Useful information for new users of the Dremel rotary tutorial
Written by Roberto Muscia. Reproduced with permission.
Diamond and CBN Bits
Abrasive and Polishing Bits
Metal Bits and Cutters
Important Information About Cutter Usage
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
This tutorial is written for those who are just starting to use the moto-tool and the bits. This tutorial also contains 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.
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 to cater for different 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.
Set your tool to about half speed, hold your rotating grinding stone to the Dressing Stone and simply reshape or clean your grinding stone. Grinding stones should normally be used at high speeds got the greates effictiveness.
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 and CBN Bits
There are two types of coated bits available, diamond and CBN (Cubic Boron Nitride).
Diamond is used as an embeded coating onto the surface whereas CBN is usually applied as a bonded coating but these are similar in use hence why they are grouped together.
The cheaper diamond coated bits only have a thin layer of diamond material which wears out quite quickly but the higher quality bits have a deeper layer and will last much longer.
On the cheaper bits 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). The diamond-coated wheels often have gaps and holes in the wheel. This allows better cooling (and saving diamond coated area to reduce production costs.)
The CBN bits are slightly less hard than diamond and act more like a conventional abbrasive than diamond since CBN is friable whereas diamond is not. However due to the hardness of these two materials they can be grouped together by appliction.
These bits are available in many shapes and they can be used to remove material or for engraving. They are especially god at cutting and shaping very hard materials such as Tungston Carbide and stone. These bits work best at medium to high speeds.
Sanding disks are based on "sandpaper" (paper or linen backing), coated with grinding particles and they are available in different grits (=size of the particles: 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. After the layer of sanding material is worn the disk becomes useless. Lower quality sanding disks have lower quality grinding material. They may use emery instead of carborundum, they may contain particles of varying grits, as well as using 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 or metal, or to remove a coating (e.g. paint), or to grind 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 inefficiently these disks are great for detailed work because the material is removed relatively slowly. 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. The 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 disks onto the mandrel (one facing up, other facing down), you will not have to turn the disc all the time.
TIP 2: Sanding discs with differing grit are hard to distinguish from each other. You can code the the screw head on the mandrels to indicate which grit is on the mandrel. Use the two sections of the screw head either side of the slot in the screw head. To mark the bits simply mark one or both of these half circles either side of teh slot:
For making the differences even greater you could color the coarse areas with moddeling enamel for example.
- Coarse grit disc - grind the top of the screw to make it rough.
- Medium grit disc - grind one half of the top of the screw and polish the other half.
- Fine grit disc - polish the top of the screw.
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.
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 in a binder (looking at the color I think they are made of emery), they last longer and are quite fragile. The reinforced wheels (black) are a mix of grinding material (looking at the color, probably made of silicon carbide) and fibreglass reinforcing with a resounous binder. 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 they can alsocut 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 and the wheel could disintegrate.
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 it being used on other materials! For instance It works great on perspex, wire netting, aluminium sheet, copper sheet, etc. Make sure that the saw blades' teeth are pointing in the right direction (also when buying a new completely assembled attachment!). Note that it is normal for attachments which are based on a flexible core (Flex-Shaft, Mini-Saw, Right Angle, etc) to produce a weird and possibly loud noise but is nothing to worry about.
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 on which it is used. The harder the bit is the longer it lasts (first two). The 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.
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. Once the bit looks equally red you can start polishing the work piece at higher speed. You may need to re-coat the buff regurarly 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 residual polishing compound with a dry soft cotton 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.
Brushes are available in several shapes and materials. Depending on the material to be brushed you can choose from brushes with wires made of Nylon, Brass, Stainless Steel or Carbon Steel. In this order they vary from soft to hard. To distinguish Carbon Steel brushes 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 alter the surface chemistry of the srainless steel causing it to be prone to rust. 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.
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 steel (HSS) 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 Tungsten Carbide bits are designed for special purposes.
HSS 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. Tungsten carbide is also slightly heavier than HSS. 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.
Listed here are some differences between some other bits.
