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Gage Block Care & Wear Blocks

Guide · Updated October 5, 2026

A good gage block set lasts decades if you keep it clean, dry, burr-free, and protected by wear blocks. Most damage comes from rust (fingerprints and humidity), burrs (dropped blocks, grit), and wear on the few sizes that get used every day.

Handling

• Handle by the edges. Clean gloves, or at least clean dry hands, keep skin salts off the faces and limit heat transfer.
• Work over a clean surface plate or a soft pad, never over a hard floor or a chip-covered bench.
• Never slide blocks across a dirty surface, and never use them as parallels, hammers, or shims.

Cleaning and rust prevention

• After each use, wipe every block you touched with a clean, lint-free wipe and the solvent your block maker recommends.
• Apply a thin coat of a rust preventive made for precision instruments. Steel blocks rust quickly, especially where fingerprints were left.
• Store in the case, lid closed, in a dry place without big temperature swings (swings can cause condensation). Desiccant packs in the storage cabinet help in humid shops.
• Never store blocks wrung together.

Removing light burrs

If a block suddenly won't wring or feels gritty, look for a burr or nick under good light. A gage block stone (a very flat, fine stone made for this) can remove light raised burrs:

1. Clean the stone and the block. Grit on the stone will scratch the face.
2. Lay the block face flat on the stone and slide it with light, even pressure for a few strokes. Let the stone knock down the high spot; don't try to lap the block.
3. Clean again and test the wring. If it still won't wring, or the damage is a deep nick, stop and have the block checked or replaced.

Use a stone suited to the block material (follow the maker's guidance, especially for carbide or ceramic). A stone removes raised material; it does not restore size. Only calibration can tell you whether the block is still in tolerance.

Wear blocks: what they are and how to use them

Wear blocks (also called protector blocks) are sacrificial blocks placed at both ends of a stack, so contact with anvils, work, and jaws wears them instead of your working blocks. They're commonly made of carbide or steel. Inch sets usually include two 0.050" wear blocks; metric sets typically use 1 mm or 2 mm wear blocks.

• Mark one face of each wear block (or use the maker's marking) and always put that face out, so only one face wears.
• Include both wear blocks in your stack math. The calculator's wear-block option subtracts them for you (2 × 0.050" or 2 × 1 mm).
• Check wear blocks more often than the rest of the set. They're designed to wear, so replace them when they go out of tolerance.

Spread the wear

The same few blocks end up in almost every stack. When there's more than one combination of the same length, pick blocks you use less often. The GageBlockCalc calculator leans equal-length stacks toward less-used blocks for exactly this reason.

Calibration interval

No single interval fits every shop. Your quality system should set it from how heavily the set is used and its calibration history. Annual calibration is common for working sets; lightly used reference sets are often checked less often. Calibrate sooner after a drop, visible damage, or a failed check against a master.

Care supplies

• Gage block deburring stones
• Rust preventive for precision gages
• Mitutoyo 0.050" steel square block (single block for wear or replacement use)
• Metric 1 mm wear blocks (search)

General shop information only — follow your gage manufacturer's instructions and your quality system. As an Amazon Associate I earn from qualifying purchases; links marked "sponsored" may earn a commission at no cost to you.