Platen Issues

L

Living The Dream

Joined
Feb 20, 2016
Messages
158
Can any of you old hands advise of what grinding issues could occur with a platen that is not level? Out platen is bowed in the center vertically. To be more specific are belts are getting more friction on the outside. If you touch the center of the belt you can slightly push in with a pencil tip before the belt contacts solid platen. On the sides of the belt , the belt is firmly in contact with the platen. Is this common? Will this cause any issues while beveling?
 
It would probably result in uneven grinding and/or difficulty achieving a nice flat grind. But a ceramic platen liner and job weld it to your current platen. It's dead flat, lasts wayyy longer, and supposedly reduces friction.

-Jeff


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Sorry autocorrect sucks. JB weld. Look up high temp tools on Google. That's where I got mine.


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You can get the glass platens from most knife making suppliers like USA knifemaker, jantz, eBay etc. I weld a little "ledge" on the bottom of my platen for the glass liner to sit on and the epoxy or jb weld it on. Some have countersunk holes so you can bolt them on. Take yours off and make sure everything is flat and true. You can lay a sheet of sandpaper on something flat and pull the face of your platen across it and see if you have any uneven spots.
 
As Matt stated provide a ledge for the ceramic at the bottom of the platen they have been known to break free from their adhesive backing!

I have been using 3M heavy duty double sided tape and prefer it to JB Weld when it's time to replace worn or broken glass... no more chipping and grinding the old glass just use heat gun and scraper to remove.

Glass platen liner will generate static electricity very common so don't be surprised when it occurs...:)
 
on some grinders you can flip the platen to grind on a fresh spot, or turn it over and use the back until you get the glass platen.
 
Not sure if you have access to a surface grinder or not but that's another option and is what I do with mine. Just grind the surface flat every once and a while and you're good to go. I have a platen with a glass ceramic piece on it and found that belt gunk can still build up on it and cause deep scratches in it. At first I was able to clean it using a razor scraper and some elbow grease, now I think IT needs to be resurfaced. Anyone know if a glass platen would hold up to being surface ground? Not trying to hi-jack your thread but it may be something you need to consider as well down the road, should you decide to use one.

Not sure what type of grinder you have but if it's like the KMG then the threaded holes go all the way through. You can flip it over and use the back until you get something else figured out. That being said, it's not a bad idea to have a couple extra platens laying around.

BTW, if you wanted to pay the postage I could surface grind the platen for you. It won't be a mirror polish or anything but it'll be flat. I take them to 220 grit and they work fine for me.
 
Another condition - which is what I suspect here - is that tracking wheels are often crowned. Meaning, they are actually larger in diameter in the center than on the sides. This will actually stretch the belt in the middle making it slightly longer and looser as well.
If you run a belt well past its normal life, it will raise off the platen in the center. I think that's what you've got.
One way to check is by putting on a brand new belt without any run-time and see if it's the same.
 
I agree on what Karl said, it is very common.
Try a straight edge on your platen to see if it is actually dished, but if it is not try increasing the tension on the belt, it should minimize your issue. Also you could increase a bit the distance of the platen from the tangent to the wheels.
 
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