Oh Dear, I've blown the chop saw...

I've generally been pleased with my Aldo chop saw. It's gone through pretty big steel like a hot knife through butter (well, quite quickly anyway) and is a huge step up from a hacksaw.

However, it looks like I've overloaded it today. Cutting off a piece of 40 mm square bar there was a pop and the lights went out in the shed - and the saw stopped - with some lovely smoke coming out of it for added value. This is usually caused by the breaker in the house going, but not this time.

I tracked it back to the fused switch under the sink in the kitchen which feeds the shed. Replaced the fuse, lights now worked. Turned on the chop saw it started up and promptly blew the fuse in the plug.

It's well under a year old, but I probably don't have the receipt and certainly couldn't find it. Before consigning it to the Old-Chop-Saw home, is there any chance I can fix it.

When I say 'I can fix it', I mean me - no suggestions of rewinding the motor please! I'm struggling enough with making flat bits with a mill!

Angle grinders and I don't seem to get on. I've reduced several of the (cheap) ones to smoke and nothing I've done (cleaning the commutator, replacing bushes...) has done much good.

So having exposed my incompetence with grinding machinery - is there anything I can do?

Iain

First question is where did the smoke come from there is a good reason for asking. Is it direct from where the brushes are or somewhere near the cable entry. If the cable entry then the cable may need chopping back and rewired.

If not there then take a look inside to see if any swarf has short circuited any of the internals while in there check for any broken wires

We used to get guys managing to get grinder cables damaged where it entered the body.

I always told them they were putting too much pull on the cable.

But at home one day the good lady switched on the Deep Fat Fryer and "BANG" the cable blew out of the cover and the fryer shot along the worktop for about a meter and crashed to the floor.

On examination I found it was the cable clamp was responsible. it was a really bad one piece design that clipped together and bent the cable in a really tight bend.

When I examined the grinders I found the same stupid clamp.

I got our electrician to fit better clamps and I can't remember another failure.

We never replaced the fryer!

Ian, it is a sickening feeling when you see the magic smoke coming from our tools, recently had the same with my Bosch mains drill whilst drilling some hefty holes in brick. The drill had given me many years of service (abuse) so I cut my losses and scrapped it, the replacement was another Bosch drill, I was so impressed with the performance of its predecessor that I had no qualms with the same make again. I have a Lidl chop saw with which I am much impressed, fingers crossed that it’s reliability matches the Bosch drill. I think that today’s products are generally not cost effective to repair but saying that I recently bought a Silverline electric plane and that came complete with spare brushes, definitely not the norm nowadays. Probably worth checking the cable clamp as advocated by Alistair but beyond that the chop saw is probably destined for the graveyard.

Dave W

Could be Commutatus Fryii but could also just be a brush holder or controller / trigger meltdown. Time to disassemble and investigate after unplugging, I think.

I've just burnt out my cordless Bosch drill as well, must be the week for it. But I'm going to quite happily buy another as the batteries and charger are good and also it has lasted me for quite a few years of hard work.

take it to pieces, have a look. Probably can't buy spare parts, but the graveyard accepts chop saws both complete and stripped down.

If by chop saw you mean the usual 16"/355mm friction disc cut off type, it is probably toast. Once the smoke comes out, there is no getting it back in again. Cutting 40mm solid square bar is really more than they are designed for. They are designed more for cutting structural sections like 40mm square tube etc on worksites. I found this out, like you, the hard way. Now if cutting 40mm solid square bar etc, I chain drill it first with 5 or 6mmm holes then cut with the (new) chop saw. Works a treat. I also use it plugged into one of those multiple outlet extension that has a 10amp breaker built into it, so it trips before the chop saw lets its smoke out.

I have found too that buying the more expensive discs that are a mm or two narrower than the cheap ones greatly ups their performance.

