Turning a small radius corner

[Richard BrickwoodParticipant @richardbrickwood17062]

I need to turn a number of 1/32″ radius shoulders on the crankshaft for a Stewart compound twin cylinder engine.

Is there any way of achieving this other than grinding a lath tool with a suitably radiused cutting edge as my grinding skills/grinder leave a lot to be desired. A carbide insert and holder would be ideal – is there such a thing? Where?

Many thanks – Richard Brickwood

 

[bernard towersParticipant @bernardtowers37738]

The classic tool for crank journals looks like the top half of a heart emblem, it gives you a radius for the end of the journals and a good radius for a good finish

[JasonBModerator @jasonb]

Carbide parting insert of the GTN type will leave a radius to fillet the corners, you can grind the middle of the leading edge away to give the shape Bernard mentions and use it from side to side for the last 5thou without the risk of chatter.

The other option which I sometimes use is to do the sides of teh webs with a small boring bar, insert with 0.4 or 0.8mm radius will leave a fillet and then work the shaft between,

Also got a long pointy HSS tool with a small radius. DCGT insert would do similar

 

[duncan webster 1Participant @duncanwebster1]

To get small radii like this on HSS you can use a diamond file

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