View Full Version : Grinding wheel shapes
02-02-2008, 10:18 AM
Hello all, could someone shed some light on the way different shaped grinding wheels are used, I know I could just "use what works" but the wheels have been made the way they are for a reason.
I have a union tool and cutter grinder that came with lots of extras and a box of
wheels, I have straight flat wheels, tapered cup wheels, straight cup wheels, dish or saucer wheels and 2 diamond wheels. In 3 different colours:)
I'd like to know in particular about the tapered cups i.e which is the cutting face?
I'm aware of different grits and bonds and the significance of the colours, it's the way in which the wheels are presented to the job that puzzles me.
02-02-2008, 10:24 AM
I'm going through the same learning curve, since I got my Brown & Sharpe T&C Grinder. The best thing to do is to look through the Norton cutter grinder catalog, which shows all the (many) shapes and ANSI wheel designations.
So far, it seems like a 46 or 60 grit AO cup wheel does 80% of the tool grinding stuff I need in the shop.
02-02-2008, 10:48 AM
I started climbing this learning curve a while back. If you have not done so already, do yourself a favor and get the CD sold by our own Mr. John Stevenson on ebay, that contains the user manuals for a number of different manufacturers T&C grinders, as well as a bunch of other related info. It is costs less than a cheap grinding wheel and contains a wealth of information on uses and techniques. Worth every penny.
You can find it on ebay by searching for the seller name "marypoppinsbag" .
All standard disclaimers apply, no connection, just a satisfied customer, do not point at the sun, blah, blah, blah...
The colors have no particular significance. They are whatever the manufacturer decides to make them. In particular, aluminum oxide wheels can be any color at all since the natural crystal is white. Silicon carbide is a dark crystal so only dark colors are possible. Brown, green, pink, ruby, blue and any other color except natural greys are all obtained by using dyes in the grit binder. There is no standard to follow.
02-02-2008, 02:05 PM
I've just about completed a Brooks (http://www.gadgetbuilder.com/Brooks%20Grinder.html) cutter grinder and have several wheels including a CBN taper cup and an AO cup. The taper cup will be used much like the regular cup wheel - the side of the wheel is where grinding is normally done.
This CBN taper cup has a very narrow face, only about 0.100 wide(radially). The info on CBN is that it retains its shape better than AO so the thin face is supposed to survive considerable use - I certainly hope so because it wasn't cheap. Conceptually, the wheel is twisted slightly from the traverse plane so the contact area is narrowed further to minimize heat buildup in the work; the hardness of CBN theoretically allows the wheel edge to last longer than AO wheels when used this way. Mostly theoretical so far since the grinder isn't quite done... although I've sharpened a small boring bar on the taper cup, holding the bit by hand because the work head isn't mounted yet.
The side of my Norton AO cup (4x1.5x1.25) is about 1/2" wide and I expect to use the full width (vs the edge), probably for grinding lathe bits and other large items that would rapidly wear the taper cup. The 1.5" width should allow grinding quite a few bits and I have 4 more of these AO cups from an eBay purchase so I'm hoping they work well for this purpose.
02-02-2008, 02:08 PM
This CBN taper cup has a very narrow face, only about 0.100 wide(radially).
I've got two CBN cup wheels, and they're both plated on the outside rim, and the front edge. Is that what you mean?
02-02-2008, 02:26 PM
I have two CBN wheels; the taper cup wheel has a CBN section that is about 1/2" wide axially so it overhangs beyond the metal section by a fair amount as shown in the picture below. The CBN seems to be a composite mixture molded to the metal wheel.
The other wheel is very narrow (about 1/16") with CBN grit that is held in place by plated metal; I expect to use this for slotting (gashing?) the end of end mills.
Edit: Change picture to show all 3 wheels.
The big CBN cup wheel is a type 11A2. It's intended for grinding on the axial face. A similar type is the 12A2. An 11V9 shape is about the same but the CBN compact is on the outer radial rim and is meant for grinding on that rim. The type of CBN wheel you have is a resin bond wheel. There are in the last few years sintered CBN wheels but they cost more than I can afford. You can grind on the radial edge of that wheel but it will tend to change the sharpness of the corner faster than would otherwise occur.
CBN holds up extremely well and justifies the initial cost easily. It's even difficult to abuse the wheels although it can be done. Here is an example of two identical wheels. The left is chucked up in my lathe right now as I was using it for sharpening some tooling. CBN doesn't shed grit hardly at all so isn't as big a mess as mineral grit wheels.
The wheel on the left has been in use for about two years. It is getting rather glazed and I need to clean it with some silicon carbide. The wheel on the right is brand new so you can see the shape of the used wheel hasn't changed substantially. The used wheel isn't even close to being worn out so it will be quite a while before I need to put the new one into service.
As well I have a few extras for other jobs.
02-02-2008, 06:32 PM
Yep -- that's the same style of CBN cup wheel I have. Mine also looks like the CBN was deposited on the cup.
I also have a CBN cutoff wheel, and several CBN toolpost grinder wheels like the one in Evan's chuck -- I'll edit this post with some pictures later tonight.
02-02-2008, 10:31 PM
Get Norton's tool room grinding booklet, that will show you all the setups and calculations needed to sharpen your cutters.