Hugh Others - 3 Point Hitch Disc

Hugh & others:

I'm looking at a John Deere disc - I believe the model number is 617. It is a 3 point hitch model. The description of the disc calls it a "fully adjustable, offset to conventional". I sure would like to know more about this disc - do any of you have any knowledge of it? How much tractor HP needed if it were a 6 footer, if it were a 7 footer?
I simply disc some old, rocky ground, seed it and run a cultipacker over it for a few small square bales of hay. I would also use the disc in a garden. I likely would trade some other implements for this one. I'll try and post a photo. I believe the "Offset" refers to the alignment or angle of the disc. I see that it doesn't have "cutting" blades on the front. Are those cutters important for tearing up sod?

While some wear does effect the performance, it takes significant wear to noticably diminish the usefullness of a disc blade. Nothing like new. But who's to say that "new" isn't more than adaquate, while all along the serviceable wear limit is 2", 3" even 4" less than original diameter? It's highly unlikely that manufacturers would use a disc blade that is functionally obsolete with 5% or 10% wear. There's a difference between WORN and WORN OUT. From what I can gather, 20% wear (reduced diameter) is considered by product manufacturers to be with-in service limits. That would mean an 18" disc blade could loose slightly more than 3-1/2" of it's diameter and still be within service limits by most standards.

And from my own experience, disc blades remain very much useable and functional until wear approaches 3" from original diameter. They aren't scrap as soon as the paint is worn off.

Me thinks you may be over-engineering a very simple concept. We're discing dirt here, not flying to another galaxy.

The difference between an 18" disc blade worn to 16" and a new 16" is so minimal that the results of using either would be virtually undetectable.

Notched blades do dig a little better in sod, but they also tend to wear faster than plain blades, as well as they'll tend to break easier especially in rocky conditions.

The important items to watch for in a used disk are; blades, bearings, arbor bolts and spacer spools. Make sure you are getting the size of blade advertised. An 18" blade with 2" worn off doesn't make a 16" blade, the concave is different on the two. Cut away or notched blades are good, but I wouldn't turn my back on good blades without the notches. Make sure your getting 1" or larger arbors, bearings and spools. Make sure the spools are 5-6" diameter on the back side of each blade. Heavy gauge blades, along with 1-1/4" arbors, bearings and spools add weight fast, plus add a lot of strength to the disk.

Diameter is reduced equally around the circumfrence of a circle.

That is all
Robert