Some months ago I ordered a new lot of 12\u201d 20 gauge needles from Fisher Scientific.\u00a0 When they came I noticed that the box had a sticker that said Cadence Scientific instead of Popper and Sons.\u00a0 I took out three needles and very carefully rolled them between a countertop and a semi-truck tire gauge (aka the steel mandrel).\u00a0 I basically did a combination of rolling and also pulling (gently) the needle and the needle hub (as needed) to get the needle to bend in a nice symmetric gradual bend.\u00a0 Well, when I went to use these needles I found that under pressure they leak at the junction between the needle stem and the hub (all three)!\u00a0 I\u2019m going to comment further in a separate post about the nightmare I went through trying to get Fisher to simply send replacements.\u00a0 Anyway, after a long drawn out ordeal I ended up hand bending several of these needles from the same lot (as I had previously hand bent about 40 20 gauge 8\u201d and 6\u201d needles from different lots and none had leaked).\u00a0 Oddly enough when I hand bent the 12\u201d 20 gauge needles they didn\u2019t leak.\u00a0 Can someone tell me why the mandrel bent needles leak and the hand bent don\u2019t even though the radius of the bend in the former is more gradual than that for the latter?<\/p>\n
![\"\"](\"http:\/\/innovscience.com\/wordpress\/wp-content\/uploads\/2012\/03\/mandrel-vs-hand-bent-1.jpg\" "\\"Mandrel")
<\/a>Difference in bending technique leads to leakage?<\/p><\/div>\n","protected":false},"excerpt":{"rendered":"
Some months ago I ordered a new lot of 12\u201d 20 gauge needles from Fisher Scientific.\u00a0 When they came I noticed that the box had a sticker that said Cadence Scientific instead of Popper and Sons.\u00a0 I took out three … Continue reading