Machinist Glossary
Abrasive Wheels
These are wheels made from hard abrasive materials such as Carborundum, used for grinding.
Acme thread
The name of a type of screw thread with a 29-degree angle.
Acute angle
An angle that is less than 90 degrees.
Adapter
This is a device which is used to adapt one size of tool to fit a certain machine.
Allowance
This is the difference in dimensions of mating parts, some parts may require a tighter fit whilst others may need a more loose fit.
Alloy
The result of mixing two types of metal to give new properties not associated with the constituent metals.
Angle iron
Simple a piece of metal with an L-shaped cross-section.
Annealing
This is the controlled heat treatment and cooling cycles of the metal to remove any stresses which have built up and also to make the metal softer and therefore easier to work with.
Anodizing
This is a thin protective oxide layer produced during an electrolytic process in which the metal forms the anode.
Apron
The part of a lathe which contains and covers the gears, clutches, etc.
Arbor
This is a shaft/spindle for holding the cutting tool.
Assembly
Any number of parts fitted together to make up the mechanism of a machine.
Axis
This is the line passing through the center of an object about which the object can rotate. Primarily used as part of a CNC machines name, for instance, 5 Axis CNC Machining.
Back Rake
The back rake is the angled surface on the cutting edge of machining tools.
Bandsaw
This is a power-driven saw with a narrow, continuous blade moving at high speeds between a set of pulleys Check out the restoration video of our 30 year old band saw
Bar Stock
These are bars of various lengths and diameter, usually supplied in flat, round, hexagon, octagon and square shapesBearing
Rollers, and balls placed between moving parts to reduce friction and wear.
Bed
A flat, strong surface found on CNC machines. Used for the accurate machining of parts.
Bench Grinder
This is a powered machine for shaping the cutting edges of tools.
Bench Lathe
A bench lathe is a machine mounted on a bench, usually smaller than floor standing models.
Bit/Tool
This is the hardened steel tool which is very accurately machined to create a cutting part of a machine.
Various types of tools used in a CNC machine
Blind Hole
A hole made in any workpiece which doesn’t pass all the way through it.
Block, Jo (Jo Block)
The name for a Johannson gage block, a very accurate measuring device.
Brine
A saltwater solution for quenching or cooling when heat treating the steel.
Brinell Hardness
A method of testing the hardness of a metal by controlled pressure of a hardened steel ball of a given size.
Broach
A long, tapered cutting tool with serration’s which, when forced through a hole or across a surface, cuts a desired shape or size.
Bull Gear
The large crank gear of a shaper.
Burnishing
This is the process using a metal harder than the metal being finished to create a smooth and glossy surface.
Burr
These are the sharp edges left over on metal parts after they are cut.
Bushing
A sleeve or a lining for a bearing or a drill jig to guard against wear.
CAD
Computer-aided design. CAD programs allow you to digitally create a part that can be milled, 3D printed or rendered.
Caliper
A very accurate device used to measure inside or outside dimensions.
Cam
A device for converting regular rotary motion to irregular rotary or reciprocating motion.
CAM
Computer-aided machining, or sometimes known as computer-aided manufacturing. CAM is a computer program that takes a CAD file (IGES, STEP, etc.) and allows you to create tool paths for the cutting process on a CNC machine. CAM tells your CNC machine where to go, how fast to move and spin.
Carbide Tool Bits
Carbide is a very hard alloy which is inserted into a cutting tool when working with hard materials.
Carbon Steel
A broad term applied to tool steel other than high-speed or alloy steel
Carborundum
A trade name for an abrasive compounded of silicon and carbon (silicon carbide).
Carriage
The main part of a lathe that carries the cutting tool and consists of the saddle, compound rest and apron.
Case Hardening
This is a heat treating process which makes the surface layer of steel substantially harder than the interior or core.
Cathead
A collar or sleeve which fits loosely over a shaft to which it is clamped by setscrews.
Center
A point or axis around which anything revolves or rotates.
Center Drill
A combined countersink and drill used to prepare work for mounting centers.
Center Gage
This is a small, flat gage with 60-degree angles and is used for grinding cutting tools in a lathe.
