On May 27, 1:31*am, "Michael Koblic" wrote:
I have to cut 2 perfectly matching slots in a 5 mm thick flat semicircular
piece of steel, each 15 mm by 5mm.....

Michael Koblic,
Campbell River, BC

"perfectly matching slots" cut by hand???

Try a dish wheel in your angle grinder to gouge out most of the slot,
otherwise this is a job for cold chisels. Use a "cape" chisel to cut
narrow slots on the sides and a regular cold chisel to remove the
center. You still need good eye protection but this is a lot safer
than watching the line closely in a shower of sparks.

Grind the teeth off one edge of a file to make it cut sharp inside
corners and only work one surface at a time. Coarse files are better
for long cuts because the teeth don't fill with chips halfway through
the stroke.

The real answer is to pull yourself out of the 18th century and get
adequate machine tools. The skill to do good work by hand takes a long
apprenticeship to acquire but has almost no commercial value any more,
unless you are an artist. What's your time worth?

I picked auctions and second-hand dealers as my best time-vs-money
tradeoff. Even very old machines can cut metal more quickly and
accurately than I ever could by hand. My time is spent fixing/
restoring them and sharpening cutters. Almost everything I own was
broken when bought and still has problems but they work well enough
most of the time. When I'm stopped by one of their problems I fix it.

I think the minimum satisfactory home or experimental shop equipment
is a mill-drill or small vertical knee mill and a 9" - 12" lathe.
Smaller machines are OK to make models but not for equipment that does
useful work.

I have a Clausing vertical mill, a 10" South Bend lathe, a 4X6 bandsaw
and don't see the need for anything larger, and I built a log
splitter, a sawmill, and bucket loader for my garden tractor with
them. I could put up with a mill-drill for most projects.

A small horizontal mill could substitute if you get a good deal but
then you need a better drill press, and new cutters are much more
expensive than end mills.

Jim Wilkins