Fixing a gunked up motorcycle carburetor

I haven't ridden my motorcycle for a long while (almost a year). So when I got it up last week, it would not run. So it is time to do some fixup work.

The Problem: The battery has been connected to a charger all the time, so it turns. The motor starts with choke on, so that was a good sign. I knew the carburetor has to be gunked up, and my plan is as long as it starts I will ride it for a while with some cleaner added in the fuel to clean it up. So it is a welcomed sign that the engine starts with choke. The troubles comes when I tried to give it some throttle. Just a little turn on the throttle stalls the motor. I did manage to get through the stall point and really reved up the engine but the second I let go the throttle, the engine went off.

The Hypothesis: After some Googling and thinking, I figured out that this is a problem with the pilot of the carburetor. The engine runs under chokes, so most of the system is doing fine. It does rev up at full throttle, so the main jet is not stuck. So it is the pilot that is clogged. The telltale sign is that the engine stalls when throttle is applied. At low throttle, the fuel is mostly supplied by the pilot system, so it must be those that are clogged.


The Fixups: It is relatively simple to take out the carburetor on a motorcycle. Here is a picture of the under side of the carburetor with the fuel bowl removed. The arrow shows the flow of air / fuel and mixture inside the carburetor body. On the pilot system, the air comes in on a long passage, picks up fuel at pilot jet, and goes into venturi at the pilot drill points and the air screw.

I took out the needle jet and the pilot jet. The needle jet is relative easy to take out, and it is not clogged (because it relatively big in size).

The pilot jet is a struggle to take out, because it is pretty deep inside the hole, and is glued to the body by the gunk. Some penetration oil did manage to loosen it up enough to take out. The pilot jet is indeed all clogged.

The holes in the pilot jet is very small. It read that people (the professionals) advice against enlarging or cleaning these holes, but with an old motorcycle like mine, I got to do whatever I felt making sense. I am not sure if I can find those replacement parts.

The head of the pilot jet has number "35" stamped on it. I guess it probably means that the hole is 35/100 of a millimeter in diameter.  (By the way, the K mark at the top indicates that this is a Kaihin part, according to this page I found.) I happened to have a lot of tiny drill bits (in various sizes) from previous work. I took those out and soon found one that seems to go through the hole just right. One of the pilot jet has a hole so clogged, that I have to put the drill bit on my Dremel tool to drill through it.

Now it is time to clean things up and put it all together. And the engine starts right away, and goes well when opening the throttle. I guess now I will need to take it out a bit more frequently.

Craftsman 109 Lathe - Chuck Backplate and Fitting

I have made a new spindle for my Craftsman 109 lathe. And I found that all the chucks need to be refitted. I have two chucks: a 4-jaw with 3/4-16 thread, and a 3-jaw with 1/2-20 thread.

When I mounted the 4-jaw and indicated it, I found that it is off now with the new spindle. I have tried to turn the surface of the front and back of the 3/4 adapter, but it does not help. I think it is because that the center line of the inside and outside thread are not matching with the new spindle. Since the 4 jaws are adjusted independently, there is not much need to remake the adapter. The only downside is there might be a bit off center mass, but that may not be much of a problem for the limited precision of my lathe.

The 3-jaw is a different story. It is off by quite a bit. My 3-jaw has a plain back and has a cast iron backplate adapter. But when I took them apart and attempt to refit it, I found that it may have never been properly fitted previously. The spigot is cut a bit too small. I will have to turn it all flat and turn a new one from what is left. I happen to have a 1" thick piece of 3" rod aluminum. So I decide that I will use that to make a new backplate and leave the old one alone.

I did some research on whether aluminum is strong enough as the backplate (the standard material is cast iron), and found no definite conclusion. Then I decided that I will just go ahead and do it. The thread mating between the backplate and spindle might be a bit soft, but it should work if I use it carefully.

So I mounted my 4-jaw chuck with the jaw facing outside (which holds the 3" piece with no problem) and started working on the backplate. The procedure is pretty simple, and there are plenty of information on Internet on how to do it. So I will skip the details here. Soon, I have this blank piece of backplate.

The hard part of this project is to locate the mounting holes. The location of the mounting holes is not super critical as the precision of the fit is decided by the size of the spigot. But I like to make them as accurate as possible. Instead of measuring the hole circle radius and dividing the circle to three parts, I decided to go with a simple method of making a few transfer punches as indicated in the picture. The mounting holes are M6-1.0. So I turned a few M6 screws down to having a small spike in the middle and cut a off-center slot so I can use screw drivers to get them in and out of the mounting holes on the chuck. A few light taps marks the location on the backplate and they are drilled to through holes for the M6 mounting bolts to pass through. The holes are numbered and marked as well as the mounting holes on the chuck, so they are always going back the same way.

