It has been a while since we started this project and it’s time to make some chips. In this instalment, we’ll go over spindle hookup.
What is a CNC Spindle?
A spindle is the rotation portion of a CNC machine on to which a cutting tool is attached. While technically the spindle is the shaft itself, it has become common place to refer to the motor and shaft assembly as the spindle.
There are many shapes and sizes of spindles. First, let’s look at low speed and high speed spindles.
Low Speed Spindles
Low speed spindles are used primarily in machines that need to do milling operations on metal. They are needed when drilling larger holes may be required or for turning very large tools.
Milling machines like the one shown in here, use a low speed spindle. This spindle will run at an RPM range of 500-2500 RPM. Since most motors don’t run slowly enough, a belt or gear reduction is used to slow down the spindle shaft in most cases. Needless to say, we won’t be using a low speed spindle on the KReduCNC.
High Speed Spindles
Most CNC machines designed to mill wood, plastic, and some non-ferrous metals, use a high speed spindle. While there are several types of high speed spindles, I will be talking about two types, routers and rotary tools.
Router spindles can be broken down into full size routers and trim routers. The routers shown in Figures 2 and 3 are full sized routers. Due to the weight and size of these routers, they are used on larger CNC machines. These are both 2-1/4 HP routers. They have plenty of power for most operations, and work well for cutting wood, plastics, and aluminum. Full sized routers can handle tool shanks from 1/4" to 1/2” and with adapters or special collets, down to 1/8”
The routers shown in Figures 4 and 5, are trim routers. Most trim routers work just like their larger counterparts, but are smaller and produce less horse power. These routers are just under 1HP. Trim routers are common on many small to medium CNC machines. Most can handle tool shanks of 1/4" or 1/8” with and adapter.
There are dozens of rotary tools of all shapes and sizes. Most of these were meant to be held in your hand and used to engrave, cut, grind, and drill various materials. Unlike routers they are not meant for the larger tasks that routers can handle.
Two rotary tools that represent most rotary tools you will find a most home centers or hobby shops can be seen here. While they are well suited for hand held use, they are not suited for CNC use. They have slop in the bearings and tend to have too much runout to get an accurate cut.
There are tools that fall into the rotary tool category but are better suited to CNC use. Lets talk about three of them.
The first is the Wecheer WE248, shown in Figure 7. This is the first rotary tool I attached to the KReduCNC that produced results that were accurate and repeatable. The tool has no slop and very little runout. It’s powered with an included AC adapter and proved to be very easy to make a spindle mount, as shown in Figure 8.
I used this rotary tool and while I was able to cut softer materials, I found it to be under powered. It also has an auto shutoff if it senses too much load. I did find it worked very well for PCB work.
After playing with the WE248 for about a week, I realized I was not pushing the KReduCNC as much as I could. It was time to look for a better suited spindle. I could probably get a trim router to work, but I would have to slow down the Z-axis due to the weight.
Having good luck with Proxxon products, I selected the rotary tool shown in Figure 9. It’s the Proxxon Micromot 50/E. It has much more power than the Wecheer, and I was able to cut deeper and faster. It’s size also made it very easy to mount on the KReduCNC, as shown in Figure 10.
The 50/E worked much better than the WE248, but I still had the following issues:
- It requires a special 12V power source. While I was able to make one, it does add some complexity to the build.
- The speed control can bog down, as it has no feedback control. It can also shut down if pushed too hard.
- I still wasn’t pushing the KReduCNC hard enough.
While doing my research, I also came across the Proxxon Micromot IBS/E shown in Figure 11. This is a rotary tool that costs almost as much as a full-sized router, so I was reluctant to take the plunge. Then, while cutting some softer material the 50/E stalled out when it cut though the stock and hit the waster board. I ordered the Micromot IBS/E.
Despite the $130 price tag, the IBS/E (Figure 11) is a remarkable tool. It boasts a 1/8 HP motor, which is plenty for the KReduCNC. It is designed for continuous use and has a full electronic speed control with feedback. Its speed range is 5000-20000 RPM. I can honestly say it’s the smoothest rotary tool I have ever used. The motor in the IBS/E is the same used on the Proxxon MF70 (Figure 12) used in the CNC conversion I did a while back.
