heatreating problems/boomerang blades

PARKERKNIVES

PARKERKNIVES

Joined
Dec 1, 2008
Messages
160
Hi everyone in knifeworld,this is my first time on a knifeforum but i have been making knives for 17 years so i am not a complete nube.Anyway heres my question.I recently started heattreating my own blades and have been getting great results right from the first batch as far as my rockwell readings go.the problem is with my ATS-34 blades looking like boomerangs after quenching.No probs with 440c or D2 so i must be doing something right.I know that i have about 1 min to straighten them by hand and this works ok for the spine but i cant tweak the edges or they break.Ive tried leaving the edges a bit thicker which helps but this requires regrinding afterwards.Any ideas on keeping thin ATS-34 blades straight during heattreating?
 
Howdy and Welcome.

Best place to ask such a question is "Shop Talk - BladeSmith Questions and Answers"
It's under the "Makers" link at the top of the page. Lots of friendly folks there who are willing to share information about making knives.
http://www.bladeforums.com/forums/forumdisplay.php?f=741
 
As Knarfeng says, this is probably best asked in the Shop Talk section.

Having said that, the commonest cause of warping during heat treat is un-even heating prior to the quench. What method are you using to heat the blades ? Coke or gas forges tend to heat the steel more on one side than the other. Moving and rotating the blade around in the heat to get a more even heating should help cure your problems. If you are using a gas forge then the addition of a muffler tube inside the forge might help even out the heating but I'd still want to rotate the blade to ensure best and most even heating.

Another cause of banana blades is the way you quench. Unless you are using quench plates (which is another matter altogether) you'll get best results by quenching tip down and moving the blade as if you were stabbing the quench tank bottom repeatedly, (You'll want a deep tank for this. I use a big section of pipe with a base-plate welded on) or quench edge down and 'slice' the oil as if you were cutting bread. Wafting the blade from side to side is a recipe for bent blades every time, as are circling motions and the like. This is becuase if the blade travels sideways through the oil the oil swirls around the blade and cools each side differently.
 
Gas or coke forges are very inappropriate for those complex steels !!
Use a "plate quench " !!!
 
Thanks for your replies. I have an evenheat kiln for heat treating so uneven heat isn't a problem. Thanks for the quenching tips, am happy to try anything that helps.
 
I too have an Evenheat for my H/T-ing. :)

Are you laying the blades flat in the bottom of the oven, or propping them upright on their spine somehow ?
I've found that my blades heat most evenly if they are propped up off the bottom of the oven on a small section of angle iron flipped over to make a /\ sort of shape. If the blade is too small to balance on it's spine I'll prop it upright with either a small notch in the angle iron or with a seperate piece of metal that only just touches the blade with a sharpened point (so as to minimise the contact area)
Blades layed flat on the bottom of the oven are never going to heat evenly ;)
 
Thanks for the tips, i am sitting my blades edge up on small pieses of firebrick so they do get an even heating.I think my probs are with the quenching so i will ask about this plate quenching thing in the shop talk section.
 
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