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I have a really old Foredom I picked up at a (yeah, you guessed it) yard sale it works a pretty well but it's hard to get parts for. Up here anyway. I like the units in this video, they're way different, probably 30 years newer. I might have to put one on my Christmas wish list.

Frosty The Lucky.

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Rotary cutoff  discs

You should not use larger than 1-1/2” diameter cutoff disks on a rotary tool (32,000 RPM), or 2” disks on a micro-drill (20,000 RPM) unless they are rated for those speeds. Stop cutting short of drilled corners, when using a new cutoff disk; save that last 1/4” at the beginning or end of your cut line for a smaller diameter used disc, or a diamond coated disc.

 

Diamond coated cutoff discs, just like diamond coated burs, are meant to be used on glass,  ceramic, and stone surfaces; not on steel. But diamond coated burs and cutoff disks are quick and smooth acting on steel; diamond coated  rotary discs disks and burrs are dirt cheap. The secret to quickly finding a large selection of these accessories is inputting the right word search; try “diamond rotary disc” on Amazon.com or eBay. Disc diameters up to 60mm (2-3/8”) can be purchased for amazingly low prices, if you just search a little bit. But 22mm (about 7/8”) can actually be more useful; they are far easier to control in the cut, are perfect for grinding back to a scribed line, after cutting beside it, and far less likely to suffer a kick-back at the beginning or end of a cut; they are also quite handy for sharpening small high speed steel drill bits, and carbide teeth on saws.

 

Disc mandrels: You don’t want to employ just any 1/8” shank mandrel for the job. The standard jeweler’s mandrel, which only has a 1/16” arbor screw head, was designed for making very small cuts in soft metals; not for making extended cuts in steel. There are special mandrels with 1/16”screws that have oversize screw heads, threading into oversize mandrel faces; these far outperform the standard minimal screw head variety; you can find them offered through eBay, Amazon.com, and through some jeweler’s supply houses ( input “SEINC rotary tool mandrel” to find it quickly); these mandrels are capable of spinning 1-1/4” fiberglass reinforced corundum cutoff discs that are so handy for cutting out rectangular air openings on burners.

    Resin discs meant for work on ferrous metals are fiberglass reinforced (and that should be stated in their sales literature); also, they have course grit. If you can’t see the grit in expanded views of the product, keep on looking elsewhere. SEINC carries these disks too. The most desirable steel cutting disks are not only fiberglass reinforced, but also contain corundum grit (they are grey; not pink or red).

 

EZ lock mandrel and cutting disks (AKA Bow Tie Mandrel) are the safest way to cut steel with a rotary tool. You begin by inserting the mandrel in a rotary tool, and snugging the axel nut. To mount a disk, push the head down against its spring, drop a disk past its bow tie opening, and turn it ninety degrees. The spring driven locking system is what makes this system unique. It eliminates a locking screw, so that the disk can be used to grind and sand on part surfaces, without interference from the usual protrusion. A disc is positively locked, because there is no screw to back off, allowing the disc to spin on the mandrel. But most important of all, the spring allows the disc to move out of alignment, without shattering, during kickbacks (when you allow the disc to jam up in the part during cutting); you can order them online, and they are available from most large hardware stores.

Separating discs are standard jeweler’s thin (0.025” thick) 1” and smaller diameter cutoff discs, which come as part of most accessory kits. They are too fragile to be practical for most steel cutting tasks, but when doubled on a mandrel, they are perfect for sharpening small drill bits.

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Solid carbide rotary burrs used to be quite expensive, but are bargains these days; why? First, they are now available in 3/32’ and 1/8” shanks for rotary tools (large retail market), rather than only in 1/4” shanks (limited industrial market); second, because diamond coated burrs are even lower priced. Diamond coated accessories are almost as fast acting as solid carbide, but are much smoother to use. The larger the accessory’s diameter the greater the advantage diamond coating enjoys over solid carbide; which still leaves an advantage with solid carbide burrs around 1/8” diameter. Carbide burrs fling needle sharp debris everywhere; the larger the burr the faster the debris. Originally, burrs with 1/4” shanks where designed for air die grinders, which have less torque than most rotary tools. Today's electric die grinders are inclined to kickback far harder than air tools; especially with carbide burrs!

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Rotary tool guard

The last addition to a rotary tool you will normally encounter is a see-through safety shield; that’s because shields on rotary tools aren’t mandated by law; but they are the best investment you can make. Users have been making their own safety shields for years; you can now find them on the market. If you don’t listen to any other safety advice; at least pay attention to this.

