Note to self:

YEP! That 1/3 rule on each side is a slippery slope sometimes! ;)

Teaching moment: AFTER drilling the "raindrop" pattern with a regular drill bit...... go back in with a 60 degree countersink and heavily slope the sides of the drill cut........ that will usually prevent those cold shuts in the pattern. The reason those cold shuts happen is vertical "walls" on the drill cuts....the layers will go upward, but because they are vertical, there is no pressure present to keep the layers from separating when you're forging out the billet/pattern...... heavy sloped walls/sides will create pressure on the layers, and USUALLY will prevent those cold shuts.
 
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Oh. That hurts! I should’ve posted a picture of some san mai that blew apart on me the other day. Would’ve made this look like no big deal:p
 
YEP! That 1/3 rule on each side is a slippery slope sometimes! ;)
Teaching moment: AFTER drilling the "raindrop" pattern with a regular drill bit...... go back in with a 60 degree countersink and heavily slope the sides of the drill cut........ that will usually prevent those cold shuts in the pattern. The reason those cold shuts happen is vertical "walls" on the drill cuts....the layers will go upward, but because they are vertical, there is no pressure present to keep the layers from separating when you're forging out the billet/pattern...... heavy sloped walls/sides will create pressure on the layers, and USUALLY will prevent those cold shuts.
Ed: Thank you so much for continuing to share GREAT tips. I've been thinking about a RainDrop pattern for next time and maybe you've saved me from BIG mistake. I'm sorta on the wall between raindrop, ladder, or twist.

Chris: a really BIG THANK YOU for posting this "Ooops" so Ed could comment. We're all learning here. GREAT place.

Ken H>
 
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