Ground Steel Plate and Machined Parts

888-934-7463 (Toll Free) 205-942-2073 (Fax) mail@precisiongrinding.com Adding Value to Steel Plate Since 1971

GROUND AND MACHINED STEEL PLATE - Machine Parts
 

A36, A572-50, A514-T1, 1045, 4140, A2, D2, S7, Astralloy, Tribraze
Mild, Low Carbon, Medium Carbon and High Carbon Steel and Alloy Plate

We are your ONE STOP SHOP for CUSTOM STEEL PLATE !
CNC Flame Cutting - Plasma - Stress Relieving & Annealing - Blanchard & Surface Grinding - CNC Machining & Milling - Custom Machining & Fabrications

Precision Grinding, Inc. operates some of the largest, high-horsepower grinding machines in the country. For over 35 years, we have provided grinding services for many of the largest and most respected industrial manufacturers and machining companies in the United States. PGI offers a standard ground plate thickness tolerance of ± .005. Typical flatness tolerances are 0.002/0.003 per foot, depending upon the finish thickness of the part and whether or not the part has been stress relieved. Greater flatness can be achieved if necessary. All hot rolled plate retains some residual stress from the rolling process at the steel mill. Stress Relieving plate often increases the ability of achieving a tighter flatness tolerance in the grinding process. A typical parallelism tolerance of 0.003" - 0.005" is expected, dependant upon the size of the part and which grinder is being used. Parallelism within 0.001" can be achieved when the part is finish ground on the horizontal spindle surface grinder.

Precision Grinding offers services from one of seven (7) large grinders to compliment customers' machining requirements. PGI performs Rotary Grinding and both, Vertical and Horizontal Spindle Surface Grinding.

Some of our grinders have a rotary table (the chuck, the round magnetic platform where the parts sit) along with a  rotary head (where the grinding segments or grinding stones are located) that both rotate about the horizontal plane. These are known as Rotary Surface or Blanchard Grinders. The finish has a notable "cross-hatch pattern," due to the magnetic chuck rotating underneath the rotary head - the spindle down-feeds while the head rotates.

Other tables are rectangular, whereby the table moves forward and backwards underneath the same type rotating head. They're known as Vertical Spindle Grinders with a Reciprocating Table. Our most critical close-tolerance grinders have a vertically rotating wheel on a horizontal moving spindle-axis above a table that moves back and forth underneath the wheel. Note, the horizontal spindle moves across the plate while the vertical spinning grinding wheel rotates or performs the grinding action. These Horizontal Spindle Surface Grinders can create a reflective-type finish, one that has an extremely smooth feeling.

This near-polish surface finish is measured on an RMS, or root-mean-square scale. The RMS is the difference in peaks and valleys created by the sand specs in the segments (stones) that do the grinding. If you look closely and run your fingers across the plate, you'll notice and feel the lines, much like what's seen in the background of this page. Our normal finishes are from 16 RMS - 32 RMS - 63 RMS - 125 RMS - 250 RMS, depending upon the grinder. We can reach a 32 RMS finish and smoother. The lower the RMS desired, the higher the cost. Achieving flatness and lower RMS requires regularly dressing the wheel with a diamond (or similar) dresser (stone sharpener) and holding the spindle on location.  Machine ways, flow-critical plates, and NASA-critical parts are examples of ground plates requiring extremely smooth finishes. As a rule, we do not offer polishing. Our business is built upon stock removal while achieving a flat, parallel, and square ground and machined plate.
 

Grinding Terminology

Flat: the variance in height on one side of the plate OR the deviation from a single plane (1 side.) In many machine shops, best measured with a precision straight edge having a tolerance level of ± 0.0005, precise to ½ thousandth across one edge of the length of the straight edge. By setting the straight edge across the length, the width and the diagonals of the ground plate, one can measure flatness by noting how many 0.001 shims can fit between the straight edge and the plate. Flatness can be reached and measured through the use of various outside micrometers, depth mics, dial indicators, and precision measuring instruments. A standard flatness target is within 0.005 - 0.010", depending on the size & thickness of the plate and whether or not it's stress relieved. Grinding a longer time period upon the part without down-feeding will narrow the peaks and troughs, further flattening and improving RMS. Precise measuring instruments such as Coordinate Measuring Machines (CMM) and Laser systems can provide a more accurate flatness measurement.

Parallelism: the variance in distance from one point on one side of the plate to another coincident point on the other side of the plate. A plate can be parallel without being flat or square. Standard parallelism from PGI is within 0.005" depending upon the size of the part. Parallel within 0.0005/.001" can be achieved if finished on the horizontal spindle surface grinder.
Please, let us know your flatness and parallelism requirements.

Square (Orthogonal): within machine shop conditions, best found with a precision square. This is grinding for 90° between any two planes of the block or the 3-dimensional part. Whereas, cornering edges are deburred or "chamfered," orthogonal planes (two sides abutted) of the part are measured as square, rather than the meeting edge of any two sides. Refer to CMM & LASER inspection.

Surface Finish: RMS, a term used to describe surface roughness or finish, as measured according to a known scale. The difference in the grain depths ground onto the surface of the plate by sand-silica-ceramic segment breakaway. Grinding stones are made of Aluminum-Oxide, Ceramic, and/or some other granular substance glued or otherwise held together. When surface grinding, granular substances break away, leaving behind another layer of sharper cutting edges from the next grains in line. The smoothness of the grinding pattern on the plate after finish grinding is the same as the measurement between the peaks and valleys forming these fine ground lines. As the segments are held stable at zero-down-feed for a period of time, then retracted a thousandth of an inch at a time, the segments are less able to breakaway while hitting less plate. Sometimes, more rounded cutting edges are formed while knocking out the tallest peaks, thus bringing about a smoother finish. Surface finish RMS is often dependant upon the hardness (or softness) of the segment, the hardness of the plate, the speed of the wheel, and the lubricants used. Saint-Gobain lists an in-depth article describing the elements surrounding RMS and surface finish on their site.

High-Horsepower, Rotary Surface Grinding Plate	CNC Machining Plate - Probed to  < 0.001" Measurement

Steel plate is rarely manufactured flat when hot rolled at the mills. Ideally, seemingly rare and depending upon thickness, the mills can roll steel to within ± 0.010" uniform thickness across the top and the bottom of a 96" x 480" plate. In the real world, this is difficult to achieve. Tolerance specification levels are much less demanding for ASTM A6 / ASTM A6M standards.

Many times we stress relieve plate to undo the stresses created from flame cutting along with the natural tendency of rolled plate to curl. When cutting many shapes or holes in a part or after welding, stress relieving and presses may be used to achieve flatness. Often times, our Quality Control department performs multiple inspections on ground, machined, and fabricated parts.

Probes and probing programs further inspect machined plate during the Vertical and Horizontal CNC Machining processes. Although requiring a considerable amount of time to probe every part drilled, bore, threaded, and cut upon, our CNC Machining centers can probe for near exact precision to less than 0.001".

Final inspections are performed to guarantee our best efforts to ensure you get what you ordered.

We grind and machine plate complete for many ISO member companies.

Across America companies know of our commitment to quality and excellence in precision steel parts production. A solid industry reputation for 35 years assures the experience to get the job done right.
 

. When you need ground plate and machined parts from one vendor, please, contact us at 888-WE-GRIND.

Large Vertical CNC Machining  Centers,  Horizontal Planers and Bar Mills
Large Blanchard Grinders and Mattison Surface Grinders

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