There are four hundred videos about this and they mostly disagree. Here is what actually happens at our bench, in the order it happens, with the fewest stones that work.
An edge is where two flat surfaces meet. If the back of your chisel is convex, nothing you do to the bevel produces a straight edge. Lap the first 30mm of the back on a coarse stone until the scratch pattern is uniform, then work up to your finest grit. On a new Narex this takes ten minutes. On an old flea-market chisel it can take an hour, and that hour is the difference between a tool and a wall decoration.
Do it once. From then on you only ever touch the bevel.
Grinding removes metal to re-establish the 25° primary bevel. You only need it when the edge is chipped, rounded over from years of neglect, or the honed bevel has crept so wide that honing takes forever. A slow wet grinder is safest; a dry wheel will blue the steel and ruin the temper if you rush, and blued steel does not come back.
Set the blade in a side-clamp honing guide at roughly 30° — five degrees steeper than the grind. That gives you a narrow micro-bevel, which means you're polishing a sliver of steel instead of the whole bevel face. Twelve strokes on a soaked 1000 grit waterstone until a burr forms on the back. Flip, one light pass flat on the back to remove the burr. Move to 6000 grit, eight strokes, one flat pass again.
That's it. It should take under two minutes and you should be able to shave a patch of arm hair or slice newsprint cleanly across the grain.
25° primary grind for bench chisels and plane irons · 30° micro-bevel for general work · 35° if you're chopping hardwood mortises and chipping edges · 20–25° for paring chisels that never meet a mallet. Japanese laminated blades like the steeper end. Nobody will ever measure yours.
A 1000/6000 combination waterstone and a flattening plate. That is a complete setup and it costs less than one premium chisel. Add a 400 grit only if you restore old tools. Diamond plates cut faster, never dish, and cost more — good if you hate maintenance. Oilstones work fine and your grandfather was not wrong; they're just slower.
The flattening plate is not optional. A dished waterstone rounds your bevel and you'll blame the steel.
Whenever it stops feeling right, which for hand-tool joinery is every twenty or thirty minutes of chopping. Honing a slightly dull edge takes ninety seconds. Rescuing an edge you flogged for three hours takes a trip to the grinder. Sharpen early, often, and stop treating it as an event.