carbon steel tools and Carbide tools on CBN wheels

[john lucas]

I needed to cut a Hunter tool in half to really look at the cutting angle. I could not do it with my Dremel and a cut off wheel. Well I probably could have, it started but was going to take forever and would not have been straight. So I thought, why not grind it down. I went to the CBN wheel and ground it down to the middle so it looked like it had been sliced. I was worried it might damage the wheel. It is a 180 wheel from Dway. I dont think it damaged it but it sure seems smooth now. Maybe it's a 220 wheel. Still cuts well.
then I bought a set of Harbour Freight Carbon steel tools for $20. I wanted to see if they were any good for beginners and how much I would have to change the grinds. Surprisingly the grinds weren't terrible right out of the box. I'll be making a video showing what I did. Anyway I rough ground them on a Gray wheel and then did more shaping on my White Aluminum oxide wheel. The for final shaping went to the CBN. Totally forgot that they were High Carbon Steel. I did test the hardness with a file before I started and it just about skated across so they were quite hard. Maybe that's why they didn't damage the wheel. Either that or my now 220 wheel just won't clog because it's too fine. Anyway thought I would start a discussion about using CBN for other kinds of steel.
Here is the Hunter tool sliced. You can more easily see the cupped cutting edge and the tapered hole in the middle.

 

[robo hippy]

Well, I have touched up some carbide on my CBN wheels, but it is slow going. Can't remember any difference in wheel performance after. Any 'hardened' steel is fine on the CBN wheels, so axe heads, shovel blades, bench chisels, etc. The lawn mower blade is a softer metal and will clog the wheel up. I have intentionally clogged wheels up just to see what happens, and some times I get a little loading from sharpening my Big Ugly tools on the CBN wheels because the tantung is very hard, but the cold rolled and thick sheet stock are not. Some times I will get a little load up on the wheel, but the tantung does a great job of cutting through it. I did load one wheel up, the one I recently retired, with aluminum, brass, copper, and soft steel just to see.... It took maybe a month before all visible traces were off the wheel. Removal involved Trend lapping fluid (standard for sharpening, pipe cleaner dipped in the fluid and applied to the bevel as shown in my shear scraping video) and M42 or V10 scrapers. When the wheel does load up, you get a bumping/ticking sound, almost like hitting a nail with your gouge in a piece of wood. I have not been able to permanently damage a wheel yet....

robo hippy

 

[Gerald Lawrence]

John are you saying the HF tools are high carbon because my set says it is HSS? Don't use it as intended now it is almost all re-purposed and have occasionally sharpened on the CBN.

 

[Emiliano Achaval]

Well, I have touched up some carbide on my CBN wheels, but it is slow going. Can't remember any difference in wheel performance after. Any 'hardened' steel is fine on the CBN wheels, so axe heads, shovel blades, bench chisels, etc. The lawn mower blade is a softer metal and will clog the wheel up. I have intentionally clogged wheels up just to see what happens, and some times I get a little loading from sharpening my Big Ugly tools on the CBN wheels because the tantung is very hard, but the cold rolled and thick sheet stock are not. Some times I will get a little load up on the wheel, but the tantung does a great job of cutting through it. I did load one wheel up, the one I recently retired, with aluminum, brass, copper, and soft steel just to see.... It took maybe a month before all visible traces were off the wheel. Removal involved Trend lapping fluid (standard for sharpening, pipe cleaner dipped in the fluid and applied to the bevel as shown in my shear scraping video) and M42 or V10 scrapers. When the wheel does load up, you get a bumping/ticking sound, almost like hitting a nail with your gouge in a piece of wood. I have not been able to permanently damage a wheel yet....

robo hippy

After reading the abuse you have given your wheels, and still haven't been able to do permanent damage, its a good thing!!

 

[Emiliano Achaval]

I needed to cut a Hunter tool in half to really look at the cutting angle. I could not do it with my Dremel and a cut off wheel. Well I probably could have, it started but was going to take forever and would not have been straight. So I thought, why not grind it down. I went to the CBN wheel and ground it down to the middle so it looked like it had been sliced. I was worried it might damage the wheel. It is a 180 wheel from Dway. I dont think it damaged it but it sure seems smooth now. Maybe it's a 220 wheel. Still cuts well.
then I bought a set of Harbour Freight Carbon steel tools for $20. I wanted to see if they were any good for beginners and how much I would have to change the grinds. Surprisingly the grinds weren't terrible right out of the box. I'll be making a video showing what I did. Anyway I rough ground them on a Gray wheel and then did more shaping on my White Aluminum oxide wheel. The for final shaping went to the CBN. Totally forgot that they were High Carbon Steel. I did test the hardness with a file before I started and it just about skated across so they were quite hard. Maybe that's why they didn't damage the wheel. Either that or my now 220 wheel just won't clog because it's too fine. Anyway thought I would start a discussion about using CBN for other kinds of steel.
Here is the Hunter tool sliced. You can more easily see the cupped cutting edge and the tapered hole in the middle.

