View Full Version : Well, that didn't work...
01-29-2007, 03:31 PM
While trying to make my Forster DBT base (Inside-Outside deburring tool) an electric powered doohickey with a Dremel tool, it made me aware by freezing up in rotation it was spinning too fast from heat friction...and it locked up.
Yes, I know ball-bearings are the way to go, but you can't put them in the DBT base.
Went to a lot of trouble making an adapter that would screw onto the threads that once held the knurled knob handle. This adapter worked very well connecting up the DBT base and the Dremel tool rested on a little plastic stand with a hose clamp.
OK, go to plan B. Remove Dremel tool, and find that Skill Twist cordless screwdriver I never use anymore. It had been put away in my tool box about 7 - 10 years ago, and I found the battery is deader than a mackeral and won't take a re-charge.
That screwdriver will be getting a new batterey as soon as I can locate a place that has them, maybe Ace hardware.
Already made another adapter on my mini-lathe to work in the Skill Twist cordless screwdriver, that will connect the DBT base to batterey charged screwdrive...which rpms turn at a more sedate rotation that can be operated by a flick of a finger teater-toter switch that is forward and reverse.
If you ever decide to play around with this stuff, I'm an expert on adapter making and can help. :-?
01-29-2007, 04:24 PM
I once ran one of those skil screwdrivers off a discarded DC transformer. No battery required. Not sure what size anymore, been more than 10 + years ago. I keep all the transformers I come across for just such projects.
01-29-2007, 04:40 PM
Sounds good, but haven't a clue what type of transformer you speak of...no experience with one. Is that something like an electric train transformer? If so, don't have one of those either. :mrgreen:
01-29-2007, 06:08 PM
The charger that came with the thing would be a perfect transformer for the task. You might be able to sit the screwdriver in the charging cradle and run it right from there.
A new battery would likely cost near the same as a new unit.
01-29-2007, 06:43 PM
Tried running the tool in the charge cradle but it wouldn't work period.
I'm not an electrician, heck, I'm not much of a lathe operator either...but I'm trying.
The batterey looks like it would be an expensive one, (its pretty big) it may be cheaper to buy another cordless screwdriver...don't know yet for sure.
01-29-2007, 06:46 PM
Transformers come with lots of todays electrical devices. One of the more common is the phone answering machine, although many of those just step down 120v ac to a lower ac voltage. The type of transformer you need would be AC stepped down and converted to DC. Many devices that run on batteries have a jack to plug in a transformer. If you look real close, the transformer should have the step down listed and this number will be close, but for exact measurement, you need to measure this yourself.
I'm sure the skil screwdriver has a transfomer that plugs into the wall. However, I'm not sure if the output is DC or AC, plus I'm not sure it has the voltage and mA to run the motor. Any help with power and loads for that screwdriver will need to be refered to some one a little more knowledgeable than me.
01-29-2007, 08:59 PM
The charger transformer likely won't work. If the tool is that old, the batteries are probably NiCd and the charge rates on the inexpensive ones was slow - i.e. not much current. The tool will probably require considerably more current to work than the charger will provide. The dead battery is probably placing a high enough load on the charger that the voltage is way down - hence it not working in the charge cradle. The charger itself would likely make it turn, but the available torque would probably be pretty low due to the low current output. You can try it without the battery in place and see if that works if you haven't already.
If you're not too concerned about using the screwdriver for anything else later, you can hack into it and solder a pair of wires to the battery contacts or splice in to the wires that go from there to the "innards" of the thing and use an external power supply. How much voltage does the tool nominally use? Look at the charger, it should have an output voltage rating on it somewhere. The battery pack itself should be marked as well and would be the best number to use if the charger and battery ratings are different (charger may have a slightly higher output voltage rating than the battery). If it is 6V or 7.2V (1.2V per NiCd cell in series), then you could take a charger for your car and use it if it has a switch to back the output down to charge a 6V battery. If it's a 12V tool you can use the 12V charge setting, but I doubt that it is a 12V tool.
You can also purchase a fairly hefty wall wart at Radio Shack that should supply the correct voltage right off - but they are proud of those things... Also, the amount of current needed from the supply will be greater the lower the voltage the tool was designed to operate from. With a little more info (voltage rating and if possible current rating of the battery or it's capacity - the mAH number), I can give some better advice if you want it.
If you do go with an external supply, getting one rated for sufficient voltage and current is going to be key for reliable operation. Too much voltage and you'll let the magic smoke out of your screwdriver. Right voltage but to little current and the magic smoke will come out of the power supply. Once the magic smoke comes out, you can't put it back in and it's time to start over. [smilie=1:
01-29-2007, 09:14 PM
I have this quirk of saving ALL the wall warts and AC/DC converters around me. Some of the highest quality and most highly filtered are the old ones for computer peripherals like external CD drives, printers, and scanners. If you have any lying around, check the output. Some I have put out 2 to 3 amps.
01-30-2007, 10:05 AM
Well, you guys were right. It will probably cost more to buy a new battery than to just replace the Skill Twist drill unit with a new one.
Went to Skill Twist drill website, they show and improved model with charger for about $14.00 , while a replacement rebuilt battery will cost about $20.00.
Going to town tomorrow, will check with Radio Shack...see what they got to offer in batterys.
Found several transformers in my bottom desk drawers that were chargers for cell phones, and other gadgets, but they put out too many DC volts and amps, probably fry my Skill screwdrive charger and battery. Best nix that idea of using any of them.
And, will see what Ace hardware has to offer.
01-30-2007, 11:03 AM
chargers for tools of this nature are typically, a small percentage of motor load requirements and in the case of the cheaper tools, can be as low as around 20 milliamps while motor/amp requirement can be 2 or 3 amps at the given voltage.
Add to that, in the case of the charger/transformer possibly supplying AC current a dc converter will also be incorporated into the tool.
Perhaps a simpler solution would be find a low rpm, fractional horsepower motor, such as a condenser fan motor from an old fridge or freezer. usually around 10 or 15 bucks from places like grainger. this would be far more inexpensive than trying to find an adiquate power supply for the low voltage dc motor.
a word of caution, if one attemts to control motor speed via a rheostat controller, do NOT use a dimmer switch for lighting purposes, dimmer switches, control voltage from low to high, resulting in inadiquate start up current eventually causing motor damage. Ceiling fan speed controllers can be used, but be aware that reducing motor rpms cuts down on available motor torque also.
01-31-2007, 02:51 PM
OK, its another day, back from town with a new Black & Decker cordless screwdriver, model 9072CTN...price, a mere $18.00 and change.
Radio-Shack, Ace hardware didn't have a battery replacement for the Skill Twist unit, so, bought the B&D one...and it looks good too.
Got it home and tried it out and it turned over about six revolutions and died...battery low. Plugged it in to the little 2.4 Volt charger, (still don't know the amps it draws) it was on the charger a couple of hours and it goes like Billy Dee Blazes, which equates to 150 rpm.
The B&D unit seems to have very good torqe than the old Skil Twist unit. Does a nice job on deburring brass, and even military primer hole brass. But needs a smaller hose clamp.
Me thinks this little goodie will get more use than the old Skill unit. However, the Skill unit still needs a battery replacement. Next time I get down to Wausau, WI, will go to the battery store there and get one for it. That's about a 100 mile trip one way, so will wait until spring time.
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