 

The Autotoolhome electric grinder cover (the rest of its ‘name’ is the usual Chinese descriptive paragraph for word searches, but this will do the trick) has a thick plexiglass  shield, which slides around its threaded collar with just enough resistance to stay where it’s positioned, and is wide and long enough to do the job, without enterfering with your view. The collar is also heavy duty, and well help support a flat washer handle. Amazon.com has it for a low price, as does eBay. Dremel is selling it along with a four accessory kit.

 

The Gyros Safety Shield is the other end of the spectrum; the usual over-achieving safety guard that people can’t wait to get rid of; that is understandable in light of its being developed to protect against high speed steel saw blades.

 

DRILLING SHIELD: The only safety guard I’ve found for use on micro-drill. Only seen on eBay:

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Extra-long Nut lock drum mandrel set (1/4” shanks): These are meant for use in die grinders, where they are handy for enlarging pipe and tube interiors  for easier fit-ups. But can parts be mounted on them, and spun in drill motors/presses (at slower speeds) to decrease exterior diameters with a file? Just trying to think outside the box :)

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Eclectic Die grinders: I don’t advice the use of electric die grinders to everyone, or for every job; their sheer power can make them dangerous in weak or inattentive hands; that said, if you’re looking for more cutting speed on heavy pipe and angles, or better help in cleaning up burrs, weld spatter, or rust from curved surfaces, they totally beat out rotary tools.

    For me, nothing even comes close to a DeWalt 1-1/2” extended shaft electric die grinder for daily use in a steel shop, which doesn’t make them the best choice for part time home use. The Shop4Omni electric die grinder is almost as ergonomic as the DeWalt, and while nowhere near as tough, it is serviceable if you handle it carefully. Why carefully? This is one of several reduced-power long shaft die grinders now found on the market; like others, its spindle is housed in an extension of the plastic body, rather than in a bolted on cast aluminum extension. The stronger metal extension is intended to protect the spindle from bending during accidents caused by kickback, which can be severe in a full power grinder.  A more serious complaint is that it won’t accept ¼” shaft accessories. You’ll have to shop around for the slightly smaller 6-millimeter equivalents, or buy a Makita 763625-8-1/4 Inch collet Cone to replace its original collet.

    This grinder only generates 230 watts, versus DeWalt’s 504 watts. A disadvantage? Not for these tasks; a top  quality rotary tool generates the same wattage, but at 3200 RPM; this tool’s maximum RPM is 2500, meaning it generates more torque from those watts, and spins larger cutoff disks (1-1/2” maximum recommended diameter (unless the manufacturer states that their larger discs can be spun at 2500 RPM). You end up trading some compactness for more torque, and the use of sturdier mandrels. Which tool is best mainly depends on how much shop equipment, tables, stands, etc. you wish to build, after you complete your burner.

    While the Shop4Omni is definitely a two handed tool, you don’t want to mount a handle on it, because its power switch is located on the tool’s rear face; thus inviting disaster when you attempt to turn it off, by shifting the grip of one hand, while the other is temporarily dangling the tool from a handle; that’s just a very bad idea. Of course, you could first shift your grip from the handle to the tool’s neck, but you only have to forget to do that one time, so just don’t go there.

   

VOTOER 480W Rotary Tool has a high quality keyed chuck that varies from .6 (0.024”) to 6.5mm (1/4”); Variable speed adjustment from 5,000 to 30,000 RPM (maximum speed for a high quality 2” cutoff disc); enough accessories to build your burner is included in the one offered on Amazon.com.

    Tool length is 11” and body diameter is under 2-1/4”; comfortable to hold, even in small hands, for a two-handed tool; its power switch is the rocker type, and located on its bottom, so it could benefit from the addition of a safety handle (mounted on its chuck housing). Such a handle doesn’t require any fancy construction; you can easily mount a handle by trapping a bent flat bar between a worm gear hose clamp and the housing. This tool puts out a lot of torque. You will be tempted to turn down its power, so just order a fan speed controller right up front, to protect your investment. Enough accessories to build your burner is included in the one offered on Amazon.com. I may need to eat my words about DeWalt die grinders. Apparently something has done more than just "come close"; maybe something has surpassed them...for about one-third their cost.

    There is a look alike drill/grinder (except that it’s red) that is rated 110V/220V; its sellers claim it has 240 watts output power, but that is misleading. You don’t get half the power output from electric motors at half voltage; their power drops like they fell off a cliff; this is not the worst news about them; their customer reviews paint a picture of fall- apart junk. I can’t say for sure because I never received mine; the drop shipper refused to even answer the compliant I left on his site!            

