Reference

Machine Base and Heavy Fabrication Glossary

58 terms you will meet on a machine base drawing, quotation or inspection report, defined in the way they are actually used rather than the way a dictionary would put it. Where a term deserves more than a paragraph, there is a link to the guide.

A

Anchor bolt: The bolt fixing a machine base to its foundation. Published equipment practice calls for a stretch length of at least 12 bolt diameters and embedment of at least 10, with the upper portion sleeved so that length is free to stretch.; Read the guide
Annealing: A heat treatment that softens metal and reduces residual stress by heating, holding and cooling slowly. On castings it is often called ageing or seasoning and is done before machining.
As-welded: The condition of a fabricated structure before any machining. An as-welded surface carries normal fabrication distortion and is a poor choice of datum.
Autocollimator: An optical instrument that measures the angle of a mirror carried across a surface, accumulating readings into a straightness or flatness map. Long established for large machine tool surfaces.; Read the guide

B

Back-step welding: Depositing a long seam as a series of short runs laid in the opposite direction to the overall progression, so each run’s shrinkage partly opposes the last. A standard distortion control technique.; Read the guide
Bed: The main horizontal structure of a machine tool carrying the ways or slides. Used interchangeably with base on some machine types.; Read the guide
Blowhole: A rounded void in a casting caused by trapped gas during solidification. Often subsurface and found only when machining opens it.; Read the guide

C

Chatter: Self-excited vibration in a cut, where structural movement modulates chip thickness and feeds the vibration. A function of stiffness, damping and frequency separation rather than of rigidity alone.; Read the guide
Chill: Localised hard, rapidly cooled iron in a casting, either deliberate or a defect. As a defect it is usually discovered when it destroys a cutter.
Cold shut: A casting defect where two streams of metal met without fusing, leaving a seam that behaves like a crack.
Coplanarity: The requirement that several separate surfaces together form one plane. Expressed as a profile control across the pads, not as flatness on each one.; Read the guide

D

Damping: How quickly a structure dissipates vibration energy. Distinct from stiffness: a structure can be very rigid and almost undamped, which is the usual condition of a bare steel weldment.
DAP: Delivered At Place. The seller carries the goods to a named destination. Normally excludes unloading, which on a multi-tonne crate is a significant exclusion.
Datum: The reference a geometric tolerance is measured from. Flatness needs none; parallelism, squareness and position are meaningless without one.
Datum target: A specified point, line or area used as a datum instead of a whole surface. The correct tool for referencing a distorted as-cast or as-welded surface.
Ductile iron: Cast iron in which magnesium treatment forms graphite as spheres rather than flakes, giving toughness and elongation at the cost of damping. Graded to EN 1563.; Read the guide

E

EN 1090: European standard for execution of steel structures, defining execution classes EXC1 to EXC4. Permits ISO 13920 as an alternative to its functional tolerances.
EN-GJL: Designation for grey cast iron with lamellar graphite under EN 1561. EN-GJL-250 corresponds to the older GG25 and guarantees 250 MPa minimum tensile strength in a separately cast test bar.
EN-GJS: Designation for spheroidal graphite (ductile) cast iron under EN 1563. In EN-GJS-400-15 the first number is minimum tensile strength in MPa, the second minimum elongation in percent.
Epoxy granite: Graded mineral aggregate bound with epoxy resin and cast cold. Also called mineral cast or polymer concrete. Used where damping and thermal stability matter more than stiffness per unit volume.; Read the guide
EXW: Ex Works. The buyer collects from the seller’s premises and carries all cost and risk from there. The cheapest line on a quote and the most work for a heavy part.

F

FEA: Finite element analysis. On a machine base it is used chiefly for static deflection and modal behaviour rather than stress, since bases are rarely stress-limited.; Read the guide
Filled weldment: A steel weldment whose closed sections are filled with a mineral or concrete core to add mass and damping without a pattern or mould.; Read the guide
Flatness: The distance between two parallel planes just containing a surface. Requires no datum. Frequently written on drawings where parallelism was meant.; Read the guide
FOB: Free On Board. The seller delivers the goods loaded on the vessel; risk and onward cost transfer to the buyer at that point.

