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How to Use a Metal Lathe



A viewer had asked Kevin for basic information about his lathe so he knows where to start.

Kevin lathe is an old Sheldon toolroom lathe from the 1940s. There's a tag on the side that says "War Finish" by military order, which probably explains why it's battleship gray. He figures it served in World War II.

It's a decent sized lathe with good horsepower - enough to turn anything Kevin will need it for.

He shows you the on / off switch, which is located on the back of the machine. Rotating it forward turns the spindle one way, and backward turns it the other way for, say, polishing.

Kevin shows the chuck that holds the metal to be turned. The one in the lathe is a three-jaw chuck, and it's auto-scroll, so when you turn the key in any adjusting hole, all three jaws adjust. He also has a big four-jaw chuck in which each of the jaws moves independently so you can use it to center odd-sized pieces.

Next he shows the lathe's bed and its rails, which the carriage moves back and forth on. The apron also moves back and forth from the front of the machine to the back of the machine. It holds the tool holder. The tool holder has set screws to hold the part that holds the cutting insert. There's an adjustment wheel that moves it up and down so you're not too high or too low on your metal stock.

This particular lathe is set up for threading, so it can turn threads and make big nuts and bolts. There's also a speed adjustment chart for the feed screw that moves the carriage back and forth as you're putting threads in.

There are additional threading controls and a control to engage a different set of gears inside the gear train to slow everything way down so your stock is just barely turning as you cut your threads. There's also a lever to set the direction of the feed screw.

On the back side of the machine is a tailstock that holds the end of your piece of metal that isn't held in the chuck. If you working with a long piece of metal, you don't want it wobbling around at the far end. So you slide the tailstock against the metal to keep it centered and tighten the set nut to lock it down. Then you have an adjustment wheel to tighten the live center.

It's called a live center because it turns - it has a bushing inside of it. So when your stock is turning, the live center is turning, too. There is also a static or dead center that does not turn.

Now it's time to turn some steel!

Basic safety applies. Put on safety glasses, but don't wear gloves - you don't want anything getting caught in the moving parts, so no loose shirts, either. With the parts whirring around, if something gets caught, you'll get jerked right down into the machine. "Danger, danger, danger," says Kevin.

You can cut back and forth either direction. It depends upon how you have your cutting insert set. You want to cut on the edge of the insert, not on the point, so you don't cut grooves, like in a record.

Now it's time to make some chips! You can feed by hand or use the automatic feed. To use the auto feed, just flip down a lever, and the machine will feed by itself. You can tweak the speed with two different adjustments.

Looking at the metal, Kevin shows where he was handfeeding, then stopped. Then you can see the shiny, smooth surface where the autofeed kicked in, and finally where he made a coarse adjustment and it started to speed up and cut grooves, which is basically just cutting threads.

So that's a basic metal lathe set up. If you're thinking of buying a lathe, you can look for a good old one, but do your homework first. Or you can buy a small new one for a little more money. There also are tabletop lathes for turning small parts that aren't too expensive that are fun to play with.

Oh, and DEFINITELY don't miss the special guest at the end of the video .....


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