Alloy for checking internal threads

Citation

(1998), "Alloy for checking internal threads", Aircraft Engineering and Aerospace Technology, Vol. 70 No. 3. https://doi.org/10.1108/aeat.1998.12770cad.010

Alloy for checking internal threads

Alloy for checking internal threads

Keywords Alloys, MCP, Threads

Mining and Chemical Products has formulated a free-flowing lowmelting-point alloy to allow precision internal threads to be checked without sectioning the specimen.

Melting at 137°C, the bismuth-based metal is said to be highly stable on solidification. This enables threads to be reproduced accurately in solid male form for inspection by projected shadow, profile gauge and micrometer.

According to the manufacturer, proof castings in alloy are more faithful replications of the thread than casting in epoxy resin or wax. Neither of these alternatives has the same dimensional stability or flows as freely in the liquid condition. The MCP alloy reportedly can also cast more rapidly than epoxy resin ­ which needs curing time ­ and with less energy consumption than lead.

The alloy's low melting temperature also eliminates any likelihood of heat damage to the material or finish of the specimen.

In one application, the alloy is used for making 100 per cent checks on the interior threads in screwed extensions to rock drills. After the extension has been preheated, the alloy is melted by bench burner and poured directly into the threaded bore. On cooling, the non-shrinking plug is unscrewed and checked by Shadowgraph.

When the batch has been inspected, the plugs are melted down for re-use, an economy not available with resin plugs, which must be thrown away.

Details from Mining and Chemical Products Ltd, UK. Tel: +44 (0)1256 897200.