Mounting the IBS/E
To attach the IBS/E, you will need the following components.
- IBS/E back plate
- IBS/E upper mount clamp
- IBS/E lower mount clamp
To attach the IBS/E, you will need the items shown in Figure 13.
In addition you will need the following hardware.
- 4, #6-32 x 1-1/2" machine screws
- 2, #6-32 x 2" machine screws
- 2, #6-32 x 1" machine screws
- 8, #6-32 hex nuts
- 8, #6 washers
- 8, #6 internal tooth lock washers
Please note that I am using hex nuts with integrated washers. I find that these work better for me than separate hex nuts and lock washers.
In addition to the hardware above, you will need the following components to make the IBS/E mount.
Insert a washer onto each of the #6-32 x 1” machine screws, and slip it into each of the mount clamps, as shown in Figure 14. Secure both screws with a #6-32 hex nut and lock washer, as shown in Figure 15. Do not tighten the nuts, as you won’t be able to install the spindle later if you do.
Attach the lower mount clamp to the back plate using 2, #6-32 x 1-1/2” machine screws. Add a washer to the screw then insert into the front of the lower mount and through the holes in the back plate, as shown in Figure 16. Secure with a #6 lock washer and #6-32 hex nut, as shown in Figure 17. Finger tighten only, as you will need to adjust the mount after the ISB/E is installed.
Using two #6-32 x 1-1/2” machines screws with #6 washers, attach the back plate to the Z-plate, as shown here. Secure with two #6-32 hex nuts and lock washers. Finger tighten only.
Place a #6 washer on each of two #6-32 x 2” machine screws. Insert into the front of the upper mount clamp and through the top holes on the back plate, as here. Secure with two #6-32 hex nuts and lock washers. Finger tighten only.
Insert a 1/8” calibration blank into the IBS/E as shown in Figure 20. You may also use one of the small bits included with the IBS/E kit.
Insert the ISB/E into the mounts, as shown in Figure 21. The mount was designed to hold the ISB/E with the front (knob) of the tool facing right or left as shown. This will allow you to access to both the spindle lock and the speed knob.
Tighten the spindle clamping nuts (1” machine screws in front) on both mount clamps. Tighten the nuts holding the lower mount clamp in place.
Place a small square on the table and move the spindle until the bit is up against the square, as shown here. If the bit is not fully against the edge of square, twist the whole spindle mount assembly clockwise or counter clockwise until it is.
Tighten the upper mount clamp nuts (Step 4) and the lower back plate nuts (Step 3).
Move the X-axis to the left and place the square against the bit as shown in Figure 23. Check to see if the square is flat against the bit. Move the X-axis to the right and place the square against the bit as shown in Figure 24.
If the square does not mate with the length of the bit, you may need to adjust the upper shaft forward or backward to correct the mating issue. Adjust one side, then the other as needed. Once adjusted repeat this step until the square is flush with the bit on both sides of the CNC.
This completes the spindle hookup. I will post the drawing files for the IBS/E spindle mount on my support page for the KReduCNC. I will also post the drawing files for the Wecheer WE248.
There are other spindle options that I have used with success on the KReduCNC. Here, the spindle from a Foredom flex shaft. Since the heavy motor is mounted at the other end of a flex shaft, you have a great deal of cutting power at your disposal. It will accept 1/8” and 1/4" bits. While it uses the same mount as the Wecheer WE248, the one shown in Figure 26 is a version that has a dust shoe that connects to a vacuum.
I wrapped all my wires, cables, and cords with some split loom tubing shown in Figure 27. This protects the wires and cables and gives your machine a better look.
Split Loom Tubing
I currently have the following spindle mount drawing files available for the KReduCNC. I used 3/8" PVC, but other materials should work as well.
The smaller inner hole is for the upper mount. The larger inner hole is for the lower mount. This mount should also work for the Foredom flex shaft tool. Just make two lower mounts and use one as the upper.
The smaller inner hole is the lower mount. The larger inner hole is the upper mount.