Do I need a Rotary tool (e.g., Dremel)?

Many modelers find use for a small "grinder" (such as a "Dremel tool" or various equivalents). If you have a choice, get one with variable speed; failing that, get one with low speed(s) available (the common ones run at ~30,000 rpm - far too fast for drilling or sanding activities) - the Dremel MiniMite can be found for about $30, and provides the choice of 6,000 or 12,000 rpm operation. Many of these tools come with a sack of grindstones, etc. You'll find that you don't use most of these (they're there for other kinds of activities), so don't base you decision on the collection included; instead, get the minimum with the tool and add to your personal set as you find a need.

One thing you will find a use for is a full set of "collets" - a set typically contains 1/8", 3/32", 1/16", and 1/32" diameters. The "bits" that come with the tool usually need the 1/8" collet, but bits you scrounge from your dentist are typically 1/16" or 3/32", and drill-bits will use the smallest sizes. However, even the slowest speed is overly fast for wood, and extremely fast for plastic (you'll melt your way through the plastic rather than cutting it). Remember that the smaller the drill, the faster it can be turned without overheating the drill and work. However, the smaller the drill, the more "brittle" it is, so take great care when attempting to drill extremely small holes free-hand!

(Micro-Mark has a special little chuck for cordless screwdrivers for slow speed drilling; it is made for #60 - 80 bits: [#81653 Micro Chuck - $9.95]; cordless screwdrivers are a little bulky but they run slow and are fairly inexpensive.)

Here are some alternatives:
WWW: Dremel® Foredom®
Pictures: Click for larger image.
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  Dremels, corded and cordless Foredom Dental
Collets & Bits: 1/8", 3/32", 1/16", and 1/32" diameters. 3/32" standard. 1/16" standard (Ask your dentist for used bits).
Used: hand-held. flexible-shaft & handpiece. belt-driven arm & handpiece.
reliability: hobby/craft machines.
use for light duty use.
Industrial. Industrial.
Price: $$-$$$. $$$-$$$$. $$ (second hand)
Used by: hobbyists. Jewelers, etc. Dentists.
Note - inexpensive bench-top dental machines are bought by almost all dentistry students; when they graduate, they trade them in for professional dental drills. The result is that the dental machine suppliers often have a lot of these second-hand student machines, and no real market - you may find them for $25.
Unfortunately, these suppliers often also sell supplies, such as drugs; because of the laws in some states, the can't sell anything to a non-licenced dentist! If you run into this problem, ask your family dentist if he'd be willing to buy such a machine for you, using your money).


To summarize the posts on drilling plastic with a Dremel, I'd say:
  1. The variable-speed Dremel Moto-Tools operate at high rpm to accomplish their work rather than using low-end torque like your basic hand drill. This causes the drill bit to generate enough heat to melt the plastic you're drilling.
  2. The solution is to use a single-speed Dremel Moto-Tool which is plugged into a Dremel speed controller. You can then operate the tool down to zero rpm if that suits your purpose. DO NOT PLUG A VARIABLE SPEED UNIT INTO A CONTROLLER!
  3. The variable-speed Moto-Tools are not designed to work plugged into a speed controller, just the single-speed models.
  4. A Dremel Mini-Mite has a high and a low speed setting; the latter is used for drilling styrene. I have one, I drill a lot of styrene, and it works just as well as my single-speed Dremel tool which is plugged into a Dremel speed controller.
  5. Both the full-size Dremel Moto-Tool and the Dremel Mini-Mite will accommodate the same range of four collets which are interchangeable between the two tools. The Mini-Mite comes with, I believe, the medium collet, and so you will need the other three, available as accessories, to chuck in the full range of Dremel bits, grinders, etc.
  6. With the smallest collet, both tools will grip a #80 drill, which is .013", quite nicely.
If you need a brochure or other information, you could look into Dremel's web site.
{Bob Steinbrunn}
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