Ceramic platen liner question

[BARKER]

I was just tapering the tang on a knife. I was using the new ceramic platen liner I just JB welded on Thurs. night. I notice after tapering the tang on this knife that the platen has a crack all the way across it about 5" down from the top of the platen. Am I screwed? I'm thinking I should replace it. Anyone have this happen to them, what did you do? Thanks.

-John

[Mike Stewart]

John,

I have never heard that happening.

Were You using a push Stick ?

Is it possible that you platen underneath has a divot in the same Spot ?

Mike

[tmik]

My first glass platen was safety glass. It cracked all up and I continued to use for at least a year with no problems.

[BARKER]

Thanks guys for the posts. I've been hearing this happens frequently.
-John

[stephanfowler]

I've been using a ceramic platen for almost a year now and never had a problem with it, but I also bedded the entire thing in with JB so maybe that helped

[Pmlknives]

I've tried the pryo ceram and its hasn't worked out for me. Either with JB or super glue every time it has cracked. I don't know if it's the heat or what. I'm running at 1700 rpm so I didn't thin heating would be a problem. I hear RJ just uses regular tempered glass and if it breaks who cares right? Just a cheap peice of glass. I found it easier to just hardened a peice of O-1 and use that with no temper. Been using that for about a year now.

[stephanfowler]

shoot, I use a 3200 RPM 1.5 horse on the 2 to 1 pulley all the time for flattening and I've never cracked one (and it does get pretty warm)

[DomBunn]

Stove shops have a ceramic glass that works great cheap. Wood or pellet stoves even the glass in a electric range is the good stuff. High temp ceramic.

Stevens mentioned a bed of JB weld is how I attached it. It may be the trick to not cracking it. I have cut a plate for the KMG but have not put it on yet.

I have one on a Grizzly for 4 years now even though it is now only used for flat grinding bar stock no bevels any longer. Db

I like the HT O1 that sounds awesome with a polished finish should'nt wear belts fast?

[Danbo]

You've gotta make sure the existing flat platen underneath is flat, before epoxying the pyroceramic platen on.

[joelbolden]

The only time I've had a pyro ceram platen crack on me is when I was JB Welding it to the steel platen and clamped it pretty hard....cracked. The stuff is really wear resistant, but it's brittle also.

[RJ Martin]

Barker: Float a piece of 1/4" thick plate glass in a pool of Green Zap. push it down with your finger (lightly) Then hit it with kicker along the edges. Then wait for it to cure up.

It's the flattest, cheapest, easiest way.

If you taper your tang by hollow grinding the trough, and create the initial flats on a NEW belt before HT, you will be able to clean it up with a NEW belt after HT in a matter of seconds. If the trough is deep enough, the flats will literally be about 1/8" wide around the edge of the handle and there will be little effort required to sand them flat.

Everyone wants to lean into the flat platen HARD. What they don't understand is that the belt will actually stretch under the work, and won't stay flat. And, the tang will deflect, again defeating the purpose of your nice flat platen.

Go slow, use light but firm pressure, and (always) new belts and the glass platen will give you the flattest tang ever.

[BARKER]

Thanks for the advice RJ. Can you tell me where I should look for plate glass? Should I be able to get it from just a glass store? I'm with you on the new belt thing too.
-John