Good gears as well as bad ones get made everywhere. The real issue is building to a price point. As it happens, the lower end mass produced ones are almost all made over seas where labor is cheaper. This has a lot to do with the bad quality perception of the gears made in China and similar countries. For the most part, higher end gears are good wherever they are made because less corners are cut in the design and in manufacturing processes including quality control. The cutting edge high end gears are still mostly made in the Western Hemisphere and Japan/Korea because they spend the money on R & D. China is still relying mostly on derivative technologies much like where Japanese auto industry was in the 70's. Because of lower manufacturing cost, there has been good values to be found in the middle to upper middle class gears from China but they come with lack (for the most part) of customer support on this side of the pond. All in all, smart shoppers will find good gears at their desired price points and they can be made from anywhere on the globe except Africa and Antarctica. What you buy will depend on your budget and what type of risk you are willing to accept. In this global economy, I don't set arbitrary boundaries on production sites.
Then there is the whole used market. aa
Gears? Lets talk gears a few minutes as you've now sat down on the park bench with me. I made my living doing gears shafts and castings. The best quality gears I ever saw we from Mercedes Benze by a small margin, but they were. Each gear was ground to a nice finish. Steel they used was OK, but not anything to write home about. Profiles were standard JIC like most of the world uses (keep in mind I said most). Most Japanese gears are cut from H13 hot work steel like Mercedes uses. It's fairly good, but not for high horsepower situations (Toyota is in love with this stuff by the way). Can't say for sure what Ford uses, but they cut an excellent gear that finishes out just slightly behind a Mercedes gear at about 1/100th the cost. Their splined shafts are very good as well, and are done on the same idea that G.M. and Chrysler do as well. A G.M. input shaft that's splined is made from Timken bearing steel (the best and most costly steel made on the planet), and I suspect that Ford and Chrysler do the same. It's much cheaper to use H13 as it saves a heat treat operation (it comes in a pre-treat condition) and is similar to 4150 but not quite as good in a shear mode. All splines are cut in everything but G.M., Ford & Chrysler, and this is not very good for a shear application (H13 is really ment to be used in a compressed application as in a mold ). A typical G.M. gear will be cut and finished every 50 seconds, and be done in a five to eight micron window when finished. The Mercedes gear is over double that window in size, but it ground (cost is then passed onto the consumer). Chinese gears are usually cut fron 8260 or something close to that. The stuff machines very well, but has not good waer properties in a loaded condition. Gear finish looks like it was cut with a hatchet, and bores are rough (maybe a finish factor of 10 or more). A G.M. gear will check at about two points more than a Mercedes gear on finish, but is better in other ways. The other German manufacturers are not nearly as good as Mercedes by the way.
Now if you remember that I said something about JIC profiles; I'll tell you why. No American or Canadian automotive company (or aircraft as well) uses JIC standards anymore as they're not good enough for today's needs. They use a profiles that is much longer and with a different set of ramps on engagement and dissengagement. Why? The gear will run quieter and last longer due to contact alone. The next problem here is heat treat and then finishing out the gears. It's a trade secret that the offshore companys can't figure out how to do. Yes Mercedes has tried this on some of their items, but in so have to leave about five to six times the stock on the gear for grind out the warpage (this is not H13 steel by the way). Grinding gears can be costly by no other reason than adding a lot of time to the project. Mercedes uses CAP grinders out of Europe (we looked into them, but CAP said they couldn't meet our standards). So how do we make such good gears? After heat treat we actually shave about .001" off the face of the gears (while hard), and in some rare cases we will then hone them for finish quality. The best gears I've seen period were the ones used in the transmission on the TF-56 turboprop engines used in the C130 airplane. These were ground on custom built CAP grinders that were then heavilly modified after delivery (don't ask why or how). Very expensive gear sets! The next best ones I've seen were in some very sophisticated maching systems, and certain gauging equipment capable of reading in two tenths of an arc second (we didn't cut them, but were cut in the state of MA.). For high production the best I've seen are cut by Allison in Indiana by a long shot. The best unground and unshaved are the ones used in the M1 tank transmission (try cutting a gear 24" in diameter under .001").
Want to talk about ball bearings and ball screws? Nuts and bolts? Steel quality? Theft of intellectual property?
gary
