Contacts & relays · Tier B

Thermostats, Snap Discs & Limit Switches

Pop the cover and look at the contact face — real silver is a soft matte slightly domed rivet that scratches easily and tarnishes brown-black at the edges; a hard mirror-bright button that resists a file is tungsten carbide and guts the lot's value.

Ag 0.4–1.6 g/lb as whole discs; 408–431 g/lb as harvested contactsBase bimetal steel discBase Hg ~3–4 g per bulb thermostat ampoule

eBay typical$25–120per lb

Refiner pays$2per lb

Metal in it$1.71per lb at 4 Aug 2026 spot

Confidencemedof the yield figures

How to spot it

Snap disc: 3/4 in or 1 in dished bimetal disc in a metal cup with two 1/4 in spade terminals, stamped L150-20F or OPEN 150 CLOSE 130, by Therm-O-Disc, Senasys, Fenwal, Elmwood or Klixon. Limit switches carry a lever or roller actuator in an industrial body from Honeywell or Omron. Mercury thermostats show a coiled bimetal and a sealed glass ampoule with a silver bead. Found on HVAC, water heaters, dryers, ovens, motor overloads and transformers.

Metal content

Metal	Quantity	Notes
Silver	0.4–1.6 g/lb as whole discs; 408–431 g/lb as harvested contacts	Contact alloys assay 90–95% Ag — fine Ag, AgNi, AgCdO, AgSnO2
Base metal	bimetal steel disc, 95%+ of mass	Zero value
Base metal	Hg ~3–4 g per bulb thermostat ampoule	Widely repeated but unverified against a primary source

At 4 Aug 2026 spot prices that works out to $1.71 per pound of contained metal — Silver 0.9 g = $1.71. A refiner paying $2 returns about 117% of that, which is normal: refining costs money and the buyer takes a margin.

Safe removal

Working temperature: No heat — shear cold

Prise the crimped cup, lift the bimetal disc, then shear the contact rivets off the arm with end-nippers as close to the rivet as possible — leaving copper backing dilutes your assay. Use a small bench shear for volume. Do not torch off and do not grind; sort AgCdO into a separate labelled container.

Hazards

🌡 Mercury

NEVER vacuum a mercury spill — it aerosolises it. Use a mercury spill kit or sulphur powder, or call your local hazmat line.

☠ Cadmium

NEVER grind, burn, torch or braze cadmium-plated or AgCdO material, and don't inhale the black contact dust.

⚡ Stored high voltage

NEVER short a large capacitor with a screwdriver. It welds the tip, blasts molten metal at your face, and can rupture the can.

🧱 Asbestos

NEVER cut, drill, sand, tear or blow out suspect material with compressed air.

Before you scrap it

Yes for identified parts, no for bulk — 60–200×. A working Therm-O-Disc or Klixon with a legible temperature code sells $6–20 against ~$0.10 of silver; Honeywell/Omron limit switches $10–45. Only refine discs that are burnt, welded or unmarked.

The common trap

Buying whole thermal switches by the pound for their silver. A snap disc is over 98% steel and phenolic; you need roughly 6,000–20,000 discs to accumulate one pound of contacts. The same alloys sit in contactors, motor starters and breakers at 10–100× the contact mass per unit — that is where this activity actually pays. Also, silver contact does not mean fine silver: AgCdO and AgSnO2 run 85–90%.

Questions

How much gold is in thermostats, snap discs & limit switches?

Silver: 0.4–1.6 g/lb as whole discs; 408–431 g/lb as harvested contacts. At current spot that is about $1.71 of contained metal per pound.

How do you identify thermostats, snap discs & limit switches?

Pop the cover and look at the contact face — real silver is a soft matte slightly domed rivet that scratches easily and tarnishes brown-black at the edges; a hard mirror-bright button that resists a file is tungsten carbide and guts the lot's value.

How do you remove thermostats, snap discs & limit switches safely?

Is thermostats, snap discs & limit switches worth more working than as scrap?

Related in Contacts & relays

Pogo Pins & Spring-Loaded Test Probes Contacts & relays · $200–500/lb Au 1.4–3.0 g/lbCu ~330 g/lbBase steel springs S Silver contacts (switches, breakers, contactors) Contacts & relays · $400–550/lb Ag 180–400 g/lb of clean cut contacts S Silver-Graphite Brushes & Slip Rings Contacts & relays · $150–400/lb Ag 40–95% by weightCu pigtail + commutator segmentsBase electrographite S Aerospace Connectors & Backshells Contacts & relays · $25–70/lb Au 0.3–0.8 g/lb complete; ~3.6 g/lb de-populated contactsCu ~80 g/lbBase Backshells: ~0 g Au/lb A IC Test, Burn-In & ZIF Sockets Contacts & relays · $15–60/lb Au 0.5–2 g/lb complete; 3–8 g/lb de-populated contactsCu ~60 g/lbPd Pd-Ni with gold flash on high-cycle sockets A Mil Circular Connectors (D38999/MS) Contacts & relays · $25–60/lb Au 0.20–0.50 g/lb whole; 2.5–4.0 g/lb de-pinned contactsCu ~80 g/lbBase 70–85% Al 6061-T6 shell A

Get this offline → The full guide runs in your browser with no signal, and you can add your own photos.