Tool Bit Grinders
I just got a H.F. 6" tool bit grinder (I know, but it only cost me a hundred bucks new, minus manual). It came with two S/C green wheels. I touch up a lot of carbide bits, as well as frequent grinding of HSS bits. Question: Since I want to finish grind carbide on one side and put an A/O wheel on the other, what grit wheels would you recommend? I will have to rough grind on the 8" grinder, what is the coarsest grit that will give me a good finish on HSS? All opinions are appreciated.
I assume you mean your grinder has face wheels on it similar to the Baldor #500 carbide grinder.
If so, I'd outfit your grinder with a 46-K AlO2 white or ruby wheels on one end and a 220 grit 50% concentration diamond wheel on the other.
I suggest getting rid of the green silicon carbide wheels altogether. They're nearly useless for getting good edges on carbide and they perform poorly on steel of any kind. They're intended only for roughing brazed on carbide tools prior to finish grinding.
I know some of you have success stories grinding carbide with green wheels but trust me, a 220 grit diamond outperforms green wheels and gives superior finishes to such an extent you'll wonder why you stuck with them. Further the green wheels micro-crack carbide making edges that crumble in use. Drives you crazy with flaking edges of threading or grooving tools, external radius tools, and where ever you need a durable edge.
Never use the diamond wheel to grind anything but carbide, not even a little bit of the steel shank. Carbon is soluable in iron. Steel of any kind will eat a diamond wheel down at a phenominal rate. If you have to relieve the shank to get at the carbide use the roughing wheel on the bench grinder.
Also invest in a diamond dresser for the AlO2 wheel. A clean, open, freshly dressed wheel ensures good finishes. A star dresser or an AlO2 "dressing stick" is a very poor substitute.
If the expense of this diamond tooling seems excessive remember that if properly cared for it will most likely last many years if not a full generation.
Yes it is a #500 style grinder with 6"x1" CBN (I believe) wheels. I guess I am trying to cheap my way out of buying a diamond wheel, but...
KEEP THOSE CBN WHEELS!
They are best for grinding hard steels - but do not grind anything on them that is softer than about 40 on Rockwell "C" scale or they wear like a bitch! You can't get a better wheel for HSS (Ruby comes close, but not close enough).
Forrest is right on about the Diamond and Carbide. I preffer a finer wheel than 600 for touch ups as it gives a better edge.
Another way to true up your standard wheels is a Norbide stick (CBN). I use these on my grinding points as well. A diamond file can also be used to true points.
To true your Diamond or CBN wheels requires a friction brake truing device. These use SiC stones to rub against the surface. The Diamond/CBN abrasive wheel will have instructions on using an abrasive stick to open the face up after truing the wheel - this allows for faster cutting action. You can also get instructions on doing this on Norton Abrasives site.
Note that grinding carbide should be done with water to keep dust down or a HEPA filter equipt vacuum to remove the dust safely. Wear a face mask either way.
[This message has been edited by Thrud (edited 08-03-2003).]
Have any of you heard the trick about using a rubber (OK, OK an ERASER! in your speak) to clean out a diamond wheel??
I picked up a diamond encrusted aluminium T&C wheel from a specialist, at a recent M.E Show. The stall holder threw in the eraser (well it was a kind of plastic eraser as was used on plastic drawing film some years ago) for cleaning out the wheel. Seems to work real well.
That grinder is on sale right now, in the stores, for $119. Includes the wheels! At 110lbs., that's a heafty piece of equipment. I gotta have one too. Enco's version is twice that and NO wheels. Baldor's version is six times that and NO wheels.
I'll put up with the shame and finger-pointing for that. At least I'll keep the local economy going.
Where would be a good place to pick up the recommended diamond wheel for grinding carbide?
And I'm curious, if diamond wheels should never be used for grinding steel as Forrest says, then how do Drill Doctors survive?
They don't. That is the point.
Forrest is right about the leaching of carbon from the diamonds into the carbon steel - can't be stopped. It greatly accellerates the wheels wear. CBN works best on hard steels, but should not be used on softer steels (<40 Rockwell C) as extreme wear occurs of the CBN - this is an unexplained property of CBN. The neat thing is, the harder the steel you grind, the longer the CBN lasts! I have verified this with a Norbide stick and later read about it in Sandvik Coromants "Modern Metal Cutting" handbook (out of print).
For wheels you can order them from any national distributor, Kennametal, Norton, etc.
Eternal tools in England (thanks John) has very reasonble Diamond tools. They can do custom stuff too. http://www.eternaltools.com/
[This message has been edited by Thrud (edited 08-07-2003).]
What is CBN? Cubic Boron Nitride?
The original poster used it interchangeably with Silicon Carbide which would be SiC I guess.
So SiC wheels are useful for shaping Hi Speed steel lathe tooling for example?
CBN=cubic boron nitride also known as Borozon. My wife also confirms that using a Borozon wheel on softer materials is not good.
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