Ceramic Glass Liner for Platen

Self Made Knives

Well-Known Member
Well, guys I did it. I got the glass from Boss and video'd the install. Tried to throw in a couple tips here and there. Let me know what you think.

[video=youtube_share;lfkf0bVQcu0]https://youtu.be/lfkf0bVQcu0[/video]
 
Thanks guys. If any of you have been using a glass liner for a while can explain the "feel" or why it works better, please share. I like the way it feels and it is different, but its hard to describe. The one test blade I ground, seemed easier to grind. A few people have already asked me what I think and I tell them, "Yes, I like it. But, I don't know why." :biggrin:
 
Thanks guys. If any of you have been using a glass liner for a while can explain the "feel" or why it works better, please share. I like the way it feels and it is different, but its hard to describe. The one test blade I ground, seemed easier to grind. A few people have already asked me what I think and I tell them, "Yes, I like it. But, I don't know why." :biggrin:

The simple answer, as far as I can tell, is "less friction". It's going to be much smoother and harder than angle iron, and belts just seem to travel over the glass easier. Another happy little byproduct is less heat. :)

When I built my first grinder, I used a piece of 3/8" thick x 2" wide hot roll flat bar for my platen, and attached that via a piece of angle iron. Unfortunately it seemed to start wearing almost instantly, and the wear marks were transferring to my flats. It didn't take long for me to jump on the glass liner wagon.
 
Something I didn't predict or know about, static electricity! I kept getting a tingle while grinding and started thinking something was wrong with my grinder wiring. After thinking about it a while, I guess there is a static charge building up on the glass. When I go into the plunges for a grind, I use the side of the platen as a rest or stop for my fingers. Zap! Only happens when I touch the edge of the glass, so... Weird.
 
I get the zap, too. If you think about it the belt is charged and separated from the platen by an insulator (the ceramic glass). That is the definition of a capacitor. Not a big one, of course, but enough that when you get near enough to the platen you get the whack as you discharge to the platen. It's worst for me when using scotch-brite belts.

I do like the glass liner a lot. I don't notice a ton of difference in grinding feel- but the flatness of my bevels improved dramatically when I added the glass liner and there is a lot less heat buildup. The glass is holding up a whole lot better than my steel platen alone, since the glass doesn't dish and groove like mild steel. It's also nice that the goo from belt backing can be scraped off with a razor blade pretty easily.

I didn't make a shelf for mine. JB Weld has held it for however long it's been on there now. I coated the platen with JB Weld like I was frosting a cake and then let the glass lie on it to cure. That's a whole lot of JB Weld that will have to let go at once. Maybe it will... I guess it has to some day... but so far so good.
 
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I was afraid of the ZAP thing, but mine doesn't sting me since i installed the glass platen...never!
I wonder why, maybe my grinder is connected to earth, since the motor shell is and it is bolted to the grinder frame instead of on a wood base?
 
Stezann, I'm sure you are correct. The zap I get is so small that I don't care about it. But a good grounding / bonding strap to earth ground should eliminate the problem, or at least greatly reduce it. There will always be some static on the belt that doesn't dissipate well through the the bearings, but not enough to really matter. I suspect people in very dry climates get the zap more than others. Here in Florida, where we are almost breathing water, the zap is so small it is not even as bad as pulling a shirt from the dryer.
 
My grinder is all steel. The frame, motor, and vfd are all grounded just fine. That's why it zaps you, the grinder is well grounded and the glass is insulating the charge. When you touch the grounded platen at the same time as the edge of the glass, zap! Even better, my hands are usually damp from quenching the blade, so the electrical connection is even better. Like John said, just a tingle. After I realized what it was I barely notice it now.
 
Same here. Wet hands and standing on rubber fatigue mats for my back. perfect combination to be a human static arrester when my hands go near the steel platen. It really isn't a big deal, but it does take you by surprise the first few times.

Static is a very curious thing, and not nearly as simple to explain or deal with as people believe. In manufacturing, we fought static at every turn. Machines running plastic film or bottles have static issues that will make you pull your hair out at times. Entire industries have sprung up to deal with static because it is not nearly as straightforward as people think. In fact, almost everything I'd ever been taught about static turned out to be wrong, or at least incomplete, in actual practice. Very similar to lightning, it simply acts in ways that don't always offer a clear explanation or solution.
 
