Why a lathe? You can use it to make beautiful birthday and Christmas pressies for family and friends and to craft all manner of things to help in other projects. To make yourself a load of wooden kitchen bowls, plates, utensils, etc. To make arrows, door and draw knobs, staffs, axles, beautiful ornaments, flower pots, light shades... The list is endless.
Making a lathe is fun! Designing one yourself and using free or cheap materials is even better.
This instructable shows how I did it. I got ideas from lots of places on the internet (including other instructables - do a search for 'lathe') and formulated my design as I collected materials.
This lathe is made almost exclusively from stuff other people threw away or didn't have use for anymore, and a big part of the challenge is creatively using these readily available materials. You will probably want to vary your own design from mine, as you will inevitably find you can get your hands on different bits. Don't worry though I will try my best to offer techniques and advice (including where the best places are to get stuff), anyway it is much more exciting when you have a hand in the design process. I would love to hear what you guys use to make your designs.
A more complete and up to date set of instructions for this project and videos of the lathe, and other bits and bobs can be found on our blog at: http://www.floweringelbow.co.uk
I use some basic power tools in making this, and I meddled (carefully!) with mains voltage, so the usual safety precautions must apply. Always wear eye and ear protection when using power tools and lung protection when making dust. Be very careful and get qualified help (if you need it) with main voltage etc.
The lathe itself can be very dangerous, following good practice, and designing in safety, is the best method of staying out of harms way. I will hopefully cover some of these points, but ultimately you're doing this at your own risk, so please take care!
Step 1: Acquiring the motor
If you do get a washing machine motor try and grab the whole machine - then in the comfort of your own home you can take your time to work out how the wiring went. If like me you were on a time budget to get it away from your parents sub-Arctic outside shed just cut it out and get as much of the electronics as possible.
To extract the motor, turn the machine upside-down and you should be able to see the motor. It is now simply a case of unbolting it from its mountings.
These motors can be run off both DC and AC making them quite versatile little beasties.
In the picture I am testing the motor with a DC bench supply, made from an old computer PSU (power supply unit - check out Sitnalta's instructable). DO NOT CONNECT THE MOTOR TO MAINS VOLTAGE without any load attached. Series wound motors have no theoretical limit to their speed and the centrifugal forces can fling the motor armature apart! Even with a modest load a direct connection to 240V mains is a bad idea, as the speeds are likely to strain the bearings, brushes and frame - all of which are not designed for unlimited power without a hefty mechanical load.
Another way to test a motor of this sort without a bench-top supply is to attach a 1000W electric heater wire between the brushes. The current passing through the resistance wire should be enough to limit the speed of the motor.
Step 2: Speed control (part 1 - general information & motor connections)
One of the down sides to modern series wound washing machine motors is that they are designed to go very fast, and when run on unfettered mains current will screech along at about 8,000 rpm with a modest load (as I already said don't run them unloaded). This uncontrolled speed is bad because:
a) it is going to make a lot of noise, annoying you and your neighbours;
b) to turn wood on a lathe we will need a much lower rpm - from about 400 - 2000. To achieve this without some sort of electronic control would mean an elaborate (read even more noisy) and large pulley system, and,
c) if connected straight to the mains the speed regulation will be poor when load is applied to the motor. In other words when you start turning your wood and you push the cutting tool into it, the speed will fluctuate wildly. Ideally you would like the rpm to remain predictably constant, rather than speeding up and slowing down as you make your master-works on the lathe.
There are various ways to build a controller - probably the minimum and most basic is to vary the voltage with a variable transformer. Although very simple, this is not a good solution because: when you set it to run at low voltage/low speed, it will also have very low torque - and it will still suffer greatly from point (c) above. This is a disaster because you often want the most torque and predictable performance at low speed.
A much better method is to make a very simple triac controller circuit, also referred to as a pulse-width-modulation or chopper circuit.
This stage required me to do fair bit of learning, but in the end I was able to build a really nice little controller that adjusts the speed quite accurately with a turn knob (an elaborately decorative new version of which I shall make once I have finished my new lathe). All that is needed are some quite cheap components (available from most electronics mail order places) and a soldering iron.
After reading lots of books and websites I found a fantastic chapter about speed control. Here is a link to the book Electric Motors in the Home Workshop by Jim Cox (pages 59 to 73 are well worth reading).