With some very careful turning, I have my backplate fitted for the 3-jaw chuck. The TIR on the backplate is almost nothing, but to my surprise the TIR on the perimeter of the chuck is 5 thou. I re-check the TIR of the spigot and found it to be nearly zero. So the chuck is not perfectly centered with the register. With a test piece mounted (and tightened with the best chuck wrench hole), the TIR is about 2 thou. That is much better than before. I will probably need to grind the inside of the jaws someday, but for now, that will do.

Here is my 3-jaw chuck mounted with the newly fitted backplate. Another good thing about my backplate is that it is about 1/2 inch thinner than the old backplate, which moved the chuck a bit closer to the spindle bearing (but still not close enough as the 4-jaw).

Craftsman 109 Lathe - New Homemade Spindle

I  have known that the spindle on my lathe is old and worn out. I am not sure if it is bent, but I like to replace it. There are spindles available on eBay and Home Shop Supply. They run for about $100. But where the fun is if I just bought it.

There are people who has made the spindles themselves. For example, this gentleman in SHDesigns made one from tool steel, and has a page for it. But he turned it on an Atlas/Craftsman 12x36. I don't have a machine of that size or accuracy. All I have is a semi-working Craftsman 109. And even if it cuts, I am not sure if I can make the finishing smooth enough for the bearing surface.

I have been thinking and search for a while. And one day, I realized something. We all know that the spindle size of the Craftsman 109 is 0.551". That is a strange number. I have seen people doing things in strange numbers, but there has to be a reason. And it turns out that 0.551" is 14mm. The all American Craftsman has a metric heart. How interesting is that.

So all I got to do is to find a grounded 14mm rod, and that could be my new spindle. But what about the collar part? I have spent quite some time thinking about it, and there are a few ways I came up with. I did a few experiment to decide the precision of my cut and measurement, and decided that I can bore the hole precise enough for an interference fit (or shrink fit), with my BBQ stove as heating source (no need for a propane torch).

So here we go. First I got the 14mm rod from eBay. It is grounded 1144 steel. Even though it is not as hard as tool steel, I figured that it will do for me now. The piece I got is 24 inches long, just enough to make three spindles (the original spindle is about 7-1/2" long).

So I cut a piece of 12L14 that is about 3/4 inch long, and bored a hole that is just one thou smaller than the spindle rod (which measured to be 0.550"). For some reason, I can not even bore a smooth surface in the collar. But I figured that this would be a good thing here, as it would grab tighter when the two surfaces are shrink fit together.

Before I shrink fit, I made a wood jig (that is nothing more than a large enough hole drilled for about 1 inch deep). That's how much I like the spindle to stick out. And then I put that collar piece on the BBQ stove. After a while, I took it out, put on the wood jig, and stick in the spindle piece. I even brought a hammer, in case I will have to force it in. But it slides right through with a light tap. I kind of worried if I have machined them too close, but it turned out beautifully when everything is cooled down.

Next I put it on my lathe to finish the backside of the collar. The rest of it can be machined when the spindle is on the lathe.

The next challenge is to get the groove for the Woodruff key. For this I just used my Dremal tool with a disk shaped cutter. It is a bit larger than the original, but it works its way in just fine.

Here are the new spindle and the old spindle show side-by-side. As one can see, I left a bit more material on the new spindle, as those will be cut down in the future when fitting the chucks. Plus I like to have some safety margin to give my shrink fit more surface to grab on.

The old spindle is shown here. As one can see, it has been worn out quite a bit on its bearing surface. I guess that this spindle might have never been replaced since the lathe is first sold in late 1940s. It is an old lathe.

Now the spindle is put on the lathe in its place, and nose of the spindle is cut down to 0.5 inches, ready to be threaded. The spindle nose on the 109 lathe has a 1/2-20 thread. It is great that I have fitted my lathe with all the necessary threading gears so I can cut those threads in place.

Because these threads are so close to the end of the ways, we need to be very careful in setting it up. I happened to have grounded a v-shaped cutter that is tilted to the right. So as we can see here, I can cut pretty close to the register surface and still have room for the indicator wheels.


