Brushes for old AEG STSZ jigsaw

[MM]

I have an ancient AEG STSZ350 jigsaw that recently started popping and sparking.

These are the brushes:

And the brush holders/commutator:

And finally the jigsaw's type plate:

I've found a company that supplies brushes purporting to be suitable for this model, but they look different:

or:

The replacement brushes have caps on the ends of the springs, whereas the brushes in my jigsaw just have the springs without caps or wires.

Are these replacements suitable? Is it a newer design?

Or is there a "universal" brush type I could use? (Maybe re-use the old springs.)

Finally, comments about the state of the commutator would be welcome.

Thanks.

MM

[Bob Minchin]

The brush holders look like they have become warm at the ends and as the length of the new ones are not that much greater than the old ones, I'd be more checking that the rushes move freely in the holders and that the springs are still exerting a good pressure. The replacements with the copper braid look much more common type than yours and could well be a revised design. The brass end cap could well fit inside or over the end of the holder. Spring steel is not such a good conductor compared to copper.

Look at the sparks. Small sparks near the end of the brushes is normally a contact problem (brush length, spring pressure or friction) whereas a ring of sparks running around the commutator is indicative of possible armature failure.

hth

[MM]

Thanks. The sparking was near the ends of the brushes.

Do my brushes look worn to you? This jigsaw is 40-ish years old, but hasn't had much use.

MM

[michael adams]

A first option might be stretching the springs. Basically if they've been sat for 40 years in a compressed state then possibly they could be expected to have lost some of their tension/elasticity. Simply by stretching them out you might be able to re-introduce some of that tension and elasticity.

Or maybe not, but it will cost nothing to try in any case.

michael adams

...

[Bob Minchin]

No they don't look that worn compared to the new ones but they have been getting a bit hot which is not good in a plastic bodied tool. Hence my suggestion to check they are completely free to move in the holders.

[harry]

You might well find that new brushes doesn't fix the problem. The armature may be shagged. Which leads to sparking and the brushes wearing out.

[harry]

[michael adams]

The OP explained that the tool has been little used.

The reason AEG hand tools were taken over in the 90's isn't because their tools and motors were rubbish; precisely the opposite. Just like German tanks in WW2 they were over-engineered to the extent that they cost that much more to produce than the Japanese Compton that was then coming on line.

AFAIAA in the 70's and 80's AEG never produced many DIY or consumer tool lines. Most if not all of their tools were heavy duty. "Heavy" being the operative word for some of them.

Providing its been stored in dry conditions the OP would need to subjecting the tool to a good deal of hard use before the motor as against the brushes would show any sign of failure.

michael adams

...

[newshound]

+1 on all Bob's comments

[MM]

It'll be a shame to junk it, because this jigsaw fits an AEG fret saw frame designed for the purpose, with a fret saw table. The base plate of the jigsaw fits into the fret saw frame and there are three screw holes (in the base plate) with which to attach the saw to the frame. I've looked at new jigsaws in B&Q, Homebase etc, but none have a suitable base plate, let alone the threaded holes.

And I'm pretty certain that a new armature is as rare as hen's teeth, if that were the cause of the problem.

MM

[MM]

Yeah, you got that right! This jigsaw is built like a Panzer!

But how can I tell whether the armature is shagged?

By the way, I left it in the garage over winter and it probably got damp. When I switched it on in February, it "popped" a couple of times (like a small balloon popping) and the sparking was noticeable through the ventilation slits. However, since I've had it indoors in the warm for a few weeks, the popping never occurred again, but the sparking is still evident. Also, the motor tends to slow down then speed up somewhat. I'm not actually trusting it to use for sawing, but am using my new Makita instead. But, as just explained to Harry above, this old jigsaw fits my AEG fret saw like this one:

MM

[harry]

Before you do anything, make sure the brushes are not worn/burned right down and are free to slide in the holders. The face of the brush should not be pitted. If the armature is OK, and the brushes are OK (as above) the brushes should "bed in" with a few minutes running. You will always get slight sparking on power tools running on AC and for other more technical reasons.

If there are sparks running round the commutator or there is popping and crackling after the brush check, it's the armature shagged.

As well as long use,this can be caused by corrosion if it's been left in a damp place or condensation or overcurrent due to partial seizure.

[MM]

I've ordered replacement brushes (£5.89) and will clean the commutator with emery. I remember when we serviced old dynamos on Ford Pops and Austin Sevens and similar, which were bread-and-butter cars when I started my apprenticeship. Some of those old cars had a third brush that you could adjust. I've watched a few YourTube vids to refresh my memory. If it carries on sparking and/or popping after I've replaced the brushes and given it a good clean, I'll junk it. The popping noise was the worst. Made me really jump! Very much like a balloon popping.

As a matter of interest, when an armature is shagged, what IS it that actually goes bad with it? The windings?

Also, I reckon I need to get some graphite grease or something for the gears before I reassemble.

