View Full Version : Thumbnail Dies?
03-22-2004, 08:30 AM
I seen on another forum someone had made some really small thumbnail dies for shrinking pieces small enough for models.
I was wondering--only because I can't recall having seen it done, do you think it's possible to makeup a set of dies for a planishing hammer and have decent shrinking results?
I'd imagine it would be similar to a pullmax, only on a smaller scale.
03-22-2004, 08:41 AM
I know that Kent White sells shrinking dies for an air planishing hammer. From what I can gather they are as much skill/technique as the design is quite different than a conventional thumbnail die.
I have always wanted to make conventional thumbnail dies for my planisher, but never quite got around to it. I am sure others already have.
Like anything it's probably more complicted than it appears, but even still I don't see why it wouldn't work.
Jacin in Ohio
03-22-2004, 09:27 AM
cool it's definitely something to keep in mind. :D
03-22-2004, 09:29 AM
I tried to make a small set pair of 3/4 inch bar ends to use in my Libert.
It may work, though Richard thought they might be too small.
When I first made them, I had too much depth and they tore the metal, I started tuning them and they worked as stretchers, I messed with them some more and got them so they would stretch out a bead and put it back where it came from, maybe with a little more work they would have shrunk.
The other thing that was pointed out at MMM 2004 was that a positive pressure on the smile area can planish and upset/stretch the material back to where it started or beyond. The pullmax style machines have a fixed length stroke and a preset depth of travel. I had not put a stop on the libert to limit the down travel at just smoothing out the thumbnail hump. It just had a foot pedal downfeed and my foot may have just been too heavy.
I'll have to try putting a stop in the mechanism.
I'm looking forward to getting that pullmax home though. Todd is sending me a set of good dies for it.
03-22-2004, 02:15 PM
Both Carey Culpepper and Ben van Berlo have made tiny thumnail dies with excellent results. Richard Klienshmidt has made a small set again with excellent results so scale is not a factor.
Here is a picture of Ben's dies.
Carey made his dies to fit a small Heck benchtop nibbler. He had them at MM03 and when I looked at them I was skeptical. Carey fired up the Heck and they shrunk very nicely. :D
Spend a couple of days going through the photo albums you'll find some cool stuff.
03-22-2004, 04:20 PM
Wray, that picture above is what actually got me to think about using the P-hammer as a shrinker also. It would be a nice to have.
-Mainly kicking around ideas.
03-22-2004, 05:57 PM
If the air hammer design has a lower arm that will drop down to make room for tooling and room for guides for directional tooling, there is no reason why a airhammer shouldn't do the same thing that a Pullmax will do.
The one big disadvantage of airhammers is the overwhelming noise factor. Richard Kleinshmidt, with his small bench top electric motor Pullmax like machines was tying to overcome the air supply and noise factors. Read in the Tools section under Pullmax and you will find a bunch of threads covering these issues.
Bottom line : Do air hammers have potential to shrink and bead etc. much like a Pullmax ? Yes .
03-22-2004, 06:51 PM
are air-hammers inherently louder than their pullmax counterparts? Regardless, I think I'd like to maximize my investment in the P-hammer by developing adequate tooling.
Wray, Do you have any suggestions on what kind of profile the dies should have for optimal results? If you'll take the time to design them, I'll do my best to con Carlos into getting them made in the CNC machine shop and I'll fit the bill for materials. :D
03-22-2004, 09:12 PM
Wray(or anyone with pullmax experience)-When using thumbnail dies on a pullmax,How many blows per minute is it usually hitting?Pardon my ignorance but I have never seen a pullmax in action.Once you have formed a series of tucks with pullmax,do you then change dies to planish?I have an air powered planishing hammer and have wondered about making thumbnail dies,but I thought with so many blows per min. I would end up streching instead of shrinking.What do you think?Greg
03-23-2004, 04:14 PM
I run my reciprocating machines at 1400 strokes per minute. I used to run at 600 but that is too slow IMHO
The dies gather the metal on the way in and shrinks the tucks on the way out.
