# Bolt Torque Calculator API

> For the complete documentation index, see [llms.txt](/llms.txt).

Recommended bolt tightening torque and preload for metric sizes and ISO grades, by the short-form K method and VDI 2230.

Use this endpoint to add the tool to your app, site, workflow, or agent without rebuilding formulas, validation, examples, and docs.

- Slug: `bolt-torque-calculator`
- Category: `science`
- Version: `2026-04-22`
- Credits per successful call: 1
- Starts on: free
- Max payload: 65536 bytes
- Privacy mode: `hash_only`
- Available on: free, starter, pro, business, scale
- Browser tool: https://miniwebtool.com/bolt-torque-calculator/

## Endpoint

`POST https://api.miniwebtool.com/v1/tools/bolt-torque-calculator/run`

## Request body

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `size` | `str` | no | M3 | M4 | M5 | M6 | M8 | M10 | M12 | M14 | M16 | M18 | M20 | M22 | M24 | M27 | M30 | M36 | custom Choices: M3, M4, M5, M6, M8, M10, M12, M14, M16, M18, M20, M22, M24, M27, M30, M36, custom |
| `diameter_mm` | `float | None` | no | Nominal diameter (size=custom) |
| `pitch_mm` | `float | None` | no | Thread pitch (size=custom) |
| `grade` | `str` | no | 4.6 | 4.8 | 5.8 | 6.8 | 8.8 | 9.8 | 10.9 | 12.9 | A2-70 | A4-80 | custom Choices: 4.6, 4.8, 5.8, 6.8, 8.8, 9.8, 10.9, 12.9, A2-70, A4-80, custom |
| `proof_stress_mpa` | `float | None` | no | Proof stress (grade=custom) |
| `yield_stress_mpa` | `float | None` | no | Yield stress (grade=custom) |
| `lubrication` | `str` | no | dry | oiled | moly_grease | anti_seize Choices: dry, oiled, moly_grease, anti_seize |
| `preload_pct` | `float` | no | Target preload as a percent of proof load |

## Example request

```json
{
  "size": "M10",
  "grade": "8.8",
  "lubrication": "dry",
  "preload_pct": 75
}
```

## cURL

```bash
curl -X POST https://api.miniwebtool.com/v1/tools/bolt-torque-calculator/run \
  -H 'Authorization: Bearer mwt_live_YOUR_KEY' \
  -H 'Content-Type: application/json' \
  -d '{"size":"M10","grade":"8.8","lubrication":"dry","preload_pct":75}'
```

## Response envelope

```json
{
  "request_id": "01K...",
  "tool": "bolt-torque-calculator",
  "tool_version": "2026-04-22",
  "credits_used": 1,
  "result": {}
}
```

## Errors

Errors are RFC 7807 `application/problem+json`. Branch on `code`, not `title`.

## MCP

Agents can discover and call this tool through `https://api.miniwebtool.com/mcp` or `https://api.miniwebtool.com/v1/mcp` using MCP `tools/list` and `tools/call`.

## Frequently asked

### What does the Bolt Torque Calculator API do?

Recommended bolt tightening torque and preload for metric sizes and ISO grades, by the short-form K method and VDI 2230. Use it to add this utility without rebuilding formulas, validation, examples, and documentation.

### How much does one call cost?

1 credit per successful call. Failed calls do not bill.

### What parameters are required?

Required fields: (none). Full schema at `https://api.miniwebtool.com/v1/openapi.json`.

### Is this deterministic?

Yes. Same input, same output. Tool version: 2026-04-22.