Center Head
A part of a combination square set that is used to find the center of or to bisect a round or square workpiece.
Center, Live
A center that revolves with the work. Generally. this is the headstock center.
Center Punch
A pointed hand tool made of hardened steel and shaped somewhat like a pencil.
Centerless Grinding
Centerless grinding is a machining process that uses abrasive cutting to remove material from a workpiece. It is typically used in preference to other grinding processes for operations where many parts must be processed in a short time.
Ceramic Cutter
These are cutting tools made from aluminum oxide or silicon carbide.
Chamfer
The bevel or angular surface cut on the edge or a corner of a machined part.
Chuck
A device on a machine tool to hold the workpiece or a cutting tool.
Clearance
The distance or angle by which one objector surface clears another.
Clearance Angle
The angle between the rear surface of a cutting tool and the surface of the work at the point of contact.
Climb Milling
A method of milling in which the work table moves in the same direction as the direction of rotation of the milling center.
CNC
No glossary of machine shop terms would be complete without this definition. CNC means Computer Numerical Control. This means a computer converts the design produced by Computer Aided Design software (CAD), into numbers.
Collet
A precision work holding chuck which centers finished round stock automatically when tightened.
Combination Square
A drafting and layout tool combining a square, a level. A protractor, and a center head.
Contour
The outline of an object.
Coolant
A common term is given to various cutting fluids or compounds used in machining to increase the tool life and to improve surface finish on the material of the parts.
Corrosion
Oxidation (rusting) or similar chemical change in metals.
Cross Feed
The feed that operates across the axis of the workpiece or at right angles to the main or principal feed on a machine.
Cross Section
A view showing an internal structure as it would be revealed by cutting through the piece in any plane.
Crucible Steel
High-Grade tool steel made by melting selected materials in a crucible.
Cutting Speed
The surface speed of the workpiece in a lathe or a rotating cutter, commonly expressed in feet per minute (FPM) and converted to revolutions per minute (RPM) for proper setting on the machine.
Cutting Tool
A hardened piece of metal (tool steel) that is machined and ground so that
it has the shape and cutting edges appropriate for the operation for which it is to be used.
Cyaniding
A process of case hardening steel by heating in molten cyanide.
Extrusion
A shaped part resulting from forcing a plastic material such as lead, tin, aluminum. zinc., copper, rubber, and so forth. through a die opening.
Edge gate
An opening aligned with the parting line of the mold where resin flows into the cavity. Edge gates are typically placed on an outside edge of the part.
EDM
Electric discharge machining. A moldmaking method which can create taller, thinner ribs than milling, text on top of ribs and square outside edges on parts.
Ejection
The final stage of the injection-molding process where the completed part is pushed from the mold using pins or other mechanisms.
Ejector pins
Pins installed in the B-side of the mold that push the part out of the mold when the part has cooled sufficiently.
Elongation at break
How much the material can stretch or deform before breaking. This property of LSR allows for some difficult parts to be surprisingly removed from molds. For example, LR 3003/50 has an elongation at break of 480 percent.
End mill
A cutting tool that is used to machine a mold.
ESD
Electro static discharge. An electrical effect that may necessitate shielding in some applications. Some special grades of plastic are electrically conductive or dissipative and help prevent ESD.
Fixturing
A term given to the apparatus or structure that is holding your work which is often custom-made to hold your specific part.
Flange
A relatively thin rim around a part.
Flute
The grooves found in cutting tools which provide a cutting edge and space for the chips to escape and allow the cutting fluids to reach the cutting edges.
Follower Rest
Support for long, slender work turned in the lathe. It is mounted on the carriage, travels close to and with the cutting tool, and keeps the work from springing away.
Free Fit
A class of fit intended for use where accuracy is not essential. or where large temperature variations are likely to be encountered which allows the metal to expand.
Fulcrum
The point or support on which a lever turns.
Gage
Anyone of a large variety of devices for measuring or checking the dimensions of objects.
Gage Blocks
Steel blocks machined to extremely accurate dimensions.
Gang Milling
A milling setup where a number of cutters are arranged on an arbor so that several surfaces can be machined at the same time.
Gear Blank
A stamping, casting, or any, piece of material from which A gear is to be machined.