Cutting the threads are largely uneventful. I did have a few mistakes when the gear pops out. But I got it realigned easily. I finished the thread with a die. As always, that is not an easy work, and took significant force at the end. The die set I have is a cheapo set from Harbor Freight. Maybe I will need a better die set someday.

So finally, here is my new spindle on the lathe. All home made cheaply and proudly on the Craftsman 109 lathe I have.

Craftsman 109 Lathe - Easy Tool Post Steady Rest

My Craftsman 109 lathe does not come with a steady rest. That makes it really inconvenient to drill a center hole at the end of a long slender piece.

I was looking around Internet the other day, and found this article in an old issue of Popular Mechanics. That is really a smart idea. The tool post steady rest goes on the tool post, so it would preclude cutting with a tool at the same time. So it is not a real steady rest. But for the purpose of drill a center hole, it works perfectly.

So I went out and build one myself. This is how it looks on my lathe. Now I can work on the spindle to replace the one I have.

Craftsman 109 Lathe - Spindle Adaptor 3/4-16

Using tailstock to start a straight tapping

To make the lathe usable, I will start with the chuck. First I would need to get a chuck that is shorter. It looks like that all the plane back chucks stick out too much because of the extra space taken by the back plate. So the one that would fit well would be the screw mount chucks. I happened to have have read about the 3/4-16 adapter for Taig chucks in Dean's website. So I put in an order to purchase one of 4-jaw chucks from Taig, and getting ready to make the adapter.

Finishing tapping on a vise

To start out, I have cut out a piece of 12L14 round rod. For my weak lathe, it seems that the only steel I can cut at this time is the free machining 12L14. The rod is held in my old 3-jaw chuck, and it is faced and drilled a through hole to about 15/32. Then the hole is tapped with a 1/2-20 tap. The tap was held in a drill chuck from endstock to start the thread straight. It went pretty well initially, but soon it become really hard to turn. Maybe it is because that I don't have a sharp enough tap, but I have to take it out from the lathe to be held on a vise. This is different from what Dean did on his page. Everything looks so easy there. Another thing that I did differently is that I didn't turn the outside down in this step. Part of the reason is because I am not sure if my lathe can turn well with the chuck it has. Well, I am fortunately I didn't, because holding it in a vise will ruin the finish, and it did slip pretty badly. Like all my projects, I always have to go through some rough patches along the road.

Then the piece is thread on the spindle nose and faced. Since the thread on the nose did not go all the way to the register surface, a few threads need to be bored away. I don't have a boring bar, so I have tried to grind a drill bit to be held on tool post as a boring bar. I have tried it on aluminum just to make sure it works. It did. But when I put it on use on steel, it turns out did not cut as well. Maybe I didn't grind the cutting edge well enough. But I ended up just enlarge the hole with the 1/2 drill I have to get it against the register.

3/4-16 Adapter

The picture to the left is the piece mounted on the nose ready to be turned down. A hole is drilled on the back for inserting a bar to remove the adapter if it gets too tight. The front 1/2 in or so is turned down to 3/4 in size. The turning down was so smooth, and it cuts like butter. Turning steel has never felt so good with my mis-aligned chuck. That further confirmed to me that it can work well if I can bring it closer to the nose and the spindle.

As I mentioned earlier, I was able to get the thread cutting of the lathe working. So I got that ready and start threading it. Contrary to Dean's experience, I was able to cut the entire length with the threading indicator mounted. This is the first real thread I am cutting, so I have also bought a 3/4-16 die ready to finish it. I really have no idea how deep it should go, and learnt my share of lessons there. I thought I got it deep enough, and tried it with the die. In the process, I have removed the tool and soon realize that it would not be in the same place when I put it back. Fortunately I have the die ready, and  I would finish the thread with it.

That turned out to be another tough operation I have to drive to the maximum that my little vise can handle. In that process, the surface is destroyed again, which I have to turn down afterward to clear the deep marks. But all in all, I have a cool looking adapter ready to mount my Taig chuck (which I purchased for this modification).

So here is my new chuck, sitting nicely on the lathe ready for the next project.

Craftsman 109 Lathe - Thread Cutting Gears

One reason that drives me to keep the 109 lathe as my project is that it has building setups to for thread cutting. I have got many gears with my original acquisition of the lathe. However, the set is not complete. I have asked the seller about it, but he said that he has never used it.

