Check your platen

A flat platen gets things only kind of flat. Usually the belt puckers out just above the work and also gathers up below the work piece. This slightly rounds off the top and bottom edges. This usually shows up as a slight gap between a metal bolster and a tang. Most scale material will show this also but it isn't as pronounced looking or it is just accepted as normal. This affect varies with the type of belt, speed and belt tension.

The work around is to have your work profile oversize, grind it flat on the platen and then grind back the profile to tighten up the gap between the mating surfaces.

Hand lapping on a surface plate gives better results but there is some technique to it or you end up chasing your tail. To get things flatter, you need to use a disc (or surface plate) with the abrasive glued to the disc (or surface plate).
 
j elky said:
Where do you guys get your glass and what size and type?

Jeff
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1/4 thickness pyroceramic glass. (fireplace glass) in the dimensions of your platen. I went to a local glass shop and asked for a piece. They cut me a piece on the spot.

This site (USA KNIFEMAKER) often has it for the more common grinders.
 
Glass platens still freak me out, I can't get over it. I'm concerned about it shattering and throwing shards. I've ground on a few and just don't see the value for me.
 
I have a glass platen and bought the glass from USAknifemaker. If you have a glass cutter it's easy to trim to size. Since it's embedded in JB weld I don't have a lot of concern about it shattering. If it did for some reason I believe the JB weld would keep most of it together. But that's just my opinion. I don't have any data to back that up.

Personally I think one would be more at risk from cutting themselves on a knife blade than on a glass platen.
 
I was worried about the glass when I first began to use it, too. The idea does seem sketchy. For a very long time I babied it and wouldn't profile blades on it. After all this time I just stopped worrying. Honestly, there just isn't very much force acting on it, especially when you consider that the entire surface area is JB Welded to the steel platen. If it ever did break free it would likely fall out into your spark bucket in a total anti-climactic non-event.
 
John Wilson said:
I was worried about the glass when I first began to use it, too. The idea does seem sketchy. For a very long time I babied it and wouldn't profile blades on it. After all this time I just stopped worrying. Honestly, there just isn't very much force acting on it, especially when you consider that the entire surface area is JB Welded to the steel platen. If it ever did break free it would likely fall out into your spark bucket in a total anti-climactic non-event.
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Agree. I think the only way the glass will break is if you slam a tool rest into it on accident. I put out a youtube video on installing mine a long time ago and I put a little shelf to support the bottom edge just in case the jb weld let go. If I were to do it again, don't think I'd even bother with the little shelf. I got my glass from Boss.
 
I just replaced my glass. It was originally put on with JB Weld. In order to get the old one off, I had to break it up with a hammer. Then I had to heat it up with a torch and chip the pieces off one by one. I don't think the glass would ever shatter. Even if it did, the pieces are going nowhere!
 
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