Cobalt? Dull?

M

mpj13

Joined
Oct 5, 2001
Messages
108
Well, I finished cutting out my first knife tonight, it was a lot of work just cutting the steel, I used a dremel with the cutoff disc it works well, just takes a while.

I had a problem with drilling the steel I was going to drill out the shape of the knife and then cut the web, but my brand new cobalt drills got dull after drilling about 4-5 holes, is this normal? It seems like I should be able to drill a lot more than 4-5 times until it gets so dull it just sits there and spins. The first few time the cobalt bits would cut the 1084 very well, one hole took about 15sec after 4-5 it would not cut through. Maybe the steel needs to be annealed, I emailed Texas knives and they said it is anneal, I don't think it got hot enough to harden (Not sure), if it seemed like it was getting hot I dunked it in water, I used cooking oil and water for cutting oil, I know this is not the best but I was told by someone at Sears that I could use this. So to sum it up, why can I only drill 4-5 holes before it wont cut the steel anymore? This started with a 3/32 bit, after 4-5 holes it would just spin then I tried a larger bit and it cut about 4-5 holes and then would just sit there and spin.

How hot does the steel need to get when drilling for it to harden? When I was cutting the steel it got hot too, I placed it in water when it was like this. If I annealed the steel even if they say it is annealed would it help out with cutting and drilling?

I am grateful for any help on the subject. Thanks.
 
in my personal experiance the hot rolled stock always has hard spots and is rough on drill bits. I always throw it in my heat treating oven at 1320f for an hour, pull it out and let it air cool, before I try to drill it. This saves on drill bits.
 
Try slowing the speed of the drill press down and then don't try and cut trough as fast as you would with a regular high speed bit..
And once you spin a bit in the hole you need to re sharpen the bit and if you let it spin very long the piece that you are drilling can and will work harden and you may need to anneal the bar againg to finish drilling the hole..
Aint KNife Making fun,Every time you turn ariund something else is messing up and you got to figure out why and how not to do it again...I wouldn't change none of it for anything in the world,that is what is so addicting is finishing a Knife after all the trials and the Blood Sweat and tears that went into making it..
Good luck
Bruce
 
You could try masonary drill bits they are not perfect but will drill a hole in hard steel, a carbide spade drill will drill hardened steel but are expensive,your bigest problem is you are drilling at too high a speed..
 
I think I must have been going to fast. From now on I am going to anneal all my steel from the start just to make sure it is soft. Are there any tools to sharpen bits? I saw one machine that cost >$100 I would like to buy this after a while, but for now any ideas on how to sharpen a bit?

I have my knife filed down, I just need to go over it with a low grit sandpaper and then harden it. Is it best to put an edge on it and then harden? It seems like once you harden it you don't want to do any more grinding, I just don't want to let it crack. Do you guys allways finish it by hand to get all of the scuff marks out? Next week I am getting a disc sander so I have not been able to try it out yet. Thanks for all the help it makes a world of difference to have some were to go for help when your just starting out.
 
You can sharpen your drill bits with a bench grinder or in a pinch with your disc grinder, its quite trickey to cut the angles correctly, but once you learn how you won"t have to buy that $100 drill sharpener.Re hardening your blade you should not sharpen prior to heat treating.leave your edge the thickest of a nickle, heat treating decarbonizes the outer surfaces,which should be removed how you can remove the hardened surface without power equipment i don'tknow.when i started out i finished several knives with a disc grinder....Hope this helps, goodluck....and be careful....
 
Yes it can be finished up after the heat treat.Just make sure you have a really sharp file and allot of sand paper to finish it out by hand.Or you could wait till you get your disc to do the final grind,then hand rub the finish out.You do need to get the really deep scratches out before heat treat,But it isn't neccesary to go any higher than 150 grit before the heat treat.
Just take your time and when you get it done you will be proud of it and yourself just because you did it the hard way,and don't compar your first to allot of us other guys that have a few years and different equipment tan you..
Good luck,
Bruce
 
Yeah, I think I'll wait until I get my disc so I can get the marks out, I got the basic shape with a stone wheel and files, the files help put a much smoother surface on it compared to the stone wheel.

Anyone know were to get some info on how to sharpen a drill bit with a grinder? Maybe a web site or book?

One other question. When you grind out the blade what's the best method to get a straight line were the edge tapers into the top of the blade, the way I am doing this knife is the edge will be filed in most of the blade leaving about a 1/2" wide 2 1/2" long flat surface on the blade. I was told once that you could use a piece of hard steel and clamp it down so you file straight, it seems hard to do with a small blade because of the thickness of the steel. Maybe I should just file out the edge all the way through the surface. Any advice on this? Thanks again for the help.
 
When you get your disc grinder, you'll be able to make discs out of very fine grit paper which saves LOTS of hand sanding.
 
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