Sharpen two-piece threading dies

I use these Greenfield "Little Giant" two piece threading die inserts. It says in this catalog I found that they are easily sharpened.
These are GREAT dies! They have gotten very expensive. ($30-$60) I haven't found the correct way to sharpen them and my attempts over the years aren't that great. When new, they cut like butter, when they are dull. they rip the steel. They get a lot of use on tool steel and other tough steels. I have saved all the used inserts for decades in the hope of sharpening them. Is anyone familiar with sharpening these?

(see page 123)
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The picture at the bottom of the page on http://www.accarbide.com/sharpening.html should give you an idea. If I remember we made a small fixture to hold the inserts, just as shown, and then ground them on a tool and cutter grinder. I don't remember where we got the dimensions and angles from but I'd guess they can be found.
We had some (don't remember brand) threading heads that held four inserts and while it wasn't an everyday task we did sharpen them when they got dull.
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    [ ... ]

    Those are like the Geometric chasers which I mentioned in a followup just posted (thus you can't have seen it at the time of posting this). And those are easier to sharpen on a surface grinder than the ones for the Little Giant dies because it is four pieces, instead of two chasers with two threading edges each.

    Geometric? (what I have), Landis? (Both used on turret lathes), and the Rigid ones mentioned in the caption are pipe threading chasers used in hand tools -- though I guess that some are also on machines set up for production pipe threading.
    Enjoy,         DoN.
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On 8/3/2013 8:02 AM, John B. wrote:

I see, that will sharpen the flats and jigging is easy. I've done that on the surface grinder but sharpening the flats alone isn't the whole solution. The hole also has to be ground and keep the relationship with the material removed on the flats and the material removed in the hole so that the right teeth cut the right depth and distribute the force over the whole die.
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I'm not sure what you are referring to "flats" and "hole". The inserts are sharpened by grinding the face of the insert. The hook angle is controlled by the fixture and the radius of the "hook" by dressing the grinding wheel.
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On 8/4/2013 8:12 AM, John B. wrote:

Here's a better picture:

See how on each insert there are two flats on the outside of the threaded area that cut and two cutting edges, one on each side of the hole? There are four cutting edges on each insert that have to be dressed.
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I tried to look at your reference and got this error message:
"A .NET Framework error occurred during execution of user-defined routine or aggregate "getOnetoManyMap": "
I also tried "www.gfii.com" and got the same error.
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While your reference wouldn't work I did look around a bit and found some "U" shaped die inserts that are possibly what you are talking about. If so then my explanations are wrong as I was thinking about the flat inserts that fit a "geometric" head.
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    Now *that* is a pain. This is just part of a catalog, and the PDF view of it is that your (and the catalog's) page 123 is actually only page 9. :-)
    Without ever having tried to sharpen them (though I have *used* a set of them at work years ago), my feeling would be that you would make a holder for a surface grinder to hold them at the proper angle, and cut back the leading face of each just a bit -- being careful to maintain the original angle.
    You might be able to get a clue by downloading the information on the Geometric die site on how to sharpen the chasers for their self-opening die heads (for use on turret lathes and the like). Of course, those have the advantage that there are four individual pieces, so getting access to the leading edge is easier. But those sets of chasers are *expensive* -- even for a single thread.
    Good Luck,         DoN.
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On 8/3/2013 5:06 PM, DoN. Nichols wrote:

I hope Greenfield comes through with info. Of all the dies I've ever used, these are simply the best! I've had them my whole machining life and I'll buy new as required, but.....
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I have a KO Lee B300 tool and cutter grinder Id be most happy to put on a pallet and sell you, along with all the accessories for $2500 OBO
A very good deal btw.
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On 8/4/2013 9:14 AM, Gunner Asch wrote:

Trade for brushes?
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