It's probably a spot of thinner steel where you didn't get a complete weld. And YES full body weight is way too much push on a grinder!

When you really push a grinding disk or cut off wheel the hot cuttings weld into the grit forming a glaze on the wheel and really slows down the grind or cut. 

Rushing metal work, especially precision work like knives only guarantees making your mistakes permanent more quickly. Not to mention wasting all the work you've put into it already. Make sense?

Take your time. Your patience will be rewarded.

Frosty The Lucky.

The groove on the right, about 2/3  towards top

I was leaning on it to take time and do it well vs freehand

Looks like you didn't get welding heat all the way through the billet. Make sure you let it "soak" in the welding heat a while to heat it through. Patients in the fire is a virtue, don't rush things. I would cut the billet half way through and fold it over and re-weld the whole mess.

Also get some cut off wheels for the angle grinder.

I can't control the wind, all I can do is adjust my sail’s.
Semper Paratus

 

I thought id read that folding cable diminishes the figure. (But draw out length of billet, fold it with hammer, flux the middle and beat it flat?)This billet was really weird, becsuse due to migged ends, i only twisted it about 1/2 turn. I have 0 clue what this figure will even look like. So it looks like angle grinder is causing the dark spot as opposed to it being an ugly burned end just mashed in hot metal. i think im getting speed better. How long on average should i hammer each heat forging ( i weld in 15 seconds  a little hotter)how long to resoak in forge if its a storebought vevor running good. (Resoaks are blazing at 2 minutes nonrmal round.) Shouldnt i be able to psi. control 50 degrees below burning, never go higher, shouldnt i be able to full soak without bjurning? Welding has to continue with each forging as long as i start yellow right?

Tx

You started with 2" cable soak time would've been 3-4 minutes at least once it reached welding temp. I don't know the specific times off the top of my head but do know cable takes a lot longer to heat through because it's a bunch of small wires close together not one piece. 

Do NOT put the cable in a HOT forge, start heating at orange and let it set for maybe 10 minutes when it is the same color as the forge. Flux it thoroughly, be generous. Then turn the psi up a little bit, say to high orange and let it sit and soak again. Flux again, turn the psi up a little and let it sit again. Once it has soaked (5+ minutes at the same color as the forge) at high orange twist and hammer lightly to consolidate the wire. Re-flux and let it soak at high orange. 

Repeat that till it feels like a steel bar under the hammer, THEN flux and soak at welding heat before trying to weld.

Turning 2" cable into a blade is NOT a quick process, you have really rushed it already but it can be saved if you slow down in the forge. Turn the psi down till the billet is the same color as a high orange forge, then turn it up to low yellow, soak before you turn the forge to welding heat and let it soak again.

The more consolidated the cable becomes the faster it will come to heat but as you can see where you ground into it you did not let it soak long enough.

If you want this to work for you you must slow down and that includes not trying to force the grinder disk.

Frosty The Lucky.