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New To Me Lathe

scatgo

Plastic
Joined
Dec 3, 2023
Just got a Model A and I have few questions. For starters what is that lever for in the picture? All it looks like it is going to do is remove the power from the spindle when the motor is running. And what is that tailstock thing for? I worked in a machine shop for 12 years and have never seen one of those. And how can I remove the huge amount of backlash from the cross feed?
 

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The first one is the back-gear engagement lever. When disengaged, there is a plunger in the inboard end of the spindle that locks the cone pulley to the spindle for a 1:1 drive ratio.

As for the second, I don't know what that is for.
 
Congrats on your new lathe! The second is a crotch center. You can use it to hold a rod and with a drill in the chuck you can drill a hole in the side of that rod. Not super easy to use I imagine but better than nothing if you don't have a drill press or mill
 
Gene and Matt have your first two answers.

For your cross-feed, how much is 'huge'? Even brand new pieces will have some, but how much is too much kinda depends on what you're doing and how you're doing it. Many first timers have the bad habit of trying to find their position from both directions. IOW, you zero your cross slide, move .100" forward then .100" backward and then see that they are not at '0' again. If this is what you're seeing it's not a problem with the machine. If you zero your cross slide moving forward, you have to find all your positions moving forward as well. So even if your cross slide has a half rotation back-lash, you would zero, move forward .100", move backwards at least the amount of backlash plus the .100", then move forward to zero. This is the case with all traditional acme-thread lead screw machines. Some more advanced machines have some fancy mechanical back-lash adjustments, but IMO even on those it's best to find your positions from the same direction. The only 'fix' for this to be able to position from both directions is by upgrading to ball-screws (which AFAIK isn't an option on a South Bend cross slide).
 
Congrats on your new lathe! The second is a crotch center. You can use it to hold a rod and with a drill in the chuck you can drill a hole in the side of that rod. Not super easy to use I imagine but better than nothing if you don't have a drill press or mill
He said crotch. LOL. Thanks for the information. I never would have guessed. And your right that sure as hell sounds like a sketchy way to drill a hole.
 
Gene and Matt have your first two answers.

For your cross-feed, how much is 'huge'? Even brand new pieces will have some, but how much is too much kinda depends on what you're doing and how you're doing it. Many first timers have the bad habit of trying to find their position from both directions. IOW, you zero your cross slide, move .100" forward then .100" backward and then see that they are not at '0' again. If this is what you're seeing it's not a problem with the machine. If you zero your cross slide moving forward, you have to find all your positions moving forward as well. So even if your cross slide has a half rotation back-lash, you would zero, move forward .100", move backwards at least the amount of backlash plus the .100", then move forward to zero. This is the case with all traditional acme-thread lead screw machines. Some more advanced machines have some fancy mechanical back-lash adjustments, but IMO even on those it's best to find your positions from the same direction. The only 'fix' for this to be able to position from both directions is by upgrading to ball-screws (which AFAIK isn't an option on a South Bend cross slide
I may have jumped the gun on this. I dont think all of the backlash is in the lead screw and or nut. When i back the cross slide out a gap comes up between the dial and its bearing surface. My guess is the dial and its bearing surface may have more to do with it. thumbnail (4).jpgthumbnail (3).jpg
 
I may have jumped the gun on this. I dont think all of the backlash is in the lead screw and or nut. When i back the cross slide out a gap comes up between the dial and its bearing surface. My guess is the dial and its bearing surface may have more to do with it. View attachment 418996View attachment 418997
Is the ball crank nut loose? Loosen the set-screw on the dial and try tightening the nut on the end of the ball crank. The nut is round on the OD and takes a special driver, but you can make one from an extra slotted screw driver by cutting a slot in the middle. If I remember right, the ball crank and nut should tighten up to a shoulder.
 
Is the ball crank nut loose? Loosen the set-screw on the dial and try tightening the nut on the end of the ball crank. The nut is round on the OD and takes a special driver, but you can make one from an extra slotted screw driver by cutting a slot in the middle. If I remember right, the ball crank and nut should tighten up to a shoulder.
Just looked into that and the nut was tight. But you gave me the idea of maybe placing a shim between the handle and dial to hold me over. If I were to turn the handle in to the max would I be able push the cross feed futher forward so I can remove it so I can take a closer look at things?
 
Just looked into that and the nut was tight. But you gave me the idea of maybe placing a shim between the handle and dial to hold me over. If I were to turn the handle in to the max would I be able push the cross feed futher forward so I can remove it so I can take a closer look at things?
Yes, if you crank the cross slide in away from you the nut will eventually run off the end of the screw, then the bearing behind the dial will thread out of the saddle, taking the screw and the crank with it. You might need a spanner wrench or a snug fitting dowel pin to break it loose though.
 
OK Great information. Thanks for the help everyone. Just one more question and I should be on my way to getting some work done. For some reason when I engage the feed clutch the carriage will move to the left but when I shift the lever to power the cross feed it moves to me. Now that just dont seem right to me. Every other lathe I have used the cross feed moves forward for facing. Is it me or did someone goof when the put this machine together?
 
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The power feed issue you see is normal. If you keep the reverse tumbler lever in the same position, power feed will be right to left and crossfeed will be towards the outside.

The gap between the dial and bushing is a direct result of wear between the backside of the bushing (buried in the carriage) and the front of the flange on the leadscrew that bears on the bushing. A simple, rough fix is to dismantle the assembly (the bushing can be unscrewed from the apron to make this easier so you can do it on a bench) and manufacture a brass or bronze washer of the correct thickness to install on the crossfeed screw shaft to close that play up.
 








 
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