I looked through the gears that I have. It looks like that I am missing the gears that are on the tumbler assembly. Those gears are available on eBay, but are generally going for $15 to $20 a piece. I have been contemplating about cutting them myself, but I would need to build a milling attachment as well as an indexer. Thread cutting seems to be a rather important part of the projects I have in mind. So I decided to get those gears complete first.

On Dean's webpage (from the same gear cutting link above), it was stated that the 109 lathe uses the same gear as the 618 lathe. So I have been scouting eBay for some time, and found a tumbler assembly. I got it for about $40 (including shipping). But when it arrives, I found to my surprise that they don't fit the tumbler I have. Didn't Dean said so? I went back to read his comments, and it turns out that what he says are that the gears fits (I think he means the change sets).

Fortunately, I think the gears pretty much looked in place, except with a bigger hub size. That should be easy on the lathe. I quickly machined some bushing, and now it goes on like they are made for it.

After some work and additional money out of pocket, my lathe is finally up cutting threads. I have heard that people complaining that the motor is too fast for cutting threads, but mine works just fine for me. I will be using that in my coming projects.

Craftsman 109 Lathe - Chatter

My 109 lathe has serious chatter problem. It is so bad that I could not even turn a small aluminum piece. I have made a few small modifications previously (such as replacing all the jibs with copper ones following Dean's webpage). But it helped little.

The chatter remains, even when the piece was relatively short and hold close to chuck. I have tried may tricks I read on the Internet, slow feeding, deeper cuts, etc. The vibration will still come. The only way I have found that I can turn anything on this lathe is to hold the end of a piece with a center from tailstock.

After playing with it for some time, I finally got a lathe dog so I can turn between centers. Finally I was able to turn a piece and it cuts smoothly. What a wonderful feeling when the cutter just glide through steel like butter.

I have tried to measure the vibration frequency, and it is somewhere around 100 Hz. My lathe at the setting I used most is turning at around 700 RPM. Interesting at one of the pieces I can see the chatter marks that goes about 8 cycles per turn. For 700 RPM and 8 dimples per turn, it turns out at right about 100 Hz. That's what I am seeing.

I have tried to tighten down my tool post, and it did not help. And the disappearance of chatter when turning between centers confirmed that the vibration is probably in the headstock and chuck.

On this lathe I have a standard plain back 3" 3-jaw chuck. It extends quite a bit from the headstock. And it is a big piece of steel. I took the chuck off, cleaned it, and faced the backplate. And it did not help.

Then I realized that the problem is probably with this size of the chuck and the lathe. The chuck is quite heavy, and it sticks out quite a bit. At the same time, the spindle that supports it is relatively small 0.5" steel rod. That is an ideal case for some good oscillation. This chuck does not fit this lathe. I will need a lighter chuck that sits closer to the headstock. It turns out there are many choices.

Why Craftsman 109 Lathe

I happened to have bought the Craftsman 109 lathe more than a year ago. I believe I paid about $140 for it. It comes with gears but not a complete set.

The 109 lathe has a lot of weakness. The most obvious ones are:

• A weak spindle. The spindle is 0.55" diameter. From what I read, it is very easily bent. I suspect that in my playing with the limit of it, I have probably bent mine also.
• No graduated dial.

While contemplating on different options, there are a few choices when it comes to hobbies lathes. Among the most obvious ones are:

• Chinese made 7x series mini lathe,
• Sherline,
• Taig.

Each have its advantage and shortcomings. I have been scanning the local Craigslist hoping to find something interesting. Soon, a HF 7x10 came up at an amazing price of $150. That is a very good price. And I am the first one to respond to the buyer and setup the time to take it.

I thought through that again and again. Yes, at that price the value would be hard to beat. But I don't need two lathes. Yes, I can sell the old one and get my money back probably. But what is the purpose of having a lathe? I am not having a project that needed a lathe to complete. The lathe itself IS the project. Indeed, I have more (easier projects, for beginner at least) to work on on the old 109 lathe than those of the HF lathe. Plus, it is a simple lathe that everything is out in the open. The fact that it is weaker could actually be its strength for me to really learn how to do things properly.

We all know the most important use of a tool is to build other tools. So to build these I have in mind with the challenging weak inaccurate lathe would make things really interesting. These weaknesses are not insurmountable. They just require you to be more creative and do things properly. Take for example the weak spindle. If I am doing something that bents a half inch steel bar unintentionally in my garage, I am probably doing something wrong.

So I have cancelled my appointment with the seller. My project is now playing with the 109 lathe and see where I can bring it up to. I think it will be a fun journey.