03-23-2004, 08:35 PM
So is the tuck formed and shrunk in the same operation without changing dies?I think I'm begining to understand how they work.Thanks ,Greg
03-24-2004, 04:12 AM
The shrink dies make the tuck and shrink the tuck in the same die.
First some terms and assumptions.
1. The front of the die is the side toward the macine operator.
2. The back of the die is away from you the operator.
The bottom die.
A. The back half of the die has a "thumb" protruding from the surface. This thumb gathers the metal and forms the tuck.
B. The surface surrounding the thumb is formed to be slightly angled downward from the center of the die to the rear edge.
C. The front half of the die is basicly flat (perpendicular to the shank of the die. The front edge and front sides are radiused to allow curved work to feed in and out easily.
D. The area surrounding the base of the thumb is called the "Smile". This horseshoe or U shaped area is where the metal is shrunk. The smile area is flat and perpendicular to the die shank.
The top die.
A. The working surface of this die is flat and perpendicular to the die shank.
B. The back half of the die is cut away in a 1/2 round trough to match the thumb on the lower die. Clearance is added to allow for metal thickness. A 5/8 diameter thumb would need abiut a 13/16 dia through. (5/8 plus 16 ga 1/16" x2 plus a bit of clearance.)
C. The transition areas where the trough imeets the flat is very important. This area needs to be a large radius.
Stroke and speed Fast and short. with a polished die equals minimal tool marks. Speed 1200 - 2000 strokes per minute. Stroke about 1/8 to 3/16"
The metal is fed in the front of the die, as it passes over the thumb the metal is tucked ( gathered from the sides) into an upward scallop. This step must pull the metal from the left and right sides, not just deform or stretch the metal at the thumb. You should be able to feel the sheet deform as you feed in. As the material is pulled back toward the operator, the tuck is shrunk (flattened by the flat front half of the top die onto the smile area. The clearance here is critical. If it is too tight the metal will be compressed and actually be stretched back to near original size. As the metal is pulled back toward the operator a slight downward pressure is helpful to get max shrinkage.
03-24-2004, 06:31 AM
Hi Richard, I never really understood how they would work, in my mind it would just stretch the heck out of the steel. A very clear and understandable answer, I can see it now. Thanks.
03-24-2004, 01:03 PM
If you try a die on say a 6" x6" piece of sheet metal, you will actually feel the sides being pulled into the die.
03-24-2004, 03:46 PM
Richard, that was another "keeper" answer. I wis I could have attended MMM. I would like to have a look at your new machine, I know it's trick............john
03-24-2004, 05:40 PM
Thank you Richard,I've been trying to figure out how dies work,Your answer explains it perfectly,Thanks for drawing too.I think I will try to make some dies for my P-hammer.I'll let you know how it works,Greg
03-25-2004, 08:13 PM
Spent most of afternoon making and testing thumbnail dies on P-hammer. Used Richard's drawings as my guide.I acually got them to work although I need to do some more fine tuning.Seems biggest problem is holding upper die from moving forward & backward as metal is moved in and out.The shank on air hammer has too much play,need to make something to hold it vertical.May end up scrapping whole idea but at least I have a good idea how these shrinking dies work now.Greg
04-30-2010, 09:02 AM
BTTT! Post #12 especially. Very good info on thumbnail die design! Thanks Richard!! http://metalmeet.com/forum/images/icons/icon14.gif
04-30-2010, 12:13 PM
How about you or Richard Crees drawing up a couple of sets dies and adding arrows and wording. A couple more things could be added and you could have a nice keeper post for the library or wiki. Why a couple of drawings? it seems there are couple of styles of thumbs (short/long) maybe even a number pics of different shrink dies would be good for reference purpose. (i know one of these decades I'll learn to do it, but you guys are GOOD!) tt
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