The good thing about a triac system is that you don't need to faff about with changing pulleys or drive belts. Also you get to learn some cool electronics jazz!
Working out which connections do what on the motor, is one of the first steps (see the photo below in which one of the brushes has been unbolted for clarity). Also check out the diagram that shows what bits of the motor are what.
There will likely be 3 stator coil connections,
2 brush contacts,
2 tachometer contacts,
and an earth connection on the motor frame.
Step 3: Speed Control (part 2 - making a simple circuit)
I chose to make my own (to better understand it and to and add some mods). It is essentially very simple and can be made using some strip board and a few cheap electronic components.
The stuff needed is as follows (maplin code in brackets):
C1 Polyester capacitor 0.1uF 250V (BX76H)
C2 Polyester capacitor 0.047uF 250V (BX74R)
C3 Polyester capacitor 0.01uF VAC (got off e-bay)
D2 Suppressor 250VAC (HW13P)
VR1 Variable resistor or POT 220k (FW06G)
R1 Min Resistor 4k7 (M4K7)
R2 Min Resistor 22k (M22K)
R3 Min Resistor 100R (M100R)
D1 Diac DB3 (QL08J)
T1 Triac BTA26-600B (UK56L) (the 16A version would suffice - I was in an overkill mood)
Some strip board to put it all on.
Optional components (more on this later):
2X Rectifier J04 (BH46A) ~ �3 each (but I got very similar ones on e-bay for 99p each)
50VA Step down transformer 240V to 9V - (search out old power supplies, audio amps, hi fi's, etc.)
The triac itself can often be salvaged from the washing machines along with the motor. I could have also ordered some spade connectors to make the 'live', 'neutral', 'the armature' and the 'stator coil' contacts, but I felt like making my own to save a few pennies (see photo). I used some standard 2mm copper wire scavenged from some old house wiring, and soldered on some cut (using a hacksaw) and flattened (hammer or vice) scrap of copper pipe.
When it comes to actually making the circuit, there is loads of good advice on soldering here on instructables, so I will not talk much about that. Enough to say that is is not a complex circuit and it should be pretty straightforwards if you read the instructions here carefully. Thanks to Westfw for the Eagle schematic 'able (http://www.instructables.com/id/Draw-Electronic-Schematics-with-CadSoft-EAGLE/).
Step 4: Speed Control (part 3 - thinking about heat)
I used a section of aluminium channelling (same as used on the lathe bed) bolted together with a bit of old heatsink rescued from a discarded computer PSU, with a bit of flattened copper pipe.
As far as I know copper is better at conducting the heat, and aluminium at radiating it to the surrounding atmosphere. Hence the copper helps disperse the heat throughout the sink and the aluminium radiates it off.
Whatever you find to use, cut your metal to a sensible size with a hacksaw , or similar (if you only have a junior hacksaw make or buy a full size one or you will waste a lot of time). Drill your holes, then, clean and polish all joining surfaces. The cleaner and flatter the meeting surfaces the better the heat will transfer. If you have some, apply thermal paste before bolting up the assembly.
Step 5: Speed Control (part 4 - testing time)
If all is well you can test it with a 60W incandescent light bulb. It has to be this old type - new compact fluorescent ones will not like the chopped current.
Turning this baby on is one of those exciting moments where things should work nicely.
By using the variable resistor you should be able to vary the light from completely off all the way through to full brightness.
Be very careful. Remember that as soon as you plug this little thing in it will have uninsulated mains voltage all over the place, including over the heatsink. Make absolutely sure the workspace is clear and safe and your not going to have it accidentally knock over or into something conductive. Test it briefly then disconnect from the mains (well ok, you can play with it a little bit, but remember those connections are live, and the crock clips don't exactly meet domestic wiring regulations). Clear away as soon as you're done so no stray or inquisitive fingers can easily plug it in.
Step 6: Speed Control (part 5 - Improving speed regulation and low speed torque)
An optional further increase can be had in speed regulation and low speed torque by effectively converting the machine to a direct current shunt wound motor. To do this we rectify the speed controller output and supply the motor with DC (direct current). We also use a very low voltage (and high current) to energize the field coil.
As shown in the diagram, we still keep the 240V DC running through the field coil as well, this gives the benefit of reducing starting current surges. It is important to wire the two rectifiers such that they are pushing current in the same direction through the field coil (see diagram).