XSVF JTAG Programmer

Now I need to have a device that glitches my Xbox 360. For my pursuit of frugal fun, I chose to use a cheap Coolrunner (I bought off eBay for $8) instead of the Team Xecuter CR4 XL (which is currently $33 plus shipping, not to mention the QSB kit). But there is one more problem. The Coolrunner I bought comes blank (not programmed). The information to program the Coolrunner with (in XSVF file) comes with the JRunner software, and XSVF files are for being written to device through JTAG interface.

I have a Matrix NAND Programmer to read and write NAND from Xbox 360. That process seems to use an interface that is SPI (or very similar to it). On internet, I have seen people post connection diagram for connecting  Maxtrix NAND Programmer to the JTAG interface of the Coolrunner. Interestingly, the programmer does have six connection pads on the side, and the JTAG interface is pretty similar to SPI. Because of that, and also the fact that the other NAND programmers / software can also be used to program JTAG, I had assumed that I can do that same with Matrix NAND Programmer.

It turned out not working. As mentioned in my other post, the Matrix NAND Programmer is compatible to NAND-X with drivers from NandPro 2.0. But it turns out that NandPro 2.0 does not yet accept xsvf option (that programs JTAG using a XSVF file). That feature is added in NandPro 3.0, but the NAND-X driver with NandPro 3.0 would not work with Matrix NAND Programmer.

So I am stuck here. Basically, I would still need to buy a NAND-X or JR Programmer to program the device, or I will have to find some creative way to get it done cheap. I read about the JTAG spec, and it is just four lines which seems to be quite straight forward. Then I found some code about playing XSVF through Bus Pirate. Bus Pirate is a very useful tool I have always wanted. But it is another $28 even though it beats buying CR4 XL. There has to be a better way.

After some more search, I found this library of writing XSVF files, called libxsvf. It is an open source project that programs XSVF files to an interface that you can provide. That is great. All I need is a bit-banging interface, and I can program the JTAG. I have thought about building a quick bit-banging interface with an AVR processor, or even an Arduino Pro Mini. But I happened do not have an 3.3V Pro Mini at hand, and my Coolrunner seems is marked 3.3V (but I don't have any data sheet on it). The next option is the well used FTDI USB-Serial interface, and I happened to have one of such (FT232R Breakout) which can be configured to either 5V or 3.3V.

Libxsvf comes with the main code compiled into a library and a couple of sample code that uses the library. One of the simple code is using simple GPIO in synchronous mode, the other one uses FT232H's MPSSE in asynchronous mode. My board is a FT232R, it can not use the later one. Oh well, I will just program the FT232R bit-bang as synchronous GPIO then.

Here come out my compiler and pretty soon I am writing to my Coolrunner. There are a few tricks to get it to run fast enough (mostly dealing with USB latency timers). It is possible to use the asynchronous mode to make it faster, but for the purpose of getting my Xbox 360 to work, that is enough. It takes a couple of minutes to program a 32KB xsvf file.

The source file of my program is xsvf_bang.c. It is based off xsvftool-gpio.c of libxsvf, and I hope I do get the license right. It needs to be linked to libxsvf (compiled as static library) and ftd2xx.lib (download driver from FTDI and extract).

 So after much trouble (all in the name of saving some $40 and having fun), my Coolrunner is ready to work with my Xbox 360.

Homemade CNC2 (Electronics - Part 1)

I needed the electronics to run the CNC. When I started out (and with my last CNC build) I have been running it with Arduino Mega 2560 with a RAMPS shield. You can immediately recognize that this is a 3D printer electronics setup. Indeed, I have converted my last CNC into a 3D printer to learn the in and out of it. So with this CNC2 build, I have also started with the same setup, which I happened to have laying around.

For the firmware, I have been using Marlin. In order for it to run CNC, I have to modify the configuration file to disable temperature sensing otherwise it would not move (this is a safety feature for 3D printer to prevent extruding before the hot end is hot enough). For the host software, I have been using Printrun.

This setup works out fine for a while, but then I felt that I will need more. First of all, the Marlin firmware does not work with inch as unit. In this part of world where I am living, the English system is still commonly in use. It is a lot easier to go down to my local hardware store to buy stuff in English then mail order then on Internet and wait for them to arrive. The second thought is that I know there are CNC specific firmware out there, such as GRBL. If I can have a firmware that not wasting the processing power on checking the temperature, why not go for it? GRBL has been proven working by years of experience in the community and it has a few neat features from what I read (such as command to change steps per distance). The third things is that while using Marlin, I for a few times have the firmware paused in the middle of a long run. I somehow suspect there might be un-found bugs in the Marlin firmware, at the same time GRBL is simpler (thus less chance of bugs), better tested (it is there longer than any 3D printer firmware), and I especially like its soft reset that retains machine coordinate while resets the processor state. So I have set to move to GRBL.

