Ceramic Platen cracked quickly, ideas?

pwheeler

pwheeler

Joined
Dec 30, 2013
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I got the ceramic platen from USA knife maker, and built a whole new platen head to accommodate it. The backer is a piece of 2.5x2.5 angle iron, that I milled to match the width of the ceramic. I milled the face to be flat and machined in a lip to sit under the platen, attached with JB weld. After about 3 days of use, it cracked horizontally while doing a flat grind. I don't see how I could get the steel any flatter than it is, any ideas what could have gone wrong?
 
I've had this happen a couple of times. First time was when I went to assemble the platen to the brackets and theI tightened the bolts to hard and cracked the glass, this was because the jb weld leaked into the hole and as I tightened it it pushed the glass. I fixed this by masking the hole next time.

I also had it crack a couple other times for no apparent reason. The two I have on now have been holding up for a couple months...
 
Could some of the JB Weld have been uneven? Possibly creating a fulcrum.
 
For sure, if the JB weld was uneven this would happen or if you were using a "ceramic tile" like many are now doing and it was uneven on the back.
Frank
 
I think ya did too good a job there. I just glued one the a piece of angle iron with no milling or grinding & used 5 minute epoxy. This was 15-20 years ago ....
 
Did you clamp it when it was drying or just let it sit there?

Also, as pittknife pointed out, what did you do about the bolt holes and are you sure your machine screw are short enough to not impact the glass?
 
razor-edge-knives said:
Did you clamp it when it was drying or just let it sit there?

Also, as pittknife pointed out, what did you do about the bolt holes and are you sure your machine screw are short enough to not impact the glass?
Click to expand...

I did clamp it, I will not do that next time. No bolts on mine, just glue and a lip to rest on at the bottom.
 
pwheeler said:
I did clamp it, I will not do that next time. No bolts on mine, just glue and a lip to rest on at the bottom.
Click to expand...

Ok. That was the issue I'm sure of it... I've made 3 or 4 and not clamped them and have never had an issue.
 
FWIW, I've used 3m exterior grade double sided tape, and have never had an issue. I do have a ledge, and I make sure to thoroughly clean all surfaces. I put one piece on the glass and firmly press, and then one piece on the platen, same thing. Finally, peel the paper and stick together, tape to tape. Two pieces probably aren't necessary, but I figure it gives a little extra buffer for any small irregularities on the surface. In the years I've been doing this, I've never had one move, much less try to come loose. That's also despite the platen backer getting too hot to comfortably touch after extended periods of grinding.
 
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