On Saturday 23 January 2016 12:51:59 Peter Blodow wrote: > Gene, > 0.091" (=2,3 mm) would be perfectly in the DIN / ISO range. I use 2.4 > mm for easy working if strength is not the issue. > More, my drills are all produced a little under their nominal size, > maybe a few hundreths, to allow for de-centering of the cutting blades > in order to give a correct result when the hole is done. Admittedly, > it's not easy to keep that up when re-sharpening by hand... > In order to reduce the cutting forces and risk of breakage, all hand > tap drills come in sets of three beginning with a straiht tip with > drill blades to make sure the hole is not too small and keep the > threads perpendicular to the surface. > Peter
That bit of luxury has appeared to have faded from the scene with the shift of so damned many of the tools we can afford to buy, being imported from China. I can recall in 1959, when I was a bench tech for Oceanographic Engineering, the machinist we hired to help us make the pressure cases for the tv cameras we installed on the Trieste just before its singular trip down into the mohole in Feb 1960, and who came with his own tools except for a huge english made lathe we bought, & one of his prized posessions was a full set of fractional, lettered, and numbered drill bits, for brass. All straight flute. He also had a small electric motor that spun a 3" brass disk that was occasionally annointed with a drop of oil & diamond dust, and had several jigs drilled at all sorts of angles that he used to sharpen tools with. No carbide tools in his kit, but he spent perhaps 2 minutes tuning up a 1/2" square lathe tool, and it carved bronze (we started with a 7" diameter "Naval" bronze rod about 2 feet long for each camera housing) and made a couple lbs of swarf before it went back to the diamond again. And left a finish you could have used for a shaving mirror in a pinch. The Navy gave us the quartz windows for the front of it, along with the drawings for how to seal it into the front of the case. But at an estimated psi of nearly 18,000 down there, that machinist was schmardt enough to adjust the dimensions just enough to keep the bronze from crushing the quartz while still remaining tight and waterproof at only 1000 feet down. Since it was powered by a piece of RG-59 thru a packing gland in the rear of the case, I wanted to see that, and how it was prevented from squirting thru the gland, but he worked a weekend I didn't and it was already done Monday morning. It got its 12 volt power, and shipped the video back on a 10 Mhz carrier in the same cable. But the Trieste had no coax ports into it. The Navy gave us 9 ea 16 gauge pieces of Packard automotive wire to run 2 cameras and 2 pan & tilt assemblies with. We had an engineer who was good with sequentiaL relay logic who worked out how we could do all that on 3 wires, leaving 6 for the cameras. As for the video, we thought we'd better test that wire, so we bought a 1000 gallon stock tank, threw 500 lbs of salt in it and filled it with a small pump and a hose from mission bay which was in our back yard. Stired it up till the salt was all disolved, threw in 50 feet of that wire in random loose fashion, and put our sweep generator on it. Blew us away when we found that as long as our gear was grounded to the tank, it was, as said by another of our design engineers "flatter than a plate of pee", and it actually worked quite well when hooked up in the gondola & set back down in 15 feet of water off the end of our dock. And worked equally well down in the mohole. Only one casualty to that gear in that dive. We had taken a more or less std issue Halomore pan & tilt assembly, cut the top of the housing off, filled it with ATF and after drilling a vent hole in the top, put it back on with a rubber gasket diaphram to keep the oil & sea water separated. Sealed with RTV IIRC. But one of them must have had an air pocket and didn't fill to a no void condition. At nearly 18,000 psi, the middle of the diaphram pushed down far enough a tilt gear ground a hole in it. So when we opened it up to see why it wasn't working a week later, we found the hole, and the unit full of seawater & oil sludge. But it had done the job it was sent to do so it was just a shrug for all concerned. Way off topic but possibly interesting to others. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
