Servo Toleransky's machine shop

Servo Toleransky's shop has high windows, a CNC mill behind glass, a granite surface plate and a robot arm that waves at visitors. The plaque over the bench sums up the department: measure twice, cut once, log both. The Manufacturing calculators are in the mill, on the chart board, on the bench, in the rack and on the floor.

Machining is a balance between cutting fast and cutting well. Spindle speed comes from the cutting speed the material allows and the diameter of the tool; the feed per tooth sets both the load on the cutter and the roughness it leaves; and every dimension carries a tolerance that adds up across an assembly. The calculators here cover speeds and feeds, surface finish, tap drill sizes, bolt circles, sheet-metal bend allowance, press-brake tonnage, drilling cycle time, stock weight and tolerance stack-ups.

One rule to remember at the machine: halve the feed and the theoretical roughness drops to a quarter.

“Halve the feed and the theoretical roughness drops to a quarter.” — Servo Toleransky

In this office

• CNC Speeds & Feeds: Spindle speed and feed rate for a milling or drilling operation
• Tap Drill Size: Drill diameter to use before tapping a given thread
• Bolt Circle Pattern: Angle and chord spacing between holes on a bolt circle
• Sheet Metal Bend Allowance: Bend allowance and deduction for a flat-pattern layout
• Metal Stock Weight: Weight of a length of round, square, flat, or tube stock
• Surface Finish Estimate: Theoretical surface roughness left by a turning feed and tool nose radius
• Tolerance Stack-Up: Worst-case and statistical (RSS) stack-up of four toleranced dimensions
• Press Brake Tonnage: Tonnage needed to air-bend a sheet metal part
• Drilling Cycle Time: Machining time for a set of drilled holes at a given feed and speed

Project guides

• Machine a Part from Raw Stock: Weigh your starting stock, dial in the spindle speed and feed for the drill you'll use, then estimate the cycle time of the drilling operation.

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