Adhesives for holding "Glass" to platen

EdCaffreyMS

EdCaffreyMS

"The Montana Bladesmith"
Hey Gang! I just had an almost catastrophic experience.

Last time I applied "glass" to a platen, I remembered reading here on the forums that someone had done it with JB Weld, and decided to give it a try versus using Acragls as a normally do. Didn't work out so well for me! I ground 7 EBKs today, and when I was changing from 50 to 120 grit belts..... the glass literally fell off the platen, and just by reflex I caught it! Had it not been for the little "shelf" that is built into the bottom of my platen face, that glass would have been "sucked" down between the belts, and 3" wheel at the bottom of the platen!!!!
Last time that happened was years ago, and Cindy was picking glass outta my face for a week!

SO......IF YOU HAPPEN TO USE JB WELD TO HOLD GLASS TO A PLATEN FACE.......BEWARE!! Luckily, no injuries, I save the glass, and cleaned up everything, and it's now sitting on the bench, glued on with Acraglas, and waiting to cure.
 
EdCaffreyMS said:
Hey Gang! I just had an almost catastrophic experience.

Last time I applied "glass" to a platen, I remembered reading here on the forums that someone had done it with JB Weld, and decided to give it a try versus using Acragls as a normally do. Didn't work out so well for me! I ground 7 EBKs today, and when I was changing from 50 to 120 grit belts..... the glass literally fell off the platen, and just by reflex I caught it! Had it not been for the little "shelf" that is built into the bottom of my platen face, that glass would have been "sucked" down between the belts, and 3" wheel at the bottom of the platen!!!!
Last time that happened was years ago, and Cindy was picking glass outta my face for a week!

SO......IF YOU HAPPEN TO USE JB WELD TO HOLD GLASS TO A PLATEN FACE.......BEWARE!! Luckily, no injuries, I save the glass, and cleaned up everything, and it's now sitting on the bench, glued on with Acraglas, and waiting to cure.
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Glad you're ok, Ed. Safety first...specially when it concerns glass and centrifugal forces!
 
Wow...glad you're OK. I used JB Weld on my glass platen and it's held successfully for over a year now. I smeared it on as thick as I would a peanut butter sandwich. And I like peanut butter. I think I let it cure for about three days if I remember right.
 
I’ve used JB without any problems but I put it on pretty thick. Might have just gotten lucky. The last one I mounted I used some Scotch extreme mounting tape. I took that off to change glass the other night and had to torch it off. And I mean I had to get it smoking hot before it would come loose This is what I’ll be using from now on. Alot less messy than JB Weld.
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I've had good luck with Duck brand exterior grade double sided carpet tape from my local big box store. Every once in a while I'll give the glass a side to side wiggle while changing belts, just to make sure nothing has let loose. So far so good.....

VHB tape is good stuff too.
 
Randy Lucius said:
I’ve used JB without any problems but I put it on pretty thick. Might have just gotten lucky. The last one I mounted I used some Scotch extreme mounting tape. I took that off to change glass the other night and had to torch it off. And I mean I had to get it smoking hot before it would come loose This is what I’ll be using from now on. Alot less messy than JB Weld.
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That is the same stuff I use as well...I had a glass platen crack in the middle and had to replace it after 2 years of having that tape on there...it took me hours to get it cleaned off enough to put the new platen on.
 
I must be doing something different than everyone else. Tape of any kind will not hold for me. I've tried both what Drew and Randy mentioned, and it came loose within a few minutes, I suspect from heat build up/melting the adhesive. Based on my experiences with any kind of double backed tape, it's not for me. The only thing that has reliably held glass to a platen for me is the standard Acraglas. Just goes to prove that things are hugely different, condition wise, from shop to shop, and what works well for one person in their own shop, may not for another.
 
Interesting. I remember getting my mild steel platen backer so hot that I couldn't comfortably touch it for more than a few seconds, and never had an issue with the tape coming loose. It did get "softer" to be sure, but was still quite tacky. Full disclosure, my backer is very flat and roughed up, and I typically use two pieces of double stick tape so that I can get a good bond. When I apply the tape, I clean my backer with acetone or denatured alcohol, very well, then hit it with a torch to burn off any film or excess debris that may have stuck while wiping it down. I'll then apply the tape with the tape lining still on, and use something hard, flat and smooth to "burnish" the tape onto the backer. This smooths out any air bubbles and makes sure that the bond is even throughout. I repeat this process with the glass liner, then remove the lining from each piece of tape and stick both pieces together.
Then I take a 2 lb hammer and aggressively smack the glass liner into the platen backer. Just kidding.
I just press firmly up and down the length of the platen and that's usually all she wrote until the platen wears out. Removal is as simple as heating a thin metal putty knife and carefully prying it loose.
 