G

GD&T: Geometric dimensioning and tolerancing. The system for specifying geometric relationships, codified in ISO 1101 and ASME Y14.5.
GG25: Legacy German designation for grey cast iron equivalent to EN-GJL-250. Still in daily use on drawings.
Grout: Material placed between a machine base and its foundation to transfer load continuously, hold alignment and couple the masses. Epoxy grout dominates precision and vibrating equipment; cementitious grout suits static installations.; Read the guide

H

Heat affected zone: The parent material adjacent to a weld whose microstructure has been altered by welding heat without melting. Harder than the surrounding plate, which is why machining across a weld causes trouble.
Hold point: A stage in an inspection and test plan at which work stops until the specified party has inspected and released it. Distinct from a witness point, where work continues regardless of attendance.; Read the guide

I

Incoterms: The ICC rules defining who books carriage, who pays and where risk transfers in a sale of goods. Current edition Incoterms 2020.
Interpass temperature: The temperature of the joint immediately before the next weld pass is deposited. Controlled within the welding procedure to keep conditions consistent along a seam.
ISO 13920: General tolerances for welded constructions, in four graduated classes A to D. Governs the geometry of the finished fabrication, not weld bead quality.; Read the guide
ISO 3834: Quality requirements for fusion welding, in comprehensive, standard and elementary levels. ISO 3834-2 is the comprehensive level.
ISO 5817: Quality levels B, C and D for imperfections in fusion-welded steel joints. Covers weld quality, where ISO 13920 covers dimensions.
ISPM 15: International standard requiring solid wood packaging in international trade to be heat treated or fumigated and marked. Heat treatment and fumigation are different treatments.
ITP: Inspection and test plan. A table giving, per manufacturing stage, what is checked, against what criterion, by whom, and what document results.; Read the guide

M

Machining allowance: Stock left on a weldment or casting so functional faces can be cleaned up after distortion. Sized to the structure and the tolerance class rather than to a universal number.
Mineral cast: See epoxy granite. The terms are used interchangeably in machine tool work; suppliers apply their own trade names.
Modal analysis: Analysis or measurement of a structure’s natural frequencies and mode shapes. The mode shape tells you where to add material; the frequency tells you what to avoid.

N

Natural frequency: A frequency at which a structure resonates. Machine tool structures are commonly designed to keep the first natural frequency clear of the machine’s excitations, with targets above 80 to 100 Hz frequently quoted.
NDT: Non-destructive testing. On a machine base typically visual, magnetic particle, dye penetrant or ultrasonic, selected by material, thickness and criticality.

P

Pattern: The tooling a sand mould is formed around. A real capital cost and lead time, and the reason a casting design change is expensive.
Porosity: Fine voids in a casting or weld caused by trapped gas. Severity depends almost entirely on location rather than on the defect itself.
Pre-setting: Deliberately positioning parts off-dimension before welding so that shrinkage pulls them to nominal. Depends on knowing how far the joint will move.
Profile tolerance: A geometric control bounding a surface within a tolerance zone about its true form. Does the work of several controls at once and is how coplanarity across pads is specified.

R

Residual stress: Stress locked into a structure by welding or uneven cooling. Released by machining, which is why a part flat on the table can move days later.; Read the guide
Rib: An internal stiffening member. Machine tool practice favours I-section ribs for bending and diagonal layouts for torsion, commonly spaced around 200 to 300 mm to control panel buckling.; Read the guide

S

Setup: One orientation of a part on a machine tool. Each setup on a multi-tonne structure means craning, clocking and re-datuming, so setup count drives both cost and accumulated error.
Sole plate: A machined plate grouted to a foundation and levelled first, with the machine then set on it. Separates levelling from machine setting, and the usual choice for large or precise equipment.
Stability lobe diagram: A map of which combinations of spindle speed and depth of cut are stable for a given machine, tool and workpiece. Explains why a higher speed is sometimes more stable than a lower one.
STEP: A neutral CAD exchange format (ISO 10303) and the usual way a 3D model is sent with an RFQ.
Stress relief: Reducing residual stress, either by a furnace thermal cycle or by vibratory treatment. Not every specification accepts both, so the method has to be stated.; Read the guide

V

Vibratory stress relief: Exciting a structure at its resonances to redistribute peak residual stresses. Far faster and cheaper than a furnace cycle and not accepted by every specification.

W

Way: The precision guiding surface a machine slide runs on, whether an integral machined way or a mounted linear rail.
Weldment: A structure made by welding plate and section together, as opposed to one cast or moulded in a single piece.
Witness point: A stage in an ITP at which the specified party is notified and may attend, but work proceeds if they do not.
WPS: Welding procedure specification. The document telling a welder how a joint is to be welded. Supported by a WPQR that records the qualification test proving the procedure works.

A term missing that you think belongs here? Tell me and I will add it. Related: the standards index andthe construction comparison.