Hi All, OK, I've read enough of Harold's posts that I have decided it is time to upgrade my grinding capabilities. I presently have a fairly old and not super great tiawaneese 6" bench grinder with the original crappy wheels. I would like to at least make this passable for general use until I get my KO Lee T&C grinder together. Even then, I still need a bench grinder, for , well, bench grinder stuff, you all know. So to that end, I am planning to make some good flanges, replace both of the wheels, banish my (Harold, close your eyes till this next line passes...)star wheel dresser, and get a diamond dresser.
(Harold can open is eyes now) I was perusing a few catalogs looking at single point hand diamond dressers. At least I think that is what I want.Please correct me if I am wrong. Anyhow I was looking at ones similar to this:
The thing I noticed, was that these come in various carat sizes, 1/4,
1/2,3/4,1, etc. Why is that? What would determine which one I would want or need?
Second question is, for general shop stuff, HSS tool grinding, tweaking the ends of screwdrivers, etc., what is a decent compromise for wheels? I am not snagging castings or grinding welds and such. I have to admit to being a bit confused by the bewildering number of choices of grits, compositions and bonds. I understand that there is a "tool" for every job, but a bit of general guidance would make me feel a bit less dumb.
You might design your wheel flanges so they incorporate a thick (1/4") washer drilled all around the edge with holes, and a secondary washer which half covers the holes. That way you can put weights in the holes to balance the armature/shaft/wheel assembly.
I also have heard Harold's views on star dressers, but they do a great job of deglazing bench grinder wheels. I don't know about handheld diamond dressers, what's the point? Why not just get a Norbide dressing stone and be done with it? They cost like $5 and if you wear one out in a lifetime I'd be amazed.
The thing about grinding wheels is: for harder materials use softer wheels, for softer materials use harder wheels; keep your wheel balanced, trued and dressed, and understand the metallurgy behind grinding and heat treating. I tend to buy wheels that do a good job on HSS, and live with the results on softer materials.
Don't throw away your star dresser. I have a couple of diamond dressers and a couple of star dressers. The star dressers get used more often than the diamond ones. The diamond ones are great for trueing up a wheel, but dull the wheel. The star dressers open up the grain so the wheel cuts faster and cooler, but are not so great for trueing.
I like a 36 for coarse and a 80 or 100 for fine. Plus a wire brush sometimes.
Grant, thanks for the reply. I like the idea for the flanges, I will incorperate something like that.
I am only kidding about banishing my star dresser, I'll just put it
*way, way* over there where Harold won't see it and yell at me. (Just kidding Mr. V.!) As to what is the point of a diamond hand dresser, I don't really know, that is why I asked. I have just seen lots of mention of their use, and asumed that that was the "proper" tool for the job. Actually I do have Nobride (or something equivelent) stone. Is that essentially the same thing, or used in the same ways?
That's never been disputed. Not by me. My point is that star dressers are quite wasteful of a wheel, particularly as the dresser shows signs of wear and "chatters" as it dresses the wheel. For offhand grinding, there is no better wheel surface, but when you grind toolbits by the method I use, a star dressed wheel is worthless. It's difficult to get the wheel to run smooth enough, whereas the use of a diamond to true the wheel brings it in almost instantly, and a dressing stick to break the fine surface yields a wheel that will grind nearly as well as a wheel prepared with a star dresser. That makes the use of a star dresser not worth the trouble. By contrast, if you're using your grinding wheels for rough grinding, a star dresser is the ultimate.
I don't know about handheld diamond dressers,
Bad advice. For starters, a Norbide costs around $30, not $5. You're far better served to buy a small mounted diamond, which is far more aggressive towards grinding wheels and easier to apply. Unlike the typical silicon carbide dressing stick that is 1" square and 6" long, the Norbide dressing sticks are made of boron carbide, solid, typically 3/16" x 7/16" x 3" long, and are not made of small bits that are bonded. Because of that feature, they don't perform well. Bonded silicon carbide sticks keep sloughing off the dull grain, presenting new, sharp cornered grains to the wheel, so they do a better job of dressing. As you use the Norbide, it slowly wears until it is well polished and lacks a sharp edge that is mandatory to get a sharp wheel. The polished surface that results tends to dull the abrasive grains of a wheel instead of cut or otherwise dislodge them, so the wheel doesn't perform well. You'd be far better served to stick with a star dresser in that case.
