Atlas 12/36 Question

I appears that your chucks may have what is called bell mouthed. They are tapered with the open end to the outside. Your work piece is moving around on the first one.
Yes even a pita beatter should still give you a decent finish. Try re running the piece but use the hand wheel to feed instead of the leadscrew. Just curious.

I would suggest resetting the preload on the spindle bearings. There was a posting about it here just recently.
Pierre
 
If you turn a longer piece as sssfox suggest, try in between centers to remove any excess play and deflections.
 
ChuckB,

Have you ever leveled your bed? If the bed isn't level left to right and front to back, all sorts of wierd things can happen. This is a critical step in setting up any lathe, whether flat bed or inverted V bed. A carpenter's level is OK for roughly leveling the stand or cabinet but not for leveling the bed. Actually, before someone else brings it up, you can do acceptable work if the machine is on a moving ship at sea (if you've never been to sea, nothing is ever level more than momentarily). So it isn't really the levelness of the bed that is critical. But the flatness of the bed, regardless of what type of bed it is. And the cheapest tool for ensuring this is so on a flat bed lathe is a flat bottom precision level.

The carriage (saddle) only has one gib. The cross slide has one. And the compound has one. All can contribute to bad cutter behavior if loose, regardless of the make of lathe. If the carriage gib is loose, the carriage may twist in either direction in reaction to cutter pressure. If the cross slide gib is loose, the cross slide may lift on one side in reaction to downward force on the cutter (depends upon where the cutter tip is in relation to the C/L of the cross slide). Same with the compound. As with a QCTP a turning or facing cutter tip is more often than not hung out over the left side of the carriage, the net force is usually down on the headstock side (up on the tailstock side) and CCW.

<Deleted because it was wrong and might confuse someone in the future.>

Robert D.
 
Last edited:
sssfox said:
I don't think that's causing your problem. If you want to test, get a longer piece and turn the end where the carriage is tight.

What is the diameter of your workpiece? Still 1.47 or so? Are you making multiple cuts without advancing the cutter into the work? That helps to counteract deflection.

What kind of steel are you using? Some of it is difficult to finish.

Try the Shear Tool that I sent the link for. It's supposed to be really good for difficult to finish materials.

Right now, we don't know if it is the machine, the material or the user. We need to figure some way to narrow it down.

Set the power feed to the lowest setting. I think it's .047. From what I've read, that is twice as fast as other lathes anyway.
Click to expand...

The piece I am using now is about .8 inches. I alway give it another pass or two and material always come off as if I had turned the cross feed. The steel I am using is unknown. Drops bought at a salvage yard. I tried aluminum and it looks even worse. For the most part, I have been turning by hand. When I have used the cross feed, I set it at .0042 and keep the rpms high
 
Hi Chuck I have not had a chance to read all the replies but I had the same problem as you I re-worked everything and the real cause was the 3 jawed chuck itself. I made some blocks for the jaws to clamp down on but still left the surface exposed I then made a mount to hold a die grinder onto the tool post. Turning the chuck very slowly and at a very slow feed I reground the jaws just enough to clean them up. Cleaned out the chuck and to my surprise it turned the shaft with no taper. Now this was not an old chuck knor was it a cheap one but 15 minutes of grinding cured that problem. Ray
 
wa5cab said:
ChuckB,

Have you ever leveled your bed? If the bed isn't level left to right and front to back, all sorts of wierd things can happen. This is a critical step in setting up any lathe, whether flat bed or inverted V bed. A carpenter's level is OK for roughly leveling the stand or cabinet but not for leveling the bed. Actually, before someone else brings it up, you can do acceptable work if the machine is on a moving ship at sea (if you've never been to sea, nothing is ever level more than momentarily). So it isn't really the levelness of the bed that is critical. But the flatness of the bed, regardless of what type of bed it is. And the cheapest tool for ensuring this is so on a flat bed lathe is a flat bottom precision level.

The carriage (saddle) only has one gib. The cross slide has one. And the compound has one. All can contribute to bad cutter behavior if loose, regardless of the make of lathe. If the carriage gib is loose, the carriage may twist in either direction in reaction to cutter pressure. If the cross slide gib is loose, the cross slide may lift on one side in reaction to downward force on the cutter (depends upon where the cutter tip is in relation to the C/L of the cross slide). Same with the compound. As with a QCTP a turning or facing cutter tip is more often than not hung out over the left side of the carriage, the net force is usually down on the headstock side (up on the tailstock side) and CCW.

<Deleted because it was wrong and might confuse someone in the future.>


Robert D.
Click to expand...



Robert, I have leveled my lathe and Have it bolted to the floor. I even tried just snugging up the 4 bolts at the top portion to ensure I am not twisting the bed.

I don't see how the shim can raise or level the carriage. They are located on the bottom, under the bearing plates.. In order to raise or level the carriage, shims would have to be on the top between the ways and the top of the carriage, right? The only thing I can see shims doing is to prevent upward play when the carriage is lifted up. The more shims, the more the carriage would lift up. Know what I mean? In my case, no shims and the carriage has about .006-.007 of play when I measure using a dial indicator and lift up.
 
Last edited by a moderator:
Chuck,

You're absolutely right. I think that's the worst Senior Moment I ever had. I described part of something I built on an inspection machine in the 1970's. And hadn't thought about in nearly that long
Robert D.:whiteflag:
 
wa5cab said:
Chuck,

You're absolutely right. I think that's the worst Senior Moment I ever had. I described part of something I built on an inspection machine in the 1970's. And hadn't thought about in nearly that long
Robert D.:whiteflag:
Click to expand...

I had a terrible senior moment today.. drove off with all my tools/cart/ladder left behind in the parking lot of a hospital.. didn't realize it till about 5 hours later at about 10:30 PM.. called the night maintenance guy who looked in the parking lot.. Nope! no tools.. I asked him to look in the maintenance shop.. sure enough.. someone rolled them in! Left the house right away and got them! Whew!! that was close :)

Let me run this by all of ya'll.. on my lathe, the front way seems to be worn more than the rear.. makes sense.. when the tool has pressure on it, it is pushing down on the carriage and causing more wear on the front way.. with this in mind and plus being told time and time again how critical tool alignment is, it made me think.. that tool is always going to be at the wrong angle on the work due to the front way wear, right? I clamped a small percision level in the tool holder of my QCTP.. I wanted to see how much out of level the tool post was holding the tool.. wow way out of level.. I then commenced to sliding feeler gages as shims on the back side of the QCTP.. it took about .005 to get the bubble centered on the level.. coincidentally about the same amount of lift that I measured with the dial indicator at the carriage before I took the bottom brass shim out.. I turned a piece of rod about 1" in diameter and you know what?? much better. I was using a poorly ground HSS bit that I made and it still came out decent.. not a perfect finish, but better than the last couple of days.. I think I'm on to something.. I would post a pic, but I am out of batteries.. What do you think? am I barking up the wrong tree??
 
Keep barking, the coon will stay up the tree and out of your garbage.
 
ChuckB said:
why is it that when I make a pass and back it off more metal comes off.. and then going foward again without turning the dial even more metal?
Click to expand...

Are all the gibs really tightened correctly? I was getting the same thing on my Leblond and because I was a newbie I thought it was either normal or meant that my lathe was worn out. Then I read somewhere that I shouldn't be able to jiggle the compound like a bowl of jello so I tightened the two gibbs until I couldn't wiggle it by hand. It took about 30 seconds and I'm getting much more consistent results now - and when I use the slower auto-feed there isn't extra metal coming off when I back up or if I make a second pass.


Joe
 
You must log in or register to reply here.
Back
Top