Kehren Pharama RW6 Rotary Surface Grinder
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  1. #1
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    Default Kehren Pharama RW6 Rotary Surface Grinder

    Hi
    I am looking at buying an old (1956) Kehren Pharama RW6 rotary surface grinder (Ring grinder?).
    600mm table.
    Anyone on the forum had anything to do with them?
    I have a job face grinding rings from 300 to 700mm, just light grind till cleaned up.
    I am currently doing these jobs with a tool post grinder but it is hard yakka.
    The machine is a runner and I am going to have a look at it tomorrow, is there anything I should check for out of the ordinary, this I might add is my first go at a serious grinder?

    Best Regards
    Burgs

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    Is this like a Blanchard? Vertical spindle, rotating chuck?

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    Hi
    No it is a horizontal spindle with rotating table, the table moves out from and into the column.
    20171220_180821.jpgkehren-prahama-high-production-surface-grinder_14611875.l.jpg
    Now have bought it arrived this morning, I have removed the way covers and looks ok but lack of lube was a problem.
    Before I bought it the owner ran it and all sounded good.
    I have cleaned out all the lube ports, fixed the lube distributer block, leaking, and filled the lube hand lube pump tank, primed and now the table feed feels real nice, before it was grabbing and hard to move with the hand wheel.
    The was no evidence of galling so hopefully it will be ok.
    Cleaned all the crud from the coolant system, drain pipes were packed solid.
    Tonight I drained the rotary table oil and all I got was water
    There is no information on how to drain the oil from any compartment so I am taking best guess.
    The rotary drive gearbox if I am correct is also showing no oil but then again it could be water in there also?
    Can't find where to drain the rotary drive so sat back and had a beer or two 41C here today, so lost a lot of fluid, time to replace it .
    I spelt the name wrong or the seller did, it's a 1958 Kehren Praehoma RW6
    Best Regards
    Burgs

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    Hi
    Thought I would top up the spindle lube, but it came out as quick as I put in.
    Reading through the old history on the machine that the original spindle failed and a new ball bearing spindle was supplied under warranty.
    There was nothing on lube though.
    The spindle was further updated in 1996 to angular contact bearing and on the drawing it says to pack the bearings with grease.
    So I will leave the spindle as is for now and work on the rest of the machine, as I have a few jobs lined up to do ASAP.
    The only way I can see to change the rotary table oil is to remove the oil level glass and blow it out with air down the filler port.
    This I will do then connect power and see what else is not right.
    Burgs

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    I have never run that type grinder. I suspect that the chuck is like a Blanchard. They have a plug in the center, remove it and put in a lifting eye. The chuck should then lift off. It rotates on a babbit ring submerged in the oil. There should be brushes contacting slip rings for the magnet. Go easy lifting. If it does not lift right off then a plan B is required.

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    Hi TD
    Thanks for that it is in the manual about lifting the magnetic chuck, but I was worried about brushes, I would like to have a look at the brushes and whatever else is there so will lift it off in the morning.
    I got as much oil out as possible with blowing air through the fill port, filled both housings with oil.
    Connected the power this afternoon, and mostly OK but a few things to address.
    The rotary table gear oil is still got water in it, the hydraulic table movement slows down in a couple of places each stroke, the auto feed down is working but the controls for feeding down each stroke isn't work (Jammed), and auto feed stop is not working it is also gummed up/jammed.
    The electric relays may have been bridged out as you can start the table up with out turning the magnet on, could be a disaster waiting to happen.kehren-prahama-high-production-surface-grinder_14611874.l.jpg

    Best regards
    Burgs

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    I've never worked on a " Kehrens " ring grinder but I have worked on several other makes. The one's I'm familar with are the type were the wheel head moves in and out in a ram style fashion across the mag chuck which just revolves.

    I see " Kehrens " are still in business over in Germany. I've never seen one in the flesh over here. The British market was dominated by " Churchill " but you did see a few " Heald" and " Arter " ring grinders from the USA.

    If you've got the work for them they're a very useful machine to have in your shop.

    Regards Tyrone.