Gun Drilling
Gun drilling is a deep hole drilling process which uses a long, often thin, cutting tool to produce holes in metal at high depth-to-diameter ratios.
Gun Drilling machine
Handwheel
Any adjusting or feeding mechanism shaped like a wheel and operated by hand.
Hardening
A heat-treating process for steel which increases its hardness and tensile strength and reduces its ductility.
Headstock
The fixed or stationary end of a lathe or similar machine tool.
Helix
A path formed as a point advances uniformly around a cylinder, as the thread on a screw or the flutes on a drill. Think DNA or a ‘spiral’ staircase.
Helix Angle
The angle between the direction of the threads around a screw and a line running at a right angle to the shank.
Hex
A term used for anything shaped like a hexagon. Usually applied for bar stock.
High-speed Steel
This is alloy steel which is commonly used for cutting tools because of its ability to remove metal at a much faster rate than carbon steel tools.
Honing
The process of finishing ground surfaces to a high degree of accuracy and smoothness.
Hot-rolled Steel
Steel which is rolled to finished size. while hot. Identified by a dark oxide scale left on the surface.
Idler
A gear or gears placed between two other gears to transfer motion from one gear to the other without changing their speed or ratio.
independent chuck
A chuck in which each jaw may be moved independently of the others. Useful for some types of parts.
Indicator
A precision instrument which shows variations of thousandths of an inch or less when testing the trueness or alignment of a workpiece, fixture, or machine.
Jacobs chuck
A common term for the drill chuck used in either the headstock spindle or in the tailstock for holding straight-shank drills, taps, reamers, or small diameter workpieces.
Jarno
A standard taper having 0.600-inch taper per foot used on some machine tools.
Jig
A production work holding device that locates the workpiece and guides the cutting tool (see fixture). Used primarily for accuracy and in production machining.
Kerf
The width of the cut left by a Saw.
Knee
That part of a column of a knee-type milling machine which carries the saddle and the table and provides the machine with vertical feed adjustments.
Knurl
A decorative gripping surface of straight-line or diagonal design made by uniformly serrated rolls called knurls provides better grip.
Lead
The distance a thread will advance along its axis in one complete revolution.
Lead Screw
The long, precision screw located in front of the lathe bed geared to the spindle, used for cutting threads.
Machinability
The degree of difficulty with which a metal may be machined, view metal data sheets.
Magnetic Chuck
A flat smooth-surfaced work holding device which operates by magnetism to hold ferrous metal workpieces for grinding.
Mandrel
A precision-made tapered shaft to support work for machining between centers.
Metal Plating
This is a method of plating where metals are deposited on the substrates. This process is used to coat and and other materials by forming a thin layer of metal over the substrates.
Mild Steel
A term used for low-carbon machine steel.
Mill
A milling machine; also, the act of performing an operation on the milling machine. milling, climb – See climb milling. milling, face-See face milling.
Multiple-thread Screw
A screw made of two or more threads to provide an increased lead with a specified pitch.
Nitrating
A case hardening process in which ammonia is introduced to the surface of certain alloys.
Nonferrous
Any metal containing no iron, such as brass and aluminum.
Normalizing
Process of heating a ferrous metal or alloy to above its critical temperature and cooling in still air to room temperature to relieve Internal stresses.
Oil Hardening
The process of quenching in oil when heat treating alloy steel to bring out certain qualities.
Parallels
Hardened steel bars accurately ground to size and made in pairs in many different sizes to support work in precision setups.
Pilot
A guide at the end of a counterbore which keeps it aligned with the hole.
Pilot Hole
A starting hole for large drills, reducing the resistance, and aid in maintaining the accuracy of the larger hole.
Pitch
The distance from any point on a thread to the corresponding point on the adjacent thread. measured parallel to the axis.
Pitch Diameter
The diameter of a thread at an imaginary point where the width of the groove and the with of the thread are equal.
Plain Cutter
A milling cutter with cutting teeth on the periphery only.
Pyrometer
A device for measuring the high temperatures in a heat-treating furnace.
Quench
To rapidly cool heated metal in water, oil brine, or air in the process of heat treating.
