In this instructable i will show you how to turn a useless piece of junk, with rotten batteries into a handy tool.
If you happen to still own a "roto-matic" then this is made just for you
Ok what is a "roto-matic"?
a roto-matic is a piece of junk, plain and simple, beyond that its a dremel wanna be, that was sold on infomercials in the early 2000's
it touted special features like
--10,000 RPM !!!!
-- BATTERY OPERATED, NO CORDS TO TANGLE!!!!
-- 40 BITS INCLUDED
while visiting my aunt and uncle in Lake Mary, Florida, I took my niece to the mall (a few times), and they had an "AS SEEN ON TV" store. I ended up with a assortment of stuff, some awesome and some not so much, the roto-matic with its "featuers" and 40 bits for a sale price of 15 bucks seemed like a steal
And it was a steal! From my wallet!
A little back history
growing up i lived (basically) in a fully functional wood shop, dad had everything, including a old 1970's dremel and all the attachments, which he still owns today and is in perfect working order
and let me tell you, that is a man's tool, if you don't plug it into the vintage speed control (steel box with a knob) when you flip it on, it will jerk your wrist 25% clockwise!
steel meh! just like butta!
so when i moved away, i wanted a tool that i had become dependent on, and when i saw the roto-matic i jumped on it, got it home and tried to cut a rivet head off and learned my awful mistake
heres the crap factor of the roto-matic
10,000RPM, 0 Torque, i could equip this thing with a cutting disk and touch my finger on it and stop the motor
battery's, 3.6v, and after spending nearly 30 min i had barley made a dent in the rivet, and the battery's were dead, 1/16th of an inch in and i needed an 8 hour recharge
Bits, while most (like 3/5ths) were the same size of a dremel, the rest were not, which you were required to keep track of 5! collars, wanted to grind and buff? Well you had to remove the chuck screw, replace the collar, refit the chuck, fit the bit and go on. Im sorry, thats stupid
I think it lasted a week before i threw away all the non "standard" size bits and collars, it maybe lasted about 2 months before i just threw it in a box to forget, since at the time i only lived 10min away from my parents house, and access to real tools
fast forward 6-7 years, and i live across town, im married (which sometimes prevents me from just up and leaving the house) and i want a dremel darnit!
i looked at the 26$ battery operated one at walmart, with 0 bits, and remembering my dislike for a "dremel on a cell".
Also the "engraving" model which is 120v powered, down at Lowes, again with no bits, and the real dremels, which, honestly the 20$ model + bits is not really in my budget atm, let alone a 60-100$ kit.
Darn, all i want to do is cut, sand, and drill some pcb's or abs project enclosures ...
enter mom, who was cleaning out the garage and presented me with a box of "my crap", that i had forgotten i was storing there. Digging tru the box of crap, i found a hot knife (sweet) a glue gun (sweeeeet) and my roto-matic (ugh, well maybe not?)
Welcome to my instructable! (gah finally, you friggin windbag!!!)
Step 1: Basic Plan & Stuff Needed
Turn this useless dead hunk of junk into a usable tool by removing the dead / useless battery pack and hooking it up to a wall wart
Phillips head screwdriver with a narrow / small tip
Soldering iron, mines a 15/30 watt radio shack, and i have not used the 15 watt setting in the nearly 20 years I have owned it
Damp "yellow" sponge
Solder sucker or wick, i just use the red bulb from radio shack in this case
jewelers file, fine grit sandpaper, or any other similar abrasive to clean off the corrosion from the solder points
Solder, 60/40 rosen core in this case (ill switch to silver when this spool is used up)
Zip Lock style baggie (for the nasty battery to go in)
the wall wart i choose is a 5v switching model with a 2.5 amp load rating, ... why?
well theres no way this motor is speced for exactly 3.6v, thats what the old battery pack took to charge
The motor itself, probably can take 12 or more volts, but theres no markings on it, so i choose 5v @ 2.5 amps because its what i found in my "box of warts" with a similar voltage, and a nasty amp rating.
