A precision inside micrometer — tubular type and 3-point bore mic — for measuring internal diameters accurately in machining and inspection; Multi Trade Combines stocks Mitutoyo measuring tools at AT Road, Guwahati, price on request.
An inside micrometer is a precision measuring instrument used to measure the internal diameter of a bore, hole, cylinder or slot to an accuracy of 0.01 mm (or 0.001 mm on high-resolution models). Unlike a vernier caliper's internal jaws — which measure most bores adequately — an inside micrometer gives the accuracy required for engineering fits, bearing housings, sleeve dimensions and quality-control inspection in machining.
Two types are commonly used in Indian precision workshops. The tubular inside micrometer uses a thimble-and-spindle reading mechanism similar to an outside micrometer, with interchangeable rods to extend the measuring range. The 3-point inside micrometer (bore mic) uses three equidistant contact points for self-centring — it reads directly on a thimble scale and is faster for repetitive bore inspection.
Multi Trade Combines is an authorised Mitutoyo dealer in Guwahati and stocks both types at our AT Road counter.
| Brand | Mitutoyo |
|---|---|
| Category | Measuring Tools |
| Key specs | Tubular & 3-point bore |
| Resolution | 0.01 mm standard; 0.001 mm on high-resolution models |
| Type | Tubular type with rod extensions or 3-point self-centring bore mic |
| Availability | In stock — price on request |
A complete precision measurement kit includes:
A tubular inside micrometer uses two measuring anvils on a telescoping spindle and is ideal for measuring internal diameters in a range set by interchangeable extension rods — a common set covers 50–150 mm or 50–300 mm. It requires skill to rock the instrument to find the true diameter. A 3-point (tri-bore) inside micrometer uses three equidistant contact points and is self-centring — it finds the true bore diameter automatically, making it faster and more repeatable for production inspection. The 3-point type is preferred in CNC machining shops and quality-control labs; the tubular type is the workhorse for general precision work and is more economical.
Yes — a tubular inside micrometer or a 3-point bore mic is the correct tool for measuring engine cylinder bores to determine wear, ovality and taper before reboring or honing. A standard engine bore inspection set covering 50–150 mm handles most petrol and diesel engines used in Assam — cars, tractors, gensets and small marine engines. Pair the inside mic with an outside micrometer to verify the measurements against piston dimensions. For high-volume automotive machine shops in Guwahati, a dial bore gauge is an alternative for faster repetitive measurements.