An outside micrometer measures external dimensions — shaft diameters, disc thickness, bar stock — to 0.01 mm, far tighter than a caliper can hold repeatably. If your everyday micrometer has been dropped, worn at the anvils or lost its zero, the PROSTER 6-piece metric set covers 0–150 mm in 25 mm steps and ships next working day in the UK.
What an outside micrometer actually does
An outside micrometer clamps a part between a fixed anvil and a spindle driven by a precision screw. On a standard metric tool one full turn of the thimble advances the spindle 0.5 mm, and the 50-division thimble resolves that to 0.01 mm. The ratchet stop applies the same light force every time, which is why a micrometer repeats where a caliper drifts. It is defined by ISO 3611, the international standard for external micrometers.
It measures external features only: shaft and pin diameters, brake-disc thickness against the minimum stamped on the disc, bearing journals and bar stock. For anything inside a hole you need a different family of tool (see below).
What is in the PROSTER 6-piece metric set
- Six frames covering 0–25, 25–50, 50–75, 75–100, 100–125 and 125–150 mm
- Carbide measuring faces that resist the flat spots hardened-steel anvils develop over time
- Ratchet stop for repeatable pressure and a spindle lock for reading off the part
- A setting standard for each frame so you can check zero, plus a storage case
It is an analogue set — you read the sleeve and thimble scales; there is no LCD. At £126.13 for six ranges, the cost per micrometer undercuts buying single instruments piecemeal.
Replacing a worn or dropped micrometer
When the works is still queued and your main tool is out of action, the fault is usually one of three things: it will not zero against its standard, the anvils have worn flats that skew every reading, or a drop has knocked the frame out of true. A borrowed shop tool that someone else has re-zeroed is not something you can trust for a paid job.
This is where UK stock matters. The set holds in a UK warehouse with free delivery and next-day dispatch when you order by 3pm, so a same-week replacement is realistic rather than waiting on a slow purchasing route. You already know the spec you want — a metric outside set to 150 mm — so the decision is really about getting a dependable one back on the bench quickly.
Outside, internal or bore — pick the right family
An outside micrometer cannot reach inside a bore. For internal diameters you need an internal micrometer or a bore tool. See our guide to internal micrometer types, or the practical method in our bore micrometer guide. Deciding between a screen and scales? See digital micrometer vs mechanical.
PROSTER Outside Micrometer — 6-Piece Metric Set
Six metric frames covering 0–150 mm in 25 mm steps, carbide measuring faces and a ratchet stop, with free UK delivery, 30-day returns and a 12-month guarantee.
Honest limits
This is a workshop set, not laboratory metrology, and it does not arrive with a UKAS-traceable certificate. If a customer or an audit needs traceable calibration you should budget for a calibration service. Whatever you buy, check the zero against the setting standard the day it arrives — that first check is the cheapest insurance there is.
Frequently asked questions
Is the PROSTER outside micrometer set digital or analogue?
It is an analogue (mechanical) set: you read the sleeve and thimble scales and use the ratchet stop, and there is no LCD. If you specifically want a screen, pair a single digital tool with it.
What ranges does the 6-piece set cover?
Six frames cover 0-25, 25-50, 50-75, 75-100, 100-125 and 125-150 mm, so you can measure up to 150 mm without buying single micrometers piecemeal.
How fast can I get one in the UK?
Free UK delivery with next-day dispatch when you order by 3pm; stock is held in the UK, which is why it suits a same-week replacement.
Can it measure inside a bore or cylinder?
No, outside micrometers only measure external sizes. For an internal diameter you need an internal or bore micrometer.