Speed control for a 115mm angle grinder

[gerrymoore]

I need to be able to slow down my grinder. I do have a Bosch variable speed model but I'm fed up changing from a cup brush to a flap disc so want a cheaper one...can I use this safely?

http://www.ebay.co.uk/itm/NEW-Volta...053340?hash=item25b6772c1c:g:aHEAAOSwUuFWvFXi

I can get a Bosch 750 watt for £45 and the controller for a few quid as opposed to nearly £200 for a variable speed model.....

Thoughts/experience welcome!

 

[rtbcomp]

From the description he says it's a voltage controller, although it uses an SCR and a small heatsink which suggests it chops the waveform like a drill-speed controller. If it's the former I'd say no, if it's the latter I'd say yes.

The motor it controls must be one with a commutator & brushes (universal motor), I'm sure this would apply to all angle grinders, although you'll need a basic grinder that doesn't have any of its own electronics built in.

 

[eSCHEn]

My experience of eBay electronics like that is to derate them heavily, 50% is my normal. That gives you ~12.5A and the grinder would draw ~7A, more on startup.

I'd say it would work but I'd grab a controller and use my cheapest grinder to test.

The monies definitely make sense to me.

Edit: rtb has better info than me

 

[gerrymoore]

This is the grinder I'm thinking of.....

http://www.ebay.co.uk/itm/272127799286?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

Says input of 720 watts and output of 300 watts...will only be used for light buffing with a flap disc..for not much more dosh I can get the same scr controller with 4000 watts capacity...I've used a house dimmer switch in the past to control drills and even a small router but they use triacs I think rather than an scr...wondering if I should just make one??

 

[daleyd]

Unless you just want an exercise in doing it just because you would like to try, in which case that's fair enough I won't knock anyone for having a go, but you can buy variable speed angle grinders cheaper than that anyway. (Not Bosch but good enough for diy type use I would have thought)

Lidl or Aldi usually have the 5 inch ones come up now and then for not much more than £20 - £30.

 

[eSCHEn]

It's not a complicated thing to construct, especially for a man of your talents Gerry. Thing I find is that the damn project sucks you in and I end up not doing the job on time!

How do you find those Bosch grinders incidentally? I'm getting a lot of gyp from my Silverline special so want something with less vibrations.

 

[gerrymoore]

I've had the Bosch variable speed grinder for 23 years!! How do I know...the on/off switch broke and I tried to get a replacement...not available now...wonder why?? Anyway I managed to replace the switch with a micro switch and it works great again. It's a magical tool but now very expensive to replace.

I did buy a 'cheap' 115mm variable speed drill for just £35 but bloomin heck it's just too big and heavy for me...great product, and well made, but way too heavy for what I need fettling my 'sculptures'! I need to be able to finely control the grinder and the size and weight make a huge difference even after a few minutes (well at my age it does!!)

I might see if I can find a decent diagram for a triac based controller and build my own....or just pay up for another Bosch!!

 

[eSCHEn]

Yes that's exactly what I found. This one is big, heavy and gutsy. It's also beastly on my hands and I can't do more than ten minutes before I have to stop.

I've a Makita battery powered one and that is brilliant at getting into the small spaces. Really nice and comfortable as well but always out of juice!

 

[gerrymoore]

Can't seem to find a Bosch one now...except from the USA....De Walt do a model with some sort of balancer for around £130.00....progress?

 

[eSCHEn]

You've got to think that the price would fall over the years.

Whether the quality has as well is honestly difficult to say until you own one and use it properly.

I don't think you'll get another 23 years out of a more modern one though

 

[gordon stephenson]

Gerry, Aldi and Lidl both do variable speed 125mm angle grinders now and again, Both priced at around £29-99, I have had one for a few years and been well used and has been great,

 

[gerrymoore]

Hi Gordon..yes..thanks for that but I think they are too big and bulky for me..the one I just bought is variable speed but just too heavy for me to use comfortably...the Bosch are very light and slim in comparison and I don't need 'power' as such.

 

[Robotstar5]

I've a Makita battery powered one and that is brilliant at getting into the small spaces. Really nice and comfortable as well but always out of juice!

If it's that good and only used in a workshop, why not ditch the (heavy) battery and hardwire it to an 18V supply?

 

[eSCHEn]

If it's that good and only used in a workshop, why not ditch the (heavy) battery and hardwire it to an 18V supply?

Lack of a workshop unfortunately. I work outdoors normally.

 

[MattF]

Lack of a workshop unfortunately. I work outdoors normally.

What voltage is the drill. 18V?

 

[eSCHEn]

What voltage is the drill. 18V?

It's a grinder Matt and is an 18V Li-on one.

 

[MattF]

It's a grinder Matt and is an 18V Li-on one.

Oops. Sorry. You can order 1.5V cells from Chinese suppliers cheaply enough. Could be worthwhile rigging up a pack from those and chucking it in a belt pouch, with flyleads going to the grinder. Did that once with a meter of mine.

 

[ford34/2]

Similar idea to some Hilti stuff, they had a Body belt to clip the battery into, attached to a coiled lead, reduced the weight of the drill/or screwgunn, and it made a hell of a difference when you used it 8 hrs a day. Dry linning lads loved them.
takes a bit getting used to putting the tool on Ya belt with the clip instead of lying it down. Yonks back I had a 12 volt one rigged up to a car battery, Bosch one-- when batteries cost more than a new drill charger and batteries. Charged the battery every night and never run out of juice. Even rescued cells out of knackered drills and rebuilt the other battery case with the newish cells.

Stan

 

[slim_boy_fat]

I work outdoors normally.

Unless you can sweet-talk Mrs E.

 

[eSCHEn]

Unless you can sweet-talk Mrs E.

I fear that grinding (well this sort) is something that even she draws the line at being indoors.