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KMG rotary platen


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Anyone here using this attachment that can comment? I have a need for slack belt grinding with the wheels closer together than the standard platen. The rotary platen looks like the ticket but I wondered how well the rubber tracking belt holds up, general tracking and overall durability is?

 

Dan

Dan Pfanenstiel

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Dan-

 

I own one, and am quite fond of it.

 

When I first tried one, it was a prototype Rob made for a Burr King. It worked well, but I didn't love it... just thought it was neat-O.

 

Got one for the KMG's last December during Rob's sale and definitely like it. It is a finishing tool, not an aggressive grinding tool. IMHO. :)

 

So long as you look at it that way, I think you'd be quite pleased with it. I have plenty of contact wheels, so I don't use the rotary platen wheels as such. The belt seems to be holding up very well, and it tracks just as smooth and true as the grinder does with all of the other attachments.

 

The really great thing is the fact that there is such a varied configuration of wheels, and with the rotary belt tension adjustment, you can achieve a very broad spectrum of "give" behind your grinding belt.

 

It is an expensive attachment, but when you see it, you can see Rob is charging a very fair price for what it takes to make it. While I could live without it, I'm certainly glad that I DO have it. :)

 

I know this would be a whole lot better with pics, but I simply don't have any. I might be able to snap some this weekend though.

Edited by Nick Wheeler
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Nick, could you describe at what point in your process yo use it, and just what you are doing on it when you do?

Let not the swords of good and free men be reforged into plowshares, but may they rest in a place of honor; ready, well oiled and God willing unused. For if the price of peace becomes licking the boots of tyrants, then "To Arms!" I say, and may the fortunes of war smile upon patriots

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Can see the unit here KMG Rotary Platen

 

Thanks Nick, helps a lot. I'm pretty much hoping the unit would allow various degrees of tension on slack belt grinding. I have done a bit on a standard KMG platen, with the platen removed, between the wheels, but only adjustment there is minimal with belt tension. With the rotary platen, seems like the various closer wheels and tension adjustment would be the ticket.

 

My motivation in all this would be to create different levels of niku in blades, convexity, on the grinder, and be able to follow up with finer grit belts.

 

Dan

Dan Pfanenstiel

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Thanks Nick please do :D. I usually flat grind until I am roughly close to where I want the geometry to be, then I move to slack belt. A problem I encounter however is always ALOT of work to get out this little center part of the grind that refuses to grind away. Would a heavier backing like the rotary platen move more material quicker to bring things from flat to convex?

Let not the swords of good and free men be reforged into plowshares, but may they rest in a place of honor; ready, well oiled and God willing unused. For if the price of peace becomes licking the boots of tyrants, then "To Arms!" I say, and may the fortunes of war smile upon patriots

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Would a heavier backing like the rotary platen move more material quicker to bring things from flat to convex?

 

Yup. The rotary platen is the spiffiest piece of equipment Rob makes, in my opinion. It's a truly remarkable doohicky. I want one. I've played with them in other peoples' shops, but I don't have the cash at the moment. :(

 

With the close rollers in front and the tension cranked up it grinds almost like a flat platen, and if you roll it around to the wideest spacing and loosen the tension it's almost like the normal slack belt, but with a bit more oomph. Plus you can adjust it anywhere in between for just the right convexity.

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Thanks Alan, sounds like it'll be what I was expecting. It's nice to get some input from people who have used them before buying.

 

Dan

Dan Pfanenstiel

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Dan if you're ever in the Los Gatos area I'd be happy to let you spend some time on mine you can also visit your old treadle hammer.

 

Tim

Tim Musselman

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Idea: Has anybody tried taking the "variables" out of slackbelting by creating a concave platen? Something that a slack belt bottoms-out against in the profile of the edge geometry you're after?

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Hey Tim! Hope you're putting that hammer to good use. I miss it every once in a while, although an air hammer might cure that one of these days.

 

A concave platen might work I suppose, not as variable as the KMG thingy. The slack belt approach evens the pressure out over the blade. Could use a leather pad on the solid platen, or graphite, to soften it up a bit.

 

Dan

Dan Pfanenstiel

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I just put my rotary platen to work today! I am making a tool called a knife froe, it is a smaller version of a froe with a handle inline with the blade. The blade requires a convex wedge shape. I rough ground 12 of these tools in about 5 hrs. and used up 3 belts. The tools were hardened and tempered and the belts were 80 grit. This includes profiling the tool on the flat platen, rounding the shoulders with the small wheel attachment, convex grinding the blades and cleaning up the tangs on the flat platen. Having the rotary platen under the belt stiffens it up considerably and allows you to grind more aggressively. You can also move your work vertically on the platen to get the curvature where you want it. Higher on the platen and more material is removed near the edge, lower and material is removed more towards the spine. You can also tip the edge into the platen to control where material is ground as well. I find that for doing an appleseed grind the rotary platen is a lifesaver. It sure beats chasing a floppy belt around while trying to slack grind above the contact wheel.

 

~Bruce~

“All work is empty save when there is love, for work is love made visible.” Kahlil Gibran

"It is easier to fight for one's principles than to live up to them." - Alfred Adler

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