Small deep pits in blade

[Upperpeach]

Hey guys,

 

I've just completed forging my first knife today using some flatbar i bought at a local hardware store. Everything turned out great except for that while I was sanding it and polishing it up a little bit, there were deep pits in the blade. I know this is why I should sand and polish the blade, but after close to 2 hours of working with a electric hand sander with a very course grit, I still had the pit marks.

 

I thought it was from the hammer strikes during forging, but these pits seem too small in area to have been caused by my hammer. So my question is does anybody know what these are, and if so how to prevent them in the future? 

 

Any advice is greatly appreciated.

 

Thank you.

[billyO]

Were you diligent in cleaning the scale off the metal each heat?  Without any more info, that's my first question.

[Rashelle]

The bladesmith people will be able to tell you more with more information from you. Though random flatbar from the hardware store is likely mild steel and you probly woudn't of been able to harden it. Makes good practice though.

 

Rashelle

[DSW]

Electric hand sander to me says palm sander or small orbital sander. Not exactly the tool I'd choose for finishing a blade. If it's a hand held belt sander, then maybe. I'd have to agree store bought steel is just mild steel, and usually fairly low quality at that. Scale would be my 1st thought as well as far as small "pits", but without picts it's impossible to say.

[jmccustomknives]

First red flag. :o   You got the steel from a hardware store? <_<   I've never seen blade quality bar stock at a hardware store.  I'm thinking you were using mild steel.  Second you are probably working the steel at the wrong temp.  Using mild steel will hide this as it will move at lower tempuratures (knife quality steel is hard to impossible to forge at low temps).  That plus heavy scale and the hammer will drive the scale down into the metal causing pitting.

Lastly, hammer control and using good forge theory (start hot, finish at red) and using the "finishing heat" not to move the metal but to smooth it will help clean thing up.  There are a few smiths who need very little cleanup, they are just that good. 

Start with good metal.  Most aren't like me, I'm hard headed and like a challenge, so buy stuff that you know what it is.  Study the methods to work with it, steels like 5160, 1070-1084 will be the easiest to work.  Stay away from higher alloy steels as these can be difficult to work.

Don't be afraid to post pics.

[homeshow]

First red flag. :o You got the steel from a hardware store? <_< I've never seen blade quality bar stock at a hardware store. I'm thinking you were using mild steel. Second you are probably working the steel at the wrong temp. Using mild steel will hide this as it will move at lower tempuratures (knife quality steel is hard to impossible to forge at low temps). That plus heavy scale and the hammer will drive the scale down into the metal causing pitting.
Lastly, hammer control and using good forge theory (start hot, finish at red) and using the "finishing heat" not to move the metal but to smooth it will help clean thing up. There are a few smiths who need very little cleanup, they are just that good.
Start with good metal. Most aren't like me, I'm hard headed and like a challenge, so buy stuff that you know what it is. Study the methods to work with it, steels like 5160, 1070-1084 will be the easiest to work. Stay away from higher alloy steels as these can be difficult to work.
Don't be afraid to post pics.

Exactly. Practice your technique with high carbon. Like old leaf springs. They will give you a good feel for how to work a quality knife steel. Then go buy a good bar or rod and make a blade. I would try to use someone else's quenching techniques that works for them for the steel you decide on. You can always tweak your quench technique as you gain experience.

[Upperpeach]

As i said before this was my first knife. That being said, I wasn't exactly expecting everything to be perfect and was using this blade to test the waters and get some practice. I thought I was diligent in cleaning off the scale, but truth be told I probably missed some. I know/have read about the quality of hardware store steel but that brings me to a much bigger question of where to buy higher quality flatbar? I have looked all around locally and am having trouble finding a non-bulk supplier of blade quality steels.

[jmccustomknives]

I've bought from Admiral Steel.  Others swear by New Jersey Steel baron.  Homeshow suggested getting some old car leaf springs.  A lot of the bladesmiths will have a bad opinion about this.  I've had good results from blades made from old spings.  If you stay with springs that are from the '80's and up they should be a version of 5160.  You should be able to get these from a wrecking yard as at low cost or even free (develope the "art of the trade") plus you may also find that steel will come to you.  I call it the "magnetic personality.

Study up on how to work it.  A good pair of truck springs will give you a bunch of knives.  

Starting with a known steel is always best, if you have a bunch of an unkown steel to practice with you can usually work out the heat treat for it with practice.  To do it correctly you have to immerse yourself in metalurgy. 

[homeshow]

Use the leaf springs for practice or persomal use. Best in my opionion to use new steel for blades for other people. Have fun first off.

[Stefflus]

My impression is scale, slag and bits of coal doesn't constitute much of a problem until you get the workpiece close to welding temperature, that is, the need to brush is linear to the temperature. That also means it should be unnecessary to have this problem with mild steel unless you're trying to weld it. (Although I'm along with jmccustomknives view for practice purpose and efficiency)

My pictureless guess is the pits are slag or coal hammered into the steel.

[Upperpeach]

I've bought from Admiral Steel.  Others swear by New Jersey Steel baron.  Homeshow suggested getting some old car leaf springs.  A lot of the bladesmiths will have a bad opinion about this.  I've had good results from blades made from old spings.  If you stay with springs that are from the '80's and up they should be a version of 5160.  You should be able to get these from a wrecking yard as at low cost or even free (develope the "art of the trade") plus you may also find that steel will come to you.  I call it the "magnetic personality.

Study up on how to work it.  A good pair of truck springs will give you a bunch of knives.  

Starting with a known steel is always best, if you have a bunch of an unkown steel to practice with you can usually work out the heat treat for it with practice.  To do it correctly you have to immerse yourself in metalurgy. 

Thanks for the tip, I've looked into NJ Steel baron and am probably going to order some 1084  for my next project. I've heard about leaf springs but have never really known much about the steel quality. I suppose in hindsight it would have been better for me to look into getting a leaf spring as opposed to flat-bar from the hardware store but I can use this blade as practice for remaking it with better steel.

[Rich Hale]

And of course we covered forging and finishing blades in the knife making section of the forum. And included a list of suppliers for knife making supplies that have been used by members of this forum.