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Dremel Tutorial

Useful information for new users of the Dremel rotary tutorial
Written by Roberto Muscia. Reproduced with permission.

Introduction

Distinguishing Grinding Stones

Diamond Coated Bits

Distinguishing Sanding Disks

Distinguishing Cut-off Wheels

Distinguishing Abrasive and Polishing Bits

Polishing

Distinguishing Brushes

Distinguishing Metal Bits and Cutters

Important Information About Cutter Usage

Engraving

Something About Hardness of Bits

Increase The Life of Your Bits

Other Helpful Tips

Working On Aluminium

Working On Materials That Easily Melt

Cutting Soft Material And Still The Bit Gets Dull

Introduction
I wrote down some helpful info for those who are just starting to use the moto-tool and the bits. I also added some helpful tips that could be useful to more experienced users. I posted this info because users quite frequently do not find the books which came with the tool very helpful to get started. The people who are new to the rotary tool often get lost with the number of different bits that are available nowadays or they just give up using this GREAT versatile tool (actually: there is a versatile collection of bits available) after they do not achieve the expected results after reading the manual and playing around with it for only a short time.

I also would like to take this opportunity to thank those who passed on some recommendations and extra info to me after reading this or a previous version of this tutorial.

Distinguishing Grinding Stones
Grinding stones are available in many shapes, sizes, grits and grades, and in two common materials.

The two available basic (grinding) materials are: Silicon Carbide ("carborundum": green bits - very hard (hardness 9.5) and Aluminum Oxide ("emery"/"korund": brown, orange, pink and grey bits - a bit softer but still very hard (hardness 9)).

Grinding stones are generally used to remove material from hard materials or to engrave in hard materials, like iron, steel, stone, ceramics, glass, etc. There are many shapes available because every person prefers certain shapes for certain jobs. However, grinding stones will wear in time (especially when used at low speeds!) and the bit will loose shape. In order to restore the shape of a grinding stone or to create your own shape there's a simple but VERY HANDY accessory available: the Dressing Stone from Dremel. It's just a small bar of Silicon Carbide.

Hold your rotating (about half speed works fine) grinding stone to the Dressing Stone and simply reshape or clean your grinding stone. Grinding stones should be used at high speeds.

NOTE: Pure powder of aluminum oxide has a bright white color and silicon carbide has a black color. To "color-code" the grit of the grinding stones and to bind the grinding particles together manufacturers use additives to the pure material. The more pure stone has a quality called friability - that is it easily fractures along crystal faces. This causes the grinding particles to maintain their sharpness but it wears quicker. This is because the edges of the exposed crystals wear giving them round edges and on the more pure stones (used to achieve sharper edges on the ground piece) the worn crystal faces flake off exposing the sharp edges. However the darker stones wear more slowly but produce more heat and create a rougher finish.

Diamond Coated Bits
Diamond Coated bits have a thin layer of diamond particles. Cheap diamond coated bits only have a thin layer. The layer is not very saturated with diamond particles and the carrier material and production process is of lower quality. (The diamond particles do not stick onto it and are are not held into it very well). Diamond is extremely hard (hardness 10) and without wearing fast they can be used on almost all materials (materials that easily melt excluded). These bits are available in many shapes and they can be used to remove material or for engraving. These bits work best at medium to high speeds. The diamond-coated wheels often look weird because of their gaps and holes in the wheel. This allows better cooling (and saving diamond coated area to reduce production costs?).

Distinguishing Sanding Disks
Sanding disks are based on "sandpaper" (paper can be replaced by linen), coated with grinding particles and they are available in different grits (=how many sanding particles fit in an area of a fixed size: low grit = course sanding, high grit = fine sanding). The expression "grit" also is used for grinding stones and grinding powder. The grinding particles of sanding disks are made of hard material but there's only a thin layer of sanding material on the disk. So after the layer of sanding material is worn the disk becomes useless. Low quality sanding disks have lower quality grinding material (hardness: emery in stead of carborundum, contains particles of different grit) as well as lower quality glue so that the particles do not stick to the paper or linen as well which causes them to wear faster.

