Is this possible on a milling machine

[hunter27]

My son has just bought a Tom Senior milling machine (just for messing about with) neither of us have used one before.
The bronze water pump on my boat stopped priming itself last year and at the time I had to replace it at around £250
I would like to refurbish the old pump as a spare. These pumps have a rubber impeller inside the housing to pump sea water that has to be changed regularly but eventually the pump body wears and you don't get a good enough seal for it to prime.



Normally the front plate wears most and can be replaced or turned inside out to regain a seal but it is the rear face that has worn down on my pump especially near the centre of the hub. My question is with a small milling cutter could the back face be skimmed flat again and a bit milled of the face of the pump to make up the difference?
One problem is that the cam in the pump is not removable and if I ended up with a step in the corners it would soon beggar up the impeller, is there a cutter that will follow the wall without cutting into it.

This is a picture of the same pump.The spindle and bearings all come out.
Thanks for any help.
Pete

 

[Spark plug]

Now that is a trickery one, I can't see any straight forward way to skim that back face.

Ile keep thinking.

 

[ronan]

The only way i could see of doing it is on a rotary table, finding the centre of each of the curves of the cam, milling the back in sections. It would be extremely time consuming. It would be a job to run a mile from.

 

[Digger6135]

It looks to me like that inner cavity is removable if so, it would be a easy job on a lathe to face off the damaged face then, silver solder a new flat bronze face on and then face that to the correct depth then bore out the centre hole and reassemble.
Or alternatively you could build up the wear with Belzona molecular ceramic, or metal.

Digger6135

 

[Pete.]

You could probably clean the rear face up by carefully hand milling but you'd need to do something special to protect the inside wear faces.

does the impellor have bendy rubber vanes or something?

 

[Wallace]

Looks like a Jabsco pump, if so, do you know the model number as spares are available?

 

[brightspark]

use a ballbearing router bit it will follow the wall without cutting in to it .if u cant get one small enough in depth . make one yourself out of tool steel and a roller bearing http://www.stewmac.com/Luthier_Tool...Bits/Ball_Bearing_Router_Bits_-_Set_of_2.html

 

[hunter27]

Digger6135. The inner cavity is not removable, the groove on the outer face is for a large O ring to seal the front plate. I will look into the Belzona molecular ceramic. Because it is in sea water dissimilar metals can cause problems electrolysis (I think that's the right word )


Pete. The impeller is some kind of rubber and it does have bendy vanes.


Wallace. It is a Johnson pump and spares are available but the body is all one piece complete with the cam ! on some pumps the cam is removable.

It might be possible to turn it down on a lathe removing the cam in the process and try to fabricate a new cam tapped and screwed in through the side of the pump
thanks for all the replies.
Pete

 

[hunter27]

Thanks Brightspark I will look into that, I wondered about router bits but have only seen router bits with bearings on the end. As you say the only problem may be the radius size for getting into the corner of the cam.
Pete

 

[garethp]

Could you get a sheet of brass/bronze or stainless steel a couple of mm thick and make an insert to sit inside the pump? if it was made a close fit in the body it should seal ok but you could put a thin smear of something like tiger seal on the back of it to fill where the body is worn? You might need to skim the impeller or put a spacer of the same thickness under the cover but if it works you've got a plate than can be replaced again in the future if it wears.

 

[Wedg1e]

If most of the wear is near the centre I'd try milling a circular recess, concentric with the shaft, of as large diameter as possible without hitting the side wall, as deep as you can get away with (2-3mm?) and inset a disc of replacement brass/ bronze. The remaining bit of end face that's worn would then have minimal effect on the sealing.
You coud probably turn the recess on a lathe rather than use a mill, as long as you can get the shaft bore properly on-axis with the lathe spindle.

 

[roofman]

cant you just take a few thou off the face and try bring the impeller tighter to the back to allow for the loss thats worn

 

[addjunkie]

cant you just take a few thou off the face and try bring the impeller tighter to the back to allow for the loss thats worn

This is a simple solution.

On a mill that wouldnt be easy, rotary table would be best imho, expensive to fix a pump you could probably replace in plastic for less than the cost of the rotary table. Even then extreme care would be required not to make it worse. With an old mill and a long cutter to reach inside it would be difficult to get any kind of accuracy.

Nice boat by the way, is the hunter 27 the one built post impala etc as a half tonner, nice bendy mast quite light displacement, and good up wind performance if you can keep it upright.

 

[penfold]

Wallace. It is a Johnson pump and spares are available but the body is all one piece complete with the cam ! on some pumps the cam is removable.

It might be possible to turn it down on a lathe removing the cam in the process and try to fabricate a new cam tapped and screwed in through the side of the pump
thanks for all the replies.
Pete

I think this is the best option if it's possible, combined with a wear plate bonded to the back face once it's turned out to bring it back to depth as otherwise the impeller will be flailing about achieving nowt. Even if 'routing' it is possible you still need to build it back up to depth, and it will be a funny shape rather than round.

 

[hunter27]

PDG The problem I thought would be keeping tight to the pump side (corners) when following the cam profile without leaving a step.

Garethp I had thought of this and would have rebated the cover plate to allow for the plate.

Wedg1e I think this may be the answer, it is the impellers hub that has caused most wear and a simple bronze washer will be easier to make than a complete backplate. I do have an old clunker of a lathe.

Roofman I don't fancy this idea. The impeller needs to be a good fit and it's recommended to change it every year as it is they can also self destruct especially if they run dry.

Addjunkie The hunter27 was my old boat I believe they were a stretched hunter delta which may have links to the impala, it did certainly had a bendy mast . The present boat is a Beneteau oceanis clipper 311 a bit bigger and heavier and it can dry out on the sand twice a day (my mooring)

Penfold. I might try Weg1e's idea first and if that doesn't work out go for the full cam removal and shim the backplate I would then have to locate of make a new cam.

Thanks for all the replies I have got plenty of ideas now.
Pete

 

[Pete.]

You could mill that just using hand controls on the mill. Grind the side flutes of a slot drill so it only cuts on the end then follow the profile carefully by hand. You might have a little polishing to do but not too much especially if you grind some relief in the flutes except right at the bottom.

 

[hunter27]

Update

Thanks for all the ideas. As there was no cost involved to me using Wedg1e's method and the pump was mainly worn around the centre I ended up setting it up in my lathe and rebating the back of the pump body from its centre out to the start of the cam to around 2mm deep. I then turned an old bronze pump face plate (about 3mm thick) down to fit into this rebate, soldered it in then flatted the step off in the lathe.

Initial trials seem to be good, I connected the pump up to my battery drill and even on slow speed it pumps quite well and will prime itself from dry, on high speed it is even better (I ended up having to dry off the ceiling b4 the wife came home )

I brought my boat ashore off it's mooring this week for the winter months so it will have to wait until next year before I can give it a true test at its normal running speed.

Thanks again for all the suggestions

Pete

 

[addjunkie]

Ah the joys of wet and dry in january, before the spring antifouling.