big_lathe

machine#current_designs: big_lathe

A Big Lathe

How to build a big deluxe lathe from scratch, using the bootstrap machine tool or small import_tools for most of the construction work.

Features requested

• vertical headstock movement as in Urwick's MetalMaster?
  (if you havent seen the metalmaster you should at least look at the pictures on their yahoo group)
• discussion of proportions and how this affects performance, what type of work you will be able to do with a given set of proportions
  • show some example calculations (oh boy)
• acme threaded leadscrew with "real" split nuts
• boring table, removable compound slide
• standardized modern taper spindle nose like D1-4 or ???
• internal taper considerations (like for ER or 5C collets)
• spindle clutch and brake
• taper roller bearings & sources
• [[chucks & faceplates>accessories_chucks & faceplates]]
• variable speed motors/drive systems(? opinions requested. is back gearing necessary if i have a variable speed motor?)
• milling attachment ideas
• quick change tool post designs
  • piston dovetail, wedge dovetail, clamp dovetail
  • block on a stick design
  • various toolholder designs
• Capstan & Turret toolposts
• dual micrometer/lever action tailstock
• viscoelastic shear layer

What if i just double up a gingery lathe?

As a first approximation, with the good old cube-square laws, simple doubling of all dimensions means 8-fold increase in weight for same metal. Easy then to translate from Al to cast iron.

Gingery uses a #6 crucible, so, a doubled lathe will need at least a #50 crucible (6X8).

Not saying this will end up with a good lathe mind you. For that you'd also need to do some not as simple beam stiffness calculations.

And I have to admit as I build my furnace its sized for that size crucible for a reason. Call me nuts, won't be the first time.

Jeff Anderson

Right now, the cupola iron furnace I'm building is based on an old

medium/small sized water heater. I can roughly estimate it should

take about 4-5 times the volume of the little furnace in Gingery's

book. I shouldn't have any problems with being able to keep up with

the increased size of the parts since I'm only shooting for double

the size.

If your cupola can take 4 times the volume of Gingery's furnace, it's
half the size it needs to be to cast an exact (no beefing up) double
size copy of the Gingery bed. If you make a bed twice the width,
height, and length of Gingery's, it'll be 2x2x2=8 times the volume, and
your furnace will only half fill the mold. And if you somehow manage to
get a full pour (by altering your furnace design to allow for still more
metal -- and how will you lift and pour a crucible containing at least
sixty pounds of white-hot molten iron?), an exact upscale of the Gingery
bed design will still be too flexible (even if the cast iron does soak
up vibration to some extent), the more so because on larger work you'll
want/need to take heavier cuts to get jobs done in a reasonable time.

If you want to make a roughly 12x24 lathe (which would be double the
swing and length of a Gingery, near enough), and have it really usable,
you'll need a bed/ways casting that weighs something like 150 lbs,
minimum, and the better lathes in this size range have beds weighing as
much as 500 lbs. Your headstock will need to be correspondingly heavier
as well, and your tailstock and saddle, but the bed has to be cast in
one piece to avoid both huge amounts of labor fitting up parts to be
joined, and problems with vibration and corrosion at the joint(s). And
then you still have to mill (or plane, more likely) and scrape the ways.
Know anyone who has a mill or planer with a 24 inch cutter or work
travel on a single setup?
*1