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Safety handles on rotary tools

A rotary tool can be braced in an inline, rather than transverse position (similar to angle grinders), by mounting a small handle next to its spindle; this provide superb control. Years ago, 2” angle grinders like the Proxxon’s Long Neck Angle Grinder LHW/E were the only small power tools that could easily make small cuts in burner parts. A rotary tool with a safety handle can now do the same job, more safely, for a small fraction of the price. What has changed since then, to make this possible? Practical see-through guards didn’t exist back then; they do now.

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Electric rotary tools & die grinders

Expense once limited the use of rotary tools to professionals; their prices, with that of their accessories and attachments, have been steadily falling for more than two decades. During that period, equipment choices have expanded. Today’s hand held inexpensive rotary tools give wonderful control for building a small burner, and then help in constructing the equipment that burner heats. Rotary tools can have attachments added (ex. flex shafts) to enhance their performance even further. Now for the bad news.

    Nearly all of this equipment is imported from countries like China, India, and Mexico. While prices are generally remarkably low, you will find some marketers asking much higher prices than the rest of the pack. A high price generally just shows the seller’s contempt for your intelligence.

    The other way to get bilked is with shoddy goods and service; there is a whole ‘industry’ that has grown up around drop shipping overpriced junk; before purchasing online, look at other customer’s evaluations of the item, and the seller.

    Where do you think look- alike super cheap tools come from? Foreign factories have quality control too, but their rejected parts are sold; not scrapped. Another favorite “bait and switch” tactic is a seller with the lowest initial price, followed with ridiculous shipping fees.

    American brand names your grandpa trusted can mean zilch nowadays; some companies are having their power tools built in China, and then charging the highest prices you’ll see in that tool’s category. Before paying an outrageous price, in hope of buying quality, thoroughly read through customer reviews of the product; they are likely to provide some chilling surprises.

    But the one who needs watching the most, is you. Tools are only what they are; not what you wish they were, or what you think they should be. When you go looking, leave all of your hopes and dreams behind. Go beyond practical, to outright cold-blooded. And when it comes to buying power tools, remember that old street adage; “nothin’s fer nothin.”

    Before running your new tool, be sure to understand its limitations. Most people treat an old jalopy better than their power tools.   

 

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Angle grinders

When I wrote Gas Burner for Forges, Furnaces, and Kilns, hand held rotary tools were still expensive, as were their accessories. The “newfangled” 4-1/2” angle grinders of the day, were really just re-geared 4” grinders being marketed because their grinding wheels were far less expensive than the 4” wheels. At the time, these grinders were a little under powered, which made them a lot safer for cutting work than the high-power models being pushed in the market today.

    Also, the that text’s smallest burner was ½”, which is the largest size 1'm building now. Times have changed. You don’t need to use an angle grinder on burner work..

    But what about people on a shoestring budget? What about using your existing angle grinder for cutting into forge shells? High-speed plus high-power still equals high hazard…but hazard levels can be reduced. Starting with one of the weaker grinders from Harbor Freight Tools, you can bring its power down to the level of a 3” angle grinder (big bucks and hard to find) by reducing it to half power with a router speed controller; these are also cheap.

    The hazard level can be further reduced by changing out the 4-1/2” grinding wheel for a well-used cutting disc (around 3”), or employing a new 3” disc with a 5/8” arbor hole; is this a perfect solution? No, but it’s a whole lot better than nothing.

 

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Balancing accessories

I have yet to find an accessories kit that doesn’t include a little blue or green oblong silicon carbide dressing stone; they are used to balance aluminum oxide grinding stones, wheels, and cutting discs, to keep your rotary tool from suffering degradation from excessive vibration. Cheap tools are as likely as not to have spindles, which were machined out of true with the tool’s axis; add unbalanced accessories to that, and bent mandrels and flung accessories are the next trouble that will rapidly be served up. A few light touches with a dressing stone on your accessory can save a lot of grief.

    It is also helpful to move an accessory (like a brush or drum) a quarter turn at a time, to improve balance.

 

 

Freeing up jammed accessories

Collet nuts (spindle caps) on rotary tools frequently need to be sharply tapped with the tool’s tiny wrench, or very lightly tapped with a butter knife, to free up jammed accessories. Unscrew the nut a partial turn, so that the accessory can slide free; commonly, they will revolve, but cannot be slid forward and removed. What has happened is that a collet, which the accessory’s shank (shaft) slides into has jammed in place against the inner bevel of the collet nut, locking the accessory’s shank together with the collet and nut. A gentle tap or two on the end of the nut, will transmit just enough of a shock wave through the three parts, and the collet will release its grip.

