Thread: Dumbo needs HELP!

IMG_6539.jpgIMG_6538.jpgIMG_6540.jpgIMG_6541.jpgIMG_6543.jpgI have a Proth 2550 grinder which uses the larger wheels with the large inside diameter. I need to change out the stone. I have taken out the 8 or so machine screws that hold the front flange on and have removed the front plate. I am now looking at a recessed nut inside a tube which has a fine thread on the bore. I have attempted to remove the nut but am not getting anywhere. With out a doubt I am going about this the wrong way. Can some bodies give this Dumbo some easy to follow instructions on what I should be doing please???? With Regards To All Norm

Can you post a pic, for those don't own one of these machines, but might be able to offer a suggestion?

Sent from my SM-G970F using Tapatalk

Did a quick search to see what a Proth 2550 was, and as I suspected it's a surface grinder.

https://www.grays.com/lot/1508-30143...l-psgs-2550-ah

If you scroll through the pictures there, you'll see one with a bunch of arbors sitting on a pallet, which is the part I assume you've disassembling on the machine. Now I'm by no means an expert on surface grinders, but my understanding is that you would normally have an arbour for each grinding wheel you use, and change the entire assembly over - the only time you'd normally pull the cap screws out is when you need to replace a wheel on the arbor (the ultimate goal here I guess). So I doubt they have anything to do with holding what you're currently trying to remove on, as normal procedure would be to remove the entire wheel/arbor assembly first, then disassemble the arbor on the bench via the 6 or 8 screws, replace the wheel, reassemble and balance the assembly, then finally refit the wheel/arbor as a single balanced unit.

Further to that, my understanding is that quite often the arbors on a surface grinder need to be removed from the tapered spindle with a special puller, which is likely what the fine thread inside the bore is for, so you may need to make something up for this purpose. Without seeing the nut in question I don't know whether that is what retains the whole shebang or not, but if I'm remembering correctly, it wouldn't be uncommon for this nut to be a left hand thread if it is.

Hopefully someone can be more helpful than that, but hopefully between the pictures and my comments you might get some clues as to how to look at the problem a little differently.

Have added pics to original post. Thanks for your replies. Regards all Norm

If it is anything like my SG- and it appears that it is a similar setup but with a larger spindle (larger everything in fact)- then the arbor is removed by undoing the bolt in the centre, then using a tool that screws into the big fine thread and has a push bolt threaded into it to pull the arbor off. I only have one arbor for my grinder, every time I want to change a wheel I have to balance the new wheel on the arbor. With the minimal use mine gets, it is not a huge issue.

May be a totally different manufacturer 2550 surface grinder but found this manual.
https://images.machineryhouse.com.au...n%20Manual.pdf


Instructions appear to indicate the flange retaining bolt is left handed thread. Page 24

Which way have you tried to undo the nut ?

Is it left hand thread?

Originally Posted by Pete O

If it is anything like my SG- and it appears that it is a similar setup but with a larger spindle (larger everything in fact)- then the arbor is removed by undoing the bolt in the centre, then using a tool that screws into the big fine thread and has a push bolt threaded into it to pull the arbor off. I only have one arbor for my grinder, every time I want to change a wheel I have to balance the new wheel on the arbor. With the minimal use mine gets, it is not a huge issue.

That's how our Bemato is set up too, remove spindle bolt (or nut, can't remember) then screw in the supplied puller and remove spindle and stone as a unit, then tear it down on the bench

Thanks for advice so far. It was a left hand thread and came out nicely. The machine came without any tooling and Would it be possible for some one to add a couple of pics of the screw in "remover"? Regards All NormIMG_6561.jpg

Mostly guessing here but I would think it is similar to this -

https://www.amazon.com/Bikemaster-Ma.../dp/B0012TYU8Q

I have one like this somewhere that I have stored away for future use, but have no idea where it is right now.

If you know the thread size you could probably get one like in the ling pretty cheap or make one.

Yes the dreaded left hand thread to start with. Then the taper to overcome without the the screw in extractor ( three legged puller sorted that). All off then a small birthday present for machine "clean up" Wheel mounted in hub and balanced, then remounted on machine. I checked the diamond dresser while in there and have just ordered some spares in. Also I am not overly happy with only having one hub for the machine so have started the process of tracking a couple down. With luck back to grinding soon. Regards Norm

Originally Posted by Betnorm

Yes the dreaded left hand thread to start with. Then the taper to overcome without the the screw in extractor ( three legged puller sorted that). All off then a small birthday present for machine "clean up" Wheel mounted in hub and balanced, then remounted on machine. I checked the diamond dresser while in there and have just ordered some spares in. Also I am not overly happy with only having one hub for the machine so have started the process of tracking a couple down. With luck back to grinding soon. Regards Norm

I think u would be very lucky for mine to fit but if your ever near Fremantle u can have a look. I ordered 5 hubs to fit my machine and each one came with an extractor and your welcome to have one if its of help.

IMG_20210606_170053.jpg