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YOU CAN MAKE PRECISE METAL PARTS WITHOUT ANY TOOL TOUCHING THEM

Make precise metal parts by exposing a pattern onto resist and etching the metal away — no tool touches the workpiece, so there is no burr and no minimum radius.

by Ben Krasnow

FULL CAD BOM FIRMWARE DOCS

Workshop

difficulty
●●●●○
time
multiple weekends
license
license not specified
repo
repo 0 stars

WHAT YOU’LL NEED

Videos
1
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COMPAREE VERDICT

Ben Krasnow shows how to make precise flat metal parts at home by photochemical machining: print a photomask, laminate dry-film photoresist onto sheet metal, expose it with 405 nm light, develop it, and etch away the unprotected metal in a heated spray etcher. Because nothing cuts the part, there are no tool forces on thin sheet. The catch: there is no repository or formal parts list. The video description links the key consumables and tools (dry-film resist, the DuPont Riston processing guide, mask ink and film, registration pins, 405 nm lights and the ink-tank printer he used), but the spray etcher and process settings you work out from the footage. Ben himself notes that edge quality and resist adhesion were still a problem, and suggests compensating the mask for undercut. Etchants are corrosive and spent etchant is hazardous waste. If you have done PCB etching before, this is the natural next step; budget several weekends of test pieces before you etch anything you care about.

GOOD TO KNOW

  • —No repository exists. The entire process is demonstrated in a single 22-minute video.
  • —No CAD files or formal parts list, but the video description links the key materials: dry-film photoresist, the DuPont Riston processing guide, special ink and transparency film for masks, 405 nm lights, registration pins and the Epson tank printer Ben used.
  • —The video covers the chemistry, the resist lamination, the UV exposure, and the spray etcher build in detail.
  • —This is a technique demonstration, not a step-by-step build guide. The spray etcher is shown but not dimensioned.
  • —No licence because there is no code or design file to licence.
  • —The single biggest barrier is not the chemistry — it is finding or building a heated spray etcher that keeps the etchant warm and moving.

Parts to buy

6 items

From our check of the build. Exact quantities and part numbers are in the creator’s BOM.

  • Sheet metal stockFind
  • Dry-film photoresistFind
  • Etchant (ferric chloride or cupric chloride)Find
  • Transparency film for masksFind
  • UV light sourceFind
  • Materials for a heated spray etcherfrom the repo files

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Can I build this?

Printnothing required
Buysheet metal stock, dry-film photoresist, etchant (ferric chloride or cupric chloride), transparency film for masks, UV light source, plus materials for a heated spray etcher (pump, heater, enclosure)
Toolslaser printer or inkjet for masks, laminator or hot roller, UV exposure box or strong UV source, spray etcher (shown in video but not sold as a kit), basic metalworking tools
Skillsintermediate chemistry and workshop skills — you need to be comfortable with caustic etchants, heated fluid systems, and reverse-engineering a build from video. Prior PCB or photolithography experience helps but is not required.
Timemultiple weekends — one to source materials and build the etcher, one to test the resist and exposure, then iteration on real parts
Cost$$ — dominated by the dry-film photoresist, the etchant and the components for the spray etcher. Sheet stock and transparency film are cheap; the chemistry is not.
Safetyetchants are corrosive and must be handled with gloves and eye protection. The spray etcher aerosolizes hot etchant, so ventilation is required. No mains voltage or lithium risks beyond what the pump and heater introduce.

Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.

Videos

Creator’s build video

The full process from mask printing to finished part, including the spray etcher build. No step-by-step instructions but every stage is shown on camera.

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Gallery

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Start here

Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.

  1. 1.Watch the video end to end and note every chemical, material and tool shown (There is no formal parts list — start from the links in the video description and fill in the rest from the footage.)
  2. 2.Source dry-film photoresist, etchant and transparency film(The resist is the hardest to find. Look for PCB photoresist suppliers.)
  3. 3.Build or buy a spray etcher that heats and aerates the etchant(The video shows the design but does not provide dimensions. Still or cold etchant gives ragged edges.)
  4. 4.Run test pieces on scrap metal to dial in exposure time and etch rate(Expect to throw away the first few attempts.)

KNOWN ISSUES

  • The single biggest mistake is starting without a working spray etcher. Still etchant in a tray gives uneven depth and ragged edges — the fluid has to be warm and moving.
  • There is no formal parts list. Start from the links in the video description (dry-film photoresist, mask ink and film, 405 nm lights) and fill in the rest from the footage.
  • The resist lamination has to be bubble-free or the etch will undercut. A hot laminator or roller is not optional.
  • Under-exposure leaves resist where you do not want it; over-exposure eats into fine detail. Test pieces are the only way to find the right time.
  • Etchant temperature and agitation are not suggestions. Cold or still fluid wastes hours and ruins parts.
  • The video does not show disposal. Spent etchant is hazardous waste and cannot go down the drain.

Is there a repository or parts list I can download?

No. This is a technique demonstration in a single video. You are building the materials list yourself from what is shown on camera.

Can I etch in a plastic tray instead of building a spray etcher?

You can, but the edges will be ragged and the depth uneven. The spray keeps fresh etchant moving across the surface, which is why industry uses it.

Where do I get dry-film photoresist?

PCB supply shops. It is the same resist used for making circuit boards at home.

What metals can I etch this way?

The video shows the process on thin sheet metal. Which metals you can etch depends on the etchant you choose; check the chemistry for your metal before you start.

How fine can the detail go?

Fine detail is limited by the resist, the mask and undercut during etching: the etch also eats sideways under the resist. Ben suggests expanding the dark areas of the mask and etching longer to get straighter edges.

Community builds

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Discussion1

FROM THE COMPAREE TEAM

The spray etcher is the part most people stumble on — still etchant gives ragged edges, so the fluid has to be warm and moving. Have you built one, and what did you use for the pump and heater?

CompareeTEAM1mo agoedited

Practical notes from our verification: there is no repository and no written build guide. The whole process is demonstrated in one video of about 22 minutes, and the video description links the materials used: the dry-film photoresist, the DuPont Riston processing guide, ink and film for the masks, registration pins and 405 nm lights. The spray etcher is shown on camera but not dimensioned, so you are reverse-engineering it from the footage. Ben also notes that edge quality and resist adhesion were still a problem for him. If you have done PCB etching or photolithography before, the resist and exposure steps are familiar ground. If you have not, budget a weekend just for test pieces before you etch anything you care about. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.

Ben Krasnow

Ben Krasnow runs Applied Science, a YouTube channel that demonstrates scientific and engineering techniques at home. He has built electron microscopes, superconducting magnets and precision measurement tools in a garage workshop. The photochemical machining video is one technique in a library of processes that are normally locked behind industrial doors.

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  • Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
  • Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
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