Cheap Die Grinder

[Hood]

The top diagram is almost what the wee circuit board is
Trying to measure the resistance of the variable resistor and I am getting different values depending on which way my meter leads are connected so looks like I will have to try and cut the traces to take it out of circuit for measuring.

 

[Hood]

One other thing, the white "plastic" board that the circuit is printed on is one amazing heatsink. Touch a soldering iron onto the legs of the triac for a second or two and the "plastic" is that hot you can't hold on to it. Not sure what it is actually made of but obviously not a standard plastic.

 

[Seadog]

That's because you're changing the polarity and forward biassing the DIAC/TRIAC. It's only necessary to disconnect one side of the pot.

 

[Hood]

Well I tried to cut the trace and it is not happening with the knife I was using. It is not like a normal copper trace, seems to be a very hard material and maybe actually formed into the "plastic" board. So I desoldered one leg of the cap and also one leg of the diac but still I get different readings so looks like I will have to grind away the trace at the variable resistor that goes to A2 on the triac.
One way the readings are fairly stable at around 430K, the other way they seem to jump around between 430K and 800K. So maybe 500K would do the job.

 

[Seadog]

It's probably a 470k pot

 

[Hood]

It's probably a 470k pot

Yes that would be it because I was also measuring the fixed resistor area which was 30K. Not sure what wattage would be required for the pot but probably if I select too small a pot the worst that will happen is it will burn up.

 

[Seadog]

Not sure what it is actually made of but obviously not a standard plastic.

I'd have thought it was a ceramic substrate.

It doesn't need to be too high a wattage, around 2 Watts should do.

 

[Hood]

I'd have thought it was a ceramic substrate.

Yes did a search and saw you get ceramic heatsinks.

It doesn't need to be too high a wattage, around 2 Watts should do.

Thanks, now looking to see if I can find something suitable that is switched as that would be the best option.

 

[Windy Miller]

Was using my die grinder today, and had a bit of an 'incident'. Opening up some chain drilled 9mm holes to make a slot, and all of a sudden the carbide burr dug in and ripped the 50mm length of 40x8 flat bar out of the jaws of the vice. I expected it to come flying off and take my ear with it but instead it just kept on spinning. Obviously it was all 'slightly' out of balance now, so the whole thing vibrated like crazy - it was all I could do to hold onto it!

I considered launching the lot and making a dash for the plug, but I imagined it chasing me around like a mental dog snapping at my ankles!

Eventually I managed to find the off switch and shut the bl00dy thing down, but I don't mind admitting that I very nearly soiled myself in the process!

I've had a few dig-ins before, but not like this one. I was using a brand new Garryson 6mm straight burr, and it's as sharp as hell. Much more so than the no name ones I'm used to. Maybe that's why it dug in so violently. I reckon the no name ones would have just snapped off and shot the job off out through the wall!

Clean pants please!

 

[Hood]

Well I just about had a great idea.
Was looking to see if I had a suitable pot and spied an Alpha planetary gearbox and had a thought.
Hauled the front end off the grinder and saw how it was attached and that it would be an easy mod to fit the gearbox. Instant 1/3 speed and 3x more toque.
Perfect!!!

Then the penny dropped, the max input speed of the gearbox is 5-6,000 rpm, gave myself a slap round the chops and went back to, unsuccessfully, looking for a suitable pot.

 

[Windy Miller]

HOT GRINDER UPDATE:

Well I had an email from them this morning, and they are sending me a new grinder, and I can keep the old one for £10. How good is that?

Will certainly add these guys to my favourite sellers list. That's how Customer Service should be. Very happy indeed!

 

[Hood]

Got the ebay speed controller today, works great, better than the one hauled out the old drill.
It is obviously bigger so no way it will fit inside the handle but I think a small plug in box will be the way I go, anyway here's a rubbish vid.
It sounds a bit rattly at first but that is because I am holding the phone and the grinder in one hand so the phone is vibrating off the grinder body.

 

[Hood]

This will do for now until I either get or make a more suitable enclosure.
Found an old HP printer power supply, 30v AC output, cracked it open and hauled out the transformer and capacitor. Broke a few of the internal webs off and drilled a hole in the top, job done

 

[whm_fab]

great work hood! have you a link to the controller you bought? i recently bought a new makita die grinder, and this is something id like to incorporate. cheers

 

[Hood]

great work hood! have you a link to the controller you bought? i recently bought a new makita die grinder, and this is something id like to incorporate. cheers

This was the one I bought.
http://www.ebay.co.uk/itm/SCR-Volta...var=452050917144&_trksid=p2060353.m2749.l2649

 

[Windy Miller]

I think I'll have to get me one of them. I have had a few more minor dig-ins whilst using the 6mm straight Garryson burr, and now I'm nervous about using it! Maybe it'll behave better if I slow it down.

 

[whm_fab]

I think I'll have to get me one of them. I have had a few more minor dig-ins whilst using the 6mm straight Garryson burr, and now I'm nervous about using it! Maybe it'll behave better if I slow it down.

to be honest, i find using a die grinder the faster the less chance of digging in. i want to slow it down for use with flap wheels, wire wheels etc. carbide burrs are well able to handle the heat and speed

 

[zeppelin builder]

metabo do 240 v 125 grinders with speed control and die grinders

 

[Hood]

metabo do 240 v 125 grinders with speed control and die grinders

Aye but not for £20

 

[optima21]

I've jumped on the band waggon and got one of these, has anyone else tried to read the instructions that came with them