Drive Dogs etc

[HopperParticipant @hopper]

Jenny leg calipers, centre punch, drill press.

Before Slocombe centre drills they just drilled a hole with a normal small diameter drill bit then opened the end of the hole out with a normal larger diameter drill bit ground to a . 60 degree angle. Still done that way today on some larger lathes (think 15foot+ beds) with large centres rather than use a giant centre drill bit. Less chance of breaking the tit off the end that way too.

[Neil LickfoldParticipant @neillickfold44316]

I worked in a place that had a centre drilling machine. It had a spindle, and various V blocks with clamps. On the bottom plate was a centre pin. Then there was an adjustable plate that rose up , that was keyed to the column and could be reset from the one on the ground. This matched the centre of the spindle. The Vee block could be moved in or out and the centre of a part could be corrected for its position as well. We used it for drilling the centre of quite large bars, then they were put into the lathe for turning between centres. We often made custom dogs for parts, and others had drive pin holes placed into the main drive end of a part.

[Andy StopfordParticipant @andystopford50521]

Some of those very entertaining "Safety Last" YouTube videos from Pakistani machine shops show them marking out the end of a bar with odd-legs and then giving it a really good whacking with a large (home made) centre punch, no centre drill required.

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