worm

v-6

v-6

Joined
Nov 24, 2007
Messages
952
i have a worm groove in the middle of my blade while flat grinding.
what went on there. this is 1095 the belt was 120 , so i still have time to do something with it, you can rub your finger over it and you can feel it.
help me please
vern
 
That happened to me after I surfaced my platen. The screws that bolted in on were sticking out past the platen because it was thinner. I had to shorten the screws and problem solved.
 
well i don't think thats my case, cause i have a ceramic platen
 
Are you getting a bump every time the belt splice crosses the platen, Vern? That can cause some odd grinding flaws on flat grinds.

What brand of belt are you using? Make sure they're butt spliced and not overlap joints.
 
I just thought of another thing that can cause this. If the platen does not stand slightly proud of the wheels so the belt stays tight, and there's not enough belt tension, then the belt can literally bunch ever so slightly right where you're pressing the blade in. That will result in some odd grinding marks, too.
 
That happened to me while I was using a 220 grit belt on the first knife I forged. Looked like the blade had been attacked by a herd of mad termites. Traced the problem down to a blob of plastic on the back of the belt. The plastic came from overheating a contact wheel I made from a Sunray caster. The polyurethane covering melted and the belt smeared it on the other wheels. Didn't notice the problem until I put on the thin 220 belt and it picked up some of the melted crap. The blob made a high spot on the belt which happily chewed grooves in my poor blade. I said some bad words, cleaned everything up and reground the blade.
 
the first belt was Blaze Ceramic 60 grit, then i went to a Blaze Ceramic 120Y grit which is where it goofed up.
i think i will take and set that belt aside and see how it works then.
vern
 
Sounds like a decent place to start, changing belts. Make sure and take your belts off the machine when done with a grinder session for the day, too. You can create some funny stretching and puckers in a belt leaving them on the machine and not running.
 
fitzo said:
Sounds like a decent place to start, changing belts. Make sure and take your belts off the machine when done with a grinder session for the day, too. You can create some funny stretching and puckers in a belt leaving them on the machine and not running.
Click to expand...

Mike thats good advice. I never take mine off and the other day one just blew. It was load enough to make me cuss.:eek:
 
I did a little research when I was buildin my beltgrinder to see how much tension is supposed to be on a 2" belt ...3M tech support told me between 30 to 40 lbs was about right...I still think I can create a "standing wave" effect with a thin belt and to much pressure which causes little divots and I also thinks speed can magnify that too...any concesus on this?
 
You may also be catching the platen a little high and grinding at the top edge. That will leave a worm too.

Gene
 
thanks guys, i changed belts and that took care of it.
thanks vern
 
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