ridges in platen

D

deckerjm

Joined
Dec 3, 2012
Messages
13
Hi,

Newbie here, and I have a question about ridges in the platen on my KMG grinder.

When I'm hogging metal off a blank with a 50- or 60-grit belt, it only takes four or five blades until I get ridge lines in the platen. Those lines then transfer to the blade when I move to much thinner 220- and 400-grit belts.

I suspect these lines are a result of grit getting caught on the underside of the belt and following the belt's rotation over the platen, but I'm not sure. In any case, it's a problem.

Guesses:

1. Resurface one side of the platen for finer work with higher grit belts and use the rough side for hogging with lower grit belts.

2. Use two platens, one for hogging and one for finer work. (I do have a second, unused platen.)

3. Resurface the platen when it develops these lines.

4. A combination of the above - take note of the platen's condition regardless of purpose and resurface as necessary.

Any intelligence is welcome.

Thanks,

- J
 
Well the platen that comes with the KMG is mild steel so that will happen .Make sure the platen is only slightly in front of the wheels. If it is sticking out too far I have found it will cause this to happen faster. May be 1/16". I would buy a glass platen and epoxy it to the mild steel platen.
 
Go with glass and change it when it becomes ridged. No material will be unscathed using ceramic belts other than carbide or diamond. :) I replace mine twice a year if I'm doing a lot of grinding.
 
My platen developed ridges from profiling blanks. When I would get to 400 grit, I would get ridges/waves on my bevels. Then I bought a glass platen to cover the metal platen from pops knife supply and now profile on the 10" wheel or get my blanks water jet cut.
 
You should invest in one of Nathan the machinists hardened tool steel platens. I have one and that sucker is tough. But... It's a lot easier to hog material with a wheel and save the platen for flat work. The wheel hogs steel faster anyway.
 
A wheel hogs faster and preserves the belt too. Pull less power too. Obviously a hardened steel platen holds up better than a soft platen, but depending on conditions even hard steel can groove quickly.

Any platen will last longer if it is not subjected to the rubbery grit residue that can stick to the inside of belts. If you see black gunk building up on your platen it is building up on your belt too. It is a mix of grit and grinding aids. These grinding aids are great when the belt is used in certain industrial applications such as centerless grinding under flood coolant but build up gunk when used by knifemakers. Sometimes a damp belt makes the problem worse, so I recommend folks dry completely dry or completely wet. If you're not wiping your blades dry after cooling it you're getting water on your belt. Some belts don't play well with water.
 
Wow, thanks. Excellent advice all around.

Gave things a go using the 8" wheel to hog and the platen (along with horizontal disc grinder) to flatten and the results seem to be much better. Faster for sure and the belt seems to be in better condition after the same amount of time on the platen. (Note: I occassionally get water on my belts, but I do try to wipe them after each quench.)

Probably also a good idea for me to use my gear in different configurations for different applications - only gonna help improve skills over time.

Looking into hardened steel and glass platens too. A question about the glass platen - Is it possible to grind it or put a radius along the edge? I did that to my metal platen along the edge to make the plunge cuts smoother and it helped quite a bit.

Thanks again.

- J
 
You really should check out Nathan's platen thread. He has put a radius on top and bottom and the sides are nice and crisp and make for an awesome plunge cut. You gotta check it out.

BTW Nathan isn't paying me :) just a fan of his work!
 
I agree on the the NTM platens. Simply very well made. They have an small hole for compressed air to keep things cool. They are very nice and definitely worth it. Check them out.
 
Very cool. Will do.

Found some good information on the web also and people seem to be very happy with the product.

Plus, I've got unpaid endorsements from you two. :)

Thanks again.
 
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