Metal buying guides / Fit and processing
Cut Metal Tolerances: Will the Blank Fit?
When a piece has to fit, you need to know how much its supplied size can vary. A piece ordered at 12 inches can be within the supplier's cut tolerance and still be too long for a close opening.
Updated
Quick answer
Tolerance is the permitted size variation. A 12-inch cut with a ±1/16-inch tolerance can measure from 11.9375 to 12.0625 inches. If the piece must fit an opening, compare the largest permitted piece with the smallest opening and allow the clearance the job requires.
Rapid Metals' published standard finished cut tolerance is ±1/16 inch. A tighter requirement needs review before ordering. Stock thickness, tube wall, flatness, and hole location are separate requirements; the cut-length tolerance doesn't define them.
The nominal size is the size you order. The ± symbol means plus or minus. Clearance is the space left between your piece and the opening after they are fitted together.
Turn the tolerance into a range
For a nominal 12-inch cut with a ±1/16-inch tolerance:
On a small screen, scroll the table sideways to see every column.
| Item | Dimension |
|---|---|
| Nominal length | 12.0000 inches |
| Lower limit | 11.9375 inches |
| Upper limit | 12.0625 inches |
Suppose an opening measures 12.020 inches at its narrowest point. The largest piece within that cut range could exceed the opening by 0.0425 inch. Ordering “12 inches” therefore doesn't establish that every acceptable cut will fit.
This is a dimensional example, not a recommendation for how much clearance your assembly needs. The opening may also vary, and installation can require room for alignment or movement.
Identify the dimension that controls the fit
Measure the actual interface and explain what the part must do there. Does it sit loosely between stops? Slide repeatedly? Locate another component? Finish to size in a later machining operation?
Where possible, provide an acceptable minimum and maximum dimension. If you only know the opening, report that measurement and say the required clearance is unresolved. Don't turn a guessed clearance into a finished-part specification.
Avoid one tolerance for unrelated features
The long edge of a cover may tolerate variation that its mounting-hole pattern cannot. Mark the important dimensions individually rather than placing a very tight requirement over the whole drawing by habit.
Likewise, a saw-cut edge doesn't imply a machined surface, and the supplied plate thickness may have its own material tolerance. Identify surface, flatness, perpendicularity, or stock-thickness requirements when they affect the work.
If you need a blank that will be machined, work from the machine shop's starting-size requirements.
What to send for a close fit
Material and stock form:
Nominal supplied size:
Dimension that controls fit:
Acceptable minimum / maximum:
Mating opening or part:
Finish applied before fitting:
Further machining planned:
Drawing revision:Include how and where the mating dimension was measured. An opening checked at one end may be narrower farther in. Paint, corner radii, or a weld can also affect the usable space.
Choose the right ordering path
If the standard tolerance meets the requirement, use standard cut-to-size ordering. If the part needs a closer fit or additional geometric control, send the drawing for review.
Get the accepted dimensions and scope into the quote. A note about a tight fit is the start of that discussion, not confirmation that extra precision is included.