GlossaryKind of term: Manufacturing termStock
What is stock material?
Stock is the block, bar, plate or blank a part is machined from, including the machining allowance and any clamping margin.
What counts is the form in which material enters machining: a sawn block, a length of round or hexagon bar, tube, a piece cut from plate, or a near-net blank such as a forging or casting. It is larger than the part. Every machined face carries an allowance, and there is often a portion that exists only to hold the workpiece. On bar work, the parting-off width and the bar remnant are added on top.
What decides the size of the stock?
The size follows from the part's envelope, the allowance per face and the way the part is held. A vice needs a clamping margin whose height depends on the jaws, the clamping force and the stiffness of the workpiece; dovetail jaws or a fixture can manage with less. You then round up to what can be supplied: a standard thickness or diameter, a stock length, or plate you saw yourself. How much allowance is needed depends on the condition of the semi-finished product (sawn, rolled, drawn or cast), on residual stress and distortion, and on any finishing such as grinding. A blank whose size varies often needs aligning or probing piece by piece.
How does stock work in practice?
Costing the material line on the stock rather than on the net weight of the model is the usual convention: you buy the whole block or length, saw cut and remnant included. The weight of the 3D model times the price per kilo therefore usually understates the material line. Extra allowance is also machining time, and a clamping margin that has to be removed afterwards can add a setup. Whether you credit chips and remnants back is a convention of your estimate. On small parts, sawing charges, minimum order quantities and freight can weigh more per piece than the price per kilo itself.
What is stock often confused with?
Stock is not the material specification: the specification names alloy and condition, such as EN AW-6082 T6; the stock names form and size, such as a 100 × 60 × 40 mm block. Nor is it the net weight of the part, which is what remains once machining is done. And it is not the stock length, which is the length in which a supplier holds bar or tube.
How do you see stock in Blake?
Material is its own line in the estimate, beside machining, finishing, setup and programming, per piece and per batch. Your materials catalogue keeps your own purchase prices with their source and history. The result is labelled as an estimate. More on materials.
Frequently asked questions
How do I size the stock?
Take the part's largest dimensions, add an allowance for each machined face and a clamping margin if the workholding needs one, then round up to the next available thickness, diameter or length. If grinding follows, include the grinding allowance too.
Why is the material line not costed on the part weight?
Because you buy the whole block or length, including what leaves as chips, saw cut or remnant. Net weight is what remains. Chips and remnants can be credited back if your estimating method provides for it.
How much clamping margin should I allow?
There is no fixed figure: workholding, jaw height, clamping force and part stiffness decide it. Dovetail jaws and fixtures often get by with less. If the margin has to come off afterwards, that can mean an extra setup or saw cut; include it.