Introduction

I love to build stuff using manual and power tools. I’ve not moved up to 3D printing yet, so I still tend to use materials like wood, metals and sheet plastic, hand-marked and cut. For small items, handheld rotary tools are extremely useful, and I’ve been meaning to upgrade my aging tools for quite a while. Two of the major brands are Proxxon and Dremel, and the Proxxon ones are lower cost in Europe. I decided to purchase a couple of Proxxon rotary tools, and this blog post documents my findings, and explores their usage for drilling, milling, cutting and polishing operations.

Why Proxxon?

The Proxxon tools are quite a bit lower cost than Dremel here in the UK, so the temptation was strong to purchase a couple of Proxxon tools instead of a single Dremel. I had encountered Proxxon tools before; at a couple of work labs there are Proxxon table saws. I purchased a Proxxon sander a while back, and it functions well.

In the past, I’ve used the Bohler Minitool system a lot. The system uses a 12V mains transformer and various tools like drills and table saws can plug into it.

The particular Bohler Minitool drill shown here is not like the Proxxon or Dremel tools, because it has internal gearing and the top speed is low. This tool is ideal for slow speed drilling into wood and plastics, and the chuck accommodates up to 6mm diameter drill bits. It is getting hard to find Bohler Minitool products at any reasonable prices in the UK. The Proxxon and Dremel tools run at higher speeds, and for many use-cases the high speed is quite important.

So, all things considered, I decided to try the Proxxon rotary tools for now.

Proxxon Rotary Tools Range

Some of the tools are powered directly from the mains, and others operate from a mains to 12V transformer much like the Bohler Minitool transformer shown above.

In the 12V category, there are two main series; the Micromot 50Micromot 50 series and the FBS 12 series. The products in the range can have suffixes like E, and EF. The E indicates that there is a variable speed control dial on the product. The F indicates that a chuck is supplied fitted to the tool. Collets are available to purchase too, so you don’t lose out on that upgrade capability if the chuck version is initially purchased. The Micromot 50 is lower power (40W) and is lightweight and thin. The FBS 12 is more powerful (100W) but is larger. In the directly mains powered range, there is the FBS 115 and FBS 240FBS 240 series that otherwise looks identical in specification to the FBS 12. Finally there is the IBS series, which is the more precision tool because it has a (partially) aluminium body. All the others have plastic bodies.

For the 12V supplies, there are three different mains transformers available. The largest one offers up to 5A current, and the two smaller ones (NG 2NG 2 series) offer 2A.

I tried two rotary tools; the Micromot 50/EFMicromot 50/EF and the FBS 12/EF, both with built-in speed controls. I used the NG 2/E mains transformer which offers 2A capability and has a built-in speed control.

Micromot 50/EF Overview

The tool has an interesting design, it has a long thin neck up to the drill chuck, making it possible to hold like a pen. The body is made of plastic and it feels rigid. The speed control is at the rear, and it doubles as the power switch too when turned to the minimum position and clicked into the off position. This is annoying, I’d have preferred a separate switch which the Micromot 50 (non-E version) offers.

Another strange feature is the chuck ‘key’; it is integrated into the neck of the tool, as a small metal plunger. Other rotary tools often have a hole for inserting a metal rod (or the shaft end of a drill bit if the metal rod is lost) temporarily while the chuck is loosened/tightened. The integrated plunger has the benefit that it won’t get lost, but it is in an awkward position where you might want to hold the tool. I’m in two minds about it, but overall, I think I prefer the traditional hole method. I can see that others may prefer the integrated plunger method however.

A couple of nice features relate to the collar, and the tool end. The collar of the tool is metal (likely steel; it is magnetic) and it allows for clamping the tool for certain operations if desired. There are attachments available (such as a drill stand) or a custom one could be fashioned. The other nice feature is that the chuck head can be unscrewed and replaced with colletscollets. This is great for PCB drilling or other operations where precision is needed. Collets grip the bits better and higher chance of them being fully centered. A set of collets can be purchased at low cost. The chuck head is unscrewed as if a drill bit is about to be removed, but by continuing to unscrew, the chuck head comes off the threaded shaft. The threaded shaft is hollow and has a slight internal taper, designed for the collet to be inserted inside the shaft.

I also really liked that it had an integrated speed control dial, marked with speeds, and fully variable. With the Dremel tools, that option is only on the 4000 series4000 series and above, which is more than double the cost of the Micromot 50. As mentioned earlier I just didn’t like that the Micromot 50/EF has the integrated switch at the lowest dial setting; I’d rather have a separate on/off power switch.

Still, the Micromot 50/EF is really compact and slender; there likely isn’t a lot of space to fit a switch.

Although I didn’t open it, it was possible to find a photo online at the reprap.org website showing the insides; a shaft bearing is visible at the end of the neck of the tool:

FBS 12/EF Overview

The FBS range is incredibly compact too. It is about the same length as the Micromot 50 series, but a bit fatter. It can still be held in a nearly pen-like form and there is a soft grip area to do so. With both tools (and especially the Micromot 50), the figertips can be just a few centimetres away from the work surface, particularly if collets are used instead of the chuck. The FBS range has similarities with the Micromot 50, such as the integrated plunger for unscrewing the chuck or collets, and the rotary speed control (although it only goes up to 15,000 RPM for the FBS series).

