Grind line radius help

[Kev]

I apologize in advance if this is the wrong forum, I wasn’t sure where else to put it.
I’m having trouble getting a consistent radius where my grind line meets my plunge line.
I offset the belt from the platter with x flex belts and I get a beautiful consistent radius that I can control using more or less overhang. My troubles start when I move up grits and hit the j weight belts. Using the same overhang and identical technique the radius is destroyed and there is no rhyme or reason that I can see.
I’ll see if I can get some photos to clear up what I’m talking about.
Any help is greatly appreciated.

 

[Jason Volkert]

If I had to guess: Ths belt bump in the Jflex belts are probably the problem. I only use Jflex on Handles. I use trizac at higher grits they have 95% less belt bump then Jflex.

 

[Drew Riley]

Unless you have a radius on the corner of your platen, the J-flex are always going to give you a tight radius. You may be overhanging the same amount as an x-weight, but the belt is still going to take the shape of your platen corner for the most part, which for most guys is around a 90 degree corner.

Either radius your platen edge to match the radius you want, or use a heavier belt.

 

[J. Doyle]

So much of this issue has to do with pressure.

Drew is correct in the above post, but a LOT can be overcome by paying attention to how much pressure you're using. This can compensate for these issues regardless of platen corner shape or belt weight.......though as Drew mentioned, those things can also help combat the issues.

For reference, My platen is sharp cornered and sharp edged and unaltered in any way.I finish with j-flex belts after stiffer roughing belts and can keep whatever radius I want. But I pay attention to how different belts cut and how much pressure I need to apply in critical areas.