Make your own ultra-low-cost bench drill for less than 60 yuan

Production process address: https://www.bilibili.com/video/BV1Qa411D7er?share_source=copy_web

Because it is the first generation, many problems were discovered during actual use. The following is an explanation, and you can modify it according to the actual situation:

1: Bottom plate

The counterweight of the bottom plate is not enough, and the strength is also a bit insufficient. If you use force, your head will fall down. The solution is to increase the thickness again.

Quoting a friend from ngHackerX86 in the comment area of ​​Bilibili : "It's outrageous. The next step is to directly use PCB as desktop CNC (when combining multiple layers, open some metallized holes and then fill them with tin. Maybe it can increase the strength?) "

Personally, I think this suggestion is very good. Without affecting the placement of punched parts, you can open more holes on the base plate and fill them with tin to combine the multi-layer boards. Or if you have a welding tool, you can solder the edges after filling the tin.

2: compression spring

The choice of compression spring is really important. The diameter of the compression spring in the video is 1mm, or a little thicker. I don’t know the material, but it really takes a lot of force to press it.
Later, I replaced a 0.8mm×12 compression spring, but it couldn't bear the weight of the motor area. It wasn't until I overlapped three compression springs and installed them that the strength was just right.
But the 50mm length is too short. I personally think 60mm is better.

The optical axis is 8MM, maybe 1MM×10×60mm would be better? I'm not sure about this, and I'm looking forward to everyone's feedback.

Compression spring calculation method:

Thick 1mm, optical axis 8mm. If it can be put on, you should choose a compression spring with an outer diameter of 10mm, 1mm×2+8mm, but I personally recommend buying one with a slightly larger outer diameter, unless you want the spring to get stuck. Focusing on the optical axis?

3: Shake

A single optical axis will not work. No matter how tight the screws are, as long as the deceleration layer is pushed by hand, it will deflect.
You can add a SHF8mm fixing base to the bottom plate, and buy a longer optical axis in the middle to form a dual optical axis fixation, so this problem will not occur.
Or triangular △ fixed, this kind can also use a 12mm optical axis or thicker at the back, and an 8mm or other at the front, but in fact, dual optical axes are enough.

I thought I had thought it through in the first draft, but it was not until I discovered various problems during use that it really gave me a headache.

4: Linear bearing

A friend of amarantinea in the comment area of ​​Station B pointed out this problem: "Linear bearings seem not suitable for use in rotational motion and are easy to break. The one on the chuck is more dangerous..."

At that time, it was because I had extra linear bearings at home, and there were so many parts that it took too much brain power to drill holes based on the dimensional drawings, so I didn’t even think about this issue.
solution:

Can be replaced with KFL08 mounted bearing.
Those who have money can replace it with BGRBB flange, which costs more than ten yuan each.

The main function of this component is to ensure concentricity. After all, a 12mm hole is opened in the board to place a bearing. The drill bit must not wobble.
The reason why the bearing is placed is because the area around the hole in the aluminum base plate is not that smooth. If the bearing is not placed, the sound will probably be explosive, not to mention the concentricity.

Of course, it is possible not to use this component, but as for the concentricity...it's hard to say.

5: Pressure lever

I use a right-angle corner code for the pressure rod.

But the right-angle corner code in the video doesn't work. The position of the board opening is too strict. I changed parts and changed several holes before I could install it. I strongly recommend buying adjustable corner codes.
Keywords: Stainless steel corner code with adjustable long hole
length is recommended to buy 245mm or more. In actual use, 245mm is still a bit short.

6: pwm speed regulator

I used this thing once on another bench drill. The reason was that the drill bit got stuck when drilling something. Then this thing became useless. You can buy a 12-40V 10A speed regulator for six yuan more.

Keywords: stepless speed control switch.
Or other speed regulators with high passing current.

XM109_Suggestion from a friend in the comment area of ​​Bilibili : "It's best not to buy 10a, buy a bigger one. Last time I bought a 10a and after using it a few times, I couldn't adjust it. I suspected it was burned. The power supply is 24v10a."

Whether to buy one with 10A or more depends on personal needs. I usually only drill wood or plastic parts, so 5A can actually satisfy me. If it is drilling metal parts, it is recommended that the higher the current, the better.

Another Mo Yufeng friend pointed out the problem: "The reverse current when the motor starts and stops is quite large, right? Can it withstand it? If not, get a diode and capacitor to limit the current."

It's the same reason as before. The dimensional drawing is too big for people's heads. I didn't consider this issue during production. If you need it, you can open a slot on the original board and place the current limiting plate.

I haven't considered the issue of the current limiting plate, so I need reference materials to make this thing, but I don't have the time to fiddle with it. I hope my friends can draw it by themselves and let me have a free time?

7: Bottom feet

The one I use is fixed with a nut, and it will protrude. You can use a tapping tool to solve this problem. The same goes for the nut under the 60-tooth synchronization wheel.
The linear bearing is fixed under the synchronizing wheel. I used a nut at the beginning, but after the motor started to rotate, the synchronizing wheel would rub against the nut, and the sound was terrible.
Later, I used a 3mm double-pass copper pillar and smashed it in, and the surface was quite smooth.
If possible, tapping would be better, but I don’t haha

This question can actually be linked to question 4.

Because of the size of the linear bearing, the four screw holes opened are just under the synchronizing wheel, so there will be abnormal noise.

But using the KFL08 mounted bearing, I looked at the parameters. The distance between the two holes is 48mm, and the diameter of the 60-tooth synchronization wheel is 38mm, which can be fixed by nuts.

As for the BGRBB flange round bearing seat, I saw that the hole spacing is 35. Although it is very expensive, the KFL08 mounted bearing is better in terms of fixing method.

Which one you choose depends on the individual.

At the end of editing, I suddenly thought that the feet are just for anti-slip, so... wouldn't self-adhesive anti-slip gaskets be better?

8: Motor

At that time, I had a headache looking at the dimensional drawings of the parts, and then I didn’t look at the drawings of the motor so carefully, so a hole for the bearing was opened in the motor, but the hole had to be very large, and the protruding head of the motor had to be inserted. board, so that the motor shaft can come out longer.
In actual use, I found that the motor shaft does not need to use 5mm bearings at all, it is completely useless.

8.1: Because if a large hole is made in the board, the bearing cannot be installed.

Of course, you can make another set of boards. The lower layers are large-hole plates, and the upper layer is small-hole plates, and the bearings can be put in.

8.2: Just like in my case, if you open a small hole and put the bearing in, the synchronizing wheel cannot be fixed, and the exposed shaft is too short.

8.3: Even if you follow 8.1, even if the bearing is put in, it is actually of no use. After all, it is not to ensure the concentricity of the motor, but to ensure the concentricity of the drill bit.

It doesn't matter what the concentricity of the small synchronization wheel is, the motor just plays a transmission role.