Pat Delaney has designed a lathe that's designed to be reasonably accurate and dirt cheap, because its body is made of concrete. The lathe bed is
concrete, the headstock is concrete, the cross-slide bed is concrete, and the tailstock is concrete. Those pieces are typically made from cast iron.
The precision elements are metal, as usual: the ways, the bearings, the screws. The real advantage is getting rid of the need to deal with the
structural cast iron pieces.
If this sounds absurd, Pat Delaney is the creator of the multimachine, a shop-built machine tool based around a discarded engine block. The brilliance
of that design is that the cylinder bores need to be exactly parallel in order to work, so he indexes the accuracy off a pair of those bores. Now for
this project, he's in failing health and won't be able to build his own prototypes. Nevertheless, they're worth taking a look at. Delaney is a
spiritual successor to David Gingery, although he didn't write as much as Gingery did.
So why is this significant? Fabrication is a limiting factor in lots of interesting experimentation. This is a much lower cost entry to machining than
has previously existed. It's sweat equity, to be sure, but it's still equity in the end and is available to those without the monetary resources to do
machining.
Personally, I've been scheming about building a glass lathe, because they're even more prohibitively expensive new and they're almost nonexistent
used. This basic construction technique eliminates the main hurdle I was facing, which is that I didn't have a cupola to do the cast iron.Magpie - 13-4-2012 at 08:36
Fabrication is a limiting factor in lots of interesting experimentation.
I would agree with this based on my own experience. Eg, neither I nor garage chemist have been able to fabricate a ceramic (in my case mullite) tube
with a male end that will seal satisfactorily to a standard taper female glass fitting. I'm still working on this, however.
Many times I have wished that I had a proper metal working shop complete with lathe and welding equipment, and that I knew how to use said equipment.
bquirky - 13-4-2012 at 09:12
Its a good idea and i don't wont discourage anyone that wants to give it a go to prove it can be done. or to build it as a project in its own right.
however Ill offer my own experiences and thoughts.
I built my own CNC milling machine out of random odds and ends the most expensive part was the cross slide that i decided to buy off the shelf that
was about $200 au I started with the chassie of a old drill press but there is almost none of that left now.
I had to spend a LOT of time getting the structure setup Just so in order to reduce vibration and get reasonable performance Lots of messing with
motors and bearings more broken end mills than i can count. I had a fire caused by a slipping belt an alarmed neighbor and subjected my missus hours
days and weeks of loud chattering that surely cost me some relationship capital
But i got there in the end. and im quite proud of my Frankenstein contraption
but to be brutally honest
if i had spent 1/100th that time making my own lunch to take to work I could have saved enough money to buy a cheap Chinese mill and do a cnc
conversion over a weekend
Unless you need to machine physicly large items. (like say a cannon!) i think you will be better off putting up with a cheap import and spending your
time working on what your actually trying to build
