Put an indicator on it (attached to something other than the lathe if possible) and see if the needle (carriage) doesn't dance when the chatter starts. During the unload phase, the carriage, which has been pressed down onto the bed during the load phase suddenly no longer has this downward force and will spring back, possibly lifting the carriage slightly from the bed. The chatter you hear and see on the part is the result of the tool digging in (load) and springing back (unload). I'm sure these lathes were not designed to have play under the carriage. And they take a lot of fiddling and patience to get the best results. These aren't bad machines, but you wouldn't want your livelihood to depend on them. (mine did this a little - loosened the center two gib screws slightly, snugged the outer two. You might try mounting an indicator, and checking that compound, cross slide, and carriage aren't rocking (racking) under load or feed direction - these surfaces probably don't wear uniformly and I've seen reference to carriages that pivot (slightly) going from feed L to feed R. * experimented with feeds and speeds after starting with the tables - I found slower speeds (like 1/4) and much higher feeds to alleviate chatter on a particularly tough steel bar I used for one project. * paying attention to the rake and clearance angles for HSS tooling - these vary for different materials The sharper the better, and sharp HSS seems to translate into good finish. * freshly sharpened HSS tooling - I tried, and gave up on carbide. * locking carriage and/or gibs on axes that aren't moving for the cut I'm makeing * spent some time snugging up all the gibs to get rid of any play - all drag slightly now, and the cranks don't spin Things that worked for me to reduce/eliminate chatter: You already seem to understand that the Atlas lathes are light machines, but like you, I don't think that's any excuse. I've got a TH54, similarly overhauled, and have had *some* trouble with chatter. Thanks.Ĭhatter = something is loose or flexible. What the heck is going on? I know this lathe isn't a gem but it can't be that bad or they never would have sold. Tool height is always checked and correct. The spindle turns smooth as silk and the tool post seems rock solid.
I have tried every realistic combination of feed/speed but I still get a harmonic sort of chatter, even on aluminum. I have tried everything I can think of tightened ways until they are actually too tight, snugged up spindle bearings so they are actually pre-loaded, replaced all belts with the polyurethane segmented type (excellent belts!), tried carbide inserts, brazed carbide and HSS tooling.
While turning 1018 bar even the lightest of cuts causes a herringbone pattern on the work. Final thing was to buy an inexpensive QC tool post (button type) and some nice Kennametal carbide insert tooling. I fit a used Yuasa (I think) 3 jaw chuck to the threaded spindle with a cast iron adapter. While apart I replaced the spindle bearings with good quality Timkens. When I first dragged it home I stripped it down and cleaned and painted everything like new. IF you run out of threads, you can either flip the bolt over (they're frequently threaded longer on one side than the other) or trim one end to suit.I have been battling a tool chatter problem on my 12X36 Atlas lathe ever since I bought it several years ago. Once the plate is in, thread in the bolt 'till it stops (it'll seat against the bottom of the compound) then place the post over the bolt, thread on the nut. If it's too thick, don't address the whole thing, just scribe marks and lightly file the high areas so it'll slip in, and no more.
A few minutes with a black permanent marker, a scribe, hacksaw, and bench grinder or file will do fine for trimming it to size. It MIGHT be proper thickness, but too wide. The plate will be larger in one or more dimensions, than your compound. The plate is threaded for the bolt, and with the toolpost being a 'one-fits-all' setup, you'll need to do a little shaping of that plate, and probably shortening of the bolt a little, to fit it to your machine. The square plate that it clamps to, slips into the slot in your compound, same place the lantern post did. However, it really doesn't matter wether it's metric, SAE, Whitworth, Acme. That's probably a Phase-II or copy of, and if so, it's imported, and it will most likely be metric.
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