Diagnose this grinding problem, please

Sean, I guarantee I'm not a perfect grinder, but you should've seen the trough in that platen! :eek: It made things easier, in a way, though because it added another dimension to the grinding. Kind of like when you hollow grind and you establish the hollow, it's kind of a matter of just finding the hollow and enlarging it. Once I would have my nice round shape in the "flat" blade it would find the dip and just settle in. :rolleyes: I flat ground 4 knives over the weekend and they came out really nicely.
 
Here's a picture of my platen about 10-15 minutes into the draw filing process! I filed like a madman for a good 25 minutes or so, I would guess. You can clearly see the top of the platen (it's upside down in the vice, so the top of the platen is the bottom of the picture) where I do most of my grinding, and toward the top of the pic a nice groove where I 90° everything on the workrest. Aluminum seems like a poor choice of materials for one of these. :grumpy: Up until now I had no complaints about the Coote, but this is annoying.
 

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Chiro75 said:
Aluminum seems like a poor choice of materials for one of these. :grumpy: Up until now I had no complaints about the Coote, but this is annoying.
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you may find that Aluminum will embed grit too.. this will be a pain behind the belt :eek:
 
Chiro75 said:
Up until now I had no complaints about the Coote, but this is annoying.
Click to expand...

It's called an "occupational hazard" and has little specificity to a Coote. Perhaps now you can better understand why pyroceram gets mentioned so often. Nothing like a "live demo", eh?

Fix it and move on, it's a lesson in knifemaking. :)
 
Chiro, I have the same problem with my BIII. Like Fitzo says, it is not just your Coote. Fortunately, I put mine on the surface grinder and with a 2" belt, it only takes a couple of minutes to get it flat. :D
 
And for what it's worth, this is not just a Bader problem. This concave platen issue has been haunting me for years, and I have a KMG. Pyroceramic platen liners don't work either. If you're like me you, your just going to have to get a new platen ever couple of months. Flat grinding is FUN! :D
 
Who is it that heat treats a 3/32" x2" x 8" piece of ATS-34 and super glues it to the platen every once in a while like a couple months apart? It now sounds good I thought my grinder was a POS but its the same thing Allen Elishewitz and Ray Rogers started with (they have a modifycation or two I think). Bob Engnath seemed to reface this platens alot..now I know its for anyone who flat grinds alot. How does the KMG rotary platen do with this? Can anyone report?
 
John, I'm somewhat surprised that pyroceram doesn't work well for you. What is the problem, uneven wear? Mine's not used as much as I'd like, but the glass isn't even hazed after a couple hundred hours on my KMG. I did find out the hard way not to let a student set it down on it's edge on the floor! :eek:

It seems that the only real common thing I've ever heard is that, no matter what is put on the platen, it needs periodic maintenance. It's not just a surface, but a wear surface. No magic bullets here.
 
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