There is no definitive answer to your question. There are a couple of variables that make quite a difference.
The thickness of the card will effect the reaction of the first few passes at 90 deg to the edge and the mushroom of sorts you get to start your bur.
The hardness of the steel also plays a role in how hard are soft to press for obvious reasons.
It's really one of those things you do by feel unless every card you have is identical.
Be sure you have a clean smooth 90 edge, a good smooth burnisher of material substantially harder than the scraper and a bit of oil to keep things smooth.
One of the biggest mistakes I see with those learning this skill is timidness. Don't be afraid and don't gradually work the angle. Make your mushroom (pushing as hard as you like). Then immediately go to your final angle instead of trying to roll the angle higher and higher. This will make for a keener more consistent edge.
If you don't get it right, joint the edge and try again.
You should have your scraper in a vise with enough edge above the jaws to use the burnisher...about 1/2" to 3/4".
You can use a large chrome plated screwdriver.
Use need to sharpen/flatten the edge with a mill file or sanding belt or a oil or waterstone so it's square to the plate.
THEN holding the screwdriver/burnisher at a 5 degree angle to the edge, press down gently but firmly and draw it across the edge, first on one side then the other.
The object is to roll the edge over just slightly to create the burr. You need to draw the burnisher over it about 5 -8 times to get enough burr.
You can feel it if you are doing it correctly.
Not every video has the same exact process, but they are close enough to glean the technique.
I even just use the scraper right off the belt grinder which leaves a small burr. I use a 320 grit belt.
YOU NEED to get this down as you will love the results. :yes:
+1 on the above^. I would also suggest you buy a high quility scraper if you are unsure on quility of yours. There is nothing more frusterating than trying to work with sorry steel. If you know yours is a good one,try using a high quility chrome plated srewdriver because there is a difference in hardness of chrome plating.
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