The transformer, being the most substantial electronic component is definitely worth scavenging (A new transformer is likely to set you back a good 15pounds). To our shame, in Britain at least, you will not have any trouble finding one. Likely places for the transformer are junked stereos, amplifiers, power supply boxes (though most wall warts are not up to it), and other electronic devices that routinely get thrown away.
To do this we will need the optional components mentioned earlier - a transformer (100VA should suffice - but see what you can find) and bridge rectifiers (these get quite hot, high current ones are a good idea). After flirting with the idea of using a rewound microwave transformer (and discarding it as overkill), I came across an old-school Spectrum power supply at the local tip (which is essentially a transformer with a rectifier and smoothing capacitor) - just the ticket! It is only rated (on the case) to 2.1A at 9V DC and I was needing more like 5A, but after testing it seemed the rectifying diodes were the weak link, and the transformer, when not completely sealed in plastic, as it was originally, actually runs nice and cool when delivering a steady 4.2A.
Step 7: On/Off Switch (No Volt Release Switch)
This feature is fairly standard on most decent sized power tools. You can buy them ready to fit off e-bay or make your own if you have a good high current contact relay and a push to make and push to break buttons in your scrap box. See circuit diagram.
S1 = On button (push to make)
S2 = Stop button (push to break) - if you make it this way S2 must be a very robust button as it will carry all the power going to the lathe. It should also be big and conveniently situated for quick stopping.
K1 = Heavy duty contacting relay.
Step 8: Electronic Braking
But it is nice to have the option of braking, rather than have it always imposed... Three reasons:
1. You might not always want it to rush to a halt - doing so puts extra strain on the belt, bearings and other components. In unusual circumstances, It might also endanger your work piece to have a dramatic change of speed.
2. Almost all electronic braking (on series motors) works by shorting the brushes together with a resistor - effectively turning the motor into a generator. This creates a braking force and the energy is dissipated as heat in the armature. Meaning that a lot of stopping and starting with full braking being applied can overheat the motor.
3. It is simply more fun to be able to control things.
One difficulty with this type of motor is that the field coil must remain energized for braking to work.. This is a problem because in general we want braking to coincide with a cut in the power to the unit.
My solution, is to have a push button (S1), normally open, that, when pushed (and held down), makes a separate circuit that both powers the field coil and energizes a solenoid relay (S3), which shorts the brushes through resistor R1.
Key to diagram:
S1 = Push switch - the main switch that the user pushes, and holds, to cause braking.
S2 = A relay that gets power and therefore energizes, when S1 is pressed. It cuts power to the NVRS
S3 = Another relay that, when energized, completes a short circuit between the motor brushes.
NVRS = The main on/off "no volt release switch".
R1 = A resistor of about 10ohms (the larger the value the more gentle the braking effect)
T1 = Step down transformer 240V to about 9V
D1 = A diode that ensures the field coil is maintained in one direction.
Step 9: The Lathe Bed
I had some scrap angled aluminum which I took from some old 'science draws' (it formed the handles) that my university was throwing away. This on its own looked to be a bit flimsy, so I also rescued a long peace of angle iron that was rusting away at my parents farmhouse.
As you can see the steel is well rusty and actually quite pitted but is hopefully still thick enough to add the rigidity we're after. Once the steel is cleaned up the aluminium can bolt on top to create a smoother surface for the sliding tail stock.
First I used a small cheap angle grinder to cut the steel into two lengths (a hacksaw would be OK but slower). Then I began to clean it up.. I found that belt sanding (real course 40 grit) followed by drill mounted wire brush seemed to work.
Bits of scrap like this are easy to find. Possible sources: metal bed frames, surplus construction site materials, old gates, old trailer or other large machinery framework. Basically you are looking for something long, straight, and strong enough to support a spinning log without undue flexing. My general advice would be to think about the size of lathe you are wanting to make and the kinds of things you want to make with it, and then overbuild the lathe bed. It can't be too strong, but consider the weight and size ;) Mine ended up being much heavier than expected and I need help to move it about.
Step 10: Thinking about the headstock (bearings and main drive shaft)
The materials I found for this were:
Coming from an old piece of machinery, one surprisingly heavy and large sheet of metal, about 6mm thick (strong stuff!).