Drew Riley said:
Interesting. I remember getting my mild steel platen backer so hot that I couldn't comfortably touch it for more than a few seconds, and never had an issue with the tape coming loose. It did get "softer" to be sure, but was still quite tacky. Full disclosure, my backer is very flat and roughed up, and I typically use two pieces of double stick tape so that I can get a good bond. When I apply the tape, I clean my backer with acetone or denatured alcohol, very well, then hit it with a torch to burn off any film or excess debris that may have stuck while wiping it down. I'll then apply the tape with the tape lining still on, and use something hard, flat and smooth to "burnish" the tape onto the backer. This smooths out any air bubbles and makes sure that the bond is even throughout. I repeat this process with the glass liner, then remove the lining from each piece of tape and stick both pieces together.
Then I take a 2 lb hammer and aggressively smack the glass liner into the platen backer. Just kidding.
I just press firmly up and down the length of the platen and that's usually all she wrote until the platen wears out. Removal is as simple as heating a thin metal putty knife and carefully prying it loose.
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You only use a two pound hammer?
 
I have used the original formula JB Weld as well as the UHB Tape- both worked as desired. My current glass has the JB- has been solid for the last 6 months of use.
 
I’m firmly in the peanut butter crowd. JB Weld doesn’t appear to hold well if it’s thinner than 1/16 inch. But double that thickness and I can’t break it loose with a sledgehammer. My glass platen is holding on so far at about 5 years, with no shelf (i like to live dangerously). The glass is even getting worn and pitted. I have been meaning to replace it and I don’t even think I want the hassle of trying to separate the glass. I think I’ll just get a new platen and glass and save this old one as a spare, for God knows what.
 
After reading the posts referencing apply JB Weld like "peanut butter'.... that was likely my fatal mistake..... I DID NOT apply it like that....but rather like Acraglas..... very thinly.... so another lesson from the forums! Gosh I love this place, and all you fine folks!!! ;) I do know that cleaning the platen face of latent JB Weld, was a real bugger! It laughed at my blast cabinet/AO media. I acetoned and scrapped, acetoned and scrapped.....and after exposing some bare metal, and spending a bunch of time in the blast cabinet.....managed to clean all the JB Weld off..... so that whole time I was pondering the question of why it had let go. I have several platens with glass on them, and am gona make it a point to try the "Peanut Butter" application method with JB Weld, at the next opportunity!

Do you think you just built up that much heat?
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I'd bet dollars to dog biscuits that's the cause!
After doing this for so many years, I tend to get as aggressive when rough grinding, as this old body will do, and that generates a lot of heat, even with the "glass" in place.

That incident that I spoke of in my opening post....about the glass being sucked between the belt and bottom contact wheel, happened with double backed tape.... and I was too green back then to know or consider that "little shelf" at the bottom of the platen face, and paid the price with carrying shards of glass around with me....until Cindy could find/pick them all outta my face! Why mention this again.... to drive home the importance of..... IF YOU USE GLASS, NOT ONLY SHOULD YOU USE A GOOD ADHEISVE, BUT FOR SAFETY SAKE, MAKE/INSTALL A "SHELF" AT THE BOTTOM OF THE PLATEN FACE, TO REST THE BOTTOM EDGE OF THE GLASS ON!
 
I use JB weld with a shelf. When I wish to change the glass I simply lay the glass on a board and heat the back of the steel platen with a propane torch. Comes right off. I scrape the JB off while the platen is hot. I turn the glass over and use the other side.
 
I was just watching a video on adding glass to a NorthRidge platen since I hadn't done it in several years for my old KMG and it appears that they recommend gasket bonding RTV. Hmm... They also nicely drill and tap a couple of holes for a little shelf on the bottom of their standard platen.

Not doing it right now because I'm more likely to just use the Nathan the Machinist A2 platen I was using on the KMG for now.

After saying all that, maybe I should admit to my retirement present to myself:

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