Replacing my glass platen

weo

weo

Joined
Sep 21, 2014
Messages
3,111
Hello all. The ceramic high temp glass I JB welded to my platen 2+years ago has finally cracked to the point where a groove is showing up on my blades when I grind pulling the blade across the belt while using the tool rest that I'm having to deal with by grinding with the blade held vertically on the platen without the rest to smooth out the blank (so I'm starting to grind freehand).

I'd like to put another ceramic glass platen on and would like to just JB weld it on top of the other one. This will solve a couple other design flaws with the OBM grinder.

Does anyone know if it's possible or not to do this? (JB weld another ceramic glass platen right on top of the one that's already there.)

Thanks
 
Sure it's possible.... Would I do it? That depends. I'd probably at least want to rough up the glue bearing surfaces first, and personally, I like a ledge under the platen for safety sake. I know there are a handful of makers that use only JB weld and no ledge, without issue, and I suppose if it holds the back side of your first platen, it should hold the back of the second as well. One might say with 2 jb welded surfaces that it'll stick twice as good, while other's might say that twice as many places for the adhesive to fail and blow platen glass all over the place.

What issues will this solve with the OBM grinder?

On my platens, I just use double stick tape with a safety ledge under the glass, and when it comes time to change them, a little heat, a putty knife, and some acetone makes it a quick job. If it were me, I'd probably modify the platen so that I didn't need the second piece of glass, but again, I'm not quite sure what you're trying to solve yet. At any rate, once that JB weld cured, I'd want to make sure it was stuck for good, if that's the route you take...
 
knife to a gunfight said:
I'd probably at least want to rough up the glue bearing surfaces first
Click to expand...
That was my plan...

knife to a gunfight said:
What issues will this solve with the OBM grinder?
Click to expand...
The way the platen and arm is designed, there's no way to use a filing guide on the left side because the welds get in the way. With the extra glass, this should push the belt out enough to give clearance.
Also (although this may be a grinding issue with me and not a design flaw) when holding the blades vertically on the platen to flatten out my grinds, there's not quite enough clearance between the top wheel of the platen arm and the glass to prevent me from occasionally (well, frequently) grinding the distal knuckle joint of my index finger when holding onto the hidden tang and grinding towards the riccasso and this doesn't feel good at 36 grit. (Although I kinda solved this today by thinking to use a pair of needle nosed vice grips to hold the tang...so the vice grips hit the top wheel instead of my fingers.) Getting the platen to stick out a bit more should help this.
And it should give me a bit more of a slack belt area here.
 
How about another Platen thick enough, then the glass to bring it out far enough so you can grind on both sides and vertical??
 
Assuming you have the standard OBM platen, is your first platen liner JB'd directly to the right angle bracket? Or do you have the mild steel platen still bolted underneath?

Personally, I'd just get a steel backer at the dimensions I needed, bolt that to the bracket, and then stick my glass liner to that. And (at the risk of sounding repetitive), I'd include the safety lip/ledge in the event that my adhesive failed.
 
Thanks for the thoughts and ideas all. I'm not sure what I'll do yet, but I'll let you know (life is getting in the way today....)
 
Something to consider; glass does not transfer heat well so if you put two layers of glass together atop the steel platen the heat build up will increase over what you had with a single layer of glass.
I was able to find a half inch thick piece of copper to place behind the glass platen liner when I replaced it the last time, thinking it will move a lot of the heat coming off the moving belt.

The platen can be removed and placed in an oven at 500 degrees, which will break the bond of the JB weld.

Fred
 
A propane torch got mine off easy enough last time. I think I would be more likely to bolt or weld on another piece of metal to get your thickness right with a single piece of glass for the belt. I don't think I could trust two pieces of glass epoxied together and floating.
 
What do y'all think about this? Seeing as how I'm trying to build out my platen, and that we have no problem affixing the glass to the steel platen, could I JB weld another piece of steel over the existing ceramic and then the glass to this?
 
weo said:
What do y'all think about this? Seeing as how I'm trying to build out my platen, and that we have no problem affixing the glass to the steel platen, could I JB weld another piece of steel over the existing ceramic and then the glass to this?
Click to expand...
That’s one additional glue joint to fail, IMO. I’d just get the thicker piece of steel and start over.
 
Hello again, all.
I suppose I shouldn't assume that anyone is as ignorant as myself, but I thought I'd share. I just now figured out an easy solution to my primary issue.

Why not just flip the platen upside down to get the crack out of the way???? Duh. (insert dope-slap emogee here)

Have a great weekend
 
You must log in or register to reply here.
Back
Top