Mekanism Machine Tiers: Circuits, Alloys, and Factories
Mekanism's progression is a tier ladder: better control circuits and alloys unlock better machines and factories. This guide covers how the tiers stack up.
Control circuit ladder
Basic Control Circuit — the starting component.
Advanced Control Circuit — two 
Infused Alloy plus a Basic Control Circuit.
Elite Control Circuit — two 
Reinforced Alloy plus an Advanced Control Circuit.
Ultimate Control Circuit — built from Elite circuits and top-tier alloys.
Alloys
The alloy line mirrors the circuits: Infused Alloy to Reinforced Alloy to 
Atomic Alloy, each feeding the next tier of circuits, transmitters and machines.
Factories and tier installers
Factories process many items at once. Each tier of factory — for combining, compressing, crushing, enriching, infusing, injecting, purifying, sawing and smelting — is upgraded from the previous tier with Infused Alloy, an Advanced Control Circuit and Osmium. To upgrade a machine or factory in place, apply a Tier Installer: the Basic Tier Installer uses Basic Control Circuits and iron, and the Elite Tier Installer uses Elite Control Circuits and gold. Climbing this ladder is the core of a Mekanism base.
Tiers are material, not new recipes
Mekanism's tier system upgrades machines and transmitters through the same progression of alloys rather than through separate recipe trees. That is why the mod's enormous recipe list — 204 crafting recipes and over two dozen machine categories — contains comparatively few entries for the tiers themselves.
Combining (82 recipes on 1.21.1, 66 on 1.20.1) and Metallurgic Infusing (37 and 33) are where the alloys come from, and both grew slightly between versions.
The categories that carry the volume
For orientation, the largest lists are Sawing at 440 recipes on 1.21.1, Enriching at 322, Crushing at 313 and Pigment Extracting at 226. Machine tiers touch almost none of these — they change throughput, not what a machine can make.
Version differences to watch
Seven categories are 1.21.1-only: pigment extracting, oxidizing, chemical conversion, dissolution, pigment mixing, washing and chemical infusing. 
Painting is the reverse, at 976 recipes on 1.20.1 against 176 on 1.21.1.
Sawing nearly tripled between builds, from 153 to 440.
Practical upgrade order
Upgrade the machines you run constantly — the enrichment chamber and crusher, given they hold most of the ore recipes — before the ones you use occasionally. Tier upgrades cost the same regardless of which machine receives them.
Basic Tier Installer
Elite Tier Installer
Enrichment Chamber