Sharpening carbide drill on diamond wheel?
I want to sharpen some carbide drills. I know the green wheels work but I was wondering how a diamond wheel works on carbide? Specifically, I would like to use my Drill Doctor which has a diamond wheel. I realize it's not the best or most precision way to go but it would be better than I would do by hand on the green wheel.
Green silicon carbide grinding wheels are able to remove excess tungsten carbide, as when you have a broken tool and need to grind back a bunch of material before resharpening. They are of no use at all for sharpening carbide, which is done with diamond.
As for the forbidden (it is on Millie's little list) DD machine, you are free to try it, or to inquire of the maker for advice.
On their website, they claim the wheels are diamond (no reason why not, CBN would not be an advantage for this use) and that carbide bits are amongst those than can be sharpened.
I worked in a production machine shop for about 20 years before the shop got a diamond wheel
and we sharpened carbide tools with green wheels every day.
Their manual says that you can, and I've sharpened a couple dozen carbide bits in my old 750 with no apparent damage to the CBN wheel. But maybe I have to do a few hundred before the damage shows up or something.
Originally Posted by smalltime
The original DD -- at least the one I keep around for left hand bits -- has a diamond plated wheel, not CBN.
I'm perplexed by the oft repeated notion that green grit wheels are no use for sharpening carbide.
They not as good as diamond wheels. Does that make them "of no use"?
I don't bother setting up a diamond wheel to sharpen, say, a brazed carbide lathe tool for roughing interrupted cuts hard material. Or for (as I often do) modifying a masonry drill for hard metal drilling.
Green grit is just FINE for jobs like this, and preferable to diamond IMHO in cases where the steel substrate will contact the grinding wheel (and consequently greatly reduce the life of any diamond wheel not specifically targetted towards steel grinding: slow speed, coolant....)
It's a bit like saying manual machine tools are "of no use" since the advent of CNC.
There was a time, thanks presumably to the genius of de Beers, where diamond wheels (at least in the semi third world conditions of our local industry) were pretty much something you read about rather than owned, the Lamborghini Miura to our Lotus Sevens and Mini Cooper Ss.
I'm talking about during the carbide era (I'm old, but not exactly a centenarian)
... the lucky few would tickle up the resulting edge with a pocket diamond hone (even these used to cost a prince's ransom) and be away laughing. The rest of us would be perfectly satisfied with the off-stone finish.
(Chorus from offstage: Looxury! You 'ad a green grit wheel? We had to roob tools on concrete path wit' bare 'ands!)
The issue with green wheels is that they allegedly tend to fracture the edge and lead to premature dulling, rather rapidly.
Having used diamond wheel and green wheel, both, I am tending to believe there is a definite difference. WHAT the difference is, I don't know of my own personally developed knowledge.
For sure, a carbide scraper sharpened with diamond wheel will last WAY longer in scraping than a green wheel sharpened scraper.
You-all can do as you like on that score.
Green wheels are crap for grinding carbide. There. I said it. The green wheels do not cut the carbide so much as chisel it off. Every time I use a green wheel to rough carbide tools I can see the fractured edge. Check it with a loupe if you can't see it with your naked eye, it's there. This has a major affect on tool life.
Diamond works much better.
However, if you want the diamond to last and do a good job, YOU MUST LUBRICATE THE WHEEL WHILE GRINDING!! either with water or oil.
Oil makes a mess. Water works just fine. Without lube, your diamond will "burn" and not last as long. Also, I don't think you will get as good an edge.
Green wheels are fine for shaping carbide. Use Diamond for final sharpening, grinding fine radiuses and chipbreakers. Sharpening carbide with a green wheel works if there is no other choice, but it's like sharpening your pocketknife on the sidewalk.
thanks, I think that's a helpful analogy