GRBL is very simple and easy to use. It is small enough (I have always loved simpler solution) that fits into the 32K memory of ATmega328P. I happened to have a few Arduino Pro Mini 328 (which I bought for a few bucks on eBay thanks to China). So I pulled out my AVR compiler and build the GRBL. After some struggle with the Arduino bootloader, I am able to load GRBL onto my Arduino (which I essentially used as a ATmega328P breakout board).

Onto my breadboard in a spare box, I have built a test CNC controller running GRBL. And I have added the GRBL soft reset switch to the front panel, as I really needed that "Panic Switch". I will find out why soon.

Homemade CNC2 (Enclosure)

I have been playing with my new CNC, and have machined some pieces for the Y-axis extension modification. While I am machining the pieces in ABS (which is harder and more brittle compared to HDPE), I noticed that the dust from cutting is getting in the air and making me coughing. Since part of my use of the CNC will be to do circuit board routing, it may produce some other harmful dusts as well (circuit boards are made of fiber glasses, which is really nasty if inhaled). So I decided that it is time to make an enclosure for the CNC to contain the dust from cutting inside. In additional, an enclosure will be very helpful for the safety in case some thing goes wrong or some pieces flying around. (This proved to be very useful in an event happened lately).

So with some quick scratch and using the scrap wood I have laying around in my garage, I spent a couple of days to put together a quick enclosure. In order to leave me with un-obstructed access to my working area, I used a cantilever design so the front of the enclosure is without any supporting column. I am not going to put my weight on the shelves besides my controlling electronics, so this should work pretty well. The only problem with that is from the think Plexiglas sheet I have bought. Since the sheets are the most expensive piece of the enclosure, I went for the thinnest I can get. It still cost me almost $30, but the sheet is so thin that it warps. Without the front columns for it to be fixed on, it leaves some gaps between the front and side shields. Oh well, as we know, a perfect solution is a luxury that a home shop does not have. And that is part of where the fun comes from. I used some tape to keep the pieces straight and together.

So here is my CNC enclosure in place. It is not too bad considering how much it costs me.

Homemade CNC2 (Y Extension - Part 1)

Now I got the CNC working and made some test cuts on wood, plastic, and aluminum. Everything works beautifully. It is tight and precise after calibration. And what I like most about the traditional compound table and fixed head design is that I can change the tool bits between different cuts without losing the X/Y coordinates. This was not possible with my previous ShapeOko build.

While I am continuing back to build things useful, I quickly run into a limitation of this CNC. The Y travel of the compound table is only 43 mm (a bout 1-3/4 inches). That limits the parts machined to a very small size. I have mentioned in my previous blogs that there are a couple of ways to extend the Y range (such as Retromaster and 0xFRED). Personally, I think the method by Fred is a much better solution.

First, I went out and bought some small ball bearings from eBay for a few bucks (thanks to China). The bearing is of the size 6mm ID x 12mm OD x 6mm thick. It is small and fits well into the limited space there. The stock Y axis threaded rod is just a bit short, so I also got M6 threaded rod from McMaster-Carr (a great place to source parts, material, and tools). Note that by convention, the Y axis rod is always left handed, although it does not matter if you don't plan to hand crank it. I may replace it later, but for now the center driving nut is left handed, so to make things simpler, I got a left handed rod.

Since I have a lathe, I decided to turn down the end of the rod. I have also turned a small collar to go on the rod. Since I don't like the holding pin Proxxon originally used, I decided to use a die to thread the end that I have just turned down, and to hold the collar in place with a small nut. This has proven to be a bad idea (which I plan to fix later with a different design). As one can see from the picture here. The rod is made with soft steel, which is very difficult to machine. So the thread I made on it looks terrible. Further more, I found that the holding nut will get loosen after some time. But for now, that has to be it. I will have to make it work so I can use it. Proper solution sometimes is a luxury a home shop could not have.

So after measuring the sizes, I got the CNC to cut a part for itself. (A machine that can be used to build itself - sounds like a neat line) Anyway, I made the pieces with some 1/8 inch ABS plastic I have laying around. ABS is just strong enough for a temporary piece, and if my measurement is off I can make things fit with a utility knife (as shown in the picture above).

