Surface Grinding

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Bill Shields
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Re: Surface Grinding

Post by Bill Shields » Tue Jun 21, 2022 6:57 pm

Who says that a V block has to be 90 degrees?

As long as the angle is uniform along the length...does it matter?
Considering manufacturing with a cylindrical wheel, having the included angle greater than 90 makes a lot of sense...
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ctwo
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Re: Surface Grinding

Post by ctwo » Wed Jun 22, 2022 5:41 am

https://testbook.com/question-answer/v- ... 27a8fce858

I do set square work in them from time to time.

They (B&S) don't have a relief groove but neither do the Starretts. Both were machine finished. I was wondering if there would be a specification or another reason beyond, it's easier/cheaper to make a less useful jig.
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Bill Shields
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Re: Surface Grinding

Post by Bill Shields » Wed Jun 22, 2022 7:23 am

Besides the fact that they make other products intended to hold square work?🤪
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ctwo
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Re: Surface Grinding

Post by ctwo » Wed Jun 22, 2022 10:24 am

Well, I guess after watching a Suburban Tool video, which is more accurate to use when measuring out of roundness, [strike]45[/strike] 90 or 60 degree Vs? I can say neither :D
Last edited by ctwo on Wed Jun 22, 2022 1:40 pm, edited 1 time in total.
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Bill Shields
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Re: Surface Grinding

Post by Bill Shields » Wed Jun 22, 2022 11:57 am

huh?
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ctwo
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Re: Surface Grinding

Post by ctwo » Wed Jun 22, 2022 1:36 pm

Well, of course I meant 90 or 60 degrees. I was thinking of the 45 you get when you set a square block into V.

But just in case: https://www.youtube.com/watch?v=YUeFNGslzZo
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Bill Shields
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Re: Surface Grinding

Post by Bill Shields » Wed Jun 22, 2022 2:26 pm

I say huh? not because of your specified angle, but because there is always a consideration regarding how an item is supported when measuring ->

when working in any type of "V" block -> the contact surface becomes your reference point rather than using the 'theoretical center' as the reference ->

which you cannot do in any type of a 'V' block -> no matter what the included angle.

If you have a perfectly round item, then it will matter not what included angle V block you use.

If you have a non-round item, the V block testing routine will TELL YOU that the part is OUT OF ROUND, but will rarely give you an exact value...since 'out of round' can be anything from an ellipse, to an ovoid (egg) or <use your imagination>
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ctwo
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Re: Surface Grinding

Post by ctwo » Wed Jun 22, 2022 4:15 pm

So you're saying Don is incorrect? I suspect there is a particular shape that would not reveal any out of roundness in either V-block using that method.
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Re: Surface Grinding

Post by Harold_V » Wed Jun 22, 2022 11:50 pm

ctwo wrote:
Wed Jun 22, 2022 4:15 pm
So you're saying Don is incorrect? I suspect there is a particular shape that would not reveal any out of roundness in either V-block using that method.
Don't think so.
A centerless grinder grinds parts slightly above or below center. How much isn't really critical, so long as it's not truly center. They limit the amount for various reasons, one of which is that the part must retain traction with the regulating wheel.

If parts are run on center, the end result can be a three sided grind that measures exactly the same at every point, yet the part isn't round. By checking the part by rotating in a V block of any angle, the error will be displayed, albeit without a true value. For that reason I suspect that there is no shape that would not display the error to some degree. Am I nuts? :?

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Re: Surface Grinding

Post by GlennW » Thu Jun 23, 2022 7:06 am

A 60° would be my choice if looking for tri-lobed parts such as setting up a centerless grinder.
V Block.jpg
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Bill Shields
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Re: Surface Grinding

Post by Bill Shields » Thu Jun 23, 2022 9:01 am

The number you get is all a function of how much the CENTER of the part moves up / down / left / right as you rotate an irregular shaped part in a set of V blocks.

from a mathematical standpoint, you should be measuring the distance from the theoretical center out to the edge....after all, that is what the TERM ROUNDNESS MEANS -> the difference from the theoretical circle to the actual circle... :D

which (in reality) means that you get a better number from 'on centers' than you do in any type of a V block...
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Re: Surface Grinding

Post by GlennW » Thu Jun 23, 2022 12:03 pm

"centerless" ground
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