Bosch PBS 75 Belt sander

[brocher]

My PBS75 sander has developed a problem. I know what it is, but can't find the spare part to fix it. It's the sprocket which is attached to the drive belt and drives the roller for the sanding belt. It appears that Bosch no longer supply the spare part either on its on as a complete roller assembly. I have been in touch with RAI Technical who supple Bosch parts and they tell me that they no longer have any stock and wont be getting any either as Bosch have stopped making this part!

This seems to me to be a retrograde step by them, as the machine has been very reliable and is a good workhorse for me. Does anyone know where I might be able to get one from, as I am reluctant to throw away an otherwise good machine and get a new one.

The item is marked "843" in the attached parts list for the machine - where you can see it shows both the roller and the sprocket which is screwed to the roller shaft.

Thanks

 

[Sideways]

I can't help specifically.
This is an example of a generic problem or obsolescence.
Once the last time buy stock of parts for any obsolete device has been sold, the manufactirer is unlikely to be interested. Even at elevated prices, there probably isn't enough profit, or core to their business model to justify making more.
You'll have to search the dealer network / repair shops as you are clearly doing.
But the sprocket concerned is a timing belt type, these will largely conform to a standard for teeth profile etc, and you will be able to buy a generic part if you teach yourself about these, then find a friendly model engineer to drill and tap it to match your spindle.

 

[Etaf]

we had the same issue on a coffee machine $20 bit , but not available !!!!!! for a sage machine - £210 for them to look at and repair and refurb....

Now we have part issues with Citreon C4 62reg , parts are often not available - like windscreen wipers , ended buying from manufacturer at a silly price - waiting for them to be fitted

I think there are laws coming out about making sure repairable items, but without the parts pretty useles

 

[Phill05]

Let me know the size's please as I have a part or two that "Might" match.

 

[brocher]

Let me know the size's please as I have a part or two that "Might" match.

Hi Phill05, thanks.

I have attached photos showing the part. it's 4cm at its widest on the teeth (i haven't measured the flange), and 2.5cm deep. The shaft is 8mm.

The big issue is that the sprocket has two internal flats to engage with the shaft of the roller, so I have attached a photo of the roller as well to give an idea. the flats are only about 6mm long.

Hope this helps

 

[brocher]

I can't help specifically.
This is an example of a generic problem or obsolescence.
Once the last time buy stock of parts for any obsolete device has been sold, the manufactirer is unlikely to be interested. Even at elevated prices, there probably isn't enough profit, or core to their business model to justify making more.
You'll have to search the dealer network / repair shops as you are clearly doing.
But the sprocket concerned is a timing belt type, these will largely conform to a standard for teeth profile etc, and you will be able to buy a generic part if you teach yourself about these, then find a friendly model engineer to drill and tap it to match your spindle.

Thanks Sideways, actually I do have a friendly model engineer next door to me! But my problem is that the sprocket needs to have two internal flats and am not sure that he would be able to make that for me! But I haven't asked him yet !!

 

[ChaiLatte]

In July 2023, there was someone with a very similar forum name to you posting about a very similar issue:

https://www.ukworkshop.co.uk/threads/bosch-belt-sander-pbs-75-toothed-belt-wheel-supplier.143457/

Please read that thread to see if it offers any useful advice.

 

[brocher]

In July 2023, there was someone with a very similar forum name to you posting about a very similar issue:

https://www.ukworkshop.co.uk/threads/bosch-belt-sander-pbs-75-toothed-belt-wheel-supplier.143457/

Please read that thread to see if it offers any useful advice.

Hi ChaiLatte. I have to hold my hands up - that post was me as well! I did manage to get the sander going by tightening the nut holding the sprocket to the roller, but sadly it now seems to have failed altogether! So I am back to square one in trying to find a new solution. The ideas suggested so far would appear to offer some hope. I wont be able to try these out for a few days, but will report back!

Thanks

 

[Superduner]

If you can get the actual part number and Google it you might find Bosch dealers in Bulgaria or Romania pop up. I've had good luck getting older parts from them in the past. Failing that method just Google Bosch Bulgaria - if I remember rightly there are 2.