Sanding disks are generally used for shaping soft materials or for finishing or preparation the surface of wood, metal, to remove a coating (e.g. paint), soft stones, etc. Sanding disks, as well as grinding bits are very inefficient "tools" to rapidly remove material since the particles have random shapes and orientation. Cutters are much more effective and fast. However, because of the inefficiency these disks are great for detailed work because the material is removed relatively slowly. Besides, often there are no cutters available for cutting hard materials so grinding bits, wheels, or discs are the only option.

The grit of sanding drums from Dremel can be distinguished visually. Other sanding disks also have numbers on them (80 = 80 grit (coarse), 120 = 120 grit (finer), etc. The numbers on sanding discs are printed on the back of the disks. Sanding disks generally are used at medium to higher speeds.

TIP 1: When using sanding discs it quite often occurs that you need to have the sanding side at the "bottom" of the bit instead of at the top. If you place TWO (one facing up, other facing down) sanding discs on the mandrel, you won't have to turn the disc all the time.

TIP 2: Sanding discs with differing grit are hard to distinguish from each other. You can mark the top of the heads of the screws on the mandrels. The head is "divided" in two by the slot in middle of the head of the screw. To mark the bits just take advantage of these two "redundant" areas:

For making the differences even greater you could color the coarse areas dark with a water resistant marker for example.

Note: The sanding disks available from Dremel are "close coat" whereas there are also "open coat" disks available. Close coat disks have more grit per unit area and are better for harder material and produce a finer finish. The open coat is better for softer material because it clogs less easily due to the sparseness of the grinding material. You can use a soft rubber sheet (like the rubber soles of worn shoes) to unclog clogged sanding disks.

Distinguishing Cut-off Wheels
Cut-off wheels are available in different diameters, thicknesses, and base materials. The two "base materials" are non-reinforced and reinforced. The non-reinforced wheels (brown) are made of solid grinding material (looking at the color I think they are made of emery), they last longer and are pretty fragile. The reinforced wheels (black) are a mix of grinding material (looking at the color, probably made of silicon carbide) and strong fibers which hold everything together. They are less fragile (a bit flexible) and they do not last as long (harder material but a lot of fibers). The very thin cut-off wheels can only be used to cut through materials. The thicker ones also can be used as a "thin" grinding stone for fast grinding. The thinner ones cut faster than the thicker ones. Besides cutting through materials you also can just cut slots. For example the head of a rusted screw. Cut a slot in the head and use a flat screwdriver to remove the screw. All cut-off wheels cut fastest and last longest when used at high (maximum) speeds. The reinforced wheels should not be used on the sides as you would a "grinding stone" or whole layers of fibers will be destroyed.

A special type of cut-off "bit" is the mini-saw attachment. The actual cut-off wheel is a small thin saw blade, made of HSS (high-speed steel). This attachment is very effective for cutting soft materials (that don't melt easily) really FAST, leaving a very smooth cut. Use the mini-saw attachment at higher, or highest speed and make sure the saw blade is cutting all the time. Do not allow the saw blade to rotating against the work piece without doing much cutting. The mini-saw attachment was originally designed to cut wood. However, nothing stops you using it on other materials! For instance It works great on perspex, wire netting, aluminium sheet, copper sheet, etc. Please always check if the saw blades' teeth are pointing in the right direction (also when buying a new completely assembled attachment!). By the way, it is normal for attachments which are based on a flexible core (Flex-Shaft, Mini-Saw, Right Angle, etc) to produce a weird (possible loud) noise but is nothing to worry about.

Distinguishing Abrasive and Polishing Bits
There are Emery Impregnated Polishing Wheels, Emery Impregnated Polishing Points, Abrasive Wheels, Abrasive Points, Abrasive Buffs, etc. All of these bits have a different "grade" of polishing. The results can even vary depending on the material it is used on. The harder the bit is the longer it lasts (first two). More flexible bits (stiff - flexible: Abrasive Wheel, Points, Buffs) are more convenient to use but give different results. Abrasive Wheels and Points are great for de burring, pre-polishing, roughen up a smooth surface (to be painted?). Abrasive Buffs are great for smoothing out irregularities or removing swirls produced by other bits on surfaces. The latter are available in two grits (dark (medium) and sand (coarse) colored). In general it's best to use these bits at medium speeds.