Two similar sized tray like pieces of stainless steel.
Some of the angle aluminum.
Old motor shaft, bearings and bearing housings.
The photos and descriptions tell it better than words up here.
One problem here is that the old motor bearings are not taper bearings - they are not designed for anything other than small loads in a sideways direction. My feeling was that this was outweighed by the fine axle and ready made bearing housings, and more importantly I had it all there and then, and it was free!
It is worth thinking about though. This is going to mean I have to be very careful and avoid certain (angry) ways of working when the lathe is in everyday use. If I find it unacceptable, or I destroy the bearings, I will replace them with taper bearings, that are much better with side loads. (see for more info on taper bearings: http://www.arceurotrade.co.uk/projects/C3_BC/pages/index.html)
Step 11: Making the headstock (front and back panels)
Remember the further the drive shaft is from the bed the more leverage it has and the more likely it is to do cheeky twisting, wobbling and other dangerous things. So it is a compromise of size and strength...
Once I had decided that (it was partially determined by the materials i had available), I began by cutting two equal sized pieces from the 8mm thick sheet of metal. I already had two stainless bits which would add a tough outer shell and little bit of rigidity.
Now we need to decide where and how we will fix the front and back faces. I wanted to make them identical front and back panels - I did this by clamping them together and, where possible, drilling through one and into the other a ways so it was easy to resume drilling at the right place.
Again see the pics and their descriptions for more.
Some general advice on drilling... This would have been easier with a drill press (that will have to be a future project though), but you can make do with a decent hand drill - and get quite skilled at using it in the process.. Use plenty of light oil on the drill bits, and go at a slow speed. If you go fast you will harden the steel your trying to drill and dull the drill bit, making it really difficult. Using sharp drill bits helps a lot! (see http://www.instructables.com/id/Sharpen-Your-Drill-Bits/)
Always clamp things your drilling, Its easier and safer, and you can concentrate with both hands on making a straight hole.
Consider what size bolt you are going to use in advance, so you can choose the right size bit. You can download tables with the correct corresponding sizes and print it out.
Or, a good rule of thumb is to take the bolt diameter and take away the thread pitch to give the size of drill bit.
e.g. If i want to tap a 6mm thread (because I want to use a 6mm bolt) and if the thread pitch is 1mm, then the drill bit size would be 6mm - 1mm = 5mm drill bit. Rule works just as well with imperial too.
Step 12: Making the headstock (central supports)
They also needed to be cut so that they hold the front and back panels at the correct distance - that is, the length between the drive shaft bearings. Make sure everything will fit before you start cutting or drilling - cardboard mock ups are useful!
I use some aluminium angle to bolt them in.
Step 13: Mounting the motor & the other center support
Using a tailors tape measure or a piece of string the belt length can be calculated. For this application a poly-v belt is best. This is because only the relatively flat poly-v belts can handle the sharp radius of the small motor drive shaft. Standard v-belts would need bigger pulleys. The chances of scavenging a correctly sized belt seemed minimal so I ordered mine over the phone, it was �8.
Apparently the belt tension is about right when you can just twist the belt by 90degrees but not much further without using force. Super subjective I know, so it is a good idea to design some adjustment into the motor mount.
Step 14: Attaching the headstock to the bed
Two cross bracing pieces (one made of the white metal, the other a doubled up alu sheet) will bolt onto the bed's rails. Fairly straightforward: drill the holes, and bolt up (I tapped a thread in the bed's rails, but a bolt through with a nut would probably have been ok too).
I needed to make a hole in the front panel for the bed angles to fit through, I did this with small angle grinder and some filing.
Step 15: Wiring up the insides
I tried to mount the components that might get warm, like the rectifiers and the braking resistor, to the metal panels to help dissipate the heat.
Step 16: Housing the moving bits and making it look nice
I still wanted to keep an eye on what was going on inside while the lathe was running though, so the plan was to find some thickish perspex to cover the top.
See the pics.
There has been a rubbished stainless steel kitchen sink in the woods now for about 6 months, which I walk past on my way to university most days. Not to let an opportunity to tidy up pass me by, this found its way onto the lathe (well part of it anyway - the rest went to the correct recycle facility).
As well as the sink, I used a stainless panel from a scrapped microwave to make the main control panel.
