Metal buying guides / Materials
Steel Flat Bar or Plate: What to Order
You need a rectangular piece of steel. Should you order flat bar cut to length, or a rectangle cut from plate? Start with the thickness, width and length, then check what happens to the piece after it arrives.
Updated
Quick answer
Flat bar comes in a set thickness and width and is cut to length. A plate blank is cut to your width and length from a chosen plate thickness. If a bar already matches your required section, start there. If it does not, look at another bar size or a plate blank.
A blank is the starting piece of metal, before any holes, bends or machining. The section is its thickness and width. For example, a 1/4 × 2-inch flat bar is 1/4 inch thick and 2 inches wide; its length is a separate measurement.
Read all three dimensions
Suppose your drawing calls for steel 1/4 inch thick, 2 inches wide and 18 inches long. A matching flat bar can be cut to 18 inches. If the drawing calls for 3 inches of width, you need a different bar section or a strip cut from plate.
On a small screen, scroll the table sideways to see every column.
| Required blank | What to ask for |
|---|---|
| 1/4 x 2 x 18 inches | Matching flat bar, cut to 18 inches |
| 1/4 x 3 x 18 inches | Plate blank or another bar section |
| 1/4 x 6 x 8 inches | Plate, cut to width and length |
| Any of these with holes or bends | Material plus a reviewed processing request |
These examples describe sizes to order. They do not establish whether a piece can carry a particular load.
When both forms appear to work
If either form can make your piece, ask for the same grade, dimensions and quantity in both quotes. The grade identifies the material specification, such as A36. Flat bar and plate describe the form; those names alone do not identify the steel.
Look at the edges as well as the broad faces. A strip cut from plate can have different edges from a bar, depending on how each was made and cut. Tell the supplier if an edge must slide into a slot, stay visible or be machined later.
If the drawing specifies a particular stock form, have the person responsible for the drawing approve an alternative before ordering.
Think about the next operation
Machining removes metal. If a part must finish at 2 inches wide and both long edges need machining, a bar sold as 2 inches wide may not leave enough material. The machine shop should give you the starting width.
If the piece will be bent, identify the grade and thickness and send the finished shape for review. Calling a flat blank a bracket doesn't specify the bend. If appearance matters, say which face and edges will be visible.
Our machining-blank guide explains how to separate the supplied blank from the finished part.
When the piece has to fit a slot
A listed size is usually nominal: the size used to describe and order the stock. Tolerance is the permitted variation from that size. A bar listed as 2 inches wide is not a promise of exactly 2.000 inches at every point.
If it has to slide into an existing channel, measure the opening and tell the supplier how much clearance you need. Clearance is the gap between the two parts. Ask for the supplied width range, and compare its largest value with the smallest opening. Cutting the bar to length will not correct its width.
Check the available product before entering a size
Rapid Metals lists 1/4 x 2-inch A36 flat bar and standard A36 plate options. Use the product dimensions as the starting point, then enter the dimensions that are cut. Other sections go through a custom request.
For a simple rectangle, configure a plate blank. For another bar section or added work, send the requirements. Include any critical fit, edge, or surface requirement with the dimensions.