A small spacer can control a large part of an assembly’s fit. When its description is incomplete, purchasing teams can receive the right-looking component with the wrong separation distance, thread depth or end geometry. The result often becomes visible only during assembly.
This guide explains how to specify the connection clearly when ordering custom spacers and standoffs for equipment, housings and electronic assemblies.
Describe the connection instead of relying on the name
Suppliers use “spacer” and “standoff” in different ways. A common distinction is that a spacer has a clearance hole, while a standoff has threaded features. Essentra’s PCB hardware guide uses this distinction and shows how these components position boards within an assembly. Describe the geometry explicitly so the name cannot be misread. Read the hardware reference.
| Configuration | What to specify |
|---|---|
| Unthreaded spacer | Body length, outside diameter and clearance-hole size |
| Female–female standoff | Body length, each internal thread and usable thread depth |
| Male–female standoff | Body length, projecting thread length and internal thread depth |
| Hexagonal body | Across-flats dimension and tool-access requirement |
| Shouldered or stepped part | Each locating diameter, shoulder length and mating interface |
Separate body length from overall length
Label the distance that controls the separation between the assembled surfaces. On a part with a projecting threaded end, overall length and body length describe different features. Put both on the drawing if both matter.
Identify the bearing faces, through holes and any recessed ends. If the component locates another part, specify the controlled interface rather than asking for a generally “precise spacer.” The drawing should tell the inspector which measurement proves that function.
Check the mating screw before choosing thread depth
Show the complete thread designation for both ends. Record the screw length, intervening part thickness and usable threaded depth where these are controlled. Ask engineering to review whether the chosen screw can bottom out before the parts clamp together.
For a multi-part stack, list the nominal dimensions and tolerances of the adjoining components. Request a review of the assembled stack rather than treating every component as an isolated purchase. Keep any proposed dimension changes in the controlled drawing revision.
Choose material and finish from the application requirements
Brass, steel, stainless steel, aluminum and non-metallic materials are possible categories to discuss, but a category name is not a complete specification. State the required grade, surface treatment and environment. Explain whether the part is intended to conduct electricity, provide isolation, withstand a defined load or simply maintain spacing.
Do not approve a material substitution solely because it machines easily or resembles the sample. Ask what the alternative changes in the finished assembly, and have the responsible designer approve the decision. For electrical isolation or bonding, include the relevant system-level requirements rather than assuming that a particular colour or plating establishes the result.
Prepare an inspection and packaging plan
A useful first-sample review includes the controlled length, mating fit, end condition, identification and the application checks specified by your team. Define the inspection method and reporting requirements before ordering, especially where a result must be traced to a particular lot.
For mixed sizes, use distinct item numbers and separate packaging. Make the label description match the BOM. A repeat order should reference the approved drawing and finish, with any change to material, geometry or quantity stated explicitly.
Explore machined component families and our material options. To discuss a spacer project, send the dimensioned drawing, mating screw information and order quantities.
Frequently asked questions
Is a threaded spacer the same as a standoff?
The names overlap between catalogues. Specify whether the part has a clearance hole, internal threads, projecting external threads or a combination. A drawing with both end views removes the ambiguity.
Which length should appear on the purchase order?
Reference the controlled drawing and identify the body or separation length. Include overall length and projecting thread length when applicable. Avoid using one unqualified length for geometries with shoulders or threaded projections.
Can I use the same standoff for different screw lengths?
Only after the usable engagement and bottoming clearance are reviewed for each assembly. Share the mating screw dimensions and the thickness of the parts being clamped. A successful fit in one assembly does not approve all combinations.
What information is needed to quote a non-standard spacer?
Provide the current drawing, material and finish, quantities by size, critical interfaces and inspection requirements. Add the delivery destination and packaging details, and identify any dimensions that remain open for discussion.
