Any particular reason you are using O1 for this project? Don't get me wrong, I use O1 a lot and it's a great steel. It's just not my first choice for a cleaver. O1 (and several other common blade steels) likes to be forged hot, like above 1500*F. My guess would be that the crack developed from forging too cold. Do you have any 1084 or 1095?

I don’t have either of those steels on hand in dimensions that I’d be comfortable trying to forge a cleaver from. The O1 was what I had on hand in dimensions large enough to draw the cleaver out of. 
‘I’ll look into some 1095. 
I had tried to be more careful of the heat after the first blade. But obviously I missed on it.  
‘thank you for your help

Looking at the image I would actually say you overheated it.  I have been working with O-1 my entire career and love the steel, but it will not tolerate overheating.  or at least not overheating without follow up treatments to deal with it.  Heating O-1 to 1950°F or better will cause surface crazing and cracking if you cool it to room temp from that temp.  It is better to forge it on the cooler side (around 1800°F, and even a little cooler) and if you get it too hot be sure to step it down with several reheats to 1450°F or so to reset the grain and keep it from overhardening when it finally comes to room temp.    

Posted by: @krcashenabs

It is better to forge it on the cooler side (around 1800°F, and even a little cooler)

This is a small forging window. My understanding is forge between 1950 and 1500

I cannot see the photo

@krcashenabs 
if I overheat it. Do I let it cool to the 1800 before forging? Or do I need to normalize or stress relieve, before forging?
I don’t generally let my work piece cool to room temp till the end of my forging session. The coolest it will get is if I catch a cold shut and grind it. And then I’m trying to grind it quickly to keep heat in the work piece. 

@joshua-c-states 

I attached a photo to my first post. You need to click it to view it. Haven’t found an image hosting site that lets me easily post pictures on forums. Haven’t really looked real hard though either so I apologize. 

Posted by: @squigly1965

I attached a photo to my first post. You need to click it to view it. Haven’t found an image hosting site that lets me easily post pictures on forums. Haven’t really looked real hard though either so I apologize.

I've been having trouble seeing any photos on the new site, even my own. I click the link and nothing happens. As it turns out I updated my malware before the transition to the new site and it shut down popups from the new site. Computer weirdness. I have it fixed now.

I'm going to assume that the crack developed after hardening and tempering. The grain is too large. It really should look more like this photo.

So let's talk about your process. what do you do between forging and hardening?

@joshua-c-states 

Actually that’s preheat-treat in the picture. I was grinding of scale when I noticed it. 
so I take it that makes it worse lol. 
previously I hadn’t really normalized or stress relieved. I was mainly doing stock removal. It may have needed it then but I was not doing it.

I am finally in a position to do forging again(last time was probably 8-10 years ago). It’s something I really enjoy I just didn’t have a place to do it. So I’m trying to get back into it seriously.  And am willingly to take any and all criticism and advice. 

with all that said. I have been forging the work piece and at the end of my session I have been normalizing(hopefully). I was doing it all in daylight, with the forge. So overheating was probably an issue. 

I have a heat treat oven I was using for quenching and tempering on my stock removal blades. Which I can use for accurate normalizing and stress relief.  I also recently got an infrared temp gun that I can use to help with control of the work piece. 

thank you again for your help and time

chris

Actually, the fact that this was pre-HT and your normalizing was in daylight, explains a lot about the grain. The cracking could be either overheating as Kevin postulates, or forging too cold. I would wager money that Kevin's assessment is correct! 

One of the most important things you can have in your shop is proper task lighting. That means proper for the process or function being performed. If you do your normalizing in your forge, and you are judging temp by color, you really need dim or dark conditions to accurately see what is happening. One of the best investments I ever made for my forge was a pyrometer and temperature readout. I can now do a fairly accurate step-down normalizing process before my blade ever sees the grinder. 

Try this little experiment. Find a steel tube section that is about 2-3 feet long. Stand it up on end close to your forge and bring a piece of steel up to what looks like an acceptable "color" for any given process (forging, normalizing. whatever). Remove the steel from the forge and hold it down inside the tube in complete shadow. Compare what you thought you saw in the forge with what you see in complete darkness. The difference is considerable.