How to Use a Metal Lathe to Do Case Trimming
Case trimming is the process of cutting an ammunition case so you can reload it properly. One of the best tools to use for case trimming is a metal lathe. The machine has a spindle that spins and a cutting tool that can make delicate cuts on the ammunition casing. The cutting tool on the lathe rests in a fixed position so a precision cut can be made. Since case trimming requires only a small amount of the material to be trimmed off for the ammunition to fit, the metal lathe is a good option to perform this task. You must have some machining experience to operate a lathe to perform this task.
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Instructions
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Insert the cutting tool into the turret of the metal lathe. Finger tighten the turret bolts to the tool. Turn the carriage dial counterclockwise. Continue turning the carriage dial until the tip of the cutting tool brushes up against the spindle. Position the tip of the cutting tool against the spindle face and tighten with the turret wrench. Move the turret back to its home position by rotating the carriage dial clockwise.
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Insert the ammunition casing into the jaws of the spindle and hand tighten. Tighten the jaws of the spindle enough to hold the casing but not enough to damage the diameter of the casing. Turn the spindle speed levers until the speed indicator reads 60 rpm. Engage the start button on the lathe.
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Move the turret carriage toward the spindle until the cutting tool sits right in front of the ammunition casing. Turn the cross slide dial on the metal lathe until the tool intersects the tip of the ammunition casing. Turn the carriage dial slowly so the cutting tool lightly touches the front of the ammunition casing. Make a note of the reading you get on the carriage dial. Move the turret away from the ammunition casing and turn off the lathe.
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Check the reloading guide to determine the required overall length of the ammunition casing you are trimming. Measure the current length of the ammunition casing with the calipers. Take the actual length you require for the ammunition casing and subtract the current length of the casing.
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Engage the lathe and move the turret into the previous turret reading you recorded. Slowly turn the turret carriage dial until you get the reading you calculated. For example, if your original dial reading was .075 of an inch and you must have an additional .010 of an inch, move the turret so you get a reading of .085 of an inch.
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Move the carriage away from the ammunition casing and turn off the lathe. Measure the full length of the trimmed casing with the calipers to ensure you have the required length. Insert the deburring tool on the cut end of the casing and turn it to remove any burrs that were left by the cutting tool.
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Tips & Warnings
Pay attention to your dial reading when making such a precision cut or you could trim too much off the ammunition casing.
Replace the cutting tool if you see any damage on the end of the casing after you trim the casing.
Wear safety goggles when operating a metal lathe and trimming ammunition casing.
Never stick your hand between the cutting tool and the spindle when the metal lathe is turned on.
References
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