Trad Gang
Main Boards => Hunting Knives and Crafters => Topic started by: gudspelr on June 01, 2011, 12:55:00 AM
-
When forging the tips on knives from my bar stock, I end up with those pinched, fish lip ends that I have to end up grinding off. :mad: I just watched Lin's forging demo again (learn something every time) and am wondering if I'm not pushing the corners inward enough? Am I getting the pinched end because I'm pushing the two corners too much towards each other instead of at a 45 or so degree back in towards the main body? Does any of that make any sense....?
Jeremy
-
Seems like I have to hit the ends hard to avoid those lips. Are you smacking it hard enough to drive the steel and not just let it mush and do what it wants?
-
Very common problem when starting. You do need to hammer back toward yourself. One easy tip to help avoid this in the beginning is to round/grind the corners slightly of the tip end of the bar stock before forging.
-
Another thing to remember is the amount of heat you get.
Heat up a round bar and hammer all the way around it. If the outer sides of the bar move out/longer like you want, but the center of the bar holds back and you start to create a divot in the center of your bar, then the outer portions are hotter than the inner portions.
I'm not saying this is your problem with your fish lips.
I'm just saying.
Now don't go and overheat your steel because of what I said here.
Jeff, had some great advice and should help to fix your lips.
Everything we do when forging, post forging, grinding, heat treating, building and finishing our knives, etc is dependent upon a myriad of incidental little nuances that are often unique to our style, our chosen steel types, our equipment, our experience level, etc.
And this question about "fish lips" is just one of those little things that plagues us until we overcome them as a result of putting in time in our shop and learning from our mistakes.
Most of the time, there is no simple one-answer remedy to our problems as other makers' methods do not match our own.
One needs to learn what works in HIS shop and put in the time to learn it.
-
Karl, that is a great explanation.
This might sound silly, but consider taking some stiff modeling clay and roll it into a bar shape and practice moving it with just the hammer and anvil.
-
Thanks for the input, all-it's appreciated. Karl, like you mentioned, I think there might be a few factors at work. I think angle, how hard, as well as the heat are things I need to look at. I know I've been leary of getting the steel too hot, but now that it's mentioned, I wonder if I'm not hurting myself by having it a bit too cool...
And Lin, if I ever say one of your suggestions sounds silly, someone ought to whack some sense into me :) .
Jeremy
-
I worked on my first full tang knives yesterday and that's clearly a whole different ball of wax to get figured out... But, I managed to forge the points minus any fish lips :jumper:
I worked at it like suggested and its amazing what can happen if you just change the angle of your hammer. It still takes me a while and I have a hard time forging the knife so close to shape but I see improvements each time I forge. Plus there's just something cool about hitting hot steel.... Thanks everyone for the advice.
Jeremy
-
Jeremy,
Remember to work toward the middle. When you're driving the bar corners in, you have to turn it on it's sides pretty soon and knock the waves back inward too. Dont let the material fold over onto itself. A little here and a little there. Not too much "here" or you'll have trouble "there". Know what I mean?
Soon, it'll get to be a habit.
You might want to keep a coarse rasp handy and if you think you have gone a little too far one way or the other with those waves, just hit em with the rasp and get them out of the way.
-
Good idea, Lin-heard hot filing/rasping can really remove some material. By waves, do you mean the wavy "mushroom" kind of effect from the corners as I hammer them in? I tried to hammer each corner evenly with the other and turned the bar flat to push those mushroomy portions back flat as I went along. I think it took me extra long since I was dealing with 3/8" thick barstock... I've had that "fold over" thing before that you were talking about and that just doesn't work out well. Thanks for the input.
Jeremy
-
Yes, that's it. Make sure to work it hot enough,.........but not too hot. :D
-
Thanks for the clarification, Lin. I sure wish I knew better what "not too hot" was while I'm forging... I find myself generally taking it out of the forge at an orange, but before it gets that slick looking surface (which I'm assuming is too hot?). I think part of my problem is there's too much light in my garage so only going by color isn't doing me all that well. Someday I want to try and put together a temp gauge like Ed Caffrey built-a lot cheaper than buying some of those pyrometers. On that note, is there a definitive temp for 5160 that's too hot while forging?
Jeremy
-
Jeremy, a pyrometer will only tell you so much. If it's a lazer type, you can read the steels temperature, but if it's a probe type, it reads the atmosphere temperature. If the atmosphere is 2400 degrees, do you want your steel that hot? No, not unless you're welding a billet. So, you have to watch it and see when it is ready to forge and also know when you're burning it up. You have to be able to judge the color/condition of the steel.
5160 is no different than any other steel when it comes to judging color. Any high carbon steel can be gotten too hot. It will sparkle tiny little bits of carbon and steel when you get it too hot. This usually happens to the maker when he has the tip drawn to a point and dont turn the forge down and is not paying close attention. The tip is the first thing to go. You may as well cut it off past the burnt area and put a new point on it. Forge one blade at a time and pay close attention to it.
-
Thanks Lin
Jeremy
-
You'll get to where you know. You just have to spend some time forging. You'll do fine.
-
Jeremy,
Look around on the web there are links and sites that discuss color and how to see it when your trying to judge forging temps. There are top and bottom end colors for each steel to start and stop your forging efforts. To hot it burns up the steel. Forging to cold can cause cracking and other problems in the steel. I do a lot of my forging in my shop after dark. It lets me see the steel colors a lot better and keeps the steel from overheating.
Are you heating the blade in a steel tube? I use a rectangular tube pushed up against a fire brick to help control my temps. The end against the fire brick tends to be a bit cooler which helps prevent burning the tip. I also forge with one burner instead of two on. Controlling my propane pressure and only heating the section I want to forge helps keep the tip cool enough not to burn it.
-
I remember that tube we used when I was at your place and was just thinking I needed to find myself one. I'll do some looking around for those color charts.
Jeremy
-
A local steel scrap yard should have the tube. I like a rectangular tube. Some smiths I know like a round tube. My tube is 2" X 4". I would reccomend making it longer than your forge body. By running one burner and locating your blade properly you can slowly heat the tip while more rapidly heating the main section of the blade. I use the brick since my tube is shorter than my forge body. I plan to correct this soon.
Make sure to let the tube heat up fully so the heat is even inside the heated section of the tube. If you get a pyrometer you can regulate your propane pressure and get fairly precise temperatures inside the tube.
-
I use two kinds of tubes to help me. I have a 3" diameter stainless tube that fits in my forge and sticks out the forge door. I put some scrap pieces of kaowool in the end of the tube and will push the tip into the kaowool to protect it while heating. I use this longer tube when heat treating. When forging I use a 4" section of this tube that is stuffed with small Kaowool pieces. I again use it to protect the tip and hold the spine up/ edge down when getting close to the end of my forging to help protect the thinning edge. I realize this all somewhat compensates for my first forge design.
-
gables-
Thanks for the ideas. I too could probably use some some things to compensate for my forge design....
Jeremy