Morning Lachlan, got the pump apart again and finally confirmed last night the shaft is bent by 9 thou which was creating a wobble on the seal face, I have the shaft out of the second spare pump and will aim to use that provided it checks out straight in the neighbors lathe, I couldn't get a proper reading on his portable test stand because the hole at one end of the shaft was offset for some stupid reason and it was showing a 14 thou eccentric rotation, I seem to attract the real challenging restorations for some reason!!

Thanks restore49 for that info on the taper fit, just to be on the safe side I'm getting my Fitter and Turner neighbor Geoff to cut a keyway to secure the impeller, I've been down the path of having a loose impeller in my RD6 after both the pin and key rotted away in it's shaft allowing the impeller to free wheel.
regards
Mike

cool, thanks for the update Mike.
Its harder to check an old shaft between centres like that,you can get a false reading.I would set it up in a four jaw held long as possible, taper end out.Get Bearing surfaces running true than check taper run out with dial indicator.I would than check it as a set up with the impeller on the shaft and nut tight.Evan if shaft is true the impellar may still have run out on the sealing face.If all your shafts don't check out than I would machine the face off the impellar while it is on the shaft,(is that how you machined impeller last time)??.If not that may be your problem because 9 thou shaft bend doesn't sound like a lot to me for a seal set up like that,but run out is probably a lot more at the impeller.I agree with you cutting the keyway,its one less thing to worry about if one day the temp creaps up a bit.Tapers are bloody strong as long as both tapers are a perfect match,and with out having both of yours in front of us we cant guarantee they are.Thats why I suggested the texta thing.In the last 50 odd years of that machines life somebody may have made that shaft or shafts for that machine and not got the taper correct.
Just my 2 cents worth mike!
Keep us all posted with this one
Regards

Hi Lachlan, thanks for the suggestions, initially the impeller seal face was machined on it's own because I had no reason to suspect the shaft might be bent and not having a lathe I have no way of checking shafts for straightness, I have to wait for my neighbor to be not working Monday to Friday 6am till 6pm and then not fishing all weekend when he's not working, then he's over at his girlfriends place every night of the week which leaves very few opportunities to get him to do Cat stuff for me, I keep telling him to pull his finger out and focus on my stuff!

I'll report back on this second shaft, fingers crossed it's useable though Geoff could knock a new one up pretty easily I'm sure, just like you could being the clever young Fitter and Turner you are.
All the best
Mike

Hi Mike,
you are wearing it down, as I posted else where, 0.008" TOTAL indicator reading is actually only a bend of 0.004" to straighten the shaft. The bend may only be at the threaded end, as you noted, due to unequal forces applied during nut tensioning/loosening.
As suggested above, testing in a lathe chuck, and not between centres, is about the best and most accurate way to check the shaft for truth.
The suggestion to check the impeller seal running face for run-out whilst mounted on its shaft is what is critical.
If it is high one side of the face and low opposite the poor old seal cannot rock fast enough to seal--a little sideways run-out can be tolerated--from any bend in the shaft-- as the seal running faces will slide--not ideal but beggars cannot be choosers.
Keep at it Mike.
Cheers,
Eddie B.

Hello Eddie, message read and understood thanks, when checked in Geoff's lathe next door this morning the seal running face on the impeller had a run out of over 4 thou on the original 8 thou "bent" shaft and over 12 thou run out on the straight "spare" shaft so that was a real surprise, why would the straight shaft have such a bad effect on the seal face of the impeller do you think?

Geoff cleaned up the seal face and I stressed to him to only take the bare minimum, it only took 4 thou to bring everything into line nicely, do you think I should gently hand lap that face with some fine wet rub to make it super smooth? I was going to fit new sealed 6305 bearings onto the shaft but when we did a ball count at the bearing shop there were only 7 balls in them just like the Cat Classic Part bearings, so I opted for the maximum service sealed bearings which have 10 balls like the original 305W just to be on the safe side, don't want a fan taking off into the crowd at the Echuca Steam Rally do we!!
Thanks for your help
Mike

Hi Mike,
the bend in the shaft can part cancel out the face run-out--depending on where the impeller is orientated. Turned further around it would likely be worse if the two wrongs were aligned and not opposite like now--if you get my illogic.

Famous last words, but I think you have a better chance of success now.
Yes, a very light lap by turning the impeller only enough, like maybe 2 or 3 turns to see a fine finish or you run the risk of rounding off and slanting the face again.
Cheers,
Eddie B.

I was thinking about the impeller this afternoon Eddie and I think I'll get it back in Geoff's lathe and try the impeller in different spots on the shaft because knowing my luck when I install it all I'll have the impeller in the wrong spot if that makes sense, following on from your comment of one bend cancelling out another, for that straight shaft to put a 12 thou hoof in the seal running face concerns me, yes I could simply mark the impeller position on the shaft before dismantling it but I don't trust this impeller.
Regards
Mike

Hi Mike,
like your logic to find and positively mark the truest run position for best chance outcome.
Cheers,
Eddie B.