[Public-List] Newbee Looking for help with rudder parts

[Kris Coward]

I have very limited experience with machining, but my guess would be
the bar stock and the machinist's time to rough bar stock out to the
same level of completeness as a fresh casting would be more expensive
than the casting. This is assuming that a mold already exists, or the
part is going to be made in high enough volume to spread out the cost of
mold making. For a one-off, it might make more sense just to machine it
from the get-go, but the level of interest that this topic generates on
the list indicates that's clearly not the case here.

Just stabbing in the dark; I'm sure someone with more experience in
these matters could correct me on at least some part of my guess.

Cheers,
Kris

On Tue, Dec 17, 2013 at 08:45:54PM -0800, Kristian Larson wrote:
> I have wondered if the gudgeons could be milled out of a couple pieces of
> 1" square (or larger) bronze bar stock... Seems pretty straight forward.
> Why cast them when you have to mill them anyways. More waste I guess.
>  Maybe I'm missing something. I'm not a machinist.
> Kristian
> 
> On Tuesday, December 17, 2013, Kris Coward wrote:
> 
> > On Tue, Dec 17, 2013 at 04:06:36PM -0500, Gordon Laco wrote:
> > > Thanks Jeff -
> > >
> > > I think the split ones fit rudders that have large pintles built into
> > them.
> > > Rather than a pin, there is an aperture whose mouth is crossed by a heavy
> > > shaft (the pintle) that is embedded in the rudder on both ends. You have
> > to
> > > use gudgeons that can be opened.
> > >
> > > $600 is not bad for custom made fittings taking casting, vibro-polishing,
> > > fine polishing and machining into consideration.
> > >
> > > I make self steering vanes, and had a fellow getting hot with me over
> > email
> > > last week over what I have to charge for them.  There are eleven
> > castings in
> > > a vane... He thought I was 'greedy' for asking $4,500 for a complete unit
> > > ready to install.  He thought I should charge $1,500.  I tried to explain
> > > that machining the castings costs more than that....
> >
> > But machining castings is easy and should be cheap. I mean castings
> > *always* cool evenly, and *never* have irregularities that crystallize
> > into carbides. You just have to enter a bit of gcode to blast your
> > endmill clear across them, confident that the cnc controller will take
> > care of the job for you, and that your tools won't get shattered by a
> > hard spot, nor will the impact of your tool with a hard spot jar the
> > workpiece loose, and throw off the positioning and alignment for the
> > remainder of the operation. I just don't understand why the machinists
> > get so fussy, and demand so much pay for such a simple job :P
> >
> > </sarcasm>
> >
> > -Kris
> >
> > --
> > Kris Coward                                     http://unripe.melon.org/
> > GPG Fingerprint: 2BF3 957D 310A FEEC 4733  830E 21A4 05C7 1FEB 12B3
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-- 
Kris Coward					http://unripe.melon.org/
GPG Fingerprint: 2BF3 957D 310A FEEC 4733  830E 21A4 05C7 1FEB 12B3

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