I always get into trouble with grinding angles and steepness, my brain seems to work in reverse from what others do, so bear with me.
I would say that a perpendicular edge to the tool would be of no use. Now as you grind more away from a perpendicular end, it begins to be useful. I like to use between 11 and 20 degrees from the perpendicular. Now whether that is 70 to 79 degrees, that is up to the person. In summation, I think you have ground it too far back (away) from perpendicular.
I am not an expert, but what I would do grind it back so that you get a secondary bevel that is at least 1/4 of the thickness. You will get enough meat to support the edge and not have to grind all the steal away. As you keep sharpening it you will get to the point at some point where it is all one bevel.
Mark, you need to TURN IT OVER.
Dude, it won't cut worth a chittlins with the bevel up like that, man.
Plus, the kitty is sure nice to let you use her as a tool rest like that! 'Ol sweetheart that she is. Must sure love you a lot to put up with some of your shennanagins. :7
OK, I'll quit twisstin your tail.
Straight from a book:
Scrapers normally come from the manufactures with an edge angle between 70-80 degrees. Some turners prefer a much smaller angle and they regrind their tools to a 60 degree angle or even smaller.
<Yours appears to me to be in that upper end of that degree angle>
Scrapers are best ground TOWARDS the edge.... The rotation of the grindstone helps press the tool onto the Tool Rest.
It goes on to state:
The burr, which is left from dry grinding at high speed, consists of a sintered (melted) mixture of steel waste and abrasives from the grinding wheel as well as the steel which has been pushed up by the grinding wheel. The sintered mixture will soon be worn away when you start turning. What is left is the residual edge and this cuts the wood.
However the burr is very uneven and course and it is obvious that it cannot be durable. ....
There is an even better method to make a scraper work as a cutting tool. If you press with a hard steel rod at an angle of 5-10 degrees, the tip will be bent upwards creating a micro hook. The pressure from the rod compresses the steel, smoothens the small scratches from the grindstone an makes the hook shiney.
The result is an even, sharp and durable micro-hook or a cutting edge. The method is called ticketing (or burnishing) and gives you a far better and more durable hook than a burr.
<Humm, so that's what I've been missing by just using my grindstone burr>
Ther are special ticketing tools on the market, but you can easily do the ticketing by using a 12mm (1/2") HSS bowl gouge. Clamp the scraper in your workbench vise so you can hold the bowl gouge steadily with both hands.
You must not ticket too heavily so the hook tends to be bent backwards. The tip of the hook must point towards the work.
<Much like about any card scraper we commonly use.>
End of copyright infringment. :)
Now then Marc,
For your situation, with a dry grinder, use your tool rest to get your +/- 60 degree angle, and carefully create the arc you desire on your scraper. the pictures show a circular arc. I do a more of a fingernail shape to mine, (matter of preferance.)
Here's an important tip:
If you want to match a certian angle on your tool time and time again, mark the bevel with a Marks-a-lot or simular marker. Place the bevel against the stones face and just slightly rotate the wheel enough to strike off the marker on the bevel. When it is centered or strikes off the entire bevel face, your then set to duplicate the angle.
I do that as a matter of routine to get my angles repeated when grinding. I don't often grind, but that's how I repeat the angle quickly.
Note: the first two pictures, top to bottom, show the sample woods I bought to match: mahogany, walnut, oak, the bottom is the side of the table. The remaining 3 pictures are of the wood in question...