Mending a Big Grinder

[AlanBeckett]

In the Thread about mending my Lawn Edger there were a few pictures of my new paths and patio. A mate of mine came round to help 'cause those big slabs seem to have got heavier over the years, and he's younger than me. He cut up a couple of slabs with his 9" Angle Grinder with its diamond blade - easy peasy, not at all like the old days of hammer, bolster and pray. Just in passing he remarked that it was a new Grinder as his old one had stopped working. Actually it isn't so old, so I thought I might as well have a look at it.
It's a Draper PT2023, which as far as I can tell is still in production. At least his new one looks identical. Sure enough it didn't go round. The fuse was OK, but O/C across the supply. That wasn't hard to diagnose as one of the brushes had a wire off. However, it was also impossible to turn the rotor, so it was time to dismantle it. It wasn't difficult to take it to bits, and it soon became clear that the front bearing had disintegrated. This had allowed the rotor to rub on the stator, which jammed it. I suppose that contact between the gears would have kept it in reasonable alignment for a time until the bearing finally gave up the ghost, and then it stopped. Bearing in mind the racket it makes when cutting I don't expect there was much scope for hearing anything untoward. It's also interesting to note that there is no grease on the gears whereas you might have expected that it would have melted and spread around. The bearing inner was a pig to get off the shaft and required a bit of grinding and chiseling, which resulted in nicking the shaft, but I reckoned it would be OK.
So, to fix it. A search round the Net produced a bearing and brushes. The bearing was from Simply Bearings Ltd. - http://simplybearings.co.uk/shop/index.php - a Company I can thoroughly recommend. The brushes came from a Company on the Net advertising spares. Oddly the listing said 'Brush' and I thought the price was a bit steep, but a pair arrived. The total, including Postage was £10.68.

To be continued .......

                   

[AlanBeckett]

So, to reassemble it.
There is a bit of a conundrum with the rotor. The small gear won't go through the bearing. So the sequence is to install the bearing in the housing - it's held in with a triangular plate - then press the rotor into the inner while fitting the gear over the end. No doubt on production they had all sorts of jigs and presses, but I was more lump of wood, suitable sized socket and medium hammer. I was a bit nervous about it 'cause I'd had a lot of trouble getting the bearing inner off, but it went back OK. I guess it's all arranged with the right tolerances, and the case is strong enough to stand the push. A dose of Loctite here and there made me feel better. It all turned freely so I redistributed the grease and put it mostly back together.
Next the brushes. Actually they were relatively easy, just the Fastons were a very tight to push on to what appeared to be very flimsy Males.
Finally, reassemble the handle - it rotates and test it. Lo, it works. It has some sort of Soft Start built in, not surprising as it's 2kW, which is a bit disconcerting at first. You squeeze the trigger, nothing happens then it winds up. At first it sounded a bit rattly, but it's OK now. I don't expect to give it the hammer it got before, but as a ten quid backup it's not bad
Alan

                   

[Yorkie]

Great post Alan!

Thanks for going to the trouble to post the pics.

It's a good example of something being 'beyond economic repair' is sent to a service agent due to high labour costs and VAT, but within the scope of a skilled DIY repair. You did well to track down a new bearing and brushes, and as you say, you've got a serviceable 2kW grinder for a tenner, with a list price of close on £100, and with soft start too. (I've got a cheapo Clarke sawbench which doesn't have soft start, and the 'kick' is very disconcerting when switching it on. I don't know if there are any means by which one can add soft start externaly. It does have an NVR switch).

The grinder must have been subjected to a lot of punishment to get into that state - prolonged use under heavy load, beyond what could reasonably be expected of it. It's an angle grinder - not a petrol driven Stilh-saw. Even a 5" grinder with a stone cutting disc can be used to cut 2" concrete slabs, but you have to go steady with it as cutting puts a lot more load on it than does grindidng, which is the primary intended use.

As you say, it's still in production - about the cheapest you can buy one is £75.00:

http://www.powertoolworld.co.uk/draper-d...72866.html

Thanks once more for an informative post!

David

[DODGERN]

(I've got a cheapo Clarke sawbench which doesn't have soft start, and the 'kick' is very disconcerting when switching it on. I don't know if there are any means by which one can add soft start externaly. It does have an NVR switch).


David

I made a thyristor controlled drill speed controller some years ago David. I suppose that could be used and would also give control of the motor speed, if required.

Roger.

[AlanBeckett]

The grinder must have been subjected to a lot of punishment to get into that state - prolonged use under heavy load, beyond what could reasonably be expected of it.

The owner is no shrinking violet

When I had it to bits I noticed that there was a 'black block' near the switch, but I assumed it was a suppression capacitor. Clearly not, so presumably such devices are available. My last garage vacuum cleaner did a soft start but that used discrete components.

Alan

   

[singlepentode69]

A good repair mending is better than ending is my moto throw away Britain these days
Robin

[Retired]

Hi,

Well done Big Al; with care it should last years so don't go abusing it. Have you made a start on the cast iron paper weight I collected for you?

Being retired leaves me open to all kinds of offers of "good jobs". A couple of weeks ago a neighbour paid us a visit thinking he was doing me a favour. Where he works there is a pile of around 40 power tools of all descriptions and all broken. If he paid me would I repair them for him?

The short answer was NO. Assuming I took this job on; I would end up stripping these power tools cluttering my benches up whilst I tracked down spares; I would be expected to pay up front for the spares and would no longer be able to use my workshop or garage. My time means nothing to such people although their time is precious. I would have to pay for heating and lighting.

Assuming he did pay for the job I doubt I would get anything near the minimum wage in fact I wondered if I would even re-coup the cost of the spares. I suggested he place them all on eBay and gently let him down. To add insult to injury the tax man would also want to rip me off.

Un-phased by this rejection he then asked if I had a big saw bench? He had a large table top that he wanted to reduce in width. I explained that if the table top had been mine I would not attempt to put it through the saw. I asked if he had a portable power saw and he had so I said why don't you do as I would do and attach a batten/straightedge to the underside of the table top and simply run the saw down which is much safer. I hope he doesn't return because he also broke me off from my decorating to give his car a push after the battery had run down due to the door being left open whilst he was away on holiday for two weeks.

These kinds of requests are common and in retaliation whilst at Rufforth I bought a large sign which is now displayed on the central heating boiler in the garage. A picture of the sign is below.

Kind regards, Col.

   

[pwdrive]

Well done you....Unless it's a close friend that needs a hand or a job doing then I tell everyone else to go forth and multiply 'tis the only way.

Lawrence.