I order shafts by the 100’s, machine matched in 5# groupings such as 45-50#, 55-60#, etc. The first thing that happens is that I straighten every shaft. One reason is that you want straight arrows. The other reason for me is that my spine (stiffness) tester has a dial indicator to measure deflection and requires that the shaft sits centered on the tester. If the shaft is crooked, it doesn’t rest correctly on the dial indicator. Next I mark the edge grain at one end of the shaft. This is done so that when I measure the spine, it’s done parallel to the grain. Once straightened and edge grain marked, I measure the spine of every shaft and mark the deflection in thousandths of an inch on the end of the shaft above the grain mark. (The nock will be installed so that the bending that occurs upon the shot will be in the direction of the grain, the direction that the spine was measured). Next, every shaft is weighed to the nearest grain and marked on the other side of the edge grain mark. Once I have both measurements marked on the shaft, I enter each shafts measurements into a spreadsheet (Excel) recording the spine in thousandths of an inch and weight in grains. Once entered, I sort the batch from highest to lowest spine. That displays the batch from the lowest to highest bow poundage. The results are then graphed showing the gradual reduction of spine, and an irregular display of the associated weights. I then mark the graph at one-pound increments using the Jim Hill spine chart. Next, I visually group shafts that are closest in weight and closest in deflection. My visual observation of the chart is verified using the printout of the shaft listing. Once I get the closest matches possible, I select the shafts from the batch and bundle them in “matched” dozens or half dozens, whatever I can get from the batch. I frequently can only get 6 dozen and perhaps 2 or 3 half dozens from an original batch of 100. The remainder go into a holding box to be included in the next batch I get with the same original grouping. The result is a dozen shafts both weight and spine matched. I always advise you of the spine and weight tolerances I have available before preparing an invoice for your order. Does your arrow builder do that?
Next time, How does and arrow bend when shot, and how does spine affect the results?