 

[the great waldo]

If you can get a similar size pulley I would imagine drilling and threading a couple of holes on either side of the pulley and fixing on to the shaft with a couple of grub screws loctited in.
Cheers
Andrew

 

[TomGW]

How has the existing sprocket failed? From your photos the teeth seem to be fairly much intact. Is it the flats inside that have worn away and no longer locking onto the shaft?

 

[brocher]

If you can get a similar size pulley I would imagine drilling and threading a couple of holes on either side of the pulley and fixing on to the shaft with a couple of grub screws loctited in.
Cheers
Andrew

That’s what I’m beginning to think . Thanks

How has the existing sprocket failed? From your photos the teeth seem to be fairly much intact. Is it the flats inside that have worn away and no longer locking onto the shaft?

yes the flats inside the sprocket have failed completely

 

[mrgrumpygeorge]

Have you considered creating a larger flat by filing both sides evenly and using filler pieces to make a tight fit? I would try using some plastic packaging for the filler pieces.

 

[Phill05]

Hi Phill05, thanks.

I have attached photos showing the part. it's 4cm at its widest on the teeth (i haven't measured the flange), and 2.5cm deep. The shaft is 8mm.

The big issue is that the sprocket has two internal flats to engage with the shaft of the roller, so I have attached a photo of the roller as well to give an idea. the flats are only about 6mm long.

Hope this helps

Sorry brocher, the parts I have are all smaller.

 

[brocher]

Sorry brocher, the parts I have are all smaller.

Not to worry. Thanks for looking.

 

[TomGW]

That’s what I’m beginning to think . Thanks

yes the flats inside the sprocket have failed completely

Which side of the sprocket were the flats? The side shown in the first or third photo? I'm guessing the third photo is the outside with the flats. Am I correct in assuming it's made from aluminium or some alloy?
If I'm correct, get someone with a lathe to remove the (4 or 5mm??) protruding centre on the outside, reducing the sprocket to a flat face. Then turn a steel disc of roughly 30mm to fit onto the face of the sprocket (thickness to correspond to the depth removed) and drill and form the required flats in the centre. This steel plate can then be drilled and tapped, with corresponding holes through the face of the sprocket, then fix in place with small bolts from the inside.
This will mean that the new steel plate will be the part that engages with the shaft and the sprocket/pulley is attached to the steel plate via bolts.

 

[philogos]

Another thought. If this were min, I think I'd clean the inside and maybe file a couple of grooves into it then to the depth of the flats with araldite or similar epoxy. It would then be possible to drill a hole and file a suitable set of flats in the araldite.

 

[brocher]

Which side of the sprocket were the flats? The side shown in the first or third photo? I'm guessing the third photo is the outside with the flats. Am I correct in assuming it's made from aluminium or some alloy?
If I'm correct, get someone with a lathe to remove the (4 or 5mm??) protruding centre on the outside, reducing the sprocket to a flat face. Then turn a steel disc of roughly 30mm to fit onto the face of the sprocket (thickness to correspond to the depth removed) and drill and form the required flats in the centre. This steel plate can then be drilled and tapped, with corresponding holes through the face of the sprocket, then fix in place with small bolts from the inside.
This will mean that the new steel plate will be the part that engages with the shaft and the sprocket/pulley is attached to the steel plate via bolts.

Thanks for this. I have had another look and it is aluminium/alloy but with a steel/alloy (I think) sleeve which has worn away. Unfortunately the design is such that the nut to hold the sprocket on goes on the inside of it, so I don’t think your idea would work

 

[brocher]

Another thought. If this were min, I think I'd clean the inside and maybe file a couple of grooves into it then to the depth of the flats with araldite or similar epoxy. It would then be possible to drill a hole and file a suitable set of flats in the araldite.

Hi, thanks that’s a useful thought. It might be easier for me to bodge together with a small taper lock piece of metal and glue that in, and the nut then loctited in place

 

[the great waldo]

I've just checked on this bosch site
https://www.boschtoolservice.com/de/de/boschdiy/spareparts/bandschleifer-pbs-75-0603270003
and both pulleys are listed as avaiable. Which pulley ae you looking for 831 0r 843 ? If you run the mouse over the parts diagram a price and availability box opens.
Cheers
Andrew