Its not Mickey Mouse

[Robin teslarParticipant @robinteslar]

Hi ME's

I looked on Ebay recently for an auto reverse tapping chuck for use on my Mill (something like an Etco). I was amazed how expensive they were (£250 new), Then I looked at my defunct chinese cordless 18v drill/driver which has failed batteries and too expensive to replace. I bought this out of Aldis a few years ago, cheapo price about 20 quid, so I had my use out of it

It has a 13mm auto chuck and the useful torque limiter. So I took it apart and was amazed to see that it is quite good quality, lovely little double sun and planet gear box, 100w motor. variable speed 0-500. So this will be reassembled with some external wiring t an 18v SM PSU and I shall mount it on a cheap drill stand I had for my power drill. Fix up with a control box for speed and direction.

How neat is that – well I felt a bit chuffed anyway.

and FWIW I'm sure that this system would make a good pwoer drive for my Mill table

Just need to get a toothed belt and some cogs, I think. Ive got an old Bosch lying around also

But as they say, as one door closes another on slams in your face, cos I just bought an actual tapping head for a fiver on Ebay, seems no one had spotted it

[Robin teslarParticipant @robinteslar]

Tapping machine

[Keith Wardill 1Participant @keithwardill1]

I did a similar thing sometime ago, Robin. Usual thing – the batteries died, and new one cost more than the original drill, so I just bought a new one. The old one lay around for ages, then I needed to tap multiple holes in an ally block, so it was just the job. two small (ongoing) problems – The chuck was the usual auto thing, and not particularly good quality. I find it difficult to get it tight enough to stop the taps slipping in the chuck. Its OK up to a point (good safety feature!), but its annoying with anything over about M4, because it slips too much then. Maybe a chuck and key would be better. Other problem is the bearing for the chuck – its really not man enough, and there is quite a lot of side to side play if I pull the chuck around. So far its not a big problem, because the taps are started in a pre-drilled hole, and the pressure is axial, as in the original drill.

I keep thinking about using the gearbox part to build a better machine – proper bearings for the chuck, and a geared or toothed belt drive, because the low speed torque is not so good using a variable power supply (and it draws a lot of current ! – I was lucky to have a suitable transformer, but they are expensive if you have to buy one.).

[Robin teslarParticipant @robinteslar]

Hi W

Indeed I have got to find a power supply to replace the battery source. Now I read somewhere that Switched mode supplies dont like pwm speed controllers, probably due to high frequencies interfering . I havent found a discussion on this just now, but some quick test showed me that and 18v smps with a rated output of 7,5a dc wont power this motor. I guess the starting current trips out the overload protection

Do you have any idea what sort of power these little motors draw. As a rule of thumb the current supply needs to be 6 times the fl running current, so it could be a lot of amps 10-20?

Im going to need a serious old fashioned battery charger

Back to Ebay again

Robin

[Sub MandrelParticipant @submandrel]

I fitted the 'works' of one of these inside a 2" diameter steel bar to make a toolpost milling attachment. I didn't use the clutch – but clever things those torque clutches, aren't they?

Neil

[Keith Wardill 1Participant @keithwardill1]

Robin,

I have a (huge) old tranformer which is nominally rated at 11V, 15 Amps. I have no idea what it was originally used for. I acquired it years ago to strip for the copper wire (another project), but never got around to it. I just used a solid state full-wave rectifier (easy to find), and I have a 5000 uF 40V capacitor to smooth it,. (It works without the cap, but a bit noisy for some reason).

I have to admit the whole thing was not 'designed' – I just needed something to do the job in a hurry, so whacked it all together without much thought. As you can guess from my description, as it stands, it could be a bit lethal. It all sits in a wooden case, and the only protection is a fuse in the power lead. I did have a 25A fuse in the motor lead, but this blew sometimes, so eventually I just removed it. (I know – but its my shed, and I can take my own risks!).

I can't say I have ever had problems with startup current – as you say, rule of thumb says 5 or 6 times running current. I normally switch on with no mechanical load, so the load current / inrush current is probably relatively low, so I guess this is the reason. May be a problem if I startup on-load (ie motor stalled – must try it sometime).

As I noted before, transformers now are pricey – I did run it for a while on a car battery, albeit at reduced voltage, and it still worked Ok for me – a bit down on power (18V motor). (A battery is probably cheaper than a transformer these days! – use the guts of a 12V drill maybe?)

I suspect smps supplies cannot start up under such a heavy load, but I have never investigated it.

[Robin teslarParticipant @robinteslar]

Hi W

you really should have a fuse on the output side – but its your shed

I finally got a surplus psu from a defunct laptop to work, its 19vdc and 3.8A but it wouldnt run the motor directly, so I stuck a 10ohm power resistor which dropped about 4v and it work even with the speed controller. The psu I think kept shutting down and restarting probably cos of current spikes caused by the PWM..

Since then I sourced an industrial psu giving 15vdc and 16 amps for £35 so I think that will do the job and run several small motors. Its a conventional xformer psu with volt control and o/load protection, cost £350 new

Interesting is that dropping 4 volts across 10 ohms mean its only taking 400mA but then I havent got a scope so cant see whats going on

So I think ive got it sorted at last and ive got several of these old cordless things lying around

Cheers

Robin

[Sub MandrelParticipant @submandrel]

The motor may have looked like a short to the PSU when it was stationary.

Neil

[Grizzly bearParticipant @grizzlybear]

A cheapish car / lawnmower 12volt battery could be the answer, it would last years, topped up with a battery charger. Plenty of smooth amps at your finger tips.

Regards Bear..

[Gordon WParticipant @gordonw]

Yes ,a car battery is the easy/ cheap answer. Every now and then flatten the battery using ,say, an old headlight bulb, then fully recharge. I,ve one running an electric fence for years, it was pensioned off for car use before then.

[Ian S CParticipant @iansc]

You might get an old battery at the garage, a nephew of mine needed a battery for starting his model boat(12 V electric starter motor), went to the local garage, they said round the back, help your self, if its no good bring it back. He picked the best one and took it home, found it was better than the one he had in the car, so swapped them, the battery from the car worked ok for starting the boat. Ian S C

[Sub MandrelParticipant @submandrel]

Make friends with the man who changes the batteries in fire alarms. They have to be changed every two years to be on the safe side. They are typically 7Ah which is ample for most things. Such a battery happily powers my shunter and pulls me along!

Neil

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