Which allows an increase in torque, and ensures me that if I really really push the tool I probably would burn out the motor well before even warming up the supply, remember were not trying to machine tool grade steel here, just cut, drill, and sand pcb's and project boxes
Switching, cause its what I happen to lay my hands on, and it has the bonus of being tiny, which is nice
after reading some other instructables, I thought I should test the load of this thing to ensure safe operation, with no load the motor is drawing less than a half amp, but with the motor stopped, it quickly jumps to a little over 3 amps
Step 2: Disassembly
3 are larger screws on one side of the unit
#4 is near the shaft on the opposite side , its a tiny screw next to the "shaft lock button"
After removing all the screws you should take the unit and with both hands give it a little twist, which should pop the case open
Step 3: The Guts
its a dc jack, a (nasty) battery pack, a rocker switch and a motor, nothing special
The plan of attack is as follows
De-solder the dc jack so we can recycle it in a future project
De-solder the anode of the battery from the rocker switch
De-solder the cathode of the battery pack from the motor
With regards to de-soldering the nasty, corroded lugs it helps to apply heat for a while, and then a bit of rosen core solder, avoid breathing the fumes , the wires should loosen up enough to remove them
Once the nasty battery is removed from the circuit, place it in the plastic baggie and take it to a proper disposal drop off point, you put it in the baggie so the sulfur + other crap doesn't contaminate everything around it, air flow and physical disturbance sends this toxic dust everywhere, you dont want it in your jacket pocket
Step 4: Cleaning
this includes the dc jack lugs (might as well before tossing it in your parts bin) the rocker switch lugs, and the cathode of the motor
then test the motor and rocker switch to make sure they still work ok with your mulitmeter
In my case the motor was fine, but the corrosion from the battery had wicked up inside of the switch, since most switches are "self cleaning", I flipped the switch over about 10 or 15 times and re checked it, with flawless results
Also since i had the multimeter out i went ahead and checked my supply, since the wires were not marked, I wanted to know which one was positive, and which one was negative (not that it matters much in this case), and to make sure the supply was within spec (again it doesn't really matter, were driving a motor)
Step 5: Connect Wall Wart to Motor
Again this is really simple, solder the + wire from the wall wart to the switch (which goes to the motor)
solder the - wire from the wall wart to the free lug of the motor
Step 6: Reassembly Part 1
Put the switch in first, then position the motor where its not in contact with anything
With the roto-matic the motor seems to sit at a 45 degree angle
Loosely tie a knot in the wall warts cord and fiddle with it as you tighten it so it forms a strain control near the bottom of the case, with a little bit of slack inside the unit
Step 7: Reassembly Part 2
Put the screws back in, I found it easy to put the larger case screws in first
Now you have a useful (altho still light duty) rotary tool
Step 8: Final Thoughts
Its torque is increased, at the start of this instructable I stated i could put a cutting disk in this thing and stop it with my finger, if I did this now i would have a large gash in my finger, but I can still stop it with little effort by grabbing the chuck
Of course I now am not at the mercy of batteries
It is now "corded" but its really not an issue, since the battery is removed the center of gravity is moved to the tools work end, which gives greater control, it is a bit of a nag having a wire hanging out of the backside, but no more than a real dremel, actually less, since the one im used to has a cord thicker than my pc's hanging out the back
There is more vibration, since there is not any battery dead weight to help damp it out, altho I don't recall it being any quieter
All in all I put some junk i had to good use, kept some toxic battery, plastic, and electro waste out of a landfill, saved some money, and ended up with a tool that is adequate for my uses
I hope you enjoyed this instructable
Thanks for viewing!
Step 9: Update:
which there was some concerns about powering a drill off of a wall wart, altho my little dremel wannabe is not going to see the loads that a drill would, it made me go back and think
SO, I ripped it back apart, disconnected the + power lead, and put my multimeter in series with the circuit, set to check the amperage
Without a physical load on the motor, it was drawing 0.490 amps, more than enough for the 2.5 amp supply
Sanding down the edge of a PCB, it was hovering around 1 - 1.5 amps, still fine for the 2.5 amp supply for what I would consider a reasonable use, taking into count I was pushing quite hard and dragging down the rpm to nearly stopping
But when I halted the motor with my fingers the draw shot up to 3.2 amps, and then the switching supply kicked in its overload protection, keeping it fairly steady, but if I continued it for a long period of time the supply would still most likely heat up (I did not bother to push it)
I decided to install a fuse holder, and a 2 amp fuse (probably a slow blow), but by the time I did all this, it was nearly 7pm on a Sunday, and the closest Radio Shack (located in a mall) had been closed for almost 50 min
I will have to wait until tomorrow to do this, and when I do, I will update my instructable
Why not just use a bigger rated wart? because that really doesn't solve the problem, the motor is going to suck down whatever amperage it can get, using a higher rated supply just puts bigger numbers on my multimeter
Is it really necessary? probably not, but as my old electronics teacher would say, "its better to be safe than on fire"
... TO BE CONTINUED!