Guess we're veering off into a different subject, but what the heck. When I was in the USMC, I worked avionics on F18 Hornets. The planes were always kept grounded on the flight line to an underground grid. One night in Hawaii, I went out to troubleshoot a FLIR pod and didn't notice in the dark that somehow the plane was not grounded. I opened an access panel and reached in to unscrew a big 50 pin plug, kapow! A huge static discharge, lit up the night like someone shined a flashlight in my face. I knew the planes would build up a charge, but that night, I learned just how much. Always checked grounds after that!
 
I've not really felt the need to try it, but I hear that some anti-static spray (as in for laundry) works well to keep the charges down. Just spray a little on the belt, and repeat as necessary.
 
Curious phenomenon, so you have found that you are actually "arching" the glass to its steel substrate? I have not noticed it in my setup, maybe my glass touches the steel in some spot through the glue film...i really don't know

Or, since i rest my hands on the steel workrest there is not zap since i'm continuously conducting the charge as it forms, before it accumulates enough to shot
 
Well Anthony, you've inspired me, I have the exact issue with my platen, drives me nuts. I've tried a piece of granite which was smooth but I failed in that I used the factory cut edge for the right side(which has a small bevel) and the side I cut with my diamond saw for the left(which was a direct 90'.) I will need to try this! One thing I can say since I've had the granite on I don't notice any heat build up at all as compared to just the angle iron(hot fingers, lol). Your a natural in front of the camera though, keep up the videos, I learn a lot. Been busier that a one-armed paper hanger here, and not with any knife related stuff, just my job, so I haven't had much time for knives but I was just wondering how that new old surface granger was working out for you?? Thanks for the info!

Wayne
 
Thanks Wayne. Yeah, I'm really liking the ceramic liner from Boss's store. I'm getting much flatter results now and my plunge line's shape matches a whole lot better. Here's a pic of the first one finished on the glass, maybe you can see what I mean. As for the surface grinder, you know me, I can't leave anything alone. I don't really like the grinding stone finish. I also don't really like how long the stone takes to coast to a stop. So, I've got it all tore apart now, going to put a VFD on the spindle so I can adjust the speed and it'll stop when I press stop instead of freewheeling. I'm going to convert it to run belts too, that way I can get any finish I need with my existing belts. Another project, just what I need....
DSC06283.jpg
 
A ceramic liner makes a huge improvement over a metal one.

you get significantly less friction and heat as a result.

They will wear and need to be replaced every so often. Simply use a torch to heat the glass until the epoxy fails.

JBweld has the highest heat rating of any epoxy I could find so that is all I would use. When this glass liner thing all started, people were using all different kinds of epoxy and double stick tape with catastrophic failures.....Imagine the glass coming loose when a grinder is running wide open. Not good.

a support ledge holding the glass in place is a good idea.

Once installed, you have a great static electricity generator! Keep a can of Static Gaurd laundry spray handy . Spray the inside of the belt and all around the wheels when it's dry and throwing static shocks. It will knock it down to nearly nothing just like magic.

You can can sand the edges just like a metal bar to eliminate any sharp edges from cutting the glass.

I have tried regular glass, tempered glass and safety glass. All failed. High temp or fire place glass is all I have had good luck with. Your mileage may vary.

Its really important to not clamp the glass when laying it up on your platen with JBweld. Use tape. A clamp will slightly bend the glass and set up stress when the glass bonds to the platen as the epoxy cures. When it gets used and hot, the stress built up from clamping during the install cracks the glass. It took me three installs to figure that one out. I am a slow study some days.
most days probably.

t
 
Hi Tracy,
i agree about clamping!! I used light spring clamps just to avoid any sliding and to keep it in place without it rocking on the glue bed, but the tape may act as clamp substitute.
What do you mean by failing when you used other than HT glass? Did they break?

Actually my main concern it is when i remove to put aside the platen arm...the sides of the platen are the weak points. A bump on the side of the glass may crack it very quickly
 
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