Belt - platen distance question

B

Brekfast

Joined
Dec 9, 2005
Messages
57
Hello,

I am building the platen for my grinder. What should be the distance between th eplaten and the grinding belt ? I figure close but not touching right ?


Thanks in advance


Henrik
 
You are right. You don't want a space big enough for your work to get caught in. It can be hazardous.
 
Henrik,

Your best bet is to make the platen adjustable. I've found some situation where I want the belt slightly slack, some where I want it running flat across the platen, and others where I want the platen standing proud in front of the rollers. In any event, most of your grinding will be done with the belt actually riding on the platen. That way, you have a firm backing when you start a grind, not after a little bit of slack belt which could smudge an otherwise straight grind line.

-d
 
I'm with Deker on this one. If you can make it adjustable, do it!
I bought an adjustable model for my Square Wheel from the now-closed-up Koval Knives (they were acquired by Jantz, which no longer carries this) and I swear by it. Easy to use, fully adjustable and gives me lots of flexibility! Remember to factor in a piece of ceramic platen liner, too! Belts run cooler and it STAYS FLAT. Buy it from Darren Ellis, he's a great guy with lots of good stuff:

Ceramic Platen Material at Ellis Custom Knifeworks
 
How would a ceramic platen liner affect the design ? Err, what is a ceramic platen liner exactly ? A platen but instead of metal made of ceramic ?


Thanks.

Henrik
 
Yup. It's a piece of fireplace glass (you know, like what they make the windows on a wood stove out of?). It stands up to high temperature (obviously), and it hard as heck, so it'll resist scratching or deforming. Because it's nice and smooth, it reduces drag, so belts slip across it easier. Mine mic'd at .20". I used JB Weld to stick it to my metal platen, and there's no sign of it coming off anytime soon.
 
There is actually a silicate glass that's called "Fireplace Glass" which is not exactly the same composition as the ceramics that go by the names "Pyroceram" and "Neoceram". It isn't quite as strong.

It is a wise precaution to modify ones platen slightly if the ceramic will be used. The purpose is to prevent slippage of the liner into the moving belt/roller in case the ceramic comes off. A couple of holes are drilled and tapped into the platen bottom and a small "foot" is added as a rest for the liner. I attached a piece of 3/16 x 3/4 x 2" piece of steel with machine screws countersunk slightly below the surface of the foot so they wouldn't abrade. Others use simply a couple screws, no bar. This way, if the liner gets warm during extended grinding and the adhesive fails, there is a backup.

I have heard of two cases where the adhesive let loose and the ceramic turned into shrapnel. It scared the "victims".
 
Hi Matt,
Tell Darren he owes you a "cold beverage" Using your posting of his URL, I just ordered a ceramic platten liner for each of my grinders...
Thanks for the info!

Also Thanks to Mike F. for the safety suggestion!
 
Metal platens wear rather quickly, Henrik. They can dish and develop ripples. They need to be refurbished periodically. Some folks add a piece of 'sacrificial" steel instead of ceramic, others simply periodically regrind the face of the platen. Others yet have tried leather, graphite cloth, and many other materials. The ceramic seems to have the longest lifetime.

The ceramic is an alternative that offers the benefit of also running a bit cooler than the metal surfaces.

It has a downside, though: since it is an insulator, many people experience static buildup and get frequent shocks. It is reported that proper footwear (static-dissipative soles, as in many safety shoes) cures this, though i suspect the surface you stand on is important for that, too. I use a grounding wrist-strap intended for electronics techs. Some people have no problem with it whatsoever, especially those who live in humid climates. Others report srpaying with anti-static laundry spray cures the problem, too.
 
John R. Fraps said:
....
Also Thanks to Mike F. for the safety suggestion!
Click to expand...

You're welcome, John. I consider this rather important. Ray Rogers is no candy-ass, but to hear him speak of his experience with the ceramic letting loose was enough to send me scurrying to modify both of my platens.
 
Thanks Mike,

Well I figured I would attach a changeable metal plate to the platen holder and when it wears out I'd just bolt on a new 2"x8" piece. That was my original plan anyhow. I also think I'd be kinda worried about a platen that is not securely bolted to the platen holder.

Henrik
 
YW. I don't think that's a bad choice at all, Henrik. Your grinding habits will have a lot to do with wear time, regardless, so it may be all you'll ever want or need.

John, a couple of tips if this is your first experience with the ceramic liners:

Grind a radius on the leading edge to prevent wear on the belts. A/O belts will work, albeit slowly. I recommend a 120 or 150 to reduce chance for chipping. I also recommend turning off most of the lighting, as the several pieces I've done give off an eerie light when grinding. :)

Rough up the back of the liner a little with a 60 grit or coarser to give something for the adhesive to grab.

Make sure the adhesive coating is very smooth and even. The liner doesn't flex for squat and will crack if you press too hard against an area where there's an adhesive gap. Don't ask me how I DOH that! :o
 
fitzo said:
There is actually a silicate glass that's called "Fireplace Glass" which is not exactly the same composition as the ceramics that go by the names "Pyroceram" and "Neoceram". It isn't quite as strong.
Click to expand...

Didn't know that, Mike... thanks for the correction!

Do you know how Ray had his attached to his platen (what kind of adhesive)?
 
Matt, I'm sorry but I don't remember for certain. He uses K&G epoxy, so that might have been the stuff.
 
John R. Fraps said:
Hi Matt,
Tell Darren he owes you a "cold beverage" Using your posting of his URL, I just ordered a ceramic platten liner for each of my grinders...
Thanks for the info!

Also Thanks to Mike F. for the safety suggestion!
Click to expand...

I owe Darren far more than I think I can repay him for... his help in the design and supplies for my forge put me well into his debt! Truly a great guy to deal with!

Thanks, Fitz!
 
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