I bought my wheels from DWay. Actually I ordered them from David Ellsworth. You know how much those cost, I dont allowed anything but my new turning tools to be sharpened there. I have an 8 inch Baldor, slow speed. I bought a cheap Sears variable speed for my old wheels so I can sharpen machetes, mower blades, etc... Maybe I been too paranoid?

 

[Bill Blasic]

I personally can't think of an easier way to shorten the life of a CBN wheel than to do what John did Believe it or not a white oxide wheel would do the same thing. When we had interrupted cuts (back when I worked) we would grind off the chip breaker and put a negative rake on the carbide tools (inserts) we used and this was done on a stone wheel. On my personal grinder with 2 CBN wheels Thompson tools are the only tools that are sharpened on it. I have two other grinders, one with stones and one with CBN that are available for class use.

 

[Doug Rasmussen]

John, as you've confirmed the insert you cut in half is an industry standard generic designation, an RCGT. Basically a round insert with a 7 degree relief and a "high positive" grind generally used for cutting aluminum, it just happens to work well for wood. RCGT tells you everything needed to order replacement inserts except the actual diameter of the insert.

Inserts, no matter the shape, round, diamond etc, having "GT" in their designation will almost always have a factory mirror polish with razor sharp cutting edges. A hold over from the old days of carbide cutting tools was you couldn't get as sharp an edge on carbide as on a HSS tool. That's no longer true with the new carbides. But, you can't get the razor edge with the relatively inexpensive coarse grit plated wheels.

I've noticed the makers of carbide insert lathe tools don't specify their inserts using industry standard designations. Two reasons I can think of for that. The most obvious reason would be they want you to buy from them. Another reason being the insert nomenclature can quickly get real confusing for newbies.

Grinding carbide on CBN wheels? Not recommended if you value the wheel.

 

[john lucas]

The Harbour Freight tools I bought didn't have anything written on them. They do sell a set for $79 that is HSS. I just saw these for $18 and thought, why not, lets try them out. Worst case was I could make single purpose tools out of them. I did a spark test and determined they were carbon steel. I think they will make a good set for a new turner. I'll probably donate them to the right person. Ideally I would recommend buying individual tools and getting just what you need but that would cost many times what this set did.

 

[John Torchick]

I have the HF set with the red handles that I got just after the earth cooled. They are marked HSS, if that means they are really HSS. I do sharpen them on my Rikon grinder with the factory wheels. I'm happy with them. My wife is happy that I'm not buying more tools. She spends our money on things like food, clothing, and shelter. What a waste!

 

[Gerald Lawrence]

The HF I have is marked HSS and I bought them about 12 years ago . Handles are natural and I think the price was 35-45 . At that time they also had a premium set with maroon handles. I guess they have add the even cheaper set . Like John Almost all of the ones I have are repurposed to single use. The amazing thing about CBN to me is how little definitive no-no's we have found . Guess there are exceptions to every rule.

 

[Doug Rasmussen]

.................................................................................. The amazing thing about CBN to me is how little definitive no-no's we have found . Guess there are exceptions to every rule.

Looking at D-Way's site it says the CBN wheels are "specifically designed to grind HSS". It doesn't say not to grind carbide.

I guess those of us who have been using CBN and diamond wheels for industrial grinding just know this. Given the cost of the wheels I've purchased over the years we're careful not to use the wheels for other than intended purposes. CBN for HSS and diamond for carbide.

 

[Bill Boehme]

John, as you've confirmed the insert you cut in half is an industry standard generic designation, an RCGT. Basically a round insert with a 7 degree relief and a "high positive" grind generally used for cutting aluminum, it just happens to work well for wood. RCGT tells you everything needed to order replacement inserts except the actual diameter of the insert.

Inserts, no matter the shape, round, diamond etc, having "GT" in their designation will almost always have a factory mirror polish with razor sharp cutting edges. A hold over from the old days of carbide cutting tools was you couldn't get as sharp an edge on carbide as on a HSS tool. That's no longer true with the new carbides. But, you can't get the razor edge with the relatively inexpensive coarse grit plated wheels.

I've noticed the makers of carbide insert lathe tools don't specify their inserts using industry standard designations. Two reasons I can think of for that. The most obvious reason would be they want you to buy from them. Another reason being the insert nomenclature can quickly get real confusing for newbies.

Grinding carbide on CBN wheels? Not recommended if you value the wheel.

Doug, that is good information to know, but does it help me if I'm not an industrial user? I don't know of any sources to buy the carbide cutters in small quantities. There are small differences between them that would make it a problem in getting the correct one. I only have a few carbide tools, but they all use different shaped screw heads.

 

[Doug Rasmussen]

Doug, that is good information to know, but does it help me if I'm not an industrial user? I don't know of any sources to buy the carbide cutters in small quantities. There are small differences between them that would make it a problem in getting the correct one. I only have a few carbide tools, but they all use different shaped screw heads.

