Choose a structural bolt length from the complete connection stack, not from plate thickness alone. List the connected plies, specified washers, nut dimensions and required thread projection, then check the actual bolt geometry. A bolt can appear long enough yet place its nut against the thread runout. Send the assembly detail with the RFQ so the supplier and responsible engineer can review the same dimensions before quantities are committed.
Grip thickness and bolt length answer different questions
For this purchasing worksheet, grip means the thickness of the connected plies between the bearing surfaces. Keep washers as separate line items so a change in the washer arrangement remains visible. Bolt length is generally measured from beneath the head to the end for this type of headed bolt. Neither measurement identifies the start of fully formed threads: that requires the applicable bolt dimensional specification or supplier drawing.
The RCSC 2020 specification explains that structural bolts may have a relatively short threaded portion. Its commentary warns about a nut reaching the thread transition before the assembly can be properly installed. This is a geometry issue, not something a purchasing team should try to solve by increasing tightening effort.
Build a length budget without calling it an approved size
| Input | Illustrative value | What to verify |
|---|---|---|
| Connected ply A | 24 mm | Current connection detail |
| Connected ply B | 16 mm | Any additional connection layers |
| Specified washers combined | 6 mm | Actual specified arrangement |
| Nut height | 18 mm | Selected nut drawing |
| Projection allowance | 4 mm | Project requirement, not a universal rule |
These invented dimensions illustrate arithmetic only: 24 + 16 + 6 + 18 + 4 = 68 mm. They do not establish a standard bolt length, a nut engagement requirement or structural adequacy. The next available nominal length must still be checked against tolerances, thread length, runout, washer requirements and the connection specification. Do not turn this example into an order for a 68 mm bolt.
Review the thread transition as a separate decision
A longer bolt is not automatically a better fit. Depending on the unthreaded body length, it can move the thread transition relative to the nut or a shear plane. Similarly, adding washers changes the assembly and is not a purchasing workaround to apply without approval. RCSC guidance concerns its covered structural bolting systems; do not transfer its details automatically to stainless general-purpose bolts, stone anchors or a different jurisdiction's design system.
| Observation | Next action |
|---|---|
| Nut approaches runout before seating | Hold the assembly for geometry review; do not force it |
| Drawing controls whether threads cross a shear plane | Compare the actual body and transition dimensions with that plane |
| Washer arrangement changes | Recheck the stack and approved installation detail |
| Several plate stacks share one bolt callout | Check each stack rather than approving one representative fit |
Send an assembly-level RFQ
- Attach the controlling connection drawing and revision.
- List every ply and specified washer, including dimensional tolerances where available.
- Identify the bolt, nut and washer standards, grade or class, finish and installation specification.
- Request the proposed nominal length and a dimensional drawing showing body length, thread length and transition.
- Ask which information remains unresolved before samples or production.
For multiple joints, use one row per stack and link each row to its drawing detail. A shared diameter is not proof that every connection needs the same length. Preserve the approved selection against its revision so a later plate change triggers a review.
Frequently asked questions
Can I order from the two plate thicknesses alone?
No. They omit the specified washer arrangement, nut and projection requirements, and do not establish the thread transition position.
Does visible thread beyond the nut prove correct installation?
It is only one visible observation. It does not establish pretension, component compatibility or compliance with the project installation procedure.
Can extra washers fix a bolt that is too long?
Only use an arrangement permitted by the governing specification and approved detail. Ask the responsible engineer to review the assembly rather than improvising a stack.
Does this worksheet select an anchor rod length?
No. Anchor embedment, exposed length and connection details need their own design and product-specific review.
Request a stack-specific review
Send your connection detail, quantities and required component standards through the Dashitou RFQ form. Use the drawing handoff guide to identify the revision. For related purchasing inputs, see structural bolt class and coating. Final design and installation acceptance remain with the responsible project professionals.