Help, please: What am I doing wrong?

I've also wondered if the depth of cut makes a difference to the pressure on the graver tip. For some reason I cut quite deep with the main cuts and always have done. Looking at all the work on show at Reno there is quite a difference in the depth of cuts from engraver to engraver. Some of the work is quite shallow when examined closely.

I've had exactly the same problems with carbides that Mark describes and have reverted back to Glensteel for just about everything. In saying that some people have a really good trot out of the carbides, I'm just not one of them.They seem to be temperamental little beasties that require everything to be perfect. The amount of mucking around shaping, sharpening and polishing just doesn't seem to justify the extra cutting time that you get from them. And if you have a dud one, or more, it wastes even more time.Plus the gravers wear down a lot quicker because when they break, they break big time. Even the carbide undercutting tool for gold inlay seems to break far more quickly.

Of course all that depends on what metal you are cutting as well as there's a big difference between gold and stainless. But I still find that the carbides break easily in brass!!! So it maybe just my technique..........or lack of it

The only exception to this is the carbide graver I use on the watch rotors which seems to be the only thing that will touch them. But the graver shape seems to make a major difference. I have no idea why that is, but it does.

With Glensteel the tips do break but more often than not they simply get blunt (self dubbing???) which means with main cuts you can still keep cutting but of course that doesn't work quite so well with shading cuts. Also once the graver tip breaks then it has to be sharpened or it's good for nothing.....and yes, they have to be sharpened regularly, but it is quick and efficient and doesn't have to be exacting.......... but that is just part of the job.

Well, that's my theory for the day

Cheers
Andrew

Check this out. It may give another possibility.
http://www.mmsonline.com/articles/anti-electrolysis-is-pro-edm
It seems like the depletion of cobalt weakens carbide.

I also ran across this. This explains Barrys explaination for the results of overheating.


Cobalt Leaching
Cobalt leaching also might render a tool surface unsuitable for coating. Leaching is very superficial, on the order of a few microns in depth, but its affect on the carbide’s coatability can be dramatic. The problem is somewhat like washing the tar out of an asphalt roadway’s surface with a solvent. The tar is the binder that holds the roadway’s stones in place. If enough tar is washed out, the stones at the surface of the asphalt become loose. The cobalt that holds the carbide grains together in a cutting tool is like the tar in roadway asphalt. If it is leached away, the frail skeleton of carbides that remains on the surface may lack the strength and integrity to stay together or hold a coating. Also ran across this. This explains Barry explanation of overheating.

A carbide tool’s cobalt binder is easily attacked and dissolved by aggressive acidic liquids such as contaminated coolant. The higher the fluid’s acidity or the longer the tool’s exposure to acidic liquids, the worse the leaching will be. Heat is another factor. The rate of cobalt leaching, following the general rule for most corrosive environments, roughly doubles with each 18° F increase in temperature. And leaching damage can be cumulative with multiple exposures to corrosive liquids.



Here's the link if you want to read the whole article.
http://www.ctemag.com/dynamic.articles.php?id=212

So following along with that theory Mike..........................it raises an interesting question with carbides.

When we are cutting for extended periods of time with the same graver.........what is the heat build up, caused by friction on the graver tip???

Does the acid in our fingertips cause this leeching, especially after extended periods of cutting with the same graver??

Does this help cause the graver tip breaking?

Would changing gravers regularly help the situation?

Has anyone ever measured the heat build up on a graver tip or the effect of "finger acid"???

Cheers
Andrew

That sure does bring up a lot of questions. Acid from fingers chlorine from tap water even the diamond spray don't know what is added to that.

Also cutting long border cuts without stopping would surely raise the temperature at the tip. An increase of 18 degrees F could easily be achieved when sharpening or cutting. Friction always results in heat.

This article would also verify Christians explanation that the face and heel need to be a mirror finish. That would reduce friction resulting in much less heat at the cutting tip.

Boy, after reading all the possible variables, it makes me want to give up tool sharpening, hehe.
Personally, since I noticed how easy it is to overheat the edge on carbide, and have taken care not to do it, I have had not had much trouble with it.
When I was in Gardone, one of the top engravers mentioned his suprise at the american engravers obsession with graver sharpening and geometry angles.
As a matter of fact, I have gone back to hand sharpening since my return, and notice no discernible difference in the functionality of my tools.
I think experience, and getting quick at sharpening and not being afraid of experimentation will solve most of these problems.
There are a lot of different ways to go about it, and that is one of the fun things about engraving, when you get bored with your way of doing things, you can change it around and it is like a whole new world.

The "point" (hee, hee, hee) of my original post was frustration with a single graver committing suicide every time I tried to resharpen. This discussion has turned into a very informative science lecture, and I hope many have learned from it as much as I have. Thanks for all of your helpful input!

Andrew, In regards to the tortional stress on the tip,causing it to break, the shorter the belly the better.
After all, a graver cuts by the lever and fulcrum principle, and any kid who has tried to roll a rock down a hill, knows the further the tip of the lever is from the fulcrum, the more likely it is to break.
A tool sharpened a certain way will have a width and depth it likes to cut at.
You may really notice this if you use pushgravers with no air assist, because a tool forced to cut at a depth it is not made for will slip and break constantly.
I presume if you are cutting deep and wide, all other things being equal, you have a shallow and short belly, at least thats the way it works on my tools.

Study lathe bit sharpening manuals if you really want to understand why all these angles matter.

Doc: For The Last 5 Years I Have Been Using A Micro- Grain Carbide, Called Micro 100. I Got It From Peerless Supply A Machine Tool Supplier. It Was Developed For Interupted Cut Machine Work. Calling On My 28.5 Years Of Machinist Experience, Any Time You Allow A Carbide Tool To Be Unloaded During A Cutting Process, As In Milling Across Holes Or Voids In Metal, Then Slaming It Into The Other Side Of Hole Will Often Cause Tool Breakage. Or Taking Extremely Light Cuts With Carbide Indexable Inserts When Lathe Cutting Will Overheat The Cutting Edge And Chip It Out. Tool Makers Years Ago Started Putting Titanium Nitride Coatings On Carbide Tools, Dramatically Increasing Tool Life, Especially In Turret Lathe Or Mill Applications. Although These Tools Would Normally Be Flooded With Coolant. Titanium Nitride Will Not work In Engraving Because The first Time you Sharpen It Would Be Gone. From My Own Personal Experience You Cannot Let A Carbide Engraving Tool Bounce In And Out Of A Cut While Cutting, Or Your Tip Will Shatter. When Popping Out A Chip At The End Of A Cut Is When You Will Probably Experience The Most Tool Failures. Because You Are Severely Loading Then Unloading The Tip Of The Tool Extremely Fast. So Tip Failure Is An Acceptable Risk In Engraving.

Very well put Tim.

One other factor that hasn't been adressed here is vibration. If your piece being engraved isn't rock solid expect more breakage. Doesn't matter what material the tool is made from. I also agree with Tim stoping and starting will tear uptools as well. Guess what thats what we do when engraving. The closest thing to what we do while engraving that relates to the machining industry would be hand tapping.
Doc, Did you ever try using the other end of that tool that kept breaking?

Chris, I have not yet tried to flip the graver around. It will be a bit short, but it's definitely worth trying.