The major difference is the power. The difference is very noticeable (more on that later). I also really liked that the FBS models have a separate power switch, not integrated into the speed dial. The build quality is excellent, and the tool made reassuring noises even at top speed. Nothing screamed or resonated at the high speeds.

For a more detailed photo of the insides of the mains-powered version online, see this website (the photo is taken from there, but is reduced in quality).

NG 2/E Mains Transformer Power Supply

The mains transformer/power supply has a single output (I’d initially thought it had a couple of outputs; had I known, I would have purchased the larger NG 5/E model. The attached mains cable is a good length; 1.8m.

The tools use a connector that has (approximately) 2mm diameter pins. In fact 2mm banana plugs can fit into the power supply, although it isn't intended for it.

The power supply looks fairly sturdy, although the rotary speed control on it feels a bit toy-like. From my perspective I would really have liked to see a power button on it. There isn’t one, and so the only way of fully powering it off is at the mains connection : (

I took it apart (there is one triangular security screw) to see if there was space to fit a switch, but it is tight; I didn’t have any mains switch that would even come close to fitting. Anyway, internally the construction looks good. There is some protection with a varistor on the input mains side. There isn’t much to go wrong here! Perhaps the open trimmers may need replacing one day, but this would be a minor operation. It all looks very serviceable.

The output of the supply is a rectified but not filtered output. This is deliberate, so that the speed control can be silicon controlled rectifier (SCR) switched per rectified ‘hump’ in the waveform.

At max power (setting ‘5’ on the rotary control) the output looks like this; the output is about 17V RMS:

As the control is reduced, the SCR removes part of the waveform, until at the minimum setting it looks like the white shape in the trace here (it is about 14V RMS). At an intermediate setting of ‘4’, the red waveform is visible.

With the rotary tool connected and running at full speed in free air, the output amplitude drops slightly, but not much (and some electrical motor noise is of course generated).

The top end transformer model is the NG 5/E, and with hindsight I would have purchased that, because it allows for several (three) tools to be left connected to it, offers more power, and has a built-in mains switch.

Checking the Speed

The Micromot 50/EF speed control dial is marked in RPM, and it was surprisingly accurate when checked with an RPM meter. Most of the dial covers a useful speed range of 5000-10000 RPM, and then it gets more cramped at the top end to the 20,000 RPM marking.

With the power supply control set to maximum, the speed compared to the dial position was accurate to within about 200 RPM across the 5000-10000 RPM range, which is excellent. The top speed was around 24,000 RPM although the dial was marked 20,000 RPM. With a load the speed would decrease of course.

With the power supply control set to the minimum speed, then measured rotation speed was about 2000 RPM less than the dial marking, up to about 10,000 RPM, and then the measured speed was about 4000 RPM less.

In summary, the speed marked on the tool is fairly accurate up to 10,000 RPM, and beyond that the dial is quite cramped so it would be difficult to be sure, but the maximum unloaded speed is about 24,000 RPM.

The FBS 12/EF has a lower top speed of 15,000 RPM but it gets there gracefully. On the other hand the Micromot 50/EF does not make pleasant sounds at its top speed. There is some vibration at speeds beyond 15,000 RPM, and the bearing around the shaft may be contributing to the noise too.

Drilling: What Speed to Use?

There are plenty of online resources on drill speeds for various materials, although the numbers vary from site to site, and many of the sites specify speeds in imperial measurements in surface feet per minute (SFM). I took the information from a website PDF document and metric-ized it into a chart. It can be seen that for the drill sizes that can fit in the Proxxon rotary tool (around 3mm and smaller), the tool would be fine for a variety of materials.

To use the chart, choose the curve that matches the material, then look up the desired drill hole diameter on the x-axis, and then at the intersection you can read off the guideline speed on the y-axis. The chart is also attached to this blog post as a high-res PDF file; I used that to stick the chart on the wall. The chart is for optimum conditions, so in practice the value should be halved.

For PCB drilling, the plastics/composites curve can be used. Also usually a drill press is needed because otherwise there is high risk of drill bits snapping (wear safety glasses! – I literally have half a dozen of them littered around the workshop, for myself and anyone else present).

When it comes to feed (plunge) rates into the material, as a rough guideline, for drill bits 3mm or less, with the drill bit running at speeds indicated in the chart above, a rate of about 3mm per second is adequate for most of the materials, but can be reduced to around 2mm per second for tool/die steel, and increased to 4mm per second for plastics, and 16mm per second for aluminium alloys and magnesium alloys. These are under ideal conditions (sharp tool, best coolant, etc), so the figures should be halved. But, if the drill speeds are halved as suggested above, then a quarter of these feed (plunge) rates should be used. The information is based on guidelines from this PDF document.

Milling: What Feed to Use?

