Intro: Build Your Own (metalworking) Lathe - Part I
You can make an entire machine shop worth of power machine tools, using basic hardware store/home center supplies and scrap metal. Melt aluminum in a metal-pail furnace, using sand, charcoal, and a clay flowerpot! Cast sophisticated metal tool parts using supplies from a gardening shop and modified kitty litter! End up with a full machine-shop lathe ("the only tool capable of making any OTHER machine-shop tool, including itself!") for just the cost of your time, some scrap steel and aluminum, and a motor!
Step 1: Overview
OK - we're (well, I'm - but we're using the imperial 'we') making a lathe. Like, for machining metal. Out of melted beer cans, in a flowerpot in a trashcan full of sand. As the great Dave Barry said: "I am not making this up."
Well, as the immortal John Belushi said: (loud belch) ... "why not!?"
Our Good Book is the Orange Book of St. Gingery - also known as "The Metal Lathe", by the late Dave Gingery. This handy pamphlet-ish book, the 2nd of a series of 7, has step-by-step instructions for folks wanting to build a lathe from scratch. Many folks around the world have built or are building "the Gingery lathe" -- there's an entire newsgroup on Yahoo dedicated to 'Gingery machines', as well as a ton of websites.
I'm putting together pictures, notes, and so on, to help others on this sacred journey -- and for a few friends who think I'm nuts (but secretly wish they could do this if only their wives would let them, and if they thought they could get away with it without burning their ... ummm ... fingers ... off).
The books are available at Lindsay Books' website, and/or at Amazon, Barnes & Noble.com, etc. Check out: http://www.lindsaybks.com/dgjp/djgbk/series/index.html for the main series.
This is how the project works: (a) You make 'patterns' of the parts, out of easy-to-work stuff like wood (pine is good), plywood, hardboard (the dark brown stuff that lots of pegboard and 1950s elementary-school fixtures are made of), etc. (b) You make molds in sand, with a few other ingredients; melt metal (easier than it seems, and DARN good fun!); and pour the molten metal into the mold cavity. And, (c) you combine the parts you make, with a few bits of steel, machine bolts, and such, from the local home center or hardware store.
Tools needed are simple: while a drill press is VERY helpful, the plans are designed around simple tools like a power hand drill, a few threading taps (not too hard to borrow, or fairly inexpensive at the local home center/hardware shop), etc.
The most important thing, imho: you'll learn a LOT about Making Things -- metal casting, machine tools, parts, tolerances, etc. -- it's a thrilling learning process! And - when you're done - you'll have the core component of a fully functional machine shop!
Step 2: Background, & Metalcasting Notes
A few thoughts, tips, pointers.
First of all, there's an excellent Yahoo! group devoted just to the Gingery books, machines, etc. You should definitely check out the Lindsay books (see link in step #1), and the Yahoo group: http://groups.yahoo.com/group/gingery_machines/.
There's a TON of good information and suggestions on the group. Some of the more popular ones seem to be: make the ways (a slab of 1/4" x 3" cold-rolled steel, on which the carriage (the main cutting-tool holder assembly) rides) thicker and thus sturdier; secure the ways to the bed with many more fasteners; and use a modified tool-post/toolholder. There are designs, photos, corrections, bills of materials, etc. (I'll try to add much of that information here, as I'm able.)
Secondly - the Gingery method mostly assumes using scrap aluminum. A few things I've learned:
(A) "Can you use beer/soda cans?" This is often referred to as "beercanium", or some similar funny term. The concensus I've seen, and have experimentally verified, is this: you can't really use JUST beer cans -- aluminum exposed to air instantly develops a thin layer of aluminum oxide (for fun, this is also. in crystalline form, basically ruby!). Beer cans are thin, with lots of surface area, so melting beer/soda cans alone just doesn't really work well (especially since melting tends to produce MORE oxidation.
HOWEVER -- if you melt some aluminum, such as window frames, pistons, etc. -- and THEN drop in some well-crushed and dried beer/soda cans, they'll contribute to the mix just fine.
