2x72 Grinder Tips
The Belt Grit Progression That Actually Works (and Why Your 220 Bumps)
Which grits, how many steps, and why the finish falls apart when the belts get fine. Here is the belt progression I run on my own blades, 36-grit ceramic to 400, and the fix for the bump nobody mentions.
Belt progression questions keep coming up: which grits, how many steps, and why the finish falls apart right when the belts get fine. Here is the ladder I run on my own blades, from fresh 36-grit ceramic through 400, and the fix for the bump at higher grits that nobody warns you about.
KEY TAKEAWAYS
- The working ladder: 36 or 60 to hog, 120 to shape, 220 to smooth, 400-plus to finish.
- Never skip more than one doubling. Each grit only has to erase the last one’s scratches.
- Buy coarse belts in bulk and premium quality. Knife grinding eats 36s – cheap ones cost more per blade.
- The high-grit “bump” is usually the belt splice. There is a fix.
- Slow the machine down as the grits go up. Speed that hogs will burn a finish pass.
THE LADDER
Profile and rough bevels at 36 or 60 grit with fresh premium ceramic. This is where steel actually moves, and where cheap belts rob you blind – a dull 36 rubs and heats instead of cutting. Shape at 120. Smooth at 220. Then finishing belts from 400 up if the blade wants satin off the machine, or jump to hand sanding after 220 for the hand-rubbed look. That is four or five belts per blade, not ten. Each step has one job: erase the scratches the last belt left. Skip from 60 to 220 and you will spend longer at 220 than both middle steps combined – the deep scratches hide until the fine grit shows them off.
THE BUMP AT HIGHER GRITS
Here is the one the forums keep rediscovering: you move up to 220 or 400, and now the belt slaps the blade every revolution – a tick-tick-tick that prints witness marks across a nearly finished bevel. That is the splice. Fine belts ride thinner backings, and the taped joint stands proud enough to bump. The working fix: dress the running belt’s splice with a diamond block or dressing stick – light touch, machine on, a few seconds – and the joint levels out. Better still, buy finishing belts known for flat splices in the first place. Our full belt guide covers which types earn their keep: the 2×72 Belt Buyer’s Guide.
SPEED CHANGES WITH GRIT
The other half of clean finishing is the dial. Full speed and a fresh 36 is correct – sharp coarse ceramic runs cool when it is cutting hard. Full speed and a 400 belt on a hardened edge is how tempers die. As the grits climb, the speed drops: finish passes want less than half of hogging speed, with light pressure and constant motion. We put the working numbers in one chart: Belt Speed by Task. Variable speed is the whole ballgame here – it is what lets one machine run the entire ladder right, which is exactly what the NOVA was built to do all day.
CONSISTENCY IS THE REAL PROGRESSION
The ladder only works if each pass lands where the last one did. A grinder that tracks true and holds its settings turns grit progression into a system instead of a gamble – the same argument as equipment that supports repeatable results. Pick your ladder, write it on the wall, run it the same way every blade.
A grit ladder only works on a machine that tracks the same at 36 as it does at 400. The Nova 2×72 holds its settings between belt changes thanks to machined dual-axis tracking and a stainless ratchet tensioner, and it ships assembled and tested from my shop. Build yours, write the ladder on the wall, and run it the same way every blade.
