Indicating Both Ends of the Bore

... does this have to be done under a full moon as well? :)
 
V-blocks

Or just buy a set of matching precision ground V-blocks---much easier and more accurate.;):)
 
RoyB said:
HUH?

I'm gonna need pictures on this one!
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It sounds to me like he is putting some steel balls in flat bottom holes that he mills into the side of a square bar. Two balls on each end. There are some "V" blocks made like this but they use 4 balls, two sets of 2.
He turns about 1.4" of each end of the barrel to clean up, concentric with the bore and these are what rides in the "v" block or on the balls while turning the barrel by hand to observe runout.
His bar is about 2" square and 40" long. He mills two opposite sides parallel, I assume he is starting with HRS instead of CRS or ground stock.
I've got several sets of "V" blocks and could use the mill table since I don't have a BIG surface plate. His bar could be used as a stand alone fixture.
 
fixture

You would STILL have to set his fixture on a surface plate or mill table or some other flat surface----just like you would a set of V-blocks.
It would not be a "stand alone" fixture anymore than 2 v-blocks.
You could take the time to make a fixture as described and I would not suggest that someone who wanted to make one shouldn't but, if you think about it, there is a lot of room for error in a fixture like this---especially one that is made and finished on the mill---you could get a couple thousands error from one end to the other very easy.
It still would not tell you how "straight" your bore is.


Rich
 
Rich,

I think that you could clamp his bar in a vise, attach a dial indicator to the bar and use the indicator to show the amount of barrel runout. There is no need to have the bar sitting on a surface plate or mill or anything.
If you welded two "v" blocks to an I-beam, they would then function as a stand alone unit, same as his bar made with balls.
I also think that his unit would work pretty well even if the balls were at depths that varied a few thou, one end would be slightly higher than the other. That would not affect the indicator reading. If the round bar being tested were perfectly round, the indicator would not move.
I have no interest in building a test fixture like this, I was just trying to help RoyB grasp the concept being presented by the original poster.

Jay, Idaho
 
Dipper

Jay said:
Rich,

I think that you could clamp his bar in a vise, attach a dial indicator to the bar and use the indicator to show the amount of barrel runout. There is no need to have the bar sitting on a surface plate or mill or anything.
If you welded two "v" blocks to an I-beam, they would then function as a stand alone unit, same as his bar made with balls.
I also think that his unit would work pretty well even if the balls were at depths that varied a few thou, one end would be slightly higher than the other. That would not affect the indicator reading. If the round bar being tested were perfectly round, the indicator would not move.
I have no interest in building a test fixture like this, I was just trying to help RoyB grasp the concept being presented by the original poster.

Jay, Idaho
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Shoot well
Peter
 
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Peter,
Do me a favor and write in inches. I get a headache from having to mentally convert everything so I know how far it is! Calling a 3/16 diameter bar 4.8mm makes it really tough for me to visualize! By the way, I'm just kidding; measure any way you like! Regards, Bill.
 
Bill

Bill Leeper said:
Peter,
Do me a favor and write in inches. I get a headache from having to mentally convert everything so I know how far it is! Calling a 3/16 diameter bar 4.8mm makes it really tough for me to visualize! By the way, I'm just kidding; measure any way you like! Regards, Bill.
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Than I'll have a headache. So it's better that's you rather than me. Just kidding.

Shoot well
Peter
 
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