SAFETY NOTE: if there's ANY moisture left in the cans, you are probably going to witness a SPECTACULAR explosion several milliseconds before losing your vision permanently. I'm not an expert, and if you follow my instructions, you'll probably DIE, be seriously maimed, or end up on some very, very pernicious mailing lists -- do NOT take ANYthing I say as anything other than potentially *very* dangerous activities. YOU HAVE BEEN WARNED.
(B) Using Metals Other Than Aluminum -- this is my personal choice. I cast a few parts out of Aluminum, then switched to a Zinc-Aluminum alloy (called Zamak, among other things).
Several reasons. (1) Zinc melts at MUCH lower temperatures, in the 700-degree range vs. 1,400 degrees for aluminum. (The common zinc-aluminum alloys also melt in the 700 degree range -- even though aluminum needs a higher temperature to melt, it's actually DISSOLVED in the zinc -- just as common table salt, with a VERY high melting temperature, DISSOLVES in room temperature water....).
This means you can melt zinc alloy over a propane flame -- like a barbecue or gas stove. Note: I would NOT recommend doing it on your kitchen stove. I've done this, but then you have to carry a 700+ degree pot of molten metal through your house and outside to where you have the mold. (If you try to pour molten zinc inside your house, you're insane -- just *melting* it inside is crazy enough.)
(2) Zinc alloys don't shrink nearly as much as aluminum -- so you can basically make a part prototype the size you want it to be, without calculating in shrinkage; and (3) Zinc alloys are nearly as strong as steel, in many respects.
WARNING -- the BIG drawback to zinc is this: THE FUMES ARE TOXIC. If you breathe a lot around melting zinc, and inhale a lot of the fumes, you're going to be very, very sick, and possibly die.
Now -- with lots of ventilation, and doing things outside, I understand it CAN be pretty safe. After all, gasoline fumes are toxic; so are toluene, turpentine, etc. -- and we're not utterly terrified of them. Just use some caution, mmmm'kay? And - read up on it a little.
One last note -- it's not the most economical source of zinc, but it's kind of fun, especially for small parts: you can simply use pennies. Since 1982, pennies are mostly just zinc. Look at http://www.gizmology.net/stovetop.htm for more information. Seems to me it's about 2x as expensive as what I can buy scrap Zamak for, around here, but sometimes for small parts it's just easier.
That's all for now -- on to making the lathe!
Step 3: Make the Bases & Bed
Here's the first part(s) -- the bases. These hold the bed of the lathe. On the left is the wood pattern; to the right are the two bases, now nicely (well, sort of nicely) painted.
I'm casting the parts with a zinc-aluminum alloy, instead of the aluminum called for in The Orange Book. Several reasons: (a) it melts at roughly 740 degrees F, which you can hit on a gas range; (b) it doesn't shrink much at all, and (c) it's fairly close to as strong as mild steel. Cost me about US$1 a pound (.454 kilos) at a nearby foundry company. (For curious folks - it's ZA-12.)
Legal warnings & such: Zinc fumes are reasonably toxic, I hear. Do NOT melt zinc without serious ventilation and several college degrees in chemistry. I'm an idiot, and if you try to do this stuff following my descriptions, which are NOT good directions, you'll probably die. I'm not kidding. You're responsible for your own life and safety -- I'm not.
Step 4: The Bed
Here's a shot of the bed pattern and resulting bed. This is actually the most recent casting I've done -- I was terrified and put it off until after most of the other castings. Why? Well, it's two feet (~61cm) long, probably 8 lbs. (3.6 kg) of molten, 750-degree (400C) metal to pour, and the dang mold is about 70 lbs (32 kg) of sand that needs to be VERY carefully carried without disturbing the mold cavity.
I almost succeeded. ;-)
The casting has a yucky spot in the middle (that's technical jargon, for you non-metalheads) - but that's not a problem -- it's easily filled with this miracle stuff called FastSteel I get at the Big Orange Home Store. I also like JB Weld, which'll fix anything duct-tape won't. Nay, the problem is that, somehow, the mold flexed slightly as I was carrying it, and the *&#%@! bed is just slightly curved up at both ends - about a millimeter or two. Sigh. Much filing/grinding to do.