Edited By Hopper on 23/05/2019 02:51:13

When I buy any tools from Aldi/Lidl, first thing I do is staple the reciept inside the instruction manual that comes with the tool. You do after all get a 3 year warranty!. first off, is it a soft start motor, ie does it ramp up the speed after you have pulled the trigger? if it is, suspect the thyristor control failure, which is quite common. second, check the interference suppression capacitor bridge, they blow up very loudly and frequently, and the tool will work without it anyway. Parts are usually available from Kompernass, which is the german company that imports these tools, check in the manual. Strip it down, and find where the smoke came from, it will be fairly obvious. If the commutator slots are not parralell, and burnt, armature failure may make the repair not worthwhile, but check on the price anyway, I have many Aldi/Lidl tools, and have abused some of them to the point where I was not really suprised they broke, but by and large, they do the job, and if they quit within three years, you get a new one or a free repair provided you have the reciept!

I've had a go.

I took the back off to find the commutator, which was mucky (carbon). I cleaned off the muck with a cloth and some isoproplyl alcohol. I tried to scrape between the bars with some thing steel (actually a nail file), but not sure how useful that was.

I took off the handle and found that the 'electronics' consist of an on switch and a capacitor.

I decided to see if I'd done any good. I replaced the handle cover but left the commutator cover open so I could see.

I put a 5A fuse in the plug (comes with 13, but 5A might cover it). I got a spark from the commutator and the fuse blew without the motor turning.

Next go was to use a 13A fuse. As when I tried this before, the motor spun up and almost immediately slowed down as the fuse blew. And the fuse in the house.

I don't really know what goes wrong when a motor like this gives up. It seems like there is a short circuit somewhere, but I can't imagine how I'd find or repair it.

Not sure what to do - I was tempted by the Aldi bandsaw, but they're no longer available.

Iain

You could measure resistance across commutator windings to satisfy your curiosity but frankly it's dead and needs to go to Silicon heaven

Our Bosch cordless hedge clippers let us down today. I charged the Ni-cad yesterday and aimed it at our box bush this morning. The charge was so weak the blade jammed as soon as it started cutting. I seem to remember reading that Ni-cads do not like being stored in a flat condition. This had not been used in over a year.

So no need to make up an excuse for retiring to workshop then

Rik

If the fuse blows immediately then something is shorted, it could possibly be the capacitor.

Without a reference scale of 'mucky' its hard to say for sure that the armature is toast, the commutator start off as bright copper but sometimes the area that the brushes wipe gets glazed and polished to a much darker tone.

A photo of the electrical bits switch, capacitor and the brush/commutator end) would help.

Ian

From your comments so far Ian I think you are flogging a dead horse, sorry chop saw.

Dave W

I am fairly firmly of the opinion that the parrot (sorry, chop saw) is dead....

However, I did take some pictures.

Here is the handle. I spent part of my youth as an electronics engineer of sorts and have blown many a component. I don't think the capacitor is one - also it will start up and then blows (perhaps the short is in a particular place and the initial rotation finds it).

This is the commutator. After it has been cleaned (to the best of my ability). There isn't a lot of evidence of sparking on it, but it was original flat black .

Thanks for all the responses. One can always hope.

Iain

Using power tools on a spur or extension that results in voltage drop at the too can significantly shorten motor life.

I see that the gaps between the commutator bars are wider in the middle, looks like the insulation has failed in the armature windings, test between the comm bars and the shaft of the armature, with an AVO, or a megger if you have one, any continuity, or a resistance of less than 1 Mohm and the armature is toast. Check the manual and get in touch with the spares supplier, then at least you can weigh the cost of a new armature against the cost of a new chopsaw.

actually looking at the pics again, is that a bit of blackened field coil I can see through the lower gap? Field could have failed and caused the arcing at the armature. Armature failure is more common though.

Don't entirely discount the possibility of getting spare parts. I broke a small plastic sight glass on an Aldi air Oiler/Regulator a couple of years back. I asked at the store and they gave me contact details for a spares centre which was in Austria as far as I can remember - company is called Walter I think. I contacted them and received a new part free of charge.

William.

If you are regularly going to be cutting 40mm &c solid section why not look at an Evolution (Circular TCT) Saw from Screwfix/b&q?

I have one in my van for site work and I would recommend it.

Guy