Agreed, there can be problems finding the correct insert. But, once you find it.......

For instance, Sorby has an assortment of carbide scrapers which appear to use a standard diamond shaped insert, probably a DCGT or VCGT.. Measure that insert and using online searches determine what it is. Then you can convert the Sorby scraper to a cutting tool by substituting a high positive insert. With a diamond shape insert you can get into areas a round insert can't, except by rotating the tool as John showed in his Hunter #5 video.

Industrial suppliers prefer to sell inserts in package quantities, they will sell in single quantity. There are Chinese vendors on Bay selling package quantities of inserts for less than a single insert will usually cost you, plus free shipping. I have not tried the Chinese inserts because they're likely poor quality copies of name brand inserts, they might work for wood cutting though.

 

[Dean Center]

No idea of the quality or suitability of these inserts, but MSC carries 72 different RCGT carbide inserts. You can buy as few as 1 of some, though others have a minimum number of 5 or 10. (Anybody who knows the answer, please comment on the quality/suitability)

 

[john lucas]

There are 2 advantages of buying directly from manufacturer of the tool. One is they know the composition of the metal in the bits they use. As you saw there are a lot of choices. The other is the size of the screw needed to hold them. I don't know if all of them have the same tapered hole. If you use the wrong screw or a screw that doesn't fit the taper of the hole in the bit you can fracture the bit. If you buy directly from the manufacturer of the tool you know the inserts will work. Yes they are more expensive but at least with the Hunter tools that I use I get a years worth of use or more from each tool. Break that down into cost per month and it's cheap. Now granted I don't use my carbides for turning the entire piece. Mostly use them for their superior clean up cuts. However i have been using the big Hercules for roughing some bowls and it takes a good pounding and still works.

 

[robo hippy]

Does any one know the sharpening process for these bits/cutters? Do they use ultra fine diamond wheels or some thing similar, that is not available to the general public? I know they can be 'touched up' on the honing plates, but consensus seems to be that they never go back to factory fresh. I guess I am asking because of the diamond wheel that is available, or will be available for the Tormek...

robo hippy

 

[john lucas]

Are you talking about the flat carbide or the cupped carbide. I tried all sorts of grinding and polishing wheels on the cupped carbide and all seemed to chip the edge. I even purchase several from jewelry supply houses thinking I could get a more polished edge. Nope, didn't work. CBN and diamond wheels will remove metal and change their shape but they chip the sharp edge. As far as the flat carbide it depends. The EZ wood tools don't come with a very polished edge and you could probably get close with a 600 grit diamond hone. The Woodpeckers Ultra shear carbides are almost mirror polished on top. You'll never get there without wasting a huge amount of time. Just buy a new one. The EZ wood tools seem to lose their sharp edge fairly quickly and don't know how hard it is to re-establish that. I haven't tried yet. I have only had the Woodpecker tool for a short while. Turned a bowl and spindle with them and you can't even tell I touched them. There is just the slightest mark on the bottom of the shaft where it rubbed the tool rest but even that is almost not noticeable. You could resell them as new and no one would know. It will be interesting to see how long the last.

 

[Ron Boulton]

John, as you've confirmed the insert you cut in half is an industry standard generic designation, an RCGT. Basically a round insert with a 7 degree relief and a "high positive" grind generally used for cutting aluminum, it just happens to work well for wood. RCGT tells you everything needed to order replacement inserts except the actual diameter of the insert.

Inserts, no matter the shape, round, diamond etc, having "GT" in their designation will almost always have a factory mirror polish with razor sharp cutting edges. A hold over from the old days of carbide cutting tools was you couldn't get as sharp an edge on carbide as on a HSS tool. That's no longer true with the new carbides. But, you can't get the razor edge with the relatively inexpensive coarse grit plated wheels.

I've noticed the makers of carbide insert lathe tools don't specify their inserts using industry standard designations. Two reasons I can think of for that. The most obvious reason would be they want you to buy from them. Another reason being the insert nomenclature can quickly get real confusing for newbies.

Doug
There are also RPGT inserts that have a slightly greater Relief Angle of 11 rather than 7deg for RCGT. Maybe these might be slightly better for Wood. I use Korloy RCGT1204MU-AK H01 ( 12mm Diam) and RCGT1003MO-AK H01 (10mm) for Alu in the metal shop. These inserts are ground & polished sharp and are uncoated and are designed for cutting Alu. I suspect that similar inserts, maybe by a different manufacturer, are used by Hunter
Going to make a holder and give them a try on the wood lathe. I also have the RPGT equivalents to compare. Would be interesting to have some Hunter tools to see how they fit.

 

[Ron Boulton]

John
If the Korloy inserts are equivalent to Hunters there is no need to sharpen them as they are available in boxes of 10 very cheaply on AliExpress. Korloy inserts are quite good quality and I use them almost exclusively in my metal shop.
RCGT Inserts use a standard shaped screw head.
Ron