On Friday 15 May 2015 21:44:08 Gregg Eshelman wrote: > On 5/15/2015 3:28 AM, andy pugh wrote: > > On 15 May 2015 at 03:03, Gene Heskett <[email protected]> wrote: > >> I had a session day before yesterday of the back gear countershaft > >> squawling pretty bad, so I called Chris at LMS and bought the whole > >> headstock for a $132 bill with USPS shipping, and which arrived > >> today. > > > > https://littlemachineshop.com/products/product_view.php?ProductID=22 > >99&category=1023914534 ? > > > > I hadn't realised that the 7x lathes had a back-gear. My 9x (which > > seems to be a stretched 7x) had an all-belt arrangement (using the > > tiniest of V-belts) > > http://www.micro-machine-shop.com/9x20_lathe_belts_1.jpg > > The 9x lathes are copies of the Emco Compact 8, with an extra 1/2" of > metal on the bottom of the head and tail stocks. > > The gears in the 7x aren't actually a "back gear", it's a two speed > shift that either reduces or increases spindle speed from the input > shaft speed. There's no 1:1 drive. For the vast majority of what most > people do on a 7x it's best to leave it in low speed. > Yeah. Even in low range, calling it a 7x is false advertising. The cross slide can't back that far away, and the usual motor setup cannot put enough torque in the spindle for more than a 3/4" steel round, or 1.5" alu round. The ponies just aren't there even if you have a grocery sack of fuses.
> What's surprising is that in all the time various companies have been > making copies of the Compact 8, not one of the design's deficiencies > has been corrected by any of them. They all use that weedy little > belt, no tumble reverse. Nobody has made a gear drive headstock. They > all use the same flexible 2 bolt mounting ring for the compound. That's another sore point, one that at some point will be addressed by a block of steel the correct height, with at least 4, 5mm bolts into the top of the cross-slide. > No > manufacturer has designed a proper 2 lever gearbox so change gears > aren't needed at all. > > If they did, such a gearbox would be cannibalized for many old lathes > that didn't originally have one. > > The 9x lathe could be a quite nice hobby lathe IF some company would > apply all the common upgrades and fixes various owners have developed > for them, and expand the gearbox, and upsize the 7x headstock design > to three speeds with 1:1 in the middle. The existing has a spread of 2/1, and was originally driven with a 400 watt motor that turns 5k revs according to the label. In low gear, and with the 1HP motor, the limit of the chip size it can throw is still that "weedy" belt. Checking with Boston Gear, their 5mm pitch HTC belt can probably carry 4x the power the OEM belt can transmit, and thats still somewhat less than this motor can twist. At 3500rpms on the smaller pulley it says .65HP, but that motor is seeing a 3/1 speed reduction before it gets to the pulley I am destroying. Wide open, I might get 3k rpm's on that shaft, but thats spinning that big cast iron fan/flywheel at about 10k rpm's. It is extremely well balanced, but I still get the impression it needs a shrapnel cage. A 15mm wide belt supposedly can handle the full horse. But there is no room for it. The 3mm pitch version of that tooth profile, with a 9mm belt, is rated at about 1/4 horse. That 400 watt motor destroyed the first belt & pulley, now this motor has eaten 2 more pulleys. Unforch, I haven't found a way to arrive at a cost for the Boston Gear stuff without wasting their time on the phone. So I expect I had better do that Monday. 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> ------------------------------------------------------------------------------ One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
