Replacing A Glass Platen

Randy Lucius

Well-Known Member
When I made my first flat platen I used JB Weld to attach the glass. Time to replace it. Is there anything better that's maybe not so messy?
 
we use a propane torch to soften the JB weld, carefully peel it off and flip it over to use the back side.
 
Not really the JB weld works about the best. To remove use a heat gun once you peel off the platen glass. The remaining JB Weld scraps off fairly easy!! If you get an area that is stubborn warm it with a heat gun again!! Lightly sand, and blow off the dust and wipe with alcohol! Your good to go again!!

When you lay the new glass all you need is a bed of the JB weld. JB Weld will not adhere well if you squeeze all of it out!! Clean the excess now and when you change again all you should have is a thin bed to deal with!! A lot will pop of with the old platen! Oh, and wear eye protection I have had them pop when removing!!
 
Out of curiosity, how long does a glass platen last? Does it eventually dish out? I have one, but haven't attached it yet. Still trying to decide on the method to use (straight epoxy, or add a small shelf).
 
Out of curiosity, how long does a glass platen last? Does it eventually dish out? I have one, but haven't attached it yet. Still trying to decide on the method to use (straight epoxy, or add a small shelf).

Mine is at least five years old. I only used JB Weld, no shelf.

To compare, my first steel platen lasted 6 months without glass. There is no comparison in longevity. The glass made an immediate improvement on my grinds.
 
For me it's not the dishing out but wearing on either end. I heard a lot of makers say the ends don't wear on their glass. I don't think they measure as tight as I do. Or something. Most of us buy our glass in the same places. I can't be the only one to see this.
 
For me it's not the dishing out but wearing on either end. I heard a lot of makers say the ends don't wear on their glass. I don't think they measure as tight as I do. Or something. Most of us buy our glass in the same places. I can't be the only one to see this.

That's all the wear I see for the most part. The top and bottom edge get worn into a radius by the belt. I don't know how it wouldn't do that. (?) Anyone whose glass isn't wearing at the top and bottom must not be extending the platen out beyond the rollers. I've always done that. For one it keeps the belt running flatter and also because I do a lot of vertical grinding.
 
I bought 2 glass platens but havent fitted one yet. Had intended to screw a shelf under it.
I have my present platen only a 1/16 proud of the top wheel. How much are the rest of you setting them out.
 
I have a KMG. When I replaced the glass platen, I just put the platen/glass in the oven at 450 degrees until the JB wled heated up long enough to take off the old glass with a wood chisel. It came right off once the JB weld heated up enough. A bit sticky and gross but it came right off.
 
I don't think I've ever "worn out" a glass platen. Normally I have to replace it because I've done something dumb....like drop it on the concrete floor, or smacked it against something and chipped or cracked the glass.

The most important thing that I can add to the conversation is the mounting surface for the glass..... two things.... it must be FLAT, and roughed up enough to allow for a good "grip" by the adhesive.

OH! Another thing is clamping..... don't over do it! Several times I've seen folks "glue" the glass to their platen using too much force on the clamps.....and they basically squeeze all the adhesive out.....and the glass let's go during its first use.

I'm a proponent of having a "shelf" supporting the bottom edge of the glass..... only because I didn't do it at first, and ended up with the glass trying to go between the belt and bottom wheel of the platen. It shattered, and Cindy was picking little hunks of glass outta my face for a week! o_O
 
I broke the first glass I tried to put on my platen and simply heated up the Platten with a torch and was able to work the glass off with a flat head screwdriver and a hammer
 
Normally I have to replace it because I've done something dumb....like drop it on the concrete floor, or smacked it against something and chipped or cracked the glass.
Yep. I dropped the platen and cracked the glass. I had an extra one ready to go so I just swapped it out. The extra one has radius edges. Would there any advantage to have one with "radius" edges and one with "square" edges? I need to get another piece of glass on order.
 
I’ll just copy what I recently painted in another forum:
I like exterior grade double sided carpet tape. I get the 2" wide "Duck" brand IIRC (it's more like 1-7/8"). Make the steel backer as flat as possible with a 1/8" thick ledge on the bottom. I clean the glass and steel really well (denatured alcohol works), then I put a piece of tape on the back of the glass (full length, trim flush) and one on the front of the steel backer. I do a full length piece of tape on the glass AND the steel just so I can make sure I get full adhesion across both. Then it's just a matter of sticking the two taped sides together. In all the years I've been using the tape, I've never had one fail or move at all, and I've had the steel backer hot enough that I couldn't hold my hand on it for more than a couple seconds.

As for removal, a torch and a putty knife pops it off relatively easily, and acetone or denatured alcohol cleans it back up again. Just a note: if you use acetone, make sure you clean the film/residue that it leaves behind. I normally just hit the parts with a torch to burn it off before I put my tape on.
 
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