Polishing
There are several felt and cotton wheels and bits available and polishing compound. To put the polishing compound on the bit just run at low speed and push the bit gently in the compound. The compound will melt and the melted compound will flow into the felt/ cotton. If the bit looks equally red you can start polishing the work piece at higher speed. You might need to do several runs of this process in order to finish polishing the whole work piece.

TIP: While polishing some spots of cooled down compound may show up on the sides of the work piece. Run over these spots over and over again until no new spots show up. If the polishing compound seems to have disappeared and the surface looks more shiny then it is time to stop or to get some more polishing compound onto the bit for the next run.

After polishing you can remove the greasy shine with a dry soft cloth. Some weak solvent such as alcohol can be helpful to remove the remaining (grease-based) polishing compound. Polishing works best on low to medium speeds since the soft polishing wheel should be able to adapt its shape to the shape of the surface being polished.

Distinguishing Brushes
Brushes are available in several shapes and materials. Depending on the material to be brushed you can choose from brushes with wires made of e.g. Nylon, Brass, Stainless Steel or Carbon Steel. In this order they vary from soft to hard. To separate Carbon Steel brushes more easily from Stainless Steel brushes Dremel uses a gold colored shaft on the Stainless Steel brushes.

TIP 1: DO NOT use Carbon Steel brushes on materials that originally do not tend to rust such as stainless steel. If you use these brushes on those materials the brush can leave a thin invisible layer (in scratches!) of Carbon Steel (wear) on the work piece. This layer which WILL rust in a humid environment and the extremely thin layer WILL most certainly become visible!

TIP 2: Brushes can be used together with other materials, for example polishing compound. Reading this you probably would think "why would it work, the thin brush wires will scratch the surface anyway!"... No, not if the material of the brush is softer than the material to be brushed. Besides, each bit (with or without additive fluids, pastes, etc.) will produce different effects on different materials. Just play around with bits (and additive substances) on different materials and you will be surprised by unexpected and different results.

TIP 3: When metal brushes are used for a while all of the wires will all end up facing the same direction. As a result the effectiveness of the brush is greatly reduced. To restore the brush just use it in a low speed device such as a battery powered screwdriver, rotating it in the reverse direction pushing the brush on some scrap material.

Distinguishing Metal Bits and Cutters
These are also are available in many shapes, sizes, base materials and some are specially designed for particular jobs. All cutters are normally used at higher to maximum speeds. Of corse you can run at lower speeds if the material to be cut is soft or if it melts easily but they last much longer at high speed on the harder materials.

There are two base materials commonly used for tool bits. High speed Cutters (made of the same material as ordinary drill bits) and Tungsten Carbide cutters (harder than steel but still softer than materials such as flint or quartz). The bits that are designed for special purposes all are made of Tungsten Carbide.

High speed cutters (Router bits also are made of the same material) are used for removing material from or engraving wood, "soft" metals, plastics (if not melting) and other materials that are not very hard. Tungsten Carbide cutters can also be used on harder metals (like bearings, moulds, spring steel, etc.) and other hard materials. Some of the special purpose cutters (like the tile cutter) have large teeth and can be used for fast cutting in bricks, glass, greenware, etc. All metal bits can be hard to distinguish but when you have used your bits a couple of times you will automatically notice at a glance which bit is which. At the start a lot of bits will look similar but soon you will be able to distinguish them from each other by their slight differences. For example the Tile cutter, Tungsten Carbide cutter, Drywall, Multi Purpose bit, and Grout Removal bits.

Tungsten Carbide cutters are darker grey than other bits and their shaft is shiny and polished. Other cutters are lighter grey, have a less shiny shaft, and have a worse finish. Except for the structured teeth tungsten carbide cutters they have a really matte shaft, as the shaft itself is not made of tungsten carbide. However, they are easily recognizable due to the extraordinary look of the cutting part which looks like a bunch of "large spikes" near to each other. Structured Tooth Tungsten Carbide Cutters have a silver color and the Structured Tooth Shaping wheel is gold colored. Structured Tooth Tungsten Carbide cutters are not the most effective cutters because they consist of random shaped and orientated spikes. However, they can cut soft materials rapidly because of the relatively large spikes. An example of a material that can be cut fast with these bits is "thermohardened" plastic such as Bakelite. Plastics come in two basic types, thermohardened (also called thermosetting) and thermoplastic. The former are plastics that produce powder when being cut, the latter get peeled off (with a knife/ cutter for instance), and are relatively soft and melt easily due to friction (when being ground, sanded, or cut). An example of products that often are made of thermohardened plastics are power sockets and other electrical products around the house.

