So how do they machine that?

[John Rumm]

I was looking at a steel pulley block the a while ago (the type that fits onto the end of a crank shaft on an engine and drives the belts)...

It was apparently machined from solid. The hole though the centre of the approx 3" thick pulley was perhaps 1/2" diameter. The through hole had a square cut slot (approx 5mm deep and wide) machined into its circumference for a woodruff key. I was struggling to visualise how you could machine that, anyone know?

(just occurred to me it may have started life as a casting with the key slot already cast in place - perhaps it was just drilled and trimmed up after)

[TheScullster]

Broached maybe?

Phil

[nightjar]

A broach would be the usual way to make an odd-shaped hole.

some of the shapes you can make with a broach.

Colin Bignell

[John Rumm]

nightjar A broach would be the usual way to make an odd-shaped hole.

Yup that looks like the job... in fact the wikipedia entry

explicitly cites making keyways and splines on gear wheels etc.

Not a technique I had come across before though - Hence why I was having difficulty working out how you would get an end mill in there ;-)

[Andy Dingley]

Usually cut with a slotting machine, rather than a broach. This is like a shaper, but skinny and with a long reach - they were the original form of shaper and one of the first specialised machines tools. (A shaper is a single point tool like a lathe tool, oscillating back and forth whilst the work moves sideways beneath it.)

Internal splines are usually broached, but broach tooling is expensive, and needs an expensive press to operate it. So if you're just doing a single keyway slot, a slotting machine is simpler.

[Frank Erskine]

As opposed to a planer, where the work moves back and forth and the tool (with it's clapper box) stays still; the whole shebang being hand-driven.

...Memories of room W5 at school some 40-mumble years ago.

That was a wonderful metalwork room. A couple of Harrison screwcutting lathes, two or three shaft-driven ones, forges and anvils, brazing hearths, pedestal drills, shaper, planer, power hacksaw, grinders, polishers. surface plates, metal beating/riveting benches, guillotine, moulding benches, and of course "Archie" Campbell the teacher, deaf as a post, who wore proper metalworkers glasses with springy hooks to go around the ears. He had a slogan written in gold leaf above the blackboard "Be accurate", which somebody modified to "Be a curate".

I'm allowed to reminisce - it's my birthday today ....

[David Lang]

Hi John

Hence the old engineering expression "I don't know if I'm punched, reamed, broached or bored".

No, I don't know what it means either :-)

Dave

[Bob Eager]

Sounds like something the actress would have said to the bishop...