In another picture, the moving part of the compound table is sliding beyond the end plate of the Y axis. After everything is assembled together, I got to measure the travel of my new Y axis. It is now a whooping 100mm (just under 4 inches). Now I can finally cut pieces that are wider than 2 inches.

Here is how the new extended Y axis look like now. I will come back to fix the rod with a better design and remake the end plate in aluminum. But for now, it works.

Homemade CNC2 (Y axis)

After finishing the X axis, I started to get on the Y axis. After all, what can I do when I have a one axis CNC?

The pieces for the Y axis is very similar to the X axis. Here is a picture of the original parts. The Y axis of the HF70 milling machine tables has notoriously short travel. People are coming up with various ideas to extend the travel of the Y axis (such as Retromaster and this one). I plan to do one of these at a later time, but for now, I need to push forward to finish the conversion so I can have a working machine.

So the conversion is very similar to what is done on the X axis. Same cylinder shaped piece is replacing the handle. The plastic piece is removed leaving the steel piece in place. When it is done, it looks like this in the picture below.

Next comes the stepper motor. This is much easier than the X axis, as the Y axis is sitting on the base. All I need to do here is to mount the motor somewhere with the right height.

So out come my saw and a measured cut on a wood piece. Here it is, the stepper motor is sitting on its place, connected to the end of the rod with a rotation coupler.

Here is now the completed Y axis look like. Next comes a lot of fun time calibrating the system and making test cuts. I have some left over electronics from my last 3D printer build. So it is easy and quick to get the stepper motors hooked up. And here I have a completed homemade CNC from cheap parts I can get.

Homemade CNC2 (X axis)

After a long break from this project, I am back to continue working on it. Now it is time to convert the compound sliding table to be controlled by stepper motors.

For the compound table, I used one that is the same as used as MF70. I got it for $90 on Amazon (see my previous post). There are a few articles on Internet that discussed the conversion of MF70 milling machine to CNC. They gave me inspiration and ideas.

• http://www.thebox.myzen.co.uk/Hardware/CNC_Conversion.html
• http://retromaster.wordpress.com/mf70-cnc/
• http://www.jarkman.co.uk/catalog/cnc/mf70.htm

The first axis I worked on is the X axis. The disassembly is simple. The only place that is a little tricky is to remove the pin that holds the handle to the end of the threaded rod. I used a small drill bit to punched it out.

The parts looked simple enough. Basically, I just need to make a stepper motor mount and extend it so it is attached to the end of the sliding table. At the end of the sliding table, there originally is a steel piece hold inside a (black) plastic piece. The threaded rod is turned down at the end, and fitted with a sleeve bushing which rides on the steel piece. I decided that the plastic piece is not needed, as long as I keep the steel piece in place. I may want to convert that into a ball bearing later but for now that is good enough.


I have made a small piece on my newly acquired Craftsman 109 lathe. Even though it is a beaten up old lathe from half a century ago, I found that lathe and milling machine are tremendously helpful and complementing each other when making parts. The piece I made was the small cylinder shaped piece at the lower right corner of the picture. It is drilled so the pin can hold it to the end of the rod just like it was for the handle. The coupler then connects the stepper motor to the rod.

Here is a picture when the pieces are put together and assembled on the sliding table. The rotation coupler is not installed. The cylinder piece is pined to the rod, with the sleeve and a washer act as the bearing surface between the rod and the steel piece when the axis is rotated by the stepper motor.

I used this chance to check for alignment and makes sure everything is in place. As one can see, the stepper motor is not perfectly aligned so I spent some time to get that straightened up.

Another thing I do differently here is that I used a two piece aluminum angles to make a U-channel shaped extender. I saw people on the Internet who used U-channels there. I was about to do that originally. But after some thought, I figured that this two piece is a lot easier to assemble onto the sliding table, as you can see the screws holding the steel piece (which holds the extender onto the table) is a bit hard to install if this was a U-channel. On top of that, I don't have a U-channel at hand, but do have these angles.

So finally, here is my X axis, converted to CNC.

Homemade CNC2 (Frame)

After the Z head is ready, I needed to make a frame to hold everything together. Since wood is the easiest material to work with, I put together a quick frame.

It is nothing fancy, just for everything to be put together. And with the Z head and X-Y compound sliding table mounted, the CNC is taking shape.

