Thread: Hubs
View Single Post
  #16  
Old 02-13-2007, 09:55 AM
banjo_art banjo_art is offline
Steel
 
Join Date: Jun 2006
Location: Moultonborough, NH
Posts: 52
Default Re: Hubs

Steve:

I also worked in mechanical engraving company back in the late 70's which made coining dies among other things. We had a 200 Ton hydraulic press which often times would not raise enough die metal to completly fill the hob. What we did was coat the die with a special wax, put the die back in the press and force the wax into the low spots with the hob. Then the die was acid etched to remove the die high spots, the wax was removed and the hob was forced into the die at 200 tons again. This was a difficult process with the die being annealed and fixtured to prevent cracking.

They still would crack but after awhile you would figure out what the process had to be and how much pressure could be applied. Deep relief patterns and narrow areas are difficult and it often took 5 or more applications of wax / acid to raise the die steel into the hob over a period of several days. It took many years of experience to understand both the design and process.

--Art
Reply With Quote