Anyway, here are some differences between some other bits.

Important Information About Cutter Usage
Always make sure you are doing some cutting. Prevent the bit from rotating against the work piece without doing much cutting. There are always some variables that need to be adjusted depending on the material to be cut; rotating speed, pressure, and speed of moving the cutter along the work piece. Just play around with these variables and you will build your skills in order to produce the most efficient way of cutting. This especially counts for routing. It is NOT hard to find out, it is just a matter of playing around and trial and error. If you have problems with cutting too far using a continuous cutting motion (you might accidentally cut too far into corners, or detailed curves) you should use a pulsating motion which may give you more control over the tool. Continually vary the force applied to the work piece. Do not simply slow down the speed of the tool otherwise the cutter will cut worse, and if you cut too slowly your bit may rapidly dull and the work piece may dis-colour, or it may even burn and smoke.

What about High speed Cutters and Engraving Points? Both are just High speed Cutters but the ones called "Engraving Points" got their name because their shapes are most practical for engraving jobs. If you would like to engrave with the bits called "High speed Cutters" please do not hesitate to do so. Some Tungsten Carbide cutters also have small tips and are very suitable for engraving detailed work on soft as well as hard materials. By the way, this counts for ALL bits: they have certain names and they come with a purpose description but of corse finally that's up to you which bit you use for your job. For example the tile cutter bit: they say it's for cutting tiles...yeah right. Ok it works for tiles also but it is never stated that they also work really great on hard wood, glass, hard metals, etc. It's just a matter of trial and error: if you feel a particular bit would work for a particular job you have in mind, just try it and often the bit actually does a great job! Of corse when being a newbie the results of this way of approach aren't always as expected but when you try it you know it!

Engraving
Engraving looks as simple as handwriting but it definitely takes practice to achieve satisfactory results! Engraving is the ultimate in doing detailed work, and requires concentration and the comfortable use of tools. The latter greatly is helped by the use of the Flex-Shaft. Using the Flex-Shaft your hand can hold the comfortable slim grip neir the bit and you won't have to "carry" the weight of the tool all the time (tired hands can't do detailed work).

Something About Hardness of Bits

Increase The Life of Your Bits

Other Helpful Tips

Working On Aluminium
Practically all bits get clogged with aluminum. Aluminum is soft and easily fills up the small spaces between the grinding particles or cutting teeth of your bits so that the bits cease to work. Cutters are hard to clean, but grinding stones can be cleaned with the Dressing Stone.

To cut aluminum you need a bit with more space between the teeth. The two smallest cylindrical Router bits work fast and great, but only on relatively thin work such as sheet aluminium!

Abrasive and polishing bits also work well on aluminum. Sanding bits may also work depending on the aluminum alloy.

Working On Materials That Easily Melt
Use cutters or saw blades that have relatively large teeth and run at low speed. Preferably the speed should be lower than 10k rpm (minimum speed of standard Dremel Multi 395 and previous versions). The Digital rotary tool is recommended as it has a lowest speed of 5k rpm and it still has enough torque at low speeds. When grinding, sanding or polishing you always have to deal with fine particles and a lot of friction which generates a lot of heat. In order to prevent melting you should apply very low pressure and keep the bit moving (fast). Using the bit too long at a small area the material will soften or melt instantly. Small work pieces should be "hit" with short pulses so the cutting or grinding area is allowed to cool down between the hits of the bit.

Cutting Soft Material And Still The Bit Gets Dull
At first glance some materials appear to be soft. However, often these materials are "contaminated" with slight larger particles of hard material (like Flint stones). Examples of such materials are grout and greenware (clay products) and sometimes-even metals, which weren't very well mixed while it still was liquid during the production process. You can never avoid this and you just have to live with the fact that bits need to be replaced once in a while.

Happy Dremeling :-)
Roberto

 

 

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Last updated: July 28, 2003.