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v-blocks

dian

Titanium
Joined
Feb 22, 2010
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so i have been thinking, if im measuring the runout or roundness or something else of a cylindrical object, i will put it in a v-block or two on the plate. i know nothing about v-block standarts, flatness of the surfaces, their "parallelism" (or whatever you call it), their roughness. are there any? does all this even matter or will a shaft somehow rest on three points in the block regardless of its accuracy. also when using two blocks i press the object into the blocks and thats it. now if i wanted to measure lets say to microns, maybe i should align the blocks with a parallel? but again, no idea how precise the sides are to the surfaces the piece rests on. or maybe the object also rests on three points in the two blocks and it doesn matter, unless the blocks were to move? well, a lot of question, it seems.
 
its both and nothing fancy, a shaft in a v-block for example. checking it with a 0.5 mu indicator.
 
dian --

Not answers to question you've asked, but nevertheless . . .

1) The gaging sensor wants to be structurally connected to the V-block; the goal is to minimize the probability that the sensor will move relative to the V-block.

2) Setting the gaging sensor so that its sensitive axis is perpendicular to one face of the V -- rather than the more usual parallel to the bisector of the V -- makes geometric interpretation of the gage readings a lot more intuitive.

John
 
V blocks don't work like that. You can't reference the outside of the shaft using the outside of the shaft. This is why things are turnned between centers. If you want to use two match set, V blocks and use live centres in each V-block and you want to run an indicator to reference parrell from centre or you want to reference a turned flange rotating, OK. If it is just a straight shaft use micrometres and just roll it on your surface plate with feeler gauges.
 
This doesn't answer all of your questions but will help you to understand out of roundness.

Gene
 

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