Use X-weight when you want a firm belt on a flat platen. Use J-Flex when you want the belt to follow a curve. Both Havoc belts use aluminum oxide. The backing changes how the belt sits against the work, even when you pick the same grit.
Use X-weight where you need a flat reference
A flat platen supports the belt and gives you a reference when you’re cleaning up a flat tang, a bolster face, or a blade flat. Havoc’s X-weight aluminum oxide belts have the firmer backing of the two. Start with light, even passes and look at where the new scratches show up. A narrow strip of fresh scratches can tell you that you’re contacting only part of the flat.
Use J-Flex where the handle curves
Havoc’s J-Flex aluminum oxide belts bend more readily, which helps when you’re refining a shaped handle or blending a rounded transition. On a grinder set up for slack-belt work, the belt can wrap farther around the curve. Keep an eye on crisp edges and transitions you want to preserve. The same flexibility that helps on a curve can soften a line if you spend too long there.
Try both at 220 grit
Both Havoc backings come in 220, 320, and 400 grit. If you’re unsure which you need, compare the same grit on a flat scrap and a rounded offcut. Look at how much of the surface the belt contacts and whether it leaves the edge you want. Once you’ve chosen the backing, pick the grit that will remove the scratches already on the piece.
Havoc X-weight runs from 36 to 400 grit, with selected steps in between. J-Flex starts at 220 and goes up to 600. If you still have deep grinding scratches, clear them before moving to a flexible finishing belt. See the 2x72 grit progression guide for a starting sequence.