Substitute for a Rotary Platen?`

[MTBob]

My wife is beginning to believe that I'm not making knives, just shopping for new tools. Well, that issue came up again while I was considering buying a rotary platen attachment for the 2x72. I see the purpose and have read a bunch of reviews that confirm their usefulness. So, this afternoon I began fiddling with various ways of using the stuff I've got to work around buying a new 'thing".
Here's what I came up with. I did a couple of test grinds and it seems to do the trick. It allows me to vary the firmness of the belt simply by positioning the upper wheel farther from the lower wheel. This results in an infinitely variable tension between the wheels, as opposed to the fixed wheels of a rotary platen. The belt tension between wheels certainly isn't a firm as a rotary platen that uses a secondary belt behind the primary belt.
Though I haven't tried it yet, I anxious to see how this setup works on contouring handles using a 1" scalloped belt.
So, for those of you who have a rotary platen, does it seem this setup would be adequate to replace a rotary platen? What's the downside?

 

[Sean Jones]

Interesting concept. I don't have a rotary platen so I can't comment beyond that. But it appears functional.

 

[John Wilson]

Bob, that is neater than peanut butter!

 

[Owl]

I have a rotary platen and the rubber belt behind the grinding belt does stiffen it up a lot.
But you have a great idea there, and it should work.
You could try using two 2" wheels so you could get the centers closer together if you needed a tighter belt for a convex edge, maybe with using a heavy weight belt.
I only use mine for doing convex grinds, not for handles.
What you have there with a lighter weight belt looks like it would be great for convex grinds on handle material.

 

[Drew Riley]

Well, that's certainly thinking outside the box. I might have to try that!
That said, I do have a couple of rotary style platens (one traditional, and one with a larger rubber belt and a flat platen) and the rubber belt does add to it's functionality as Owl said.
On the other hand, you've created an adjustable slack belt rig that looks like it'd be pretty handy as well. Nicely done.

 

[IJM3567]

Yeah I agree with the above comments that looks great for handles and probably useful for a more pronounced convex. I have a rotary platen that I’ve yet to use for convex grinds as it needs to be modified to fit a file guide but I will comment that most of them aren’t fixed tensions as there’s usually one wheel that can be pushed out or pulled in to adjust rubber belt tension.

 

[EdCaffreyMS]

No slack belt setup will ever match a rotary platen. With your fab skills Bob, building a rotary platen shouldn't be a big deal. If I remember correctly, the belts used are a snowmobile drive belt. The biggest hurdle is making/finding the "ribbed" wheels to run the belt on. (Hint: The belt length is 26-28")

That being said, I honestly use my rotary platen VERY little. I was a "tester" for them, and was given the rotary platen that I tested. Based on the amount of usage that it gets in my shop, I doubt I would buy one.

 

[Greg Rice]

My wife is beginning to believe that I'm not making knives, just shopping for new tools.

I too have an accumulation disorder Bob - maybe that is why we are such tinkerers - for me, my appetite for new stuff far outruns my ability to convince my wife - but your shop just makes me drool and kinda act like Patrick on Sponge Bob...

As for that slack belt set up - I would bet it would give a rotary plat thingy a run for it's money in usefulness... Just genius.. Dude - the knurled Allan-wrench handle and now this... keep it up!

 

[MTBob]

Thanks for the comments, good insights. Based on the general opinions, I think I'll keep this setup in my back pocket for periodic use and defer purchasing a rotary platen. A higher priority is purchase of a proper heat treating oven.
BTW: The grooved wheels and belt are available on Amazon and/or Ebay. For a 4 wheel platen + belt, the total cost would be roughly $250, plus some metal.