- Tilecutter - has sharp small individual teeth all the way to the top.
- Tungsten Carbide cutter - has cutting edges which are close to each other, and spiraling all the way to the top.
- Drywall cutter - has the cutting edges far away from each other not all the way to the top. Near the top the spiraling stops, and the top looks more flat.
- Multi Purpose cutter - has the cutting edges far away from each other all the way to the top like a drill. But an ordinary drill hasn't such narrow shaped cutting edges (ordinary drills are produced by twisting a slotted wire and only the top is sharpened. The Multi Purpose cutter has completely been cut or ground to its final shape).
- Grout Removal Bits - have a long shaft (do their job in an angle with the attachment) and only have a short cutting area (grout always is only a thin layer).
Important Information About Cutter Usage
Always make sure that the bit is cutting at all times. Do not allow the bit to rub against the work piece without cutting since this will cause the bit to overheat and blunt it. 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 less efficiently, 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.
High speed Cutters and Engraving Points are just High speed Cutters. Engraving Pointsare names so because their shapes are most practical for engraving jobs. You may also engrave with the bits called High speed Cutters. Some Tungsten Carbide cutters also have small tips and are suitable for engraving detailed work on soft as well as hard materials. By the way, this applies to any bit: they have certain names and they come with a purpose description. It is up to the user to use whichever bit is most suitable for the job. For example the tile cutter bitcan be used for cutting tiles but they also work really well 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 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 Flex-Shaft can assist in engraving. 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
- Diamond coated bits can be used on all materials without getting dull at once since diamond is harder than (almost) any existing material.
- CBN Cubic Boron Nitride) is a little less hard that diamond but is harder than any other grinding material. In almost any instance it may be used instead of diamond.
- Silicon Carbide grinding stones are harder than aluminum oxide grinding stones.
- Sanding, abrasive, emerald impregnated bits, polishing points, cut-off wheels, etc. are based on substances with properties lying in between aluminum oxide and silicon carbide.
- Tungsten carbide (Structured Tooth) Tungsten Carbide cutters, all "special purpose"cutters like the Multi Purpose, Tile Cutter, Grout Removal, etc) is much harder than HSS (high speed cutters, engraving points, router bits, drills, etc.)
- From hard to soft brushes: carbon steel, stainless steel, brass, nylon. (Carbon steel brushes have a silver colored shaft and stainless steel have a gold colored shaft for distinguishing them more easily.)
- When using two materials on each other with the same hardness (e.g. aluminum oxide bits on ruby or ceramics) the bit will wear but the work piece will wear faster and loose the contest. This is because moving particles have more kinetic energy than material that moves less fast or stands still. However, bits are usually chosen with an excess of hardness so they last much longer.
Increase The Life of Your Bits
- When using cutters always be sure that the bit is cutting at all times and NOT just rotating against the work piece without moving. In the latter case the contact area gets hot and when metals (including hardened metals or steel) get hot, they get softer and dull more rapidly.
- Lubrication also increases the life of the bit. This is especially useful when using bits whose effectiveness depends on the sharpness of the outer layer "particles" (coated bits, structured or sharpened teeth, etc.). As soon as the outer particles or teeth become worn these bits will not work. Lubrication helps the particles or teeth to remain cool. Water can used for lubrication. To help the water to stick to the work piece or bit you can add some soap (detergent) or some lubricating oil. This "oil" contains soap-like ingredients (emulsifiers) which cause the water and oil to form an emulsion so the oil and water do not reject each other and remain mixed. The latter type of lubricant prevents metal parts rusting when they are not dried or cleaned properly afterwards. A common lubrication for steel or brass is kerosene. A small amount may be applied to the surface being cut, drilled or ground. You can also purchase a sulphur based general purpose cutting compound from most hardware stores. This is a similar consistency to grease and can be applied to either the tool or the surface being cut. If you buy a small container of this cutting compound you can recoup the purchase many hundreds of times over in the extended life of your tools. Use a little of it every time you cut or drill and it will greatly extend the lige of your tools. There are many lubricating substances available, all of which have differering properties and purposes.
