Flat grinding platten... tempering ?

zzknives

zzknives

Well-Known Member
Hey guys,

Looks like I have to make a new flatgrinding platten.:mad:

Last time I made it out of O1 and tempered it to 60 HRC

But a dude told me that it´s not necessary and that no tempering means a harder platten which will last longer

What do you think? Is that true?

THX

AL
 
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I am not the best to chime in but, I am under the assumption that it don't really matter if it is hardened or not, it will still wear. Your best bet is to get ceramic glass to jb weld on to the platen. that way you get a smooth surface that is totally flat.
 
Thx.

have thought about that but I prefer a solid piece of steel over glass

but I could give it a shot as soon as I have finished a new platten
 
The issues with steel platens...hardened or not:

1. Wears regardless if it's hardening or not. Depending on how many blades you grind, a steel platen can start to groove up in a matter of weeks.

2. Heat build up: Steel platens produce and retain a lot of heat. This heat transfers to the body of the platen, and into the bearings that support your contact wheels/aluminum rollers, shorten their life.

3. I can't pin point the reason for this, but steel platens simply do not produce as good/smooth grind as glass platens.

Glass platens are the only way to go as far as I'm concerned. A glass platen will eliminate all the issues I mentioned above.

The keys to getting the best out of a glass platen face are:

1. The surface that the glass is glued to, MUST BE PERFECTLY FLAT AND TRUE, WITH A ROUGH (I LEAVE THE FINISH AT 50 GRIT) FINISH, WHICH GIVES THE GLUE SOMETHING TO GRIP. Otherwise the glass will quickly crack/break.

2. When applying the glue...first of all you need a PREMIUM adhesive such as AcraGlass or West System Marine epoxy. The glue MUST have FULL contact between the glass and the mounting surface. Bubbles or air pockets will result in the glass cracking/breaking at the bubbles/air pockets.

3. The lead in, and trial out edges of the glass platen face MUST BE rounded so that the belt has a smooth transition when it comes in contact with the glass. If you leave sharp edges the belt joint will catch on the edge of the glass and will blow up in your face... (just trust me on this one....you really don't want or need to experience that...I did!)

4. This is just common sense, but I think it's worth mentioning...you have to be careful not to slam the platen down on the bench, or drop it on a concrete floor...just not a good mix with the glass.

Finally, I think that once you grind a blade or two on a glass platen, you'll find yourself wondering why it took you so long to go with one. Your grinds will come out better, smoother, and cleaner. There will be far less heat build up, and the glass will outlast a steel platen by a 100X+. (I've had the same piece of tempered glass on my platen for over 3 years now)
 
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EdCaffreyMS said:
The issues with steel platens...hardened or not:

Glass platens are the only way to go as far as I'm concerned. A glass platen will eliminate all the issues I mentioned above.
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Nice to have the Shell Answer Man here! I believe you're using a piece of tempered window glass, correct Ed? Have you tried the ceramic platen plates that are being sold? If so, how do they compare to your glass plate? Did you round the top and bottom edges with a diamond wheel?

I made a wear plate from 440c many years ago. I machined a radius on the edges to form a radius at the plunges and help with my sweeping grinds. It is fully hardened and not tempered. While it's not perfect it has not worn significantly in the last 20 years. But it does get hot and belts, especially the finer grits, wear very quickly. Been thinking about upgrading.

Thanks,

David
 
OK
Ed,
How thick should the glass be? Thicker the better , thinner the better, or it doesn't matter.
I have some 1/2" thick A8 that I'm making one out of now so what size glass should I get for the next one?

Thanks,
 
Tracy has ceramic platen liners. They are not the same as glass. I have a 9" platen and a 14" platen, both with liners I got from Tracy. No problems whatsoever. I beadblasted the back surface and the platen itself and glued it on with JB Weld. I rolled all the edges using my grinder. You don't have to worry about the cracking when rounding the edge like you do with glass.
-John
 
John Barker said:
Tracy has ceramic platen liners. They are not the same as glass. I have a 9" platen and a 14" platen, both with liners I got from Tracy. No problems whatsoever. I beadblasted the back surface and the platen itself and glued it on with JB Weld. I rolled all the edges using my grinder. You don't have to worry about the cracking when rounding the edge like you do with glass.
-John
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Right, You need to use ceramic fireplace glass, That is what Tracy Sells.
http://www.usaknifemaker.com/store/...nds-grinder-parts-contact-wheels-c-99_60.html
 
You folks are about to learn just how "fugal" I try to be! :eek:

I used the Pyro-Ceram initially. I found it to work well, but I thought it was a little pricey and looked for alternatives. The ceramic is good, but I personally think that tempered glass is better. The ceramic does groove up after a while, especially if you do a lot of flat grinding on the platen. I also think the ceramic builds up heat more so than the tempered glass.

Once when I was teaching a class at Lyle Bronkhorst's place in Seattle, he was going to trash an old display case, that had 1/4" tempered glass shelves. I heard all the stories and such about not being able to "cut" tempered glass, but what did I have to loose? I tried, and it worked. I stayed after class one evening and turned 3, 1/4" tempered glass shelves into 2" strips. (I got 26 pieces of 2" X 12")...all for free. Between giving some away and using others, I'm down to about 6 left.

My Mom is big into stained glass, so I have access to a glass grinder any time I want to use it...which is how I radius the lead in/lead out edges....and have even dressed the edges of the glass to suit my needs.

Concerning thickness, my opinion is that anything less than 1/4" glass is too fragile for the application....I tried 1/8" glass once, and it cracked when I was pony clamping it to the platen when gluing it on. The thing to keep in mind is that you should use the thickness that allows you to adjust the platen face in/out, so that the platen face is sticking out SLIGHTLY further than the faces of the contact wheels with a belt in place...thats the big reason for rounding the lead in/trail out edges/ends of the glass.

David: In my experience the glass will somewhat solve the belt wear issue, simply because there is less heat buildup on the belt. When I was using a steel platen face, there were several instances where it got hot enough to literally melt the glue on the belt joint.....that made for exiting adventures! :eek:

The glass on a platen face is just like anything else we do...we have to learn how to work with it, from applying the glass to the platen face, to learning the ins and outs of using it for grinding.
 
Great thread, thanks gents!

Any tips on making sure the existing platen on my 2x42 is flat before I attempt to mount a new face on it? It has a couple grooves that are clearly noticeable to the naked eye, as well as general wear.
 
james terrio said:
Great thread, thanks gents!

Any tips on making sure the existing platen on my 2x42 is flat before I attempt to mount a new face on it? It has a couple grooves that are clearly noticeable to the naked eye, as well as general wear.
Click to expand...

Take it off and grind it flat on your flat platen:p
 
james terrio said:
Great thread, thanks gents!

Any tips on making sure the existing platen on my 2x42 is flat before I attempt to mount a new face on it? It has a couple grooves that are clearly noticeable to the naked eye, as well as general wear.
Click to expand...

Yo James,
If it's a Craftsman, get a brand new one. I forget exactly how much I paid for the last one I got specifically to use with a tile cover on it (Lowes - $2.95 for the tile), but it was almost surely less than $20 including shipping. I've used this set-up for the past 2 years and it still is true flat and has no grooves in it at all, and the belt runs much smoother than with the original platen. I did the same thing on another 2x42 Craftsman 6 years ago and it's still working fine.
Good luck!
Bob
http://www.bobroseknives.com
 
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