Step 17: The viewing window
Step 18: Speed measurement (optional little interlude)
There are a number of different ways to do this. I used the 'threaded rod and nut' technique.
Simply attach the multimeter to the tacho output, set to read voltage (20V scale).
Setup a threaded rod so it spins with the drive shaft. You need to know the pitch of the thread (i used some 1mm pitch stuff) Mark two places on the rod (A and B), a given distance apart (say 60cm).
Now set the lathe running at a slowish speed and record the multimeter reading. Hold a nut stationary on the rotating rod - it will travel lengthways along the rod, because the rod is spinning.
Start a stopwatch when the nut passes point A, stop the stopwatch when it passes point B. Record the time it took.
You can now work out the rpm (revs per minuet).. If A and B are 60 cm apart that requires the shaft to turn a full 600 rotations for the nut to travel the distance (because the pitch is 1mm - that's one rev per mm).
So what is the shaft speed if: it took 60 seconds to travel between A and B? Answer: 600rpm because it revolved 600 times in one min...
If we make a little table or rpm with corresponding voltage readings we only need a few reading and can draw a graph (which should be a straight line) to give us the rpm, at any given voltage.
Step 19: The tailstock (part 1 - the sliding base)
I got a bit carried away and decided to attach a leadscrew to my tailstock base - this just allows you to move the base along the lathe bed by turning a screw (or peace of threaded rod in this case. My plan was that I could make this movable base a multi purpose item - being capable of carrying a tailstock, but also a tool that could be accurately moved across the work piece, in the style of a metal lathe, but for wood.
Here I made three mistakes - 1) attempting to make a monster leadscrew-nut from perspex, which obligingly snapped my extra long self-fabricated tap; and 2) using a leadscrew that was only 6mm diameter. to much flex mean a lot of faf, making sure it was always under tension from both ends (it can pull well - but does a bad job of pushing). 3) It was relativity pointless complication, which introduced more bits that might go wrong.
It works ok now, but was quite challenging, and required some borrowing of tools.
Whatever you plan to do, the tailstock base will want to be a snug fit to the lathe bed, with little or no play in the joints. Mine is a VERY snug fit and was nearly impossible to push up and down the rails by hand - which is partly why I wanted the lead screw.
Step 20: The tailstock (part 2 - 'the top bit')
I am starting to think this might be my first aluminium casting experience... Now to build a small furnace that will double as a bbq ;)
Step 21: The tool rest
After a little experiment with a piece of channel clamped to the workbench, the limitations of that approach became apparent. Namely, it could not be moved in close enough to the wood - you always want the tool rest to be as close to the wood as possible without it catching when the wood spins.
What I needed was a banjo. That's right, a BANJO, a piece that fits onto the bed and supports the actual rest. Bring forth a scrap bike frame, an angle grinder, and I was on my way (see pics)...
Something reasonably rigid that swivels and can be moved towards and away from the wood and be locked in place, and that has something that the gouge can slide along, side to side.
Step 22: Parting thoughts
Some reasonably common responses: "Why the hell would you do that in this day and age", and "they are so cheap from China, what a waist of your time".
To me though, it seems completely sensible. I like making stuff, and learning about how things work. If I didn't love making things why would I want a wood lathe in the first place?
Making something that helps you make other things is very satisfying, particularly if you do it in a way that uses all your creative ingenuity. If you want to make something like this yourself, and you plan, as I did, to spend very little and to recycle other peoples landfill material, you certainly will have to think 'outside the box' as you put materials and things to new and unintended uses.
Anyway enough babbling. I hope you got something out of this instructable and look forward to any comments you might have.
Final inspirational quote from the famous mechanist Dave Gingery with a qualifier: take care and don't be reckless...
"It is interesting to note that most of our best ideas meet with opposition in our own minds as quickly as we conceive them. The objections we raise usually seem so reasonable that much of what we might do never gets done. If you don't want to do a project just write down the first dozen or so thoughts that come to your mind and you will have at least a half dozen good excuses. If that doesn't do the trick just toss the idea to the experts and they will usually be happy to kill it for you. If you really want to do it, though, it is most likely that you will find that it does not really cost very much and it is not nearly as technical and dangerous as established experts would have you believe." (Dave Gingery)
PS to see more of what I have been up to with this you may want to check out my blog: www.floweringelbow.org