A Specialised Machine Tool - The LeMaire Automatic Grinder

Posted By Tom Cropper on 14 May 2014

Posted in The Vintage Machinery Almanac

This article first appeared in Practical Engineering 1940 Vol1 No5. The contents of the article are accurate as of 1940. The article reviews new machinery at the time.

LeMaire Automatic Grinder

The new LeMaire automatic grinder for connecting-rod channels is a special machine for grinding channels in aeronautical connecting rods. It comprises a saddle and table actuated hydraulically, controlled by positive stops to give the required forward and return straight movements, and this is coordinated through a hydraulic circuit with a high-speed grinding wheel head and carrier capable of generating a true radius at each end of the stroke.

Combined with this is an automatic grinding wheel dresser device that will automatically redress the wheel to generated form and has adjustable means for control of the diamond position for the control of the final width of the channel.

Thus, the cycle moves forward longitudinally, stops accurately, generates the radius at one end, moves longitudinally in the opposite direction, grinding the opposite end of the channel, stopping accurately, and generates the radius at the opposite end and continues for 40 strokes, feeding a total of .009in. co-axially, and .006in. axially, graded at each stroke starting at .00025in., tapering off to nothing at the last two strokes, then retracting out of its axial and co-axial movement and stopping the entire machine.

Following this, the operator gives a slight turn of the adjustment, setting the wheel out for dressing and re-establishing the correct relation between the work, the wheel, and the rise and fall cam means that causes the feeding out cycle.

The Fixture

The fixture is a simple roll-over type, permitting loading in an advantageous vertical position, has a simple locking means for indexing to horizontal position, and a lever-operated means for horizontally moving the work into correct position against a micrometer adjustment that controls the depth.

The grinding wheel spindle runs at 18,000 r.p.m., for a lin. diameter wheel, and is contained in a conveniently removed cartridge unit. All the mechanisms in the head, with its movements, are submerged in oil and protected against dust and leakage.

The actuating means of the machine includes a 2 h.p., 3,400 r.p.m. motor; a 1-3/4h.p. motor, directly connected to a Vickers pump unit; a 1/40 h.p. motor, operating the wheel dresser and the necessary metering valves, relief valves hydraulic panel and electric panel.