15" flat platten?

S

setlab

Member
I'mI in the process of beefing up my grinder and am making a new flat platten for it. My old flat platen was only 6" long and caused more headaches than I care to say trying to grind a longer blade flat. To solve that I bought one of those 15" glass platen backers on usaknifemaker and plan to use every inch of it for my platten, has anyone else ever made one this big? I was wondering if I might run into tracking or tension issues with it.
 
My platen is 10 inches long with no problems,I don't use it for facing though,I use my 6 inch belt for that.
 
The limiting factor on platen length is the base plate of your grinder. DO NOT move the top platen wheel up, otherwise tracking goes way south. I have a 12" platen that I built for my KMG.....but what I had to do was "trim" the base plate, and raise the machine a bit....I'll take some pics later and post them.....once you see the picks it makes sense.
 
I think I understand, keep the top platten roller below the tracking wheel to give it more surface area to track on? I wanted to be sure before I cut into my aluminum plate, that stuff is like kriptonite to find locally in small pieces.

thanks
 
Here are the pics I promised.....

This one shows where I had to trim the base plate on the KMG......and because it was already "raised" to the correct height for me......I didn't have to do anything to the bench it's attached to.




The next pic shows why I had to trim the base.....the belt will not fit without hitting the base when a longer platen it used. And you were 100% correct about the top wheel. So many times I've had folks contact me asking for help with using a longer platen, and because it's so often the case, my first question is always "Is the top wheel any higher then it was on your original platen?" :)

 
I put a 12" platen on my kmg, I raised the top idler wheel some but most of the extra length went below the original lower wheel location, I'll post pics later. I don't have any tracking issues, just requires a little calculating to see how much the upper wheel can move. To be on the safe side I agree moving the top wheel can easily cause all kinds of problems. I also machined my extended platen setup on a Haas vf3 cnc vert mill while in school
 
Well that saved me a little bit of time, I just held my platen glass up to my grinder frame Looks like I'll have to raise it up an inch or two for belt clearance. Luckily when I designed my grinder a long time ago I didn't know where I wanted to have my tracking wheel so I made a somewhat adjustable mount for it so I can bolt the tracking arm to a higher or lower position. I'd post pictures, but my grinder is currently in 10 different pieces while I wait for my steel to come in so I can change it to accept a 1.5" tool arm and work rest.
 
With my 6" platen I would constantly grind little dents into the blade where the end of my platen was if I stopped moving the blade for any amount of time. Having a long platen I don't think I'll ever have to deal with an issue like that. Plus I think it might add some versatility to the grinder, who knows what I'll need to grind a few years down the road.
 
Just my opinion, but if you want to get something flat use a disk grinder ! I have never had any luck getting the flats on my knives "flat" on a platen, no matter how perfectly flat the platen is. Not trying to be a stick in the mud here, just say'in what works for me.
Sincerely,
Clint
 
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