high precision mechanical parts examples? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: August 10, 2019, 06:39:11 pm
content: So striving for the best with the best tools is great, but I wonder what are practical examples of super precise shapes required for functional devices?What kind of stuff is there, turbines? rocket nozzles, hydraulic cylinders, car engines, VTOL thrust directors?.. I know guns are up here, but I wanted a more interesting list then autocannons and artillery (not to mention that these things are getting outdated).I know optics and high high frequency microwave requires very good machine control, but how about other things (other then the manufacturing tools)? (and even with optics/antennas you often break down the parts into multiple pieces which can be flexed or independently aligned like for radio telescopes etc.I know alot of things that spin actually is ground 'randomly for balancing anyway, since the material used for manufacturing is not really as homogeneous as would work with the actual design for center of mass.What really stands out? (other then the grinders and measurement tools).I would imagine in alot of cases the electronic control system for things like rocket guidance fins can really reduce requirements for tolerances?

author: KL27x
author_rank: Super Contributor
timestamp: August 10, 2019, 08:53:07 pm
content: Common?Optics.Combustion engine cases. They have to contain very high pressures. The connecting pieces have to be milled flat for the gaskets to be able to contain the pressure.Firearms are not actually up there. Well, not common firearms. Many firearms do require very low tolerance in certain parts, but you could call that more of a design shortcoming than a necessity. Some of the more modern versions of handguns and rifles are made more production friendly by smarter design.Anything that spins at high rpm, yeah. But if other than balancing, if your device requires super precise custom parts, anymore, it might be more of a design bug than a feature. Even jet engines turbines spin around on?? factory made ball and roller bearings that aren't much different than what you can buy on Ebay or from McMaster Carr. Fundamentally the same things that are in your $20.00 skateboard. Ball bearings, roller, bearings, one way bearings. Dozens of different kinds of bearings. Bearings are one of the most common high precision things we commonly use, and they've been standardized and mass produces for decades, now. The amount of precision and low tolerances in a 3 dollar ball bearing put to shame anything you will produce straight off a milling machine.Increasingly, timing things with specifically shaped cams or gearing can in many cases be replaced by electronics. And the storage density of li ion batteries are making small combustion engines more and more a curiosity from a past age.If you are looking for nails to hit with your hammer, the most killer app for a metal lathe, specifically, is threading custom parts and making gears, IMO. Of course, the most basic functionality will be boring and shaping. For a mill, the most fundamental basic utility, IMO, is facing and slotting.

author: coppercone2
author_rank: Super Contributor
timestamp: August 10, 2019, 09:02:28 pm
content: with electric motor and drives, how much are belts and gearboxes being eliminated?is there a limit between the momentum/size of the EM rotor and the torque delivery possibilities ETC that make gear boxes still necessary or seen as necessary in the 50 year future for cars?like, if you want a motor that does all for a car, does it come out with preposterous dimensions or something? (if you want to field control everything with feedback).

author: coppercone2
author_rank: Super Contributor
timestamp: August 10, 2019, 09:07:48 pm
content: unfortunatly all those electrical things will not fail gracefully compared to cams and stuff in most cases

author: chris_leyson
author_rank: Super Contributor
timestamp: August 10, 2019, 11:01:58 pm
content: Maybe you could argue that a vacuum tube electrode is a precision part whether it be a, cathode, one of several grids or a plate. Perhaps a more up to date example would be a mechanically ruled diffraction grating and the machinery needed to manufacture such a grating. EDIT: Gyroscopes and satellite reaction wheels.

author: larrybl
author_rank: Regular Contributor
timestamp: August 13, 2019, 08:05:05 pm
content: look up "clickspring" on YT for some enjoyable clock making.http://www.clickspringprojects.com/

author: IanB
author_rank: Super Contributor
timestamp: August 13, 2019, 08:53:11 pm
content: Quote from: coppercone2 on August 10, 2019, 06:39:11 pmMechanical watches? The best watches can keep time to within a couple of seconds a day, and they can only do this if all the parts are machined and aligned with almost perfect precision. Anything slightly out of tolerance and the timing will be off. Furthermore, consider how small the parts are. You cannot properly see them without a magnifier. If you could manufacture such a mechanism in your home workshop you would be a master of the craft.

author: Towger
author_rank: Super Contributor
timestamp: August 13, 2019, 09:02:51 pm
content: The humble harddisk is said to be most precisely engineered item of consumer electronics.

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 13, 2019, 09:10:13 pm
content: Quote from: larrybl on August 13, 2019, 08:05:05 pmI don't think that even counts as precision machining a lot of the time, but it's gorgeous to look at.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 14, 2019, 03:05:40 am
content: Apparently the paint dispensing machines at Home Depot use hardened stainless steel pistons and cylinders, ground within a few tenths of an inch of each other -- the paint tint goop is very abrasive and variable in consistency, and to deliver accurate doses they need a volumetric pump. The tight clearance is self-sealing.Gauge blocks I guess are the commonest example of much higher precision, being lapped flat enough that molecular forces can hold them together ("wringing").Tim

author: floobydust
author_rank: Super Contributor
timestamp: August 15, 2019, 07:03:23 pm
content: Seals and glands, feedthroughs - If you needed some wires inside a pressurized tank, say a metal and teflon seal for 1,500PSI you need very tight tolerances. Temperature swings become a problem with dissimilar materials. To assemble them, placing the teflon in a freezer shrinks it enough.I am thinking of the Apollo mission oxygen tanks, propane or natural gas fuel tanks, where you need a RTC/thermistor or stirrer motor, level sensor etc. in the tank.Glass on steel (Kovar) might be used for a gland or feedthrough but not at high pressures (i.e. 10,000PSI) or wide temperature swings, as I recall.

author: tooki
author_rank: Super Contributor
timestamp: August 16, 2019, 06:44:24 pm
content: Quote from: T3sl4co1l on August 14, 2019, 03:05:40 amSurely you meant something other than "a few 1/10ths of an inch", since that's only precise enough for road construction perhaps.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 16, 2019, 08:29:14 pm
content: Right, I should've left that at "tenths", meaning tenths of 0.001" in common machinist parlance.Tim

author: duak
author_rank: Super Contributor
timestamp: August 24, 2019, 04:54:10 am
content: Fuel injectors, especially for diesels, are precisely machined and ground from some fairly tough steels. At idle, a diesel injector has to atomize a drop of fuel on the order of the size of a grain of sugar.Drill bits and end mills are amazing pieces of materials science (eg. high speed steel and tungsten carbide) and manufacturing. I have some #80 carbide drill bits for PCB that drill a 0.0135" dia hole but these aren't the smallest available. These little guys are twist drills like their larger relatives. Think about the tiny grinding wheels that are used to shape and sharpen them. End mills have precise straight and helical cutting edges that are tough enough to cut through alloy steels.

author: Jwillis
author_rank: Super Contributor
timestamp: September 02, 2019, 09:31:53 am
content: How precise are we talking. How about nano mechanics.Not so much machined but "grown" atom by atom.I recall a motor done this way but couldn't find a picture.But seriously Injection pumps can have tolerances of thousandths of an inch but that,s usually done by micro lapping with extremely fine diamond grit and believe it or not, pork lard.

author: tszaboo
author_rank: Super Contributor
timestamp: September 02, 2019, 11:32:50 am
content: High precision mechanical parts:1. PCB2. ...Cant think of anything else. It turns out we are typically a few orders of magnitude more accurate that those people with the nuts and bolts.Every time they do something for a project, I just need to lower my expectations, and triple the tolerance that I'm told. Or redesign the PCB because ME couldn't get something right.