Although I don’t currently have an intention to do so, in theory the rotary tools can be used for routing/milling operations too. These are operations where the spinning tool can cut a shape into the material. It is an advanced machining task, and care is needed not to plunge the tool too deeply into the material, move the material or the spinning tool in the correct direction, at an appropriate linear rate for the given tool rotational speed, diameter and material type, and supply adequate coolant. For milling a stand is needed and a way to move the tool or the workpiece. For routing by hand, again some stand or jig is usually needed. There is a very high risk of milling bits snapping, inadequately clamped material and clamps flying, and bits of clothing or skin being chewed up.

All that aside, there is the question of what linear rate the material should be moving relative to the tool. It is known as the feed rate, and there are tables that can specify it in inches per minute and so on. There are software applications that are usually used to work it out. These are intended for automated machinery usually, but the rotary tool user needs to know this information too. Often the tables do not have the information for the very small tool diameters that the rotary tools use. Based on various bits of information (in particular harveytool.com and the previously mentioned PDF document and mmsonline.com), the chart below was constructed as a guideline. To use it, first ensure that the speed in RPM is correctly selected from the earlier chart above. Then, look up the same tool diameter on the x-axis in the table below, examine the line intersection to see the feed speed on the y-axis in mm per second. If the speed in RPM is halved as discussed earlier, then the result from the chart below needs to be halved too. The chart is for milling tools with four cutting flutes (sharp edges). If the tool you’re using has two flutes, then the feed rate needs to be halved yet again. Two flutes are great for certain materials and tool sizes.

You don’t want to go overly slow, because it will just overheat the material and cause a rough finish. But don’t go too fast either, it can cause damage to the tool or the material, or the user!

Regarding milling depth, usually half of the tool diameter is feasible, and reduced for the harder materials, but for small diameter bits (3mm or less) then the depth of cut should be reduced further, to prevent the tool snapping. 10% of the diameter could be used as a guideline for bits less than 3mm in diameter.

Please note these are all just approximate guidelines, and a lot depends on the specifics of the setup. It goes without saying that the information here is just informational, and newcomers to milling operations should study in depth using material elsewhere; this is just a short blog post and not a complete guide.

Cutting Operations

As well as drilling operations, it is possible to use rotary tools for cutting. I had some Dremel accessories, in particular some cutting wheelscutting wheels. They require a high speed to function, so I was looking forward to using the Micromot 50/EF with them. Dremel has the nice ‘EZ SpeedClicEZ SpeedClic’ system, which does away with the screw-and-mandrel and replaces it with a single unique mandrel with a springy end that allows the cutting wheel to be pushed on and turned until it clicks and locks into position. The system is very good but isn’t totally perfect, you can see that the cutting wheel on the right has had its center dislodged.

The Micromot 50/EF worked very well with the 0.75mm thick Dremel cutting wheels. I used it to cut a 6mm diameter brass shaft of a potentiometer:

The Micromot 50/EF and cutting wheel also worked very well cutting steel screws; it also makes a nice light show.

The tool was very competent cutting such items.

The cutting wheel that I was using is not designed for plastic, however I did try slicing through some 3mm thick plastic with it. The Micromot 50/EF struggled, the drop in speed was noticeable as the cutting wheel went deep into the plastic. In contrast, the FBS 12/EF had no issue at all.

Polishing

Polishing often requires high speeds that are not possible with typical cordless drills. I had a Dremel polishing accessories setDremel polishing accessories set, and I decided to try out the polishing wheel. The Dremel set came with some polishing compound in a tiny pot, but I lost that a long time ago. It is cheaper to just buy a polishing compound block intended for large polishing machines, than the small pots from Dremel. It comes in varieties for ferrous or non-ferrous metals, and in several grades for working up to a mirror finish.

The compound is applied to the wheel as it spins, and then the wheel is slowly moved in straight motions across the item to be polished. I decided to test the Micromot 50/EF on a stamped metal (aluminium) container that had a dull surface finish. The speed was set to about 10,000 RPM.

It worked really well. The photo shows just half of the aluminium container polished, and the difference is clear.

The finish was very mirror-like (reflections were visible).

Summary

This was intended to be just a short review, but it turned out there is a lot to cover when evaluating such tools! The tools are constructed well, and their potential use for drilling, milling, cutting and polishing operations was explored.

I like both the Micromot 50/EF and the FBS 12/EF, and I will use them for different purposes. The Micromot 50/EF is very lightweight and has plenty of power for most tasks. However, the FBS 12/EF is clearly the tool to use whenever cutting substantial material, or when using certain attachments such as grinding wheels. I liked that both tools have a rotary speed control with markings, so that I can look up the ideal speeds on charts for different materials.

If I was to purchase again, I would probably go for the NG 5/EF or the NG 2/S mains transformers, because I didn’t really need the adjustable speed control on the NG 2/E model. The NG 5/EF is the one to really get, because it has a mains power switch built-in.

Attachments:

	drill-speed-guideline.pdf
	milling-feed-guideline.pdf