# Plates: which fit, specs and durability


**Draft, not yet verified on hardware.**

Choose plates that fit the SeedHammer II and know how an engraved plate holds up. Stock firmware v1.4.3 knows one plate, 85 x 85 mm: there is no plate-size screen, the machine does not detect which plate is loaded, and each job engraves one face.

<p class="alert alert-warning">Seed words are typed on the machine only and never pass through a phone, a computer or a chat assistant. An engraved seed plate gives full access to the wallet, so store it like the seed; a descriptor plate holds no secret and reveals every address of the wallet.</p>

## What you need {#requirements}

- A SeedHammer II on stock firmware v1.4.3: the start screen shows "Firmware: v1.4.3" at the bottom right.
- Square 85 x 85 mm plates: SeedHammer II plates or SH02 steel plates, from the SeedHammer shop or a reseller.

## Which plates fit {#fit}

| Plate | Fits | Notes |
| --- | --- | --- |
| SeedHammer II plate | yes | square, 85 x 85 mm, no holes |
| SH02 plate (original SeedHammer) | yes | square, with or without corner holes; the lock holds the plate and the holes go unused; hole clearance unverified |
| SH01 plate (original SeedHammer) | no | small; support is not planned |

In v1.4.3 descriptor text keeps a 10 mm square clear in each corner: lines within 10 mm of the top or bottom edge are shortened at both ends. A "QR ONLY" plate has no such gap. Its QR is centred, and a 2-of-4 QR is 72.9 mm wide, so it comes within about 6 mm of every edge and reaches into the corners.

![An SH II plate without holes beside a holed SH02 plate and a small SH01 plate](/static/img/plates-01.webp)
<!-- capture: photo, top view on a desk mat with a ruler, left to right: blank SH II plate (no holes), blank SH02 plate with corner holes, blank SH01 plate; even light, no engraving -->

## Home-made and other plates {#custom}

| Plate | Fits | Notes |
| --- | --- | --- |
| Home-made plate | if it matches the [official plate](#specs) | |
| 2 mm plate | engraves (unverified) | warps somewhat; use 3 mm |
| Grade 2 titanium plate | engraves (unverified) | dark, so the engraving is harder to read |
| Smaller plate | needs a home-made holder | gets the 85 x 85 mm layout from the same fixed start point, not scaled or moved; run the job with the solenoid unplugged first ([test](#test)) and watch that the head stays over the plate, or use 85 x 85 mm plates |

## Specifications {#specs}

| | Official plate |
| --- | --- |
| Size | 85 x 85 mm, square |
| Thickness | 3 mm (unverified) |
| Material | 316L stainless steel, 1.4404 (unverified) |
| Largest engraving area | 79 x 79 mm: the firmware keeps 3 mm free along every edge |
| Per job | one face of one plate; no flow asks for a second side; what fits: [What fits on a plate](/doc/manual/multisig-and-fit#fit) |
| Engraving depth | about 0.3 to 0.4 mm, 1.5 mm is out of reach; deeper on a 28 V supply than on 20 V, see [Engraving quality](/doc/manual/engraving-quality) |

## Durability {#durability}

- A house fire reaches about 800 °C; 316L steel melts at about 1375 to 1400 °C (temperatures only, no fire test of an engraved plate).
- A second pass of the same job engraves slightly deeper and wider. A finished job returns to the start screen, so a second pass of a seed means typing it again ([Retry, resume and restart](/doc/manual/troubleshooting#retry)).

## Test without wasting a plate {#test}

**Important:** Run every test job with a public test wallet, such as the 12-word test seed ("abandon" eleven times, then "about") or a descriptor made from it. Never test with your own seed: each test plate is one more copy of it.

- To test with engraving, engrave the job on a spare plate, over an engraved plate, or on the back of the test plate that came with the machine (if any).
- To test without engraving (v1.4.3 has no dry-run setting; v1.3.8 was the last release with one), unplug the 2-pin engraving solenoid plug as in [Unplug the engraving solenoid](/doc/manual/engraving-quality#unplug) and watch where the head travels.

![The 2-pin engraving solenoid plug on the controller board, unplugged](/static/img/plates-02.webp)
<!-- capture: photo, controller board from above with the machine unpowered, 2-pin engraving solenoid plug pulled out of its socket, arrow to the socket -->

## Load a plate {#load}

Every seed or descriptor job ends on **Engrave Plate**: "Insert a blank plate and close the lock."

- Lay the plate in the holder.
- Close the lock.
- Hold the hammer button at the bottom right for 1 second.

The rest of the job, including stop and resume, is in [Load a plate and engrave](/doc/manual/power-and-first-start#plate).

