Catastrophic Glass Platen Failure

M

Mobius1

Joined
Feb 15, 2016
Messages
133
I am damn glad I am a stickler for PPE, because my glass platen decided to do something crazy on me!

I was grinding a bevel on a knife, and suddenly part of the glass platen broke loose, and the shattered glass went around with the belt, and was flung straight into my face. I wasn't hurt thankfully, but boy was that not something I expected would ever happen. It broke right at about the point I normally grind at, and from that point all the way down, it all came loose.

I had it mounted quite well with epoxy and a support lip, so I am wondering if maybe it was a defect in the glass that caused it to break? Or maybe me using a Kool Mist system somehow weakened the epoxy over time?

Has anyone else ever had a platen shatter on them?
 
Mobius1 said:
It broke right at about the point I normally grind at
Click to expand...
Never had one shatter like that, but I'm on my second one now and both this one and the first one developed a crack right where my tool rest lines up. I think this is from being less careful than I should when putting the tool rest arm in the grinder and banging it against the platen.
 
I am glad that nothing happened. Were you wearing a face shield?

Another reason to go for hardened steel platen bolted to the grinder.
 
Mobius1 said:
I am damn glad I am a stickler for PPE, because my glass platen decided to do something crazy on me!

I was grinding a bevel on a knife, and suddenly part of the glass platen broke loose, and the shattered glass went around with the belt, and was flung straight into my face. I wasn't hurt thankfully, but boy was that not something I expected would ever happen. It broke right at about the point I normally grind at, and from that point all the way down, it all came loose.

I had it mounted quite well with epoxy and a support lip, so I am wondering if maybe it was a defect in the glass that caused it to break? Or maybe me using a Kool Mist system somehow weakened the epoxy over time?

Has anyone else ever had a platen shatter on them?
Click to expand...
Give us some pictures................we enjoy playing detectives 🔍
 
How big a support lip did it manage to bypass when it shattered?

Glad to hear you weren't hurt!!! Must have got the pulse going!
 
I'm on my fourth or fifth pyroceram and apparently consider them dsposables as there were two more in storage in my materials cubby when I went through it recently. They don't last forever before they crack, especially if it's used for general things like jamming a corner of barstock in it to break a corner instead of just grinding bevels. That's how glassbreakers work, too, so I'm not surprised I break 'em.

Glad you weren't hurt. What we do is dangerous, and needs vigilance. Now you're more vigilant and don't have to wear a scar to remind yourself.
 
Last edited:
Ok ... now I’ve GOT to get a full face shield. Safety glasses sound like they are just not enough.

I’m also taking note that your platen had a lip on it. That is *supposed* to keep a loose glass from slipping down...
 
What epoxy were you using? I don't use any lip on my pyro cream and never had an issue. But I grind wet and normally less than 50% speed. The jb weld does amazing. But I wear a 3m faceshield papr helmet when grinding as well.
 
I change mine out about every six months or so. I've never had one break. I use JB Weld and do have a lip. I do use em hard. Glad it worked out for ya.
 
I use hardened D2 platens. I keep three of them around. When it wears I flip it over. When that wears I use another one. When they're all worn I put them on the surface grinder and they're as good as new. I've been using the same hard steel platens in production for years. I personally don't understand the wide appeal of glass platens. They make sense for some people, I know, but I would think that hard steel platens would be more popular with knifemakers. We all work with steel, heat treat isn't mysterious and surface grinders are pretty common. Why isn't hard steel the norm?
 
The lip was about 1/8"....probably not big enough in retrospect. The epoxy was Gorilla Glue 10 minute. I also should add that I do grind at full speed (about 4k RPM's I believe) most of the time I am using a ceramic belt.

I actually didn't have my platen for long. This was maybe the 4th knife I ground on it. I do run my belt very close to the platen, but it was the bottom of the platen that came off, not the top, so I don't think that could have had anything to do with it.

I went with glass mostly to see how well it held up compared to steel. I wish I had a surface grinder, but I don't! (Speaking of which, if I did decide to get a surface grinder, where's a good place to start?)
 
The gorilla glue 10 min is good to around 180 degrees according to the mfg. That may be why it let go! The JB Weld is good to over 500 degrees IIRC?
 
Nathan the Machinist said:
I use hardened D2 platens. I keep three of them around. When it wears I flip it over. When that wears I use another one. When they're all worn I put them on the surface grinder and they're as good as new. I've been using the same hard steel platens in production for years. I personally don't understand the wide appeal of glass platens. They make sense for some people, I know, but I would think that hard steel platens would be more popular with knifemakers. We all work with steel, heat treat isn't mysterious and surface grinders are pretty common. Why isn't hard steel the norm?
Click to expand...
I keep hoping they'll come up for sale on your website. In the meantime I'm grudgingly planning to make my own. I'm procrastinating since I'm hoping to get a whole new grinder soon...
 
I should add that I sandblast and degrease both surfaces before I mate the glass to the platen. holds up great.
 
Taz said:
The gorilla glue 10 min is good to around 180 degrees according to the mfg. That may be why it let go! The JB Weld is good to over 500 degrees IIRC?
Click to expand...
Oh man, you are probably right! That is almost certainly what must have caused the failure. Stupid mistake on my part to not check that.

I do use the Kool Mister when I am grinding bevels, but when profiling and such pre-heat treat, I don't bother with it since I always stress relief. I definitely get it WELL beyond 180 degrees! :D
 
Suggest hardened, 1/8" precision ground D2. Secured to the regular steel platen with JB Weld and two brass pins acting as a shelf (same technique as glass). As Nathan suggests, turn over and use the other side when worn.
Saludos
J
 
You must log in or register to reply here.
Back
Top