angle of diamond when dressing wheel?

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TRX
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angle of diamond when dressing wheel?

Post by TRX »

I was just looking at a dressing fixture for a bench grinder and noticed that the diamond isn't perpendicular to the wheel face; it's tipped so its axis points about ten degrees below the wheel centerline.

I went out to the shop and looked at my Storm Vulcan crank grinder, and its diamond is tilted about the same amount... in the opposite direction.

Here I'd always thought they should be perpendicular...

Is the angle the diamond is presented to the wheel important?
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GlennW
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Re: angle of diamond when dressing wheel?

Post by GlennW »

Yes, usually 10-15 degrees as you are supposed to rotate the diamond on the holder to keep it sharp. If it was perpendicular it would just wear flat on the tip and stay that way and tend to just crush the wheel abrasive rather than fracture it.

I use hex shank diamonds on my OD grinder and rotate it one flat every few dressings.
Glenn

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TRX
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Re: angle of diamond when dressing wheel?

Post by TRX »

The diamond is hexagonal or its holder is hexagonal?
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GlennW
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Re: angle of diamond when dressing wheel?

Post by GlennW »

A portion of the steel shank on the diamond.
Glenn

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TRX
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Re: angle of diamond when dressing wheel?

Post by TRX »

Thanks!
RonnieJ
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Re: angle of diamond when dressing wheel?

Post by RonnieJ »

The real reason for the angle besides wear is to keep it from pulling out of its set. Ron
TRX
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Re: angle of diamond when dressing wheel?

Post by TRX »

How does that work when the diamond is pointed down below the centerline of the wheel, though?

That's what prompted the original question; within a short time, I saw pictures of diamonds pointed at about the same angle, but in two different directions.
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Harold_V
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Re: angle of diamond when dressing wheel?

Post by Harold_V »

The angle has nothing to do with pullout of the diamond from the mounting matrix, and everything to do with two things. One of them, as Glenn alluded, was to permit use of the diamond without promoting a flat surface. The rotation of the diamond, when set at an angle, presents a sharp corner to the wheel, cutting the abrasive cleanly instead of dulling the grains.

The second one is a consideration of what the diamond does when introduced to the wheel. The angle is a necessity, but should be presented to the wheel such that the generated forces push the diamond away from the wheel. If the angle is presented in the wrong direction, the diamond is "picked up" by wheel rotation, for lack of better description, driving the diamond deeper in to the wheel, which is not desirable. Armed with that thought, it should be clear to you folks that the angle of the diamond should be presented to the wheel with the diamond base trailing, with the tip of the diamond on the centerline of the wheel, to limit the possibility of dressing an unwanted angle on the wheel face, the result of a spindle that is not at a perfect right angle to the table.

I am unable to post any pictures showing proper orientation, but, perhaps, Glenn would be willing. He knows what I'm talking about.

H
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GlennW
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Re: angle of diamond when dressing wheel?

Post by GlennW »

The tip of the diamond is directly under the center of the wheel (or slightly aft of rotation, but never foreword) with the diamond shank tilted at a 10-15 degree drag angle.
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Glenn

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pete
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Re: angle of diamond when dressing wheel?

Post by pete »

I sure hope TRX doesn't mind me adding a question to his. I've seen lot's of mention about diamond dressing wheels but I've never run across a mention about how fast the diamond should be traversed across the wheel face. For example a 1" wide wheel. About how many seconds should it take to dress across that width of wheel face?
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Harold_V
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Re: angle of diamond when dressing wheel?

Post by Harold_V »

Considering the rate of rotation of the grinding wheel, it's not really necessary to traverse slowly, although one does not rapid across, either. I'd suggest, for a 1" wide wheel, that it should take about 10-15 seconds. On a 3600 rpm spindle, that would result in a feed rate of less than two thou per revolution. Slower wouldn't hurt, assuming one was going for a very fine finish.

Think of dressing the wheel on a centerless, where wheel width is commonly 6" or greater. That's a lot of abrasive removed in one pass, with virtually no change in the diamond after multiple dressings. Speaks volumes about the hardness of diamond.

H
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pete
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Re: angle of diamond when dressing wheel?

Post by pete »

Many thanks Harold, that's a question that's bothered me for a long time. While I've never timed it, my guess is I've been doing pretty close to your numbers. More by luck than skilled knowledge though. :-)
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