Here are shots of the pattern for the bed, above the bed casting; and then the bases and bed together.
Step 5: The Carriage
Here's the pattern and casting of The Carriage - it rides back and forth on The Bed (actually, on the "ways" bolted to the bed; more on that later), holding a fairly adjustable mechanism, which ultimately holds the cutting tool that cuts the workpiece.
The top part blew out a bit - I patched it up with that miracle FastSteel epoxy-stuff again. (Note: you can drill and tap FastSteel -- the package says so, and my experience agrees. BUT - you cannot centerpunch it. Well, you CAN - but it'll break all over the place. Finally, there's a good chunk of solid metal under the epoxy to really hold the threads. ;-) Also, I gotta fix that green paint - yuck. (Turns out you really ought to use a metal primer before paint, even though I'm using engine enamel.)
Here's a picture of the bottom side, with the clamps attached. The shims (under the clamps) need some fixing - they're snipped from a beer can, and I finally found some good brass shim stock in various thicknesses.
Note the screw-eyes in the wood pattern. They serve 2 purposes: they give you something to grab onto to pull the pattern out of the sand/mold, and they're handy to rap on to loosen the pattern so it can be pulled out.
Step 6: Gib and Set-Screws
Here's the gib and gib screws for the cross-slide (the green thing, above).
It fits under one of the two clamps (the steel pieces on the bottom that hold the carriage to the ways) -- the one on the 'far' side where the thumbscrew is.
The gib is for adjusting the tightness of the cross-slide, as well as the angle. By tweaking the two outer gib-screws, you can true-up the cross-slide to a 90-degree fit on the cross-slide. The thumbscrew lets you loosen or tighten the overall fit, including locking the cross-slide to the ways. (In practice, all 3 need to be sort of balanced for the right fit and tightness - you want it loose enough for the cross-slide to slide smoothly on the ways without sticking, but tight enough that there's no 'play' - that is, wiggle-room.)
You need the gib adjustment screws pointed, to fit into dimples on the gib -- otherwise it'll slip right out when you move the carriage. It's not quite clear in the book, but it's simplest to get a couple of cap-bolts for the gib screws, and make 'em pointy yourself (I used my 4" x 36" belt/disc sander, holding the bolts in a vise-grip, trying to keep the points around 80-ish degrees -- took about 15-20 seconds each.)
You need to dimple the gib with a drill-bit (hence the 80-ish degrees), and the dimples need to be lined up with the gib-screw holes in the cross-slide. (This part is not quite clear in the book, by the way.) Probably the most logical way is to put the cross-slide, with the gib, on the ways, and drill through the cross-slide into the gib slightly. (You'll want to do this before you tap the holes in the cross-slide, or the drill will mess the threads up.) What I did, which worked great, was to drill the cross-slide first (all 3 holes), tap all 3 holes, put the cross-slide on the ways and clamp the gib with the thumbscrew, then screw the gib screws in until they mark the gib a bit. Then I removed the gib, center-punched the gib-screw holes, and dimpled them on the drill press. (Why? It's easier to see and control the depth of the dimples, I guess. Worked very nicely for me, anyway.)
Step 7: The Cross-Slide
Things are getting seriously neat, now. This thing rides forward and back on the carriage (well, on a piece of steel bolted to the carriage). So - the carriage goes left and right; the cross-slide goes forward and back.... the only thing left is to set an angle...hmmm...is THAT why there's a circular pattern on top of this thingy...?!?!
I'm pretty pleased with how well this casting turned out. The wood pattern is coated with spray shellac, which works pretty well, and is grayish because I'm using powdered graphite as a parting dust and mold release (in English: "to slick it up so the two mold halves come apart at the right place, and so the pattern comes outa the sand"). I'm not sure graphite's the best choice, but it seems to be working. The hole in the pattern was made with a 1/2" steel rod core, which you then whack (carefully) out with a punch. The whole thing is driven forward and back by a threaded rod through the "handle" at the left; the rod goes into the "tunnel" in the carriage casting.
Here's a picture of the bottom -- as with the carriage, there are 'pads' that ride along the steel 'ways'. My next step is to drill and tap the side for 3 screws just like the carriage -- these will adjust and hold it to the ways with a gib (again, more on that later).