Star dressers are an impact tool that crush the surface of the wheel. As the "spurs" rotate, they're hammered against the wheel, sloughing off the surface. They should not be idles, otherwise the wheel grinds away the spur.
The only difference is the size of the diamond. If you use the dressing tool regularly, the larger, the better, for it will last longer. There's a small problem with using such a dressing tool by hand, however. You'll find that you'll wear the end to a rounded surface, which lessens the diamond's ability to cut. Won't happen fast, but it happens. On a machine, the diamond is generally held in a fixed position, and presented to the wheel at an angle of sorts. As the diamond wears and dulls, all that is necessary to present a sharp edge to the wheel is to rotate the diamond slightly. The edge of the flat surface created by repetitive use of the diamond in a fixed position is the sharp edge needed for efficient cutting of the wheel.
Armed with the above, you might be better served to buy the 1/4 carat tool and replace it (in several years) when it's not performing to your satisfaction. Be sure you read what I had to say about dressing sticks, so you end up with the right one for your needs.
You would be well served by a wheel that was either 46 or 60 grit, aluminum oxide, maybe an H or I hardness, vitrified bond. You'd be surprised that it will handle all your grinding needs as long as you're not grinding soft materials, and would do a good job on HSS.
Thanks, Harold. I was just not sure if there was any compelling reason to go with a larger and more costly diamond dresser. They are not all that costly and at the rate that I use this, even a 1/4 carat one will likely last me a very, very long time.
After reading your description, I took a look at exactly what a "Nobride" dressing stick is, and found that is not what I have. What I have appears to be the silicon carbide type you describe, about 1" square, 5" long, and looks sort of like a chunk of course grinding wheel. Can I take it from what you wrote that that is somewhat equivelent to the star dresser, though less aggressive?
There is a decent industrial supplier nearby. I may go by and check out what they have in grinding wheels of the sort you describe. When you say that such a wheel will serve for most applications so long as I am not grinding "soft materials", how soft do you mean? Do you mean steels softer than HSS, or do you mean stuff like brass, aluminium or maybe a piece of lamb? :) Sorry if that seems a dumb question, but I am really trying to understand how this all works.
Thanks, Dan. Like I said, I was just kidding about banishing my star dresser. I will eventually put 2 wheels on this grinder, i have a second one with the wire wheel on one side and a taper spindle on the other for buffing wheels and such. Very handy.
"Al A." wrote in message news: firstname.lastname@example.org... snip----
Actually, they're more like a diamond. The only dressing tool that works by impact is the star type, and that's the most desirable surface you can prepare.
The dressing stick you described is exactly what you want--but it works by cutting the wheel, although the hardness difference isn't as great as it would be with diamond, which goes without saying. Silicon carbide is far and away harder than aluminum oxide, so it easily cuts the aluminum wheel, although you get a combination of cutting and tearing of the abrasive due to rupturing the bond. The bond of the wheel isn't nearly as hard as the abrasive, so the majority of the dressing occurs by that process.
Due to the fact that the dressing stick is made up of small pieces, you don't get large, polished areas that won't cut (like a Norbide is inclined to do), although the slightly polished small grains do tend to dull the wheel somewhat. You can avoid that by seeking sharp edges of the stick when necessary.
There's no doubt about it, a star dresser has the advantage as far as the surface of the wheel is concerned, but you have to balance the slightly reduced cutting ability of the wheel dressed with a stick against the difficulty of preparing a dead true running wheel with a star type dresser. As I stated earlier, for me, it's a no brainer. You can make a wheel run dead true with almost no effort with a dressing stick, especially if you have a rest upon which you can place it while you're dressing. That prevents the stick from bouncing with the wheel.
In spite of the fact that I don't use a rest, I can still true a wheel by picking a corner of the stick and not press-----allow the wheel to remove itself until it's running a full circle before bearing down on the stick, if necessary. It takes a little practice, but it's no big deal to master.