- Never force the bit into the material, let the speed do the job. Make sure the tool does not bog down too much so there is insuffucient speed. Many people use ordinary cutters or cut-off wheels on a rotary tool the wrong way, pushing too hard in order to cut faster and they notice the wheel getting smaller more rapidly during the job. When you push lightly on the wheel and let the high speed do the job the motor hardly bogs down and running at high speed the sparks fly around and the work piece is cut like butter. After the job is done the cut-off wheel is hardly worn and does not get smaller. To avoid the wheel getting stuck in a deep slot you should swing slightly with the bit from the start. Swing in a direction parallel to the slot to be cut, making a long slot. This way the slot gets a bit broader than the wheel itself. This is because you can never make a perfect movement along the slot. The wheel will hit the sides of the slot in a slightly random off-angled way.
Other Helpful Tips
- Important! Tiny particles or objects fly around the area at high speed during the grinding, sanding, cutting (chips!), polishing (polishing compound!), or brushing (wires!) process almost continuously. In order to prevent your eyes being damaged by one or more of these objects you should always wear safety glasses, or goggles. When using Tungsten Carbide cutters on hard metals or bendable materials you also should protect bare skin. Whilst cutting there is a continuous stream of tiny sharp itchy, and annoying chips produced which can irritate your skin for days!
- When placing a bit in the tool do not slide it all the way in before tightening the collet nut. Keep some space underneath the bottom of the bit. After loosening the collet nut to change the bit again just push the existing bit down and it will come loose from the collet. If you do not do it this way the bit might still be held tight by the collet despite of the collet nut being loosened.
- If your bit can not cut deep enough in a surface because some part of the the the tool is in the way, you can remove the collar from the tool. This is the nut employed to protect the thread that is used to mount attachments onto the tool. This will only reduce the thickness of the tool just below the bit (useful close to the edge of the work piece). Really helpful options are to use the Right-Angle attachment or the Flex-Shaft. Both are narrower and allow you to cut slots in any surface away from the edge of the work piece.
- If you need to work in poorly lit areas (e.g. underneath a sink, in a closet, in a narrow area, or underneath a windowsill) the Mini-Light attachment can be very helpful. When using another lighting source such as a flashlight, you keep hustling with space and shadows which really holds up the job.
- If wish to mark your bits you could use colored tape. Punch holes in the tape (with perforator or hole pliers) and stick it over the holes where you hold your bits in the tray of your storage case. Next to the perforated holes you can write (with a fine water-resistant marker) something about the bit which is stored there. You could also color-code your bits using small pieces of heat shrink tubing. Sleeve the tiny tube over the shaft to just below the actual wheel or grinding stone and shrink it using a hot air gun or a lighter. Make sure to cut short pieces otherwise bit will not be able to slide into collet of the tool far enough.
- To increase the versatility of your tool you should have a variety of bits. To keep things organized a storage case with an area or tray where you can separate your bits is HIGHLY RECOMMENDED. If the bits are lying loose they can knock against each other and damage the cutting edges. Polishing wheels may be contaminated with grinding particles (causing scratches in your work!) and it becomes inconvenient using them.
- You can create your own bits for special purposes! Several mandrels are available on which you can mount a piece of any material. Before doing this make sure the piece is suitable for rotating. It should not be too large and it should be quite symmetrical and round. (e.g. piece of sponge, sandpaper, cloth, etc.). Besides, there are different mandrels available than just those from Dremel. What about the mandrels with a slot along the length of the shaft? You can mount any piece of sheet material in the slot (e.g. sandpaper). This way you create any customised flapwheel. There are many web sites where there are may different bits, mandrels, accessories, etc.
Working On Aluminium
Practically all bits clogg when working 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.
It is a good idea to use a small amount of kerosene when using a cutter on alumuinium. I prevents wear on the cutter and helps to prevent it from clogging.
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 worked 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 more often.
Happy Dremeling :-)