MM

[michael adams]

If as you say the saw has had little use, if you bought it yourself fair enough, ( if it's inherited and you took this statement on trust then possibly not, as applies to numerous tools offered on eBay) then apart from the effects of damp, rodents attack etc then there's no reason why all the electrical components shouldn't be in first class condition. The plastic sheathing may be a bit brittle but not such as to cause failure. Same with the brushes. There's no reason why the brushes should be worn if the tool's had little use. And AEG tools were designed for heavy use before needing brush replacements. My guess as suggested before is that the springs have weakened over the course of the 40 years and the brushes aren't making sufficient contact with the armature at all times. If stretching them doesn't solve the problem then possibly if you can remove the springs from the brushes you could try heating them to maybe white hot and then rapidly quenching them in cold water to restore the temper/springiness.(AINAM) At this stage its the springs I'd be concentrating on. Failing that say if you can't get them back on - new brushes.

As replacement brushes cost considerably less than would a replacement armature I'd replace the brushes first and see if that has any effect before worrying about the state of the armature.

So its first springs - then brushes - then the armature.

michael adams

...

[michael adams]

It can often be the commutator.

Everything anyone could possibly ever want to know about commutators

IMHO once you've fitted the replacement brushes and they slide easily in the shoes, the tool should work straightaway. So all the above is probably superfluous, for another 40 years anyway.

michael adams

...

[MM]

If it works, I'll be 110 before I need to replace the brushes again...

MM

[MM]

Yep, new brushes are on the way to me, and I bought a sheet of 600 wet-or-dry today (couldn't obtain emery cloth here).

Yes, I bought the tool brand-new in the mid-70s in Cologne where I lived and worked at the time. (Migrant worker!)

I suppose you wouldn't happen to know anything about the AEG fret saw attachment, which I purchased separately? I've still got all the parts, but I cannot find the darned user guide, which is NOT available on the internet. I've searched high and low. I doubt anyway that the guide ever existed as a PDF, but a few days ago I thought maybe someone had photocopied it and uploaded to the web. No dice.

This is the tool:

As I recall, the guide tube has to be adjusted as close to the workpiece as possible. It made much more accurate cuts than without this attachment.

Wolfcraft used to produce a very similar tool, suitable for any jigsaw, but while their table is still available, they've stopped making the blade guide. Mind you, I was surprised to see just how many keen DIY-ers on YouTube have constructed thei own blade guides, using skate roller bearings and suchlike!

MM

[harry]

down and are free to slide in the holders.

uld "bed in" with a few minutes running.

other more technical reasons.

crackling after the brush check, it's the armature shagged.

n a damp place or condensation or overcurrent due to partial seizure.

Any number of things can go wrong but mostly to do with insulation breakdow n. Occasionally the connections fail where they connect to the commutator segm ents. It's possible to fit new coils but uneconomic with power tools.

The latest technology has no commutator and no windings on the rotating bit (Only rare earth magnets). So, almost nothing to go wrong except the electronics that generate AC..

[michael adams]

According to one of the pictures accompanying this ebay listing, there's some information of a kind on a label inside the lid of the box.

If you blow up the picture of the label, and can remember any German maybe that might be of some use.

While from the big picture on the box it appears that the plate is included with the attachment, in all the other pictures it appears the plate is that of the saw. So the biggest problem presumably is working out how to attach the arm to the saw (plus how to mount or fix the saw in an upside down position). Maybe a bit of jiggling about is in order dunno.

Whereas you've got a blade guide but no table ?

Wolfcraft are a funny outfit. For a few years there, along with Bosch they made the best portable drill stands on the market. Movement of the head was via rack and pinion with a heavy hexagonal steel pillar with the rack machined into one face and heavy case iron bases. But the funny thing was that the first version had a one part head - the bit to which the drill was clamped - which moved up and down the pillar. It was only after a year or two, that they worked out that a two part head with the top part clamped to the pillar imparted far more rigidity. You'd imagine this was something that was discovered within a few years of portable drill stands first being developed maybe

50 or 60 years ago. Although possibly they thought that having a hexagonal pillar which prevented rotation of the head around the pillar, obviated the need for a two part head. Well it didn't.* So that second version was the best of both worlds - an expensive to produce hexagonal pillar which prevented rotation and a two part head for even more rigidity. It maybe goes without saying the present day version has a cheaper round pillar with the rack screwed on. Many of the head components on most versions appear to be cast magnesium or an alloy of the same - and going by comments online can be mistaken for plastic. And may possibly may be a possible cause of failure in the long term or at least the weakest part of the design.

michael adams

• All versions available on eBay occasionally, along with Bosch, although not always distinguished as such. And usually drowning among a sea of rubbish. The cast iron bases are prone to rust which can put people off and keep prices down in some cases.

...

[MM]

Yes, I've read that.

No, the saw is dead easy to attach. The saw table is made for the saw, but have have been another optional accessory separate to the fre saw frame. I have both parts, anyway.

The base plate on the jigsaw has three threaded holes and the saw table is attached with three machine screws from the top surface (countersunk). It's a very well-engineered piece of kit.

Problem is that I've looked at a range of new jigsaws in various outlets and none have threaded holes for the AEG fret saw attachment, or even any holes at all. The base plate on my new Makita is too large to even fit into the recess on the underside of the AEG saw table. Hence my desire to get the old AEG jigsaw working again.

The Wolfcraft saw table I mentioned elsewhere is "universal" and thus suitable for most jigsaws. The attachment is made by the use of four clamps underneath. But, as also mentioned, Wolfcraft discontinued the blade guide component.

No, I have the table as well. The one thing that's missing is a functioning jigsaw! Maybe those new brushes will arrive today. They were posted second class.

MM