![Engrave Plate screen before the job starts](/static/img/plates-03.webp)
<!-- capture: II screen, flow "Engrave Seed" with the Demo A 12-word test vector from lab/TESTWALLET.md, checkmark on "Engrave Seed", Engrave Plate idle state (screen-map section 4.2 row 17) -->

![A plate seated in the holder with the lock closed](/static/img/plates-04.webp)
<!-- capture: photo, machine from above, blank SH II plate seated in the clamp sled, lock closed, head at its start position over the plate -->

## If it does not work {#troubleshooting}

| Symptom | Cause | Fix |
| --- | --- | --- |
| "Too Large" / "The descriptor cannot fit any plate size." | The descriptor fits no layout on the one 85 x 85 mm plate the firmware knows. | A different plate does not help. See [What fits on a plate](/doc/manual/multisig-and-fit#fit). |
| Words fade toward the end of the plate | Play in the X axis, a loose set screw in a brass nut, or a loose clamp. | Reseat the brass-nut set screw and tighten the clamp. See [Engraving quality](/doc/manual/engraving-quality). |
| The QR on a plate is hard to scan | Bare steel gives low contrast. | See [Recover a wallet from the plates](/doc/manual/recovery-from-plates#scan). |

<!--
bench-checks:
  - [ ] confirm material (316L, 1.4404) and thickness (3 mm) against the current shop listing (both shown "unverified" in the specs table); note whether holed SH02 plates are still listed (listed again late March 2026; this date and the reason current plates have no holes, cheaper to make and engravable all over, live here only since the 2026-10-10 edit pass, which also folded every body "Check:" into the items below); a community spec also names 1.4571 (316Ti), cold-rolled, laser-profiled: confirm or leave out
  - [ ] holed SH02 plate on v1.4.3 (fit table: "hole clearance unverified"): a 24-word seed plate and a 2-of-3 descriptor plate ("TEXT ONLY" and "QR ONLY") clear the corner holes; measure the holes against the 10 mm corner squares the text layout keeps free; a 2-of-4 "QR ONLY" (72.9 mm, about 6 mm from each edge) is the worst case; photograph all
  - [ ] on v1.4.3: a 2 mm 316L plate (engraves, depth, how much it warps) and a grade 2 titanium plate (depth, legibility, QR scan with a phone wallet)
  - [ ] dry run on v1.4.3 with the 2-pin solenoid plug unplugged (steps now owned by engraving-quality#unplug; harmonized 2026-10-10): job reaches "Engraving completed successfully." and does not fail with "Engraving failed." / "Error: engraver: not enough power available" (the engraver reads the solenoid driver's diag pin at start, cmd/controller/engraver.go:284-287); photograph the plug position; confirm the box ships a test plate (the "bacon" QA plate; body says "if any") and that engraving over an engraved plate is harmless to the needle
  - [ ] plate loading: orientation, how the lock closes, photos (shared with power-and-first-start)
  - [ ] largest plate thickness and size tolerance the clamp accepts (community: the needle works over about 4 mm of travel, so 2 mm and 3 mm plates engrave; clamp limits in no source); a smaller plate in a home-made holder: how it fixes to the frame (community: the frame accepts 3D-printed parts), head travel with the solenoid unplugged; SH03 plate of the original machine: size, and whether it fits (not answered in the chat)
  - [ ] measured depth on a 3 mm plate at 20 V and 28 V; a second job on v1.4.3 lands exactly on the first (shared with engraving-quality; the re-run Check is owned by troubleshooting#retry)
  - [ ] source the fire comparison: 316L melting range and strength at house-fire temperatures from a 316L datasheet, house-fire temperature from a fire reference (both figures now from one community statement); say nothing about corrosion or salt water until a 316L datasheet is cited
sources: manuals/REVIEW-wave1.md sections 2 to 4 (harmonized, see manuals/HARMONIZE-wave1.md); research/device-screen-map.md (1.1 homing, then plate origin 5.0 mm / 3.2 mm; 1.2 "Firmware: v1.4.3"; 1.5 "Too Large", SquarePlate 85 x 85 mm, 3 mm safety margin, no plate-size screen; 1.6 codex32 left out (no way back, bench check 7); 1.7 Engrave Plate strings, 1 s hammer hold, done returns to the start screen, "engraver: not enough power available"; 1.8 no dry run, last in v1.3.8; 3 one face per job, QR centred for "QR ONLY"; 5 item 6 FAQ plate dimensions), research/BRIEF.md (corrections: one 85 x 85 mm plate, one face per job), firmware source v1.4.3 ea4b65b (lab/check/upstream): backup/backup.go:45-46 (outerMargin 3, innerMargin 10), :264-310 EngraveText corner skip ("Avoid screw holes"), :324-330 centred QR, gui/gui.go:399-445 validateDescriptor layouts, :2471 toPlate with safetyMargin 3 (:47), cmd/controller/engraver.go:284-287; lab/check (shcheck facts: no plate detection enters the fit decision; RESULTS.md QR widths 65.7 mm 2-of-3, 72.9 mm 2-of-4), lab/TESTWALLET.md (Demo A vector for captures and test jobs), harvest Q35 Q36 Q37 Q40 Q62 Q01, SYNTHESIS section D (fading words, steel QR contrast), section F rows 5 (scan tips need a bench), 19 (codex32), 20 (old fit table not reused)
-->