Member postings for Pete Rimmer

Interesting John, I didn't realise that a 555 tier could send variable duty pulses I thought they were always 50% duty but variable frequency. I'm very weak on the subject though.

The 20/40v batteries are just two 20v batteries in one package. Some tools use only 20v, others like this one connect them in series for 40v. The underside of that board pictured above has a heavy PCB track linking B1+ to B2- to series them.

I don't think any battery screwdriver controller will do the job unless it could be used to switch the mosfset in PWM mode.

I have looked at some of the ebay/amazon offerings and so far there are none that are powerful enough yet small enough to fit inside the housing. I was kinda hoping that the soft-start works by sending a rapidly-lengthening PWM pulse to the mosfet and that I could somehow swap that output for one from a PWM chip but I guess my 'lectronics knowledge is too scant for that to be feasible.

It's not a deal breaker. The original device is fixed speed it's just 10x more flexible if it can be varied.

Their leaf blower has variable speed but I don't fancy spending 55 quid to see if it work with my motor.

Yes I have the battery system (I obviously needed a battery so I bought one battery set and two grinders).

No marks on the motor it's just a basic PM stator and 7 segment wound commutator.

I was wondering about U3, it rather unhelpfully has no markings. Looks like the top's been sanded off.

Edited By Pete Rimmer on 19/11/2022 13:47:09

I have bought a £15 Ferrex battery grinder from Aldi with a view to removing the metal work head and fitting only the motor to another device.

This grinder uses a 40v battery and has a soft start but no speed control. I don't need the soft start since there will be no cutting disc or rotating parts exposed.

What I want to do is either junk the soft start and fit an independant speed control in it's place, or manually manipulate the soft start ramp to adjust the RPM with a speed pot or something. Here is the board and components that make up the soft start module:

The motor won't be under much load from it's retro-fitted duty, far less than when being used as an angle grinder. What I want to know is:

Does anyone know what method would be used normally to control the ramp, and could it be manipulated to work as a speed setting instead?

OR

Can anyone suggest a suitable speed control that I can put between the 40V battery and motor to vary the speed?

Please I don't want any suggestions to go and buy a grinder with speed control most are an unsuitable shape to do the conversion and since this is an experiment I don't mind trashing a £15 grinder but I'd rather not spend much more on a named brand that I might end up scrapping.

Thanks

Pete.

I'd say that was about as perfect a small workshop machine that it's possible to get for reasonable money. I would have bought it in a heartbeat.

Yes I meant standard 'type' of fitment. The odds of actually fitting a non-native one are vanishingly small.

A very standard fitment for many small lathes. Denford, Boxford, Atlas to name but three.

Personally, I would try to find a cross slide/compound assembly and transplant the whole thing. That short cross slide design is prone to wear and not very rigid. A more modern, longer type will improve your work.

I had to make my oil gun from an old grease gun. I cut it in half, turned a heavy cap to serve as a base and welded it on. Cut the handle down to 6" long and filled it with way oil.

Those reservoirs should have a losenge-shaped felt pad in them. They are just a giant oil wick that lubricates the table as it slides over.

If you get your supports somewhere near to the bessel points ( the points where the factory would put the food pads) you're not going to go too far wrong. If the plate is supported around the edges rather than at those points then it WILL bend under it's own weight and certainly if you put a heavy part in the middle, but the amount is very very little for a home shop sized plate. I could see it happen with my autocollimator (1/2 second resolution) but only just. When you consider that most sensitive levels will be in the 2/5/10 second range this means that it's so slight that it would not affect normal work.

You must have ordered the last one I put in an order for a collet chuck and collet set and they are quoting 63 days for the ER32 set.

Knock a roll pin into the hole and use the lathe to make a tapered pin.

BTW you don't need a steady to make a 25mm long 3.5mm thick pin.

Sorry it's an ordinary RH thread I don't know why I put LH. I've edited the post above to avoid confusion.

Yes it's an ordinary RH screw I think the thread is 1/4"BSW.

Edited By Pete Rimmer on 06/11/2022 11:33:50

If you're sure that you have followed the schematic try disconnecting one end of the cap and run the motor. If it behaves the same as before then the start circuit is not being invoked. Either because of a faulty cap or because of a stuck centrifugal switch most likely.

If the motor just now hums or is reluctant to start then re-visit the wiring.

Another possibility is that someone has changed the terminal connections in some fashion. I've seen this several times. How it would cause the above effect I couldn't say.

Edited By Pete Rimmer on 06/11/2022 11:04:52

Seems pretty straightforward if depicted a little strangely.

U1-U2 is the run winding, Z1-Z2 is the start winding.

The capacitor is always connected one end to live. The turn clockwise Z1 connects to the capacitor and Z2 to neutral. To turn anti-clockwise Z2 connects to the capacitor and Z1 to neutral.

The info in that video contains a couple of rather dumb stud gear selections. For example, 1.75mm pitch uses a 19tooth gear and 11.5tpi tumbler setting. The 19tpi gear is very weak where the keyway comes close to the base circle so a 38 tooth gear and 23TPI tumbler setting will produce the exact same pitch, be a much stronger gear and have better tooth engagement.

Similarly, 4m pitch also uses a 19tooth gear which is sure to break cutting that coarse thread. This is also completely unneccesary when a 34 tooth gear and 9TPI tumbler setting will produce the same thread and 34 is in use for 6 other pitches already.

5mm pitch is even worse, but could be improved by using a 26tooth gear and 5.5tpi setting, with a much smaller pitch error too.

Apart from that, his claimed % error is out by two decimals. He's quoting errors of (for example) 0.0005% when he should be using 0.05%

Depends how they implement it. I once saw a fraction-displaying device that would return daft fractions like 37/41

The one in the pic does not. Check their catalogue and you'll find it's not at all unusual.