zach124816 Posted March 14, 2013 Share Posted March 14, 2013 how can i avoid pitting when i heat a piece up to harden it? i tried covering it in borax but i still get some bad pits that take forever to grind out. most my projects haven't mattered but i am working on a couple blades and don't want to spend three days polishing. can i use something in the fire to keep my work piece from getting to hot before it all gets to temp? or is it the nature of the beast and there's just a lot of grind/sand work to do. i was thinking put a firebrick in and keep my blade on it for more even heat but my rivet forge is probably to small. any ideas? Quote Link to comment Share on other sites More sharing options...
toolish Posted March 14, 2013 Share Posted March 14, 2013 Think you are going to have to show or explain your forge set up and fuel. Type of steel be handy to. Ruff guess your forge has intense hot spots and you need to move it around more. Total guess tho Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted March 14, 2013 Share Posted March 14, 2013 i think a lot of information you could use is in one of the early knifemaking lessons on here.....Forgive me if I don't type it all again,,,lol Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted March 14, 2013 Share Posted March 14, 2013 with out more information all I can guess is if you stop burning the metal it will stop giving you pits. Quote Link to comment Share on other sites More sharing options...
basher Posted March 14, 2013 Share Posted March 14, 2013 You are most probably getting your steel too hot. I have never heard of using borax for heat treating blades, borax is caustic at high temp and likly to etch your blade. There are very good anti scaling compounds available on your side of the pond. How are you determining your ht temp? As a side note the knife making lessons on here are very hard to follow and rambling and the constant referencing of them to people who re asking reasonable questions is really confusing. Quote Link to comment Share on other sites More sharing options...
HWooldridge Posted March 14, 2013 Share Posted March 14, 2013 You can wrap a blade in stainless foil or use a commercial SS pouch to minimize scale and pitting. This is commonly done in industry with all types of tools and generally yields good results. Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted March 14, 2013 Share Posted March 14, 2013 Basher I appreciate your comments about the lessons..And i will try and keep them more from rambling..However in one of the very first lessons we covered heat treating a blade pretty well for someone new...Including wire brushing during forging and how to determine proper temp for hardening..And also an agent to prevent scaling during heat treat. All that said I suppose I will still suggest folks look into them when having a problem..as that is one of the main reasons we began this series,,,to help folks not make some of the same mistakes we have made before information was as available as it is now. Quote Link to comment Share on other sites More sharing options...
son_of_bluegrass Posted March 14, 2013 Share Posted March 14, 2013 If you have hot spots you can use a muffle pipe. If you get a lot of pitting I'd guess you either have too much oxygen or too hot a fire. (or both) ron Quote Link to comment Share on other sites More sharing options...
swedefiddle Posted March 15, 2013 Share Posted March 15, 2013 Use an Induction Forge, no scale (or very minimal). :) :) Quote Link to comment Share on other sites More sharing options...
Hilt and Hammer Workshop Posted March 15, 2013 Share Posted March 15, 2013 In general, the problem doesn't make sense. Heat treatment takes place at critical temperature, which is "cherry red" (1400-1600F,roughly) . That's not anywhere hot enough to cause pitting in your blade. As other people have mentioned ,you are getting your blade way too hot,regardless of what forging set up you have. If you just keep a close eye on the blade, turning and moving it to get an even heat throughout, and then quench it immediately once it reaches correct heat,you shouldn't run into trouble. Also, do you at least do a rough grind/polish before you heat treat? It really helps alleviate scale accumulation ,and you'll find that when the blade is nice and smooth ,it is also very easy to remove whatever scale does end up forming. Quote Link to comment Share on other sites More sharing options...
zach124816 Posted March 15, 2013 Author Share Posted March 15, 2013 i am using coal in an 18 inch ratcheting rivet forge. i use a magnet to find hardening temp. i polish before hardening and after tempering. almost completely smooth before (i know ill have more scale to take off after anyway why finish it twice) then to finish polish after. i think i am burning the metal. i'm not sure what my material is. right now i'm using band saw blades and banding to make billets to work. i know the outside layer composition makes a difference but i don't know what they are, so i dont know what layer should go outside for less scale and oxidation. i do wire brush before working the steel but i have bigger pitting problems during hardening heat. would a deeper fire give me more consistent heat?. Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted March 15, 2013 Share Posted March 15, 2013 A shallow fire with too much air can do wot you are seeing. But I think you know wot the problem is,,as youi say you are overheating the steel. No matter wot you use for heat that will continue to cause problems until you solve it. I suggest yoiu stop with billets. Get some spring steel and heat treat a out a dozen blanks or more until you find a solution. A vist to another smith to see how they work would save you a lot of failures. Quote Link to comment Share on other sites More sharing options...
zach124816 Posted March 15, 2013 Author Share Posted March 15, 2013 i made a couple "playin around throwing knifes" out of hay rake tines and had almost no pits and they worked great. i had good luck with files to but these billets are tough. im wondering if i should have left a different layer on the outside. will try next time maybe Quote Link to comment Share on other sites More sharing options...
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