Step 8: The Cross-Slide: Polishing the Swivel Pad
The cross-slide has two jobs: the bottom part rides forward and backward on the carriage; the top provides a rotational surface for the "compound swivel base" (the thingy that rotates so you can get different angles). To review -- the carriage goes lefty-righty; the cross-slide goes fronty-backy; and the compound swivel base (coming soon to a theater near you!) goes clockwise-y/coun....well, you get the idea.
SO. I thought I'd polish up the round "pad" that the CSB goes on. I had a wood disc from making the pattern, with a conveniently located center hole, so I just stuck on a sandpaper disc, put an arbor from gawd-knows-what through it, and started polishing. You can see it's about half done, mostly on the right side away from the 'handle". Looks nice! Might even be worth some of the effort.
Step 9: (Intermission) Toolzyottahave
One of the big premises of the Gingery books is that you can build your own entire machine shop out of old shoelaces, that one thing in that drawer in the kitchen that has kind of a threaded part and probably belongs to something so don't throw it out, and that old tractor part the previous tenant left in the basement, so it's all free.
Well, to echo what a few people have pointed out, I coulda just gone to Harbor ("'cause the Chinese work for free!") Freight, bought a lathe for under four hundred bucks, and have been done with it. Based on what I'd be earning per hour filling out TPS reports (extra credit if you get that), I'm probably about $50k into this project by now. ;-) BUT -- it's fun, and interesting, and fulfilling. (I figure people who build flyable R/C planes probably could've gotten a pilot's license and half a Piper Tomahawk for what they spend, timewise, on a nice model. So there.)
That said - here's the first of a few shots of the tools I've used on the project. The Orange Book (thanks be to Dave) emphasizes that you mostly just need a drill and a hacksaw -- well, ummm, hah. There are a few things you MUST have, and there are MANY more things that are, let's just say, VERY NICE to have.
The hammer handle on the left is for ramming up the sand molds. (I ended up buying some "Petrobond"-type sand from a local supplier - at $30 or so for 70 lbs, it's just too tempting vs. water-based casting sand mix.) At the top is a circle-cutter from Sears for my drill-press -- handy for the compound-slide pattern and a few other things. Continuing clockwise: a metal scribe for marking the (multiple) steel ways. You can get great results with a masonry nail (because it's high-quality steel) ground to a point -- don't get it hotter than hand-comfortable, or re-harden and re-temper it if you do. Next is a fat dowel you'll need for a sprue plug -- I'd also suggest a short length of thin-walled metal tubing of some kind for cutting sprues and risers.
On the right is a skimmer I found at the local Ace hardware for skimming dross (= 'crud') from the molten metal, followed by a standard tap. You'll need a few sizes of taps, and possibly an exterior threading die -- easy to find, but not super-cheap. A tap-and-die set at The Big Orange Store runs in the $20s. You'll need some tapping fluid or a tap-lubricant "crayon" - cheap. And - you will most probably break at least one tap. Then, you'll swear like a sailor -- taps are made out of VERY hard metal. It's a fine and delicate art to actually REMOVE a broken tap -- it's usually easier to junk the part and start over -- new part, new tap.
My advice? Never, ever, drink-and-thread. ;-) Seriously: take it VERY slowly. Do NOT use lots of muscle power when tapping/threading -- if you're applying lots of torque, you're about to break a tap. Back off a full quarter-to-half-turn EVERY quarter-turn -- it's a pain, but it's MUCH less of a pain than a broken tap.
Finally, in the center, is a cheap crappy "wrench" (I hate to call it that -- it's just stamped metal) that came with some dang thing we bought. But it seems to be ideal for rapping a pattern out of a mold. (Put wood mold in casting sand. "Ram up" (compact) sand with hammer handle etc. Screw screws or screw-eyes into (previously drilled) holes in wood pattern. Using cheap crappy "wrench", rattle the screws about so as to loosen wood mold from sand and slightly compact sand about said mold. Gripping screws/screw-eyes, gently remove wooden pattern.)
