View Full Version : Diamond honing of carbide

07-21-2003, 03:51 PM
I picked up a 3 piece set of diamond hone (blue, purple, red) "paddles" to reduce the tip radius on a threading insert and to improve a few other cutters here and there.

The finest (around 1200 grit) leaves a finish which I would expect from 320 or 400 grade paper ... nicely brushed but nowhere near the mirror I was expecting.

I tried them dry, with water and with a little oil but not much difference. Am I doing something wrong ? How do they get a mirror finish on solid carbide tools, such as the little boring bars from Micro100 ?


07-21-2003, 05:38 PM
I just asked my wife about this. The fact that your hone may claim to be 1200 grit means little. She says there are no industry wide grit standards. Different abrasive suppliers will call the same grit size by widely differing numbers and may not even be consistent within their own product lines. To obtain a mirror finish you can use powdered diamond on a hard rubber block, wet.

07-21-2003, 10:28 PM
A neat trick I have used is to first cut the carbide with the diamonds and then polish them with a piece of fine ceramic(not your wifes dishes)I have had good results with the white ceramic knife hones.You also can get from stone mason suppliers a thin plastic disc used for polishing head stones and counter tops,they use them to wet sand and I believe they go up to 8,000 grit,a bit pricey as I remember about $20.00 per disc.

07-21-2003, 10:46 PM
Okay try-
Also bear in mind that these are resin bonded discs and sould not be used for ginding,only polishing(little or no pressure and lots of water)

07-21-2003, 11:44 PM
I have some of the same type items, mine are "Eze-Lap" brand.
The finest (called super fine) gives a close to mirror finish, but there are still fine marks. I would class it as a 600 grit finish.

But the cutters don't seem to leave any marks as a result of it. Maybe you don't have to worry.

07-22-2003, 04:44 AM

You are not going to get a smooth finish without a power tool on most inserts because you are not just cutting plain carbide, but an assortment of cobalt, Tantalum, Titanium and silcon carbides as well the super hard coatings.

Make a bronze or copper lap and charge it with diamond powder. The best method I have found of charging is a common ball bearing mounted on a handle - the outside race is pressed against the spinning lap with firm preasue and move across the lap to force the diamond int the surface. A very little powdered grit goes a long way. Use one lap for each grit you use. The bearing will become frosted from the action - but don't sweat it!

This will allow you to get a true mirror like polish in a very short time. CBN is also used to touch up carbide, but diamond is faster and cheaper. Buy the diamond grits at a Lapidary supply and 100cts. should not cost more than $40(Canadian for 20 grit). The finer grits such as 100,000 mesh is about $17 for 100cts. They also sell the syringes with diamond/grease mixture for far less than the Clover or Norton equivelents. The lapidary compounds are usually water soluable rather than the oil based grease used in the Norton/Clover compounds. I prefer the raw grit as I can use any grease or lube I want to use.

Diamond gemstones are faceted on cast iron laps - BTW. They use water or kerosene for lubricant/coolant.

07-22-2003, 02:34 PM
Thanks for all the good ideas and info. I also discovered that (at least with the Eze- Laps which I bought) you need to break down the large diamond particles until only those impregnated in the substrate remain. I did it by rubbing them vigorously against each other as Eze-Lap recommended.

The final finish is now close to mirror although flatness is not exactly there (no surprise with sheet steel on a plastic wand). If I get more picky (and wealthier at the same time), I'll need to look into laps or diamond wheels.