KEVOS® MAKEOS · Manufacturing
Bar Stock for Screw Machine Parts
How many parts does each bar give, and how much bar stock do I order for this quantity?
Parts per bar and bar stock required for automatic screw machine or bar-fed lathe work, from the part length, cut-off tool width, facing allowance, bar length and the remnant lost to chucking, with the handbook’s feet-per-1000-parts estimate for 10-foot bars.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Finished part length | mm | Overall length of the finished part. |
| Cut-off tool width | mm | Width of the cut-off blade (wider for larger bar). |
| Facing allowance per part | mm | Extra length per part removed by facing. |
| Bar length | mm | Length of the bars supplied. |
| Remnant (chucking) allowance per bar | mm | Bar end left in the collet or bar feeder. |
| Parts required | Number of good parts needed (add your scrap allowance). | |
| Bar mass per metre | kg/m | Mass per metre of the bar (from a stock-mass calculation). |
Method and formulas
- Length per part = part length + cut-off width + facing allowance.
- Parts per bar = ⌊(bar length − remnant) ÷ length per part⌋; bars = ⌈quantity ÷ parts per bar⌉.
- Handbook estimate for 10-ft bars: feet per 1000 parts = (L + W) × 84, with L and W in inches.
- Example: 25.4 mm parts with a 1.57 mm cut-off give 109 parts per bar and need 10 bars.
Limitations
- Start-up and setup parts are not included.
- The handbook estimate assumes 10-foot bars and its standard chucking allowance.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Order bar stock for a screw machine job
- Quote material cost per part
- Compare bar lengths and remnant allowances
Who it is for
- Screw machine setters
- Estimators
- Production planners
What you get
- Parts per bar
- Bars to order
- Stock length and mass
Interpreting the result
- Shorter remnants (bar pullers, remnant-less feeders) can save a bar in every few on short parts.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1175–1176. Topic reference; no source tables or recommended settings are reproduced.
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