Step 10: Intermission(2): Stuffyottahave
More tools, supplies you may or will need:
Layout fluid - fast-drying blue stuff to spray on metal you want to mark for cutting, drilling, etc.
Prussian-blue oil paint - $3 or so at the local hardware/art-supply store. For coating a metal surface you want to make Very Flat.
Eye protection - every time a chip of very hot, sharp metal hits my cheek at high speed, I say a little prayer of thanks that I'm wearing these. And I'm not religious.
My rule is this: when my hand touches a power switch, I am wearing eye protection. It is SO easy to think "this quick little cut won't be a big deal" -- and have a tiny piece of wood or metal shoot straight at your eye. They do NOT yet have artificial eyeballs on the market, as far as I'm aware.
If you touch a power switch -- you're wearing eye protection. End of story.
Learn it. Live it. Enjoy stereoscopic vision for the rest of your life. It's easy - and it's free.
Other tools -- an automatic center-punch - quite handy.
A 0.001"-accuracy calipers - almost necessary.
A "Dremel"-style tool - if you do everything perfectly, you won't need this. (And, if you do, please contact me. I have some walking-on-water jobs for you. ;-)
Finally, the FastSteel I've been mentioning. (See above comment on Doing Everything Perfectly.) It's an epoxy/steel-powder mix that comes in a stick. You cut off what you need, knead it until the color is uniform, and press it into place. It's certainly not as strong/tough as steel, but it's come in handy when I need to patch an area that just didn't cast well. It will take a thread, can be drilled, etc. I wouldn't trust it to hold me over an alligator pit in the place of real steel, but it's not bad when you need something more cosmetic and/or somewhat strong.
Step 11: Starting the Assembly
Now we're starting to see the whole thing come together.
The blue parts are the bases and the bed, supporting the "ways". The ways are (is) a strip of 3"-wide, 1/4" thick cold-rolled steel (CRS). It's pretty solid and heavy, but actually can flex a bit -- which is why it's important for the bed to be very, very precisely flat, as the ways will be bolted quite tightly to the bed and thus follow its flatness (or lack thereof). The bed I cast, as you may recall, has a nearly 2mm dip in the center. That may sound like very little, but in fact would result in unacceptable imprecision -- most machine-tool work is specified in terms of thousandths of an inch. 2mm is about 1/12th of an inch -- a HUGE error in machining-land.
In any event, the "ways" are/is resting on the bed. The green piece is the carriage. On top of the carriage yet another "ways" (a piece of 1/4" thick, 2" wide CRS) for the cross-slide, and the cross-slide itself (the unpainted chunk of metal with the circular pattern on top).
So - briefly -- the bed ways will be bolted down to the bed/base; the bed/base will be bolted to the two base castings; and a long threaded rod along the front will let me crank a handle to move the carriage left-and-right.
Then, the cross-slide ways (the 7" long x 2" wide piece of steel) will be bolted to the carriage, and a screw with a crank-handle will be installed in the cross-slide (so, when I turn the handle, the cross-slide will go back and forth). Then, the compound swivel base (coming soon) will be installed on top of THAT, so I can turn the cutting tool clockwise or counterclockwise.
Step 12: The Compound Swivel
Here's the compound swivel base. A 5" piece of steel goes on top of IT, for the final thingy to ride on.
That 'final thingy' is the Compound Slide -- and it holds the actual 'tool' -- a sharp bit of very hard steel -- which ultimately cuts the workpiece.
Where are we, now? Well, let's pretend we want to make a chess piece -- a pawn, say -- about an inch across at the base.
We'd need to put a piece of inch-diameter metal in the lathe. We'd need to move the cutting tool left-and-right to cut from the top of the pawn to the bottom (using the carriage, controlled by a 2' long threaded rod we'll discuss later). We'll need to cut more deeply and more shallowly to shape the various contours -- that's the cross-slide. And, finally, we'll need to alter the angle of the cutting tool to shape, say, the round head of the pawn -- the compound.
All of this is in place. Mostly what's left is the stuff to actually hold the workpiece (a headstock and tailstock -- like the two jaws of a vise, except in this case they allow the piece to spin); and the motor to turn it.