Mini Lathe - Turning Between Centers?

[MaverickNH]

My LMS 7x12 mini lathe kit has a dead center, a live center, lathe dogs of various sizes and drive pins that mount on the spindle plate. I’ve faced and center drilled both ends of an ~8” long 1” diameter 6061 Aluminum round stock section. All for learning’s sake.

Do I understand correctly that, while I can turn a true diameter with this setup, I’ll need to cut off the clamped part of my workpiece and reface and drill to make a straight and true shaft? That seems obvious, but just wanna check for any advice - I can use it!

 

[RJSakowski]

If I understand correctly, you have faced and center drilled the bar in preparation for turning between centers. If the bare is to length, turn to diameter using a lathe dog. Then reverse the bar and turn the area which was inaccessible due to the lathe dog. If you have excess length to allow for the lathe dog, you can turn the entire bar in one setup and your final operation can be parting off your work piece to length.

You will lose center drilled hole on the driven end of the bar. If you need to redrill the center drilled countersink, you would want the indicate the bar in a four jaw chuck for zero runout. On a 7x12 lathe, you won't be able to insert the bar into the spindle so best practice would be to use a steady rest. The hole can also be done on a mill after finding the center with an edge finder or Indicol.

 

[MaverickNH]

If I understand correctly, you have faced and center drilled the bar in preparation for turning between centers. If the bare is to length, turn to diameter using a lathe dog. Then reverse the bar and turn the area which was inaccessible due to the lathe dog. If you have excess length to allow for the lathe dog, you can turn the entire bar in one setup and your final operation can be parting off your work piece to length.

You will lose center drilled hole on the driven end of the bar. If you need to redrill the center drilled countersink, you would want the indicate the bar in a four jaw chuck for zero runout. On a 7x12 lathe, you won't be able to insert the bar into the spindle so best practice would be to use a steady rest. The hole can also be done on a mill after finding the center with an edge finder or Indicol.

Thanks, RJ. Is there a recommended way to protect the newly turned surface if I reverse and clamp the workpiece?

 

[D.sebens]

Thanks, RJ. Is there a recommended way to protect the newly turned surface if I reverse and clamp the workpiece?

Beer can/soda can “shims” cut out and out between the jaws and the work. As said, you would need to use a 4 jaw to indicate the part to center. Unless this was a fast farm job and what not. If you were just facing after cutting the end off you could probably skip the 4 jaw and just use the 3 jaw(assuming what ever you are doing would allow that level of imprecision.

 

[RJSakowski]

Thanks, RJ. Is there a recommended way to protect the newly turned surface if I reverse and clamp the workpiece?

for clamping 6061, I would prefer something softer that aluminum although a thicker shim should be sufficient to prevent marring the work.. Copper is often used. Plastic shims are another possibility. Cardboard from cereal boxes or the like is another. For steel, the aluminum will work fine.

 

[MaverickNH]

Beer can/soda can “shims” cut out and out between the jaws and the work. As said, you would need to use a 4 jaw to indicate the part to center. Unless this was a fast farm job and what not. If you were just facing after cutting the end off you could probably skip the 4 jaw and just use the 3 jaw(assuming what ever you are doing would allow that level of imprecision.

Thanks, yes, I faced on a 4-jaw chuck - it takes a bit more work to get it aligned to +/- 0.0005” but it’s worth a few minutes for hobby work.

for clamping 6061, I would prefer something softer that aluminum although a thicker shim should be sufficient to prevent marring the work.. Copper is often used. Plastic shims are another possibility. Cardboard from cereal boxes or the like is another. For steel, the aluminum will work fine.

I’ve got some thick copper foil I use for Ham Radio work and will try that. thanks.

But I just now see my ~4-3/4 OAL MT3 dead end sticks out 1.5” - farther than the LMS M6 stud that fits into my spindle flange, so it won’t spin the lathe dog. Bummer! I’ll need to make a longer stud!

I guess that’s where the learning comes in - make a tool, to make a tool that makes a tool…

 

[D.sebens]

Thanks, yes, I faced on a 4-jaw chuck - it takes a bit more work to get it aligned to +/- 0.0005” but it’s worth a few minutes for hobby work.

I’ve got some thick copper foil I use for Ham Radio work and will try that. thanks.

But I just now see my ~4-3/4 OAL MT3 dead end sticks out 1.5” - farther than the LMS M6 stud that fits into my spindle flange, so it won’t spin the lathe dog. Bummer! I’ll need to make a longer stud!

I guess that’s where the learning comes in - make a tool, to make a tool that makes a tool…

Is your dog a bent tail dog or straight? If straight up bolt a bolt on the faceplate to catch the dog. If it’s a bent tail you could still probably do the same

 

[MaverickNH]

Is your dog a bent tail dog or straight? If straight up bolt a bolt on the faceplate to catch the dog. If it’s a bent tail you could still probably do the same

It’s straight, so a bolt should work fine.

 

[verbotenwhisky]

Thanks, RJ. Is there a recommended way to protect the newly turned surface if I reverse and clamp the workpiece?

I have some copper sheet and pipe I cut up for this.

 

[MaverickNH]

My first attempt turned out OK. A bit rough - I was hesitant to run over 1000rpm with the lathe dog imbalance using a carbide indexable tool, so it's not as smooth as it could be. But it indicates +/-0.0005 across 8 inches