Rack
An array of gears spaced on a straight bar.
Rake
That surface of a cutting tool against which the chips bear while being severed.
Recess
An internal groove.
Roughing
The fast removal of stock to reduce a workpiece to approximate dimensions’. leaving only enough material to finish the part to specifications, usually in a separate process.
SAE steel
Steel manufactured under the specifications by the .
Sandblasting
A process of blowing sand by compressed air with considerable force through a hose against an object.
Sand Blasting metal parts
Scale
The rough surface on hot. finished steel and castings. Also, a shop term for steel rules.
Set Screw
A plain screw used principally for locking adjustable parts in position.
Setup
The preparation of a machine tool to complete a specific operation. It includes mounting the workpiece and necessary tools and fixtures and selecting the proper speeds. feeds, depth of cut and coolants. Usually the only part of machining on CNC machines other than part removal.
Shank
The part of a tool or similar object which connects the principal operating part to the handle, socket’, or chuck by which it is held or moved.
Shims
Very thin sheets of metal machined to a very precise thickness and used between parts to obtain desired fits.
Shoulder
A term for the step made between two machined surfaces.
Shrink Fit
A class of fit made when the outer member is expanded by heating to fit over a shaft, and then contracts or shrinks tightly to the shaft when cooled.
Side Cutter
This is a milling cutter that has cutting teeth on the side as well as on the periphery or circumference.
Sine Bar
A precision instrument for laying out, setting, testing, and otherwise dealing with angular work.
Slabbing Cutter
A wide, plain milling cutter having helical teeth. Used for producing large, flat surfaces. Sleeve.
Slotter
An attachment which operates with a reciprocating motion.
Spindle
A rotating device widely used in machine tools. such as lathes., milling machines, drill presses, etc.
Spot Facing
Finishing a bearing surface around the top of a hole.
Spur Gear
A gear having teeth parallel to the axis of the shaft on which it is mounted.
Steady Rest
The support that is clamped to the bed of a lathe used when machining a long workpiece. Sometimes called a center rest.
Step Block
A fixture designed like a series step to provide support at various heights required for setups.
Stock
A term for the materials used to make parts in a machine tool., for instance, steel, aluminum, plastic, etc.
Surface Grinding
The process of grinding flat surfaces on a surface grinding machine.
Surface Plate
An accurately machined and scraped flat metal piece (usually of cast iron) used to check the flatness of surfaces.
Swiss Machining
Swiss Lathes are made specifically to provide precision accuracy down to a few micrometers. Swiss machining lathes hold the workpiece on the Z-axis using a collet and guide bushing.
Tailstock
The part of a lathe which supports the end of a workpiece with a center.
Tang
The flat on the shank of a cutting tool, such as a drill, reamer or end mill, that fits a slot in -the spindle of a machine to keep the tool from slipping.
Tap
A hardened tool used to cut threads on the inside of a round hole.
Taper
A uniform increase or decrease in the size or diameter of a workpiece.
Tensile Strength
The property of a metal which resists force applied to pull it apart.
Tenth
A machinist term for a unit of measurement equaling 0.0001″ or one ten-thousandth of an inch, NOT to be mistaken with 0.1″ or a tenth of an inch.
Tool Steel
A general classification for high-carbon steel that can be heat treated to a hardness required for metal cutting tools such as punches, dies. Drills etc.
Traverse
Movement across the surface of the work being machined.
Truing
Centering or aligning a workpiece or cutting tool so that an operation can be performed accurately.
Tube Flaring
The Tube flaring process is a method of forming the end of a tube into a funnel shape so it can be held by a threaded fitting.
Tumbler Gears
Pair of small lever-mounted gears on a lathe used to engage or to change the direction of the lead screw.
Universal Grinder
A versatile grinding machine designed to perform both internal and external grinding operations. including straight and tapered surfaces on tools and cutters.
Ways
The flat or V-shaped bearing surfaces on a machining tool that guide and align the parts which they support.
Wireframe
A type of CAD model consisting only of lines and curves, in 2D or 3D. Wirefame models are not suitable for rapid injection molding.
Working Drawing
A drawing. blueprint, or sketch of a part, structure, or machine.