    If you change accessories frequently, you may find relief from a brass collet; brass drill bit collet kits, which include 1/8” collets, go for around $2.50 on eBay. Some people simply replace the collet nut (and its collet) with a Dremel keyless rotary chuck (make sure to buy this attachment from Dremel; the cheap look-a likes don’t work very long, when they work at all).

   Disk mandrels that are appropriate for cutting steel simply aren’t included as part of rotary tool offers, nor presently in accessories kits; fortunately, they don’t cost much, but you will have to buy them separately, or suffer until you do. See more in the “mandrel” section further on.

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Accessories kits

Some tools come with a few accessories included, but not necessarily of decent quality. Most genuine bargains on accessories consist of a lot of one particular item, like stones, drums, or discs. By the time you acquire everything you need this way, their cost will be substantial. Typically, accessory kits have a lot of stuff you can’t use to work steel with, and very little of what you want. The Popoman Rotary Tool Accessories Kit is a 313-piece bonanza of mostly relevant parts for cutting, grinding, sanding, and drilling steel.

    The Populo kit contains 305 parts; they have a different set of accessories, but equally useful for building burners with. However, I think its case is far superior to that of the Popoman; it includes a usable amount of diamond coated rotary files and grinding stones, and a nice selection of drill bits. There are less grinding wheels, but their are  some flap wheels. Both kits have similar prices; I have both, and can recommend either one.

   

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The ugly truth about flex shafts

Why buy a separate flexible drive shaft, when they are cheap or even free as part of rotary tool offers? Rotary tools are designed to run at 35,000 RPM; running slower heats them up. Flexible drive shafts were designed to run at 15,000 RPM or less; running faster heats them up. Like in-built speed controls,  rotary tool mounted flex-drives are just another sales gimmick. If you want a happy ending, start from the right beginning.

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So, nobody wants to spend a small fortune in tools, while trying to build a forge. But, there are flex-shafts that aren't designed to be mounted on Foredom motors. Someone came up with a better mouse trap; flex-shafts for mounting on large drill motors; they're even better when mounted on drill presses. If you have either tool, flex-shafts are cheaper than buying a rotary tool. There are several versions of them on the market. Below is the one I chose.

.Eyech Drill to Flex Shaft converter for $28 (with 3-6.5mm keyed chuck) is designed to be mounted in a small bench mount drill press (or drill motor), letting you do a lot more than just drill.

 

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The Black and Decker RTX-6

The RTX-6 is a hand-held rotary tool that is smaller and more ergonomic than most others, but has a 240-watt brushless motor. Most rotary tools only have 160-watt motors (Dremel’s very expensive “top of the line” models are 175 watts). The RTX-6 is quieter and smoother running than most of the rest, with more power and less heat build-up than brushed motors; its speed can be varied between 12,000 and 30,000 RPM, with very little vibration. The spindle on this tool is offset toward its bottom side, rather than centrally located, providing cutoff discs better access on flat surfaces. The power switch is located top and forward on the tool’s neck; it has an especially smooth slide lever (most of them are stiff). This tool’s flip-lock spindle lock should be handled carefully; if you break it, the tool must be sent to Black and Decker for repair (have fun with that).

   Look around for the best prices, and you can purchase the RTX-6 for about $10 more than a Chicago Electric.

    While these are high quality tools in general, their speed control circuits are vulnerable; don’t employ them unless you like buying the same tool every time you turn around. Why would the speed control burn out fast on higher quality equipment? Because the RTX-6 draws more amperes then weaker tools, so there is more energy available to fry that poor defenseless little circuit. But brushless motors have less heat build-up in the first place, right? That is a separate issue from over stressing a separate control circuit.

    Be sure that the external speed controller you choose really is meant for brushless motors. Why put up with the need to deal with a brushless speed controller? This tool is more powerful than the rest of the pack precisely because of what kind of motor it has; also, BLDC motors last longer than brushed motors, and don’t need carbon brushes replaced.

    Most speed controllers are designed for motors with carbon brushes (brushed motors). Brushless motors (BLDC) need brushless speed controllers; they aren’t hard to come by, or expensive. But there are no plug and play versions available for hand tools; at present they’re only available as kits. The easiest kits to deal with have all the electronics in a perforated metal control box, to which you must add electric cords and/or wires; one incoming lead from your power source, and the other is outgoing; wire it to a receptacle, for the tool’s power cord to plug into:

The RioRand 7-70V PWM DC Motor Speed Controller Switch 30A from Amazon.com has four terminals for wires to mount on; their negative and positive “input” terminals from the power source, along with negative and positive terminals to “motor”; they are all plainly marked; there is a speed dial on the side of its perforated metal body. Why metal, and why perforated? For heat dissipation.  Remember that black wires go to negative and red wires go to positive in 110V wiring, and in direct current circuits (ex, tool motors).

