On Mon, 8 Dec 2008 15:25:43 -0800 (PST), andy
wrote:

Hi folks:
I am trying to make a skeg-mount rudder for a lobsterboat.
the rudder is made from a 1/4" thick piece of 316 stainless steel.
The rudder stock (shaft) is 1-1/4" diameter 316 stainless steel rod,
cut into two pieces and slotted to accept the rudder plate which is
then welded in. The two pieces of rudderstock are arranged so that
the lower one is held in a bearing (on the skeg for all you boat
folks), and the upper one penetrates the bottom of the boat through a
packing gland and has a keyway to attach the tiller.

My question is how do I cut the slots? they need to be through the
round stock and maybe 6 inches along the long axis of the rod. (2
pieces, top and bottom)

I have access to a Bridgeport mill with unknown tooling, so I will
have to buy a cutter for the job.
My plan is using something similar to a keyway cutter and attacking
the work from each side. Maybe leaving the very end "un-slotted" to
remain rigid before hacksawing out the last bit?

Plan B may be an 1/4" endmill attacking from the top? although this
seems like it would be too flexy for a 1-1/4" cut.

As you can probably tell, I am not a machinist. Although I do read
RCM regularly. I also understand 316 stainless is not easy to work
with.

I would love to hear what you folks think of my plan,including lubes,
speeds, what the cutter is called at Enco or wherever.

Thanks,
Andy
Lynn, MA


You could equally well cut a slot in the rudder blade to accept the
rudder stock which can be done easily with a cutting torch, a plasma
cutter or a 4 inch grinder. You will probably have to tack the upper
and lower rudder stock to a piece of angle or pipe to hold them in
alignment before you weld them to the blade, but you'd probably have
to do that anyway.

As far as strength goes I can't see much difference in the two designs
as if you put a nice fillet weld on both sides the welds will be as
strong as the 1/4" plate.

As far as stainless being hard to work with, it work hardens easily.
Use a slow cutting speed and fairly heavy feed and you can cut it
almost as easily as carbon steel (not the "almost" :-)


Cheers,

Bruce
(bruceinbangkokatgmaildotcom)