I did need to put some wood blocks underneath the compound table to get it to the right height. With a little controller I have left previously, I was able to move the Z axial up and down. It is quite a bit tight as one would expect from the imprecise wood construction. But we can improve on that later.

Here is how it is like after a first test cut on a plastic block. I have then used it in the rebuilding of the little Craftsman 109 Lathe.

Craftsman 109 Lathe - Spindle

It seems is a well known fact that Craftsman 109 has a weak spindle. The spindle is just over 1/2 inch in diameter (0.550"), and is easily bent. On the lathe I bought, with its age, I'd have to assume that it is bent. So when I have it stripped into parts, I took the opportunity to measure it.

I googled and it seems that people are checking the spindle with dial indicators. I have one which I recently bought, but I don't have a holder. Since the dial indicator does not need much force to hold it in place, I just put it on top of a few boxes and blocks and it worked fine.

It is off. So I marked it, took it off the headstock, and whacked it with a hammer. After a few tries, I have finally get it close enough, and on it goes.

Here is the test cut after straightening the spindle. On the left was the best I can get before rebuilding, and on the right is with the newly straighten spindle. It really looks much better.

The advantage of having a weak spindle is that it can be corrected really easily if needed.

Craftsman 109 Lathe - Setup

I have been thinking about getting a lathe for a while. When I was building my 3D printers and CNCs, there is constantly needs to make some parts. Some of the reasons are for lower the cost compared to buying from stores. Some of the reasons are just that the parts needed is not available commercially, and needed to be custom made.

So I finally saw this lathe on Craigslist listed for $160. It is for a Craftsman 109 lathe. I knew nothing about that lathe at the time. After some quick reading, I found that this was a really popular hobbyist's lathe in early part of last century. After a quick negotiation, I got it for $140, and went on to pick it up.

A lot of information on this lathe can be found on Internet. The lathe I have has a model number 109.20630. According to the website, it was on sale on 1945. That puts it at almost 70 years old now.

The guy who sold it to me was kind enough to show me how it works. Before that point, I have never operated a lathe. So all is very exciting. I took it home. Of course the first thing I did is promptly strip it into pieces. This model of lathe comes with thread cutting gears. The last owner has never put it up, so they are all in a tin box. After some study, I found that it is missing a few gears. And a search found that Craftsman 109 (sometimes called AA 109 for Ann Arbor who made it for Sears) is a very popular vintage lathe. Parts are are readily available on eBay and also available in the Home Shop Supply (a shop specializes in Craftsman 109 parts), but quite expensive if to get it complete. Oh well, I will figure out a way later.

The other minor issue with it is that it comes with a 3" chuck with only outside jaws. With a call to the last owner, I was told that that's all he has. Fortunately, there is the Little Machine Shop, which sales all the stuff a home machinist will need. $33 plus tax and shipping gets me a set of inside jaws that works with the chuck. It is not arrived yet when the picture below was taken.

This is how the lathe looks like when everything is put back together, spindle straightened, and everything tightened. It is really not too bad for a piece of 70-year-old machine.

Homemade CNC2 (Z Head)

The first thing I built for the CNC is the Z head. As a starting point , I went to Ebay and got a cheap linear slider for $20. It is the black metal slider you see in the picture below. It is made by DI, and has a travel range of a bit over 2 inches (which is sufficient for a CNC). I also plan to use the tool holder I have left from my ShapeOko after I have converted it into a 3D printer.

I have been thinking about different materials for the base board. Aluminum is definitely an options. But after some consideration, I decided to use wood. It is very easy to cut and shape, and has great strength weight ratio. It is cheap and easy to acquire too. The only downside of it is that the bulk of the size needed to reach the strength needed. But that is an acceptable trade-off for this build, as I can always replace them later. So here is the top plate of my Z head, with holes drilled for mounting.

These are assembled together as below, with a 300W spindle (which I also got from Ebay) mounted on the tool holder.

Next, we need put together the linear drive. For the Z-axis, I used a simple threaded rod going through a HWPE block. The HWPE block is a low friction plastic and is used here to achieve low backlash linear drive. It is a very simple setup. The threaded rod is hold with flanged bushing that fits into the wood blocks. The bushing is made of bronze with built-in lubrication. Two nylon insert lock nuts are used on each end as the holding points (which rides on the flange of the bushing). The stepper motor mount is made with an angle aluminum with a few drilled holes. Again, the coupler is purchased from Ebay.

Here is how everything are put together. A few more nuts are added for mounting the Z-Head plate to the Z post.