Round wheels vs flat platens

centennial

centennial

Joined
Oct 7, 2013
Messages
162
I see a lot of grinding being done on a wheel rather than on a flat platen. Profiling and other operations that in my mind would be done against the platen are done on the wheel.
Is there a reason, aside from not taking the time to change the machine over?
What am I missing?
Thanks
 
Belt going around the wheel means the grit is opened up a bit so it bites better. The rubber wheel face cushions the belt when the blade is pushed against it, this gives the belt an easier ride and the grit stays on the belt a bit longer. That cushion also makes it easier to grind, it feels smoother.
 
Also, where there's heat, there's friction... Profiling against a platen will eventually wear it out of true (put grooves in it). Profiling against a wheel, you're not putting pressure on the same spot(s) all the time.
 
Plus, your grinder "appears" to have more power (torque) as you aren't overcoming the friction between the belt and platen. I have a 2hp VFD and I can't stall it on my 14" wheel, where I can on my flat platen when grinding a wider blade.
 
Doing as much as you can on the wheel makes sense.
It also makes sense to lay the blade on the tool rest and finish things up so the edge is crisp and square to the faces. Kinda hard to get that exactly right, though Snody has a video on how he does that an the wheel, using a guide to keep the blade 90 deg. to the wheel.
There are spots where it's nice to use a J-flex belt hanging just a squeak over the side of the platen to work on small areas as you lay the blade on the tool rest and work it against the platen- it's surprising how much material a 120 J-flex will remove. Not that you can't do that on the edge of the wheel, too.
It's just harder to keep that edge square to the faces.
 
A platen gives double friction. The belt has friction against the platen and against blank.
Your wheel moves, the belt rides on it without friction. It only has friction with the blank being ground.

I find myself doing more on the wheel then I thought I would do.
 
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