All MetalShaping

Go Back   All MetalShaping > General Metal Shaping Discussion > Basic questions and answers
  Today's Posts Posts for Last 7 Days Posts for Last 14 Days  

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 12-16-2013, 10:59 PM
Danbrooks897 Danbrooks897 is offline
Member
 
Join Date: Dec 2013
Location: Alfred Maine
Posts: 5
Default Thumb nail shrinking dies

I've been watching some videos with power hammers and just wondering how thumb nail shrinking dies work do they run the sheet metal into it and right back out in the same spot? I'm confused on how that works.
__________________
Dan
Reply With Quote
  #2  
Old 12-16-2013, 11:41 PM
handshaper handshaper is offline
Member
 
Join Date: Nov 2012
Location: Pa
Posts: 24
Default

Hi Dan, I'm no expert but I have watched the dies in operation. As a matter of fact i have used them in someone else's shop. The die shape puts the tuck in the metal and as you pull outward you'll notice that the leading edge of the die the part closes to you is flat so as you pull the metal outward the flat portion of the die hammers the tuck flat. Best shrinking I have ever done is with thumbnail dies. I just can't afford a mechine to use them. Dave.
__________________
Dave
Reply With Quote
  #3  
Old 12-17-2013, 12:10 AM
Barry Barry is offline
MetalShaper of the Month
May 2012
 
Join Date: May 2009
Location: Stellenbosch, South Africa
Posts: 455
Default

In theory they work exactly as Dave wrote, in practice there is a little technique involved - basically pulling downwards on the outward stroke> I've also found that the metal need to have curvature to it in the perdindicular direction to get good results...
Reply With Quote
  #4  
Old 12-17-2013, 12:25 AM
Dyce Dyce is offline
MetalShaper of the Month Jan. 2011, Nov. 2016
 
Join Date: May 2009
Location: Souix Falls, SD
Posts: 901
Default

Quote:
Originally Posted by Barry View Post
In theory they work exactly as Dave wrote, in practice there is a little technique involved - basically pulling downwards on the outward stroke> I've also found that the metal need to have curvature to it in the perdindicular direction to get good results...
Like Barry is saying shrinking dies work best when you pull down coming out. I also like to set the shrink up with stretching first until I have tucks. Then I take the tucks away with the shrinking dies. The shrinking dies work better and you are relieving tension in the panel (the tension you are relieving make shrinking easier). You could make a panel with only shrinking dies and no stretch but it would be a lot of work and take more time. The tension form stretch works well for tucking forks (that's where I learned it).
__________________
Jeff Dyce
Hell, there are no rules here - we're trying to accomplish something.
Thomas A. Edison
Reply With Quote
  #5  
Old 12-17-2013, 12:31 AM
johnptc johnptc is offline
Member
 
Join Date: Dec 2013
Location: Los Angeles, CA
Posts: 61
Default

do the tucks shrink as they enter the thumbnail dies ?
__________________
John Marcus
Reply With Quote
  #6  
Old 12-17-2013, 12:42 AM
Dyce Dyce is offline
MetalShaper of the Month Jan. 2011, Nov. 2016
 
Join Date: May 2009
Location: Souix Falls, SD
Posts: 901
Default

The thumbnail dies make a tuck as the metal goes in. When you pull it out the smile part of the die crushes the tuck and draws the metal into a shrink. You can run the dies in many different patterns. You want deep shrinking you run them in deep for say 4 passes, then use the dies to blend it in, it may take 8 short passes to make the panel relax. Or you can go in with the dies a ways and do a crows foot pattern and back out in the original path. You need to planish because they do tend to leave marks. Wish I could show you but all I can say is they work very well.
__________________
Jeff Dyce
Hell, there are no rules here - we're trying to accomplish something.
Thomas A. Edison
Reply With Quote
  #7  
Old 12-17-2013, 06:56 AM
mark g mark g is offline
Metal Shaper of the Month, April 2011, December 2012, May 2016
 
Join Date: Nov 2010
Location: Southern VT
Posts: 362
Default

The dies also shrink on the way in. The tuck makes a cone that the smile shape then flattening as the metal enters. You might see it if you could open the dies at the end of the inward pass and take a peek. That initial shrink sets up the shrink on the out pass.
__________________
Mark

www.markgoodenough.com

Last edited by mark g; 12-17-2013 at 07:53 AM.
Reply With Quote
  #8  
Old 12-17-2013, 08:23 AM
Richard K's Avatar
Richard K Richard K is offline
Member
 
Join Date: Nov 2010
Location: Minneapolis, MN or On the Road
Posts: 1,131
Default

Dan, have you tried tuck shrinking by hand? If you have the shrink dies work about the same way.

In hand tuck shrinking, you use a tucking fork or a puck iron to make a tuck in the edge of a sheet. Next you hammer the tuck down, into itself. The process of hammering down the tuck causes the metal to crush in s sortof edgewise direction, reducing the surface area.

The thumbnail dies work in the same manner. On the way in the metal is "gathered" in toward the die to form the tuck (the tuck is NOT a result of stretching). On the way out of the die the tuck is flattend, the same as in hand tuck shrinking.

As in many of the operations performed by machines, they might be easier to understand if one has done a similar process manually.
__________________
Richard K
Reply With Quote
  #9  
Old 12-17-2013, 08:49 PM
Danbrooks897 Danbrooks897 is offline
Member
 
Join Date: Dec 2013
Location: Alfred Maine
Posts: 5
Default

That makes sense thank you all, I was thinking of attempting to make a power hammer and buying some dies till I saw the price I think for now ill stick with tucking forks and stump!
__________________
Dan
Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump

All times are GMT -5. The time now is 12:39 AM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.