I noticed this odd looking “varicose vein†appear while finish grinding a small 1084 blade this afternoon. Although it completely disappeared after a few 400 grit passes on the belt, it left me wondering what I did to cause this as I haven’t noticed it before.
It looks like you might have been "falling off" the bottom of the platen..... the bottom edge of a platen will leave those type of marks. If your platen is full length.... it can also be caused by getting off the bottom of the platen, and "touching" the bottom contact wheel.
Ed Caffrey, ABS MS
"The Montana Bladesmith"
www.CaffreyKnives.net
That would make sense as I was working on edge geometry using the slack area in between the upper wheel and the top of my platen when I noticed it. I remember getting a little low and contacting the top of the platen. Thanks Ed!
If you were working with a J-flex belt this is also very similar to what you get when a get a booger build up on the face of the platen that transfers through the belt and onto the blade. Look at your platen and see if there are globs an streaks of black gunk, from the belts backing breaking down and sticking to the platen. I keep a handheld belt sander in the grinding bench just to quickly dress up or clean the platens when moving to J-Flex.
"One test is worth 1000 'expert' opinions" Riehle Testing Machines Co.
I have had that problem when I am using J-flex belts and there is build up on the platen or groves on the platen. If you have that problem again check your platen, it may need to be sanded flat.
Ken
I was using a J-flex belt at the time. After reading through your replies, I inspected my platen and was surprised by the amount of black gunk that I'd allowed to accumulate on the glass since putting it into service last month. It didn't take much effort to get it shined back up. Thanks for the tips.
Its likely what the other guys who commented on this said, however to me it looks like you used a rotary tool for the first time at to high a rpm.
