The Importance of Wheel-dressing when Surface Grinding is Revealed

[ranald]

I curious & perplexed that there have been such advances in wheels, wet & dry, that there hasn't been a similar advance in holding the wheels. I'm a novice:I have seen one white wheel about 3" wide that was worn down to about 8" diameter that had cracked and broken. If such was to happen during use it would be some what like an angle grinders cutting/grinding wheel disintegrating : extremely dangerous. I had a small one cut several parts of my body & 2 very deeply. I no longer buy cheapies. For my 9" angle grinder I could never remove the flange without heat (concern for the strength of the thread & broken spanners) until i used an extra paper/thincardboard flange under the metal screwed one. End of problem but I must point out that they tighten as revolving. It would seem that bench grinders do not & loosen a tab. I always let my wet wheel dry out while running (after removing tub) without incident relative to my very limited knowledge. my dry grinders I never check, sadly it would seem but often change types & grades.
So why not better holding capacities of the stones?

[Okapi]

Reading again the post, I've just a comment from recent work I make with 50mm. dia. grinding wheel mounted on a B8 shaft with only tenths for the paper disk, I've glued the disks the day before under small pressure with wood glue because they make rule out problems with the speed and make vibrations.
Using permanent marker to control the non slipping during dressing the wheel as explained before, I always put my Vertex wheel dresser to clean before a new work in part because when I was an apprentice we learn that the surface grains come rounded and worn and need to be freshened before each new work to have the right surface grade needed on the plan.
Making that, despite the precision obtained with the B8 mounts, they are always small differences due in my opinion to the wheel used itself because the shaft is round on the 1/100mm. value.
It's totally in the sense explained by Brendon, if you neglect this operation the finish cannot be as good without any vibrations or others preventive signs, and I've no explanation to give more than grinding wheels for high speed can have differences in wearing variation on the same lot of wheels.
Your pictures with magnification are really a superb way to learn that point, using reference tables it's impossible to be precise like that on the problems.

[Toolmaker51]

Aside from imperfection of grain distribution in wheels, truing before grind work is very common. Many die shops leave the spindles run all day, but still true before next part.
An uncommon technique was taught by a Romanian grinding master, for sliding parts. With a part to size and surface finish, he'd dress wheel just tenths-worth of dust. With a few strokes of felt pen on part to monitor results, the turning wheel was rapped smartly with a wooden dowel (broomstick). This offset the trued wheel by ~ half the clearance between wheel and arbor. As the table reciprocated, wheelhead was brought closer and closer to the part; approaching last .003, a slip of paper used like a shim. The resulting finish was essentially like handscraping/ flaking, allowing lube or air minimization of friction in the tightest possible sliding fit.
Needless to say, the machine condition was excellent, but not roller ways.