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Rifles, Reloading, Optics, Equipment
Reloading
Concentricity - setting up dies - runout
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<blockquote data-quote="Mikecr" data-source="post: 510432" data-attributes="member: 1521"><p>But runout and concentricity are two different things.</p><p>Concentricity is referenced ONLY to centerline, with a quality described as hi/lo eccentricity from that centerline. With this, your DEVIATION(eccentricity) might be assumed as half the total indicated.</p><p>None of this applies to runout really.</p><p></p><p>The deviations causing runout, are a sum of ALL deviations, with possibly few if any of which relating to a centerline. TIR is just that. The total of it..</p><p>It's NOT eccentricity.</p><p></p><p>A loaded case can be perfectly concentric and still have plenty of runout from case thickness variance, or banana shaped cases, or casehead squareness, or bad seating(with adjustment}. All combining in abstract ways.</p><p>A loaded case that is perfectly STRAIGHT will be both concentric AND lowest in runout.</p><p></p><p>What is straight?</p><p>Straight means you could carefully place a low clearance chamber over a loaded round setting on glass, shine a light down the bore, and see the light all the way around the case, from the bottom.</p><p>But a loaded case that is declared concentric, yet not measured as straight, would likely fail this test. Very badly..</p><p></p><p>Then, you've got all the masking in measurement position going on with H&H type tools.</p><p>Here we go again,,</p><p>Picture a rigid jump rope(your banana case). If you care to see this deviation, and fix your processes to produce straight ammo, would you really chose to indicate nearest one end of the jump rope(it's fulcrum)? Or would you pick the middle?</p><p>You know there will be only a fraction of the actual deviation seen nearest a pinned/stationary end, right? Afterall, it's fixed in position very near that point.</p><p></p><p>With a v-block method, the center of the jump rope, and one end, are fixed. The deviation is then seen in it's entirety on the other free end.</p><p>That jump rope was always concentric. But it was never straight until measured so off a v-block.</p><p>That's an important difference.</p><p></p><p>If you've got 3.5thou deviation with an H&H, you've got seriously horrible runout.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 510432, member: 1521"] But runout and concentricity are two different things. Concentricity is referenced ONLY to centerline, with a quality described as hi/lo eccentricity from that centerline. With this, your DEVIATION(eccentricity) might be assumed as half the total indicated. None of this applies to runout really. The deviations causing runout, are a sum of ALL deviations, with possibly few if any of which relating to a centerline. TIR is just that. The total of it.. It's NOT eccentricity. A loaded case can be perfectly concentric and still have plenty of runout from case thickness variance, or banana shaped cases, or casehead squareness, or bad seating(with adjustment}. All combining in abstract ways. A loaded case that is perfectly STRAIGHT will be both concentric AND lowest in runout. What is straight? Straight means you could carefully place a low clearance chamber over a loaded round setting on glass, shine a light down the bore, and see the light all the way around the case, from the bottom. But a loaded case that is declared concentric, yet not measured as straight, would likely fail this test. Very badly.. Then, you've got all the masking in measurement position going on with H&H type tools. Here we go again,, Picture a rigid jump rope(your banana case). If you care to see this deviation, and fix your processes to produce straight ammo, would you really chose to indicate nearest one end of the jump rope(it's fulcrum)? Or would you pick the middle? You know there will be only a fraction of the actual deviation seen nearest a pinned/stationary end, right? Afterall, it's fixed in position very near that point. With a v-block method, the center of the jump rope, and one end, are fixed. The deviation is then seen in it's entirety on the other free end. That jump rope was always concentric. But it was never straight until measured so off a v-block. That's an important difference. If you've got 3.5thou deviation with an H&H, you've got seriously horrible runout. [/QUOTE]
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Concentricity - setting up dies - runout
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