, there should be little question about whether you have Machine Doubling if you're paying attention and understand what's exhibited here.

Moderators - I believe if this thread is made a sticky thread, we will be able to build upon it and answer most of the questions here by referring people to the thread instead of re-answering the same questions over and over again. Please consider.
Pillar of the Community
United States
7629 Posts
 Posted 08/12/2009  11:52 am  Show Profile   Bookmark this reply Add coppercoins to your friends list Get a Link to this Reply
Here is the diagram I created (it's rough, but gets the point across). Look at this diagram, read the post above, and refer to both when looking through your coins and you should be able to answer the ultimate question, "machine or hub doubling?" with relative ease.

Pillar of the Community
Canada
1376 Posts
 Posted 08/12/2009  12:12 pm  Show Profile   Bookmark this reply Add papeldog to your friends list Get a Link to this Reply
Thanks for this post it's very informative on this subject with the diagrams it makes it a lot easier to understand the difference in the two kinds of doubling type's.
I tried to make a print of it but it wouldn't print it out?
Pillar of the Community
United States
1794 Posts
 Posted 08/12/2009  12:19 pm  Show Profile   Bookmark this reply Add rockdude to your friends list Get a Link to this Reply
Yeah thanks, it should clear up some of the questions about whether or not it's DD or MD.
Pillar of the Community
United States
1557 Posts
 Posted 08/12/2009  12:19 pm  Show Profile   Bookmark this reply Add jasper62 to your friends list Get a Link to this Reply
Thank you coppercoins,What a great Explanation on the Difference.I'm starting to feel edumacated
Pillar of the Community
United States
2546 Posts
 Posted 08/12/2009  1:07 pm  Show Profile   Bookmark this reply Add mycrob to your friends list Get a Link to this Reply
I concur, this should be a sticky thread! This question gets asked just about everyday.
Rest in Peace
United States
3039 Posts
 Posted 08/12/2009  1:55 pm  Show Profile   Bookmark this reply Add numismo to your friends list Get a Link to this Reply
Hi Chuck:
What a wonderful post! As usual your expertise should be invaluable to those just learning this stuff and to those that think they know it. A great reference!
Moderator
Learn More...
United States
71927 Posts
 Posted 08/12/2009  2:22 pm  Show Profile   Bookmark this reply Add jbuck to your friends list Get a Link to this Reply
I am not a variety or error hunter (yet), but I definitely added this one to my bookmarks.
Valued Member
United States
257 Posts
 Posted 08/12/2009  7:34 pm  Show Profile   Bookmark this reply Add fmtaxguy to your friends list Get a Link to this Reply
What an amazingly clear and valuable post. I have not found anything close to this clarity in all the reference books on varieties I have gotten my hands on. The light switch has been flipped to 'on.' What a wonderful day! Thank you.
Bedrock of the Community
United States
27447 Posts
 Posted 08/12/2009  8:47 pm  Show Profile   Bookmark this reply Add John1 to your friends list Get a Link to this Reply
Coppercoins,
I have seen many photos and diagrams and read many articles on this subject and your explanation and especially your diagram says it all,it's the best , your a real asset to CCF.
John1
( I'm no pro, it's just my humble opinion )
Searched 5+ Million Cents Since 1971
Pillar of the Community
United States
3962 Posts
 Posted 08/13/2009  08:23 am  Show Profile   Bookmark this reply Add chuckster 125 to your friends list Get a Link to this Reply


Excellent Post.

Thanks again Chuck.

Already downloaded to my doc's for easy ref when I finally find that elusive 1969S DDO
Pillar of the Community
United States
2600 Posts
 Posted 08/13/2009  10:47 am  Show Profile   Bookmark this reply Add Jim1953 to your friends list Get a Link to this Reply
One of the best example/teaching tools I have ever seen on the subject.
Thanks, Chuck
Jim
New Member
United States
24 Posts
 Posted 08/13/2009  8:59 pm  Show Profile   Bookmark this reply Add dnsnthegrdn to your friends list Get a Link to this Reply
Time to go back through my maybes.
Pillar of the Community
United States
7629 Posts
 Posted 08/20/2009  10:24 am  Show Profile   Bookmark this reply Add coppercoins to your friends list Get a Link to this Reply
I still think this thread needs to be a sticky thread at the top of the category.
Moderator
Learn More...
United States
71927 Posts
Valued Member
United States
164 Posts
 Posted 08/20/2009  11:20 pm  Show Profile   Bookmark this reply Add JOE to your friends list Get a Link to this Reply
I have looked for a tutorial on a subject like this for a long, long time. And most tutorials I find are nearly a mile long and leave you confused in the end, But this clearly explains the process better then any tutorial I have ever seen, This has helped me immensely, and surely will help others.

I also vote for this to be stickyed, Since Machine Doubling is so common. :D

(Also, I printed out the image, nice artwork too :D)
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