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Adjustable Soft Jaw Boring Ring – 4140 Steel | Lathe Chuck Setup Tool
This adjustable soft jaw boring ring is a tool I use daily in my shop at Swartz Machine LLC. It was designed to make boring soft jaws faster, more accurate, and easier compared to traditional solid boring rings.
Unlike fixed boring rings, this design allows you to adjust the clamping diameter so you can bore jaws with minimal boring bar stick-out and excellent stability.
This helps produce very accurate jaws when chasing tight tolerances and repeat setups.
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Why This Design Works Better
Traditional boring rings force you to run long boring bars when setting up soft jaws. This adjustable ring allows you to position the clamping diameter exactly where you need it.
Benefits include:
• Reduced boring bar stick-out
• Improved rigidity and finish
• Easier setups for small or large bore diameters
• Lightweight and quick to adjust
When working to tight tolerances (.0002” runout or better), it’s often necessary to skim cut soft jaws to restore perfect concentricity. This tool allows you to dial in exactly the amount of clamping needed so you only remove the minimal material required.
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Adjustable Clamping Range
This boring ring adjusts from approximately:
.950” and larger
You can simply change bolt length depending on the diameter you want to clamp.
Examples:
• Small diameters – run short bolts or no bolts
• Larger diameters – use longer bolts for greater expansion
This makes the tool extremely versatile for different chuck sizes and setups.
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Specifications
Material: 4140 Steel
Fasteners: M6 Socket Head Cap Screws
Minimum Diameter: ~.950”
Adjustable Expansion Range
Precision machined
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Included
Adjustable Soft Jaw Boring Ring
M6 Screws
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Made by a Machinist
This tool is made and used in my own shop, Swartz Machine LLC, where accuracy matters. It was designed to solve a real setup problem and make boring soft jaws quicker and more repeatable.
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Ideal For
• CNC lathes
• Manual lathes
• 3-jaw chuck setups
• Soft jaw machining
• Precision workholding setups