There's no dumb questions, Al, only dumb answers. By soft, I mean steel items, but not cast iron. Mild steel, for example, is too soft to be ground successfully on a wheel that is intended for HSS. You'd want to step up in hardness, to an M or even higher for such an application.
The key here is to have on hand the type of abrasive that's suited to the material. Steels of all kinds (not stainless) should be ground with aluminum oxide (silicon carbide is soluble in steel at high speeds, much the same way diamond is. That's why one never chooses silicon carbide for grinding steel). All other materials, including cast iron and stainless, should be ground with silicon carbide. That includes aluminum and brass. The green silicon carbide wheels are generally used exclusively for grinding carbide (in the machine shop----I think guys that grind rock use them for that purpose). Anything else should be ground with black silicon carbide wheels. Reason? Carbide is so hard that it dulls the abrasive quickly. In order for the wheel to cut successfully, it must shed the dull grain rapidly. For that reason, the wheel is bonded quite softly, to promote breakdown. With that in mind, you can easily understand that the wheel would be way too soft for grinding other substances. The black wheels are bonded much harder, but, again, you must balance the hardness of a job with the wheel. Just like aluminum oxide wheels come in grades (J-K-L, etc.), the silicon wheels do as well. The designation of hardness has nothing to do with the abrasive, but everything to do with the strength of the bond. Soft wheels are no softer than hard wheels, but they are more friable because the bond is weaker. That's what the meaning is of a hard or soft wheel.
If you have a steady hand, it works fine on wheels, even free hand. That's a cluster diamond, and cuts quite well. It makes getting a flat wheel much easier, and actually dresses much better than does a single point diamond because the small pieces of diamond can't get polished to a ball. Diamond is so much harder than a wheel that it cuts the typical grinding wheel with ease, as long as it's presented to the wheel with a sharp edge. Clusters do just that.
We've used a norbide stick for years to rough dress the sides of our wheels, or roughing a large radius when doing form grinding. It is much faster than using a diamond. We hold the stick by hand for roughing only. When the wheel is close, we use a wheel dresser with a diamond to finish the job.
While I'd question a Norbide being faster than a diamond (I've used both of them extensively---Norbide, *unless very sharp*, does not move the wheel as fast as diamond does, nor should it. It's not as hard as diamond).
The point at hand is that *for offhand grinding*, Norbide prepared wheels are pretty much worthless----particularly when the stick isn't sharp. By the time you have the wheel running smoothly, it cuts hot and resists the work at hand, due to the polished condition of the wheel. IN essence, you've dulled the wheel in the process of preparing it for work. A diamond dressed wheel is quite valueless for hand grinding as well, due to the smooth surface. In order for a wheel to cut freely (for hand grinding), it should be prepared by fracturing, which a star dresser does very well, and a sintered dressing stick does fairly well. Don't steer theses guys down the wrong path with the notion that a Norbide is the best choice. It's not.
Remember, we're not talking about machine grinding here, where diamond dressed wheels are a requirement.
Thanks very much to Harold, and all you guys who replied. All most informative and helpful info, and just the sort of guidance I was hoping for. I have cliped and saved all of this for future reference. When I get my grinder flanges made up and get a couple of new wheels, as I tweak everything in, I will no doubt have some more questions.
I think we've had this discussion before but I thought I'd put a word in on the best dresser I've ever used for a wheel being used to grind tools offhand. The one I used was made by KO Lee and for a while MSC didn't have anything similar. But it appears that they now handle one just like it made by Desmond. You can see it here.
I've never used anything that will leave as sharp a wheel but still be a smooth and true as one of these and I've used diamond, silicon carbide dressing sticks, diamond clusters, and star wheel dressers. The one my former employer had was a single handle and for just sharpening the wheel you don't have to hold it at the angle recommended for full dressing. It will leave a smooth no run out smooth faced wheel that will still cut as good or better than the star dressers. Yes the wheel in the dresser needs to be replaced from time to time and it's expensive to buy. But I've never found anything that will leave a surface as good as one of these.
I was going to build one of these because I couldn't buy one but never had the time to. I just noticed them back in the MSC catalog a few months back when talking to a friend about grinding wheel dressers. It's going on the next MSC order I make (if I have the spare money for it).