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    Hi Tyrone
    The Kehren RW6 came through Selson 600 Machinery, 1958.
    Yes Kehren is still in business.
    Hopefully I still have the work for it as my customer just told me he has bought a flywheel grinder, but the job requires more accuracy than a flywheel grinder so he is sitting on the fence at the moment, also the OEM calls for peripheral grinding not face grinding.
    The job I have to grind are up to 600mm but the outer face is around 700mm diameter, it looks like I can spin up to 750mm,, should also be able to grind to around 700mm.
    The table moving in and out gets rid of the droop, I have not pulled the vertical travel covers off yet but the manual says the grinding head is supported by four adjustable roller bearings so need to check the adjustment/wear in here.
    I reckon I should also be able to surface grind any spacers rings etc for the machining centres.
    It also has 3+- degrees tilt on the table for saw blades?
    It has 3 speeds on the rotary table but when I select 3rd speed (Pole Changing Motor) it just buzzes, not sure what is wrong here, wiring crook relays, the two relays that supply 3rd speed both pull in ok.

    best Regards
    Burgs

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    That was the drawback with the ram type surface grinders. Grit would eventually get splashed onto the ways at the front and slowly wear the slides down so the ram would go out of line.

    You could tilt the magnetic table/chuck over so you could sort of compensate for this ram droop and then give the mag chuck a skim up to get things back to normal. The best machines had an adjustable wheel head mounted dresser so you could also true the wheel up in line with the table.

    It used to get a bit complicated so eventually one place I worked for had the ways re-ground on their machine. I think that was a " Heald " 25A, if I remember correctly you could grind almost 30" on that machine.

    What's a " fly wheel grinder " look like ?

    Regards Tyrone.

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    Hi Tyrone
    Flywheel Grinder light vertical shaft grinder Attachment 215838
    Today moved the grinder in place and leveled.

    Pulled the Diamond dresser out and looks like at some stage they have had a blow out, lots of weld and the diamond is pointing at an angle.
    Freed up the mechanism but the diamond looks past it to me, tried undoing the nut but the whole lot turns may have to make a special spanner to hold the slotted nut, looks like it is a standard diamond, with a 1/2" or 12mm shank??Attachment 215839

    Got to looking at the hydraulics again and decided to put more oil in, and that worked a treat, smooth as now no jerking, or stopping.

    Need to sort out the electrics next, you can start anything any time, and what ever order I like too.

    Tried removing the table, removed the 16mm centre screw, basically a slotted head brass grub screw, tried lifting it off with my 500kg o/h crane and no go thought I might check here again to see if there is something else to do or is it just stuck?

    Best regards
    Burgs

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    Hi Burgs, can't open either of the attachments.

    The diamond in the dresser should be at a slight angle and not square on to the wheel.

    The other problem with machine like this is they are relatively simple to operate. That means that every Tom, Dick or Harry will jump on the machine to do a grinding job. It's a bit like the shop radial arm drill in that respect. The diamonds got damaged regularly by guys winding the diamond across the wheel without actually looking how far down it was ! Hard to believe I know but it happened regularly. Maybe they thought it worked by magic.

    I can't help you with the table, the machines I worked on had the magnetic chuck bolted on from underneath as I recall. Just like the chuck on a lathe. So it was relatively easy to remove. I drilled and tapped the chuck on one machine and made some lifting brackets that bolted onto the chuck face out side where the magnetic poles appeared to be be when I came to remove it.

    Good luck with it, Tyrone.

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    Hi Tyrone
    I am having trouble s with the posts 20171222_164059.jpg
    seems I can only up load one attachment keeps saying I am not logged in?

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    20171222_164107.jpgflywheel-grinder.jpg
    This might have worked.

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    Quote Originally Posted by Burgs View Post
    20171222_164107.jpgflywheel-grinder.jpg
    This might have worked.

    I see know, we had another name fro those grinders but I've forgotten it. The angle for the dresser looks OK to me. It doesn't want to be square on to the wheel.

    Regards Tyrone.

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    Hi
    Got all the feeds freed up and sort of working, big thing is I need to start the feed from the inside of the disc, to the outside, then return to the inside, but so far all I can do is start from the outside (that's where the feed down happens) stroke to the inside , stroke back to the outer diameter then it feeds down into the job? Not sure if this ok, but I guess if small feed down it should be OK?
    I have to finish on the inside which I can do by hitting the hydraulic stop button, but if I take my finger off the button the hydraulics start up again?
    The reason I need to start and finish on the inside is because I only need to grind to about half width of the face.

    Bit long winded, I will have a few more trial runs and see if I am doing the operations correctly.
    Best Regards
    Burgs


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