 

 Power switch types: So, w

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Chicago Electric markets a low-priced rotary tool (model #68696) with a few accessories (which don’ t have kindly reviews); it’s a little louder than I like, and larger than the Black and Decker; it only produces average torque, with variable speeds from 8,000 to 35,000 RPM from its 160-watt brushed motor. My tool has held up pretty well, with occasional use; some of them don’t. Heavy vibration is typical in this tool; they are sold through Harbor Freight Tools stores, and online.

    The power switch is a rocker type, and located on the bottom of its housing, in the pistol grip. You can sand down the rear section of the plastic collar, where it surrounds the rocker switch. No doubt its collar is meant to keep the switch from being accidentally turned on, if the tool is laid down on table clutter; but it interferes with smooth functioning.

   If the plastic collar’s height gradually slopes away, starting from the center, and increasing toward the rear of the switch (its “off” side), the collar can still mostly serve its function. There will be far less interference to quick stops, using your third or fourth finger. You are marginally increasing the risk of accidentally turning the tool on, for added speed in emergency stops, with reduced risk of jarring a running tool, at a critical moment. The marginal risk is further reduced by the plastic body’s shape; the pistol grip tends to force the tool onto one side or the other; further sheltering the switch. Harbor Freight Tools has an excellent return policy, which altering the tool will void; make sure your tool isn’t a lemon before touching that collar.

    If the speed control on one of the top-rated rotary tools is its Achilles heel, how long would you expect this one to last? Employ a router speed controller, or leave the tool on its maximum setting.

    So, why not list other low-rent rotary tools? Harbor Freight’s return policy and numerous physical stores to take a reject back to is why. A drop shipper is likely to have nothing more than an ad site on the Net, and behave like a black hole, when you have a complaint.

    Why not give up endless shopping and “just buy a Dremel”? Well, the oldest models in the Dremel lineup (their 100 and 200) still get good reviews; the others? Maybe not so much. Compare their prices versus the amount of critical costumer reviews, and Harbor Freight starts looking a lot better. Dremel became famous for the solid quality of their rotary tools, in the past. On the other hand, their accessories are first rate. Am I saying that Dremel power tools are no good?

    No; I’m suggesting that you forget blind loyalty to brands; this isn’t your grandpa’s world. I despise Black and Decker, and have still bought three of their RTX rotary tools, starting with an RTX-3; the third is an RTX-6; personal animosity hasn’t prevented careful consideration of their products. Keep reading costumer reviews, and forget brand names; they’re increasingly irrelevant.

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The Dremel 100 and 200 Two Speed Rotary Tools both have a 108 watt (.9 amp) brushed motor: this is a plus for cutting small air openings in burners. This is the weakest motor you can find in a decent quality rotary tool. The 100 and 200 are the oldest models left in Dremel’s product line; they have stayed around because of their dependability. The 100 runs at 35,000 RPM. The 200 has two speeds; 15,000 and 35,000 RPM. Both tools become variable speed tools, when plugged into a router peed controller. At half speed, they should be running at in a comfortable range for micro-drilling in stainless-steel. This tool is comfortably small, with plenty of air vents that are properly positioned. their prices are a little high ($50), but the amount of critical reviews is very low. On/off and high/low speeds are controlled by a single switch near the tool’s rear on the 200; an on/off switch is located in the same place on the 100. Most people find this more convenient. I like more safety, but this is a weak enough tool to overlook this shortcoming. The 100 and 200 are available through Amazon.com. The 200 is also available at Homedepot. Unlike the bulk of rotary tools, these both have reasonably priced parts available online; even the motor. You will also find parts lists, diagrams, and repair videos for them online.

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WARNING!

Do slide accessory shanks all the way into the tool’s spindle; leaving it sticking partway out is an invitation to a bent shank, 

which does bearings and motor no good. That 1/8” shank has to stand up against concentric forces on accessories, which

aren’t perfectly balanced, revolving at up to 35,000 RPM; this is tough enough if you follow proper procedures; and impossible if you

push hour luck. Bent shanks tend to happen almost instantly, when spinning discs, or circular saw blades, because they greatly

increase those concentric forces. As soon as a shank bends, those forces are multiplied. Consider yourself lucky if you can

stop the tool before a saw blade is flung at you at high speed!

 

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