flats on my flat platen

J

jasperdog032469

Joined
Mar 14, 2007
Messages
115
I have made a flat platen for my 2x72. Works alright, however, when I try doing my flats, I get little ripple effects. I believe it is because of the seem om the belts. I can feel it jumping when it comes around.. Any suggestions on how to fix this? I'm using good belts..klingspor j flex.

thanks,
Dave
 
I don't really know, but because nobody else answered, my guess is its the seam. You should look for butt-spliced belts, if those aren't already. Hopefully someone more knowledgeable will chime in.
 
Less pressure and more movement is the only thing that helps me. I use 3M belts. I do a lot of hand sanding on flat grinds.
 
Place a scotch brite belt under your grinding belt and it will cushion and relieve the bumping while grinding. Does a super job for cleaning up the plunge line cut when finishing with finer belts as well. Don't thank me, thank Dan Graves who shared this tip and bit of knowledge.
 
Bob Ham showed me that trick for hollow grinding, never tried it on a platen. The only problem I have is that sometimes the edge of the scotch-brite belts gets in the way of a finish I have, so hard to get them to track exactly.
 
is your platen smooth and flat ? any irregularities will cause that . A problem I was having , I believe came from magnetism , using the magnet to hold the blade caused metal to get trapped between the belt and platen . I glued on a piece of glass to the platen and the problem has gone away .
Just a thought , it was driving me nuts .
 
I had that problem a while back. it was caused by actual ripples in my mild steel platen, right at the point that my removable table allowed material to repeatedly meet the platen at the same spot. 1st solution was to use one side of my platen for flat grinding only then flip around my platen for profiling. This allowed one side to take the ripples caused from profiling and the other side to stay flat. 2nd solution that is in place today, created a platen out of D2 @ ~62 RC. Don't have to worry about it any more.

Eric
 
I had that problem as well, and found out it was the mouning screw that was on the platen. I put a ceramic platen face on and problem solved.
 
adding a ceramic, or glass, or high Rc steel to the platen helped me alot.
Still, the ripples might appear after long use of one belt. It was a small buildup of backing/dirt/etc. on the platten right where the work rest was.
I took a piece of brass...maybe 1/16" by 3/4" about a foor long....groung a sharp edge on the end of the brass and use it as a scraper to clean off the ceramic plate.
also rounding the top and bottom edges of the ceramic/glass/hiRc steel seems to reduce the residue on the plate.
 
I have found that a tighter belt does not cause the ripples as bad. Especially with a J flex belt. I really believe that a loose belt and too much pressure causes the belt to bunch up under the knife and cut a ripple in the blade.
 
After rough grinding a blade on the platen, (around a 220 grit finish) I heat treat, and between the first and second temper cycle, I do a final grind, usually carrying the blade to 400.

This final grinding is done with a piece of leather glued to my platen. I use DAP contact cement. This gives a gentle cushion to the platen and totally eliminates "belt-bump". In addition, it gives your flat-ground blade a slightly convex edge. Take your time and go slow. With a little practice, you can turn out a pretty good looking blade with no "humps or bumps".

The leather is easily removed and clean-up of the platen is accomplished with a little lacquer thinner, then you are ready for the next one.

Of course, I didn't mention hours and hours of hand sanding to get that final finish.:)

Robert
 
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