need advice on modifying a Parker majestic grinder
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  1. #1
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    Default need advice on modifying a Parker majestic grinder

    I picked up a free 6X18 parker majestic grinder 2Z it is missing the spindle motor everything else on grinder is working. the motor/spindle style is the direct drive through the back. so right now there is just a hole where the spindle should be. My goal is to get it running as cheap as possible. however I have not having any luck finding a spindle anywhere and this is for hobby garage use, so I dont need anything fancy or high rpm. I was wondering if I could adapt something non standard just to give me a basic spindle with fixed RPM. i am open to any modification. I would like some thoughts and ideas.

    Thanks in advance.

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    Bare in mind the accuracy and finish is directly related to the quailty of the spindle and it's bearings! Grinding wheels are designed to be run at certain RPM for best results with a max RPM marked on the wheel. Exceeding marked RPM can lead to exploding wheels and too slow changes the cutting character of the wheel.
    Bottom line free is sometimes more expensive than buying a good working unit. Also if you try running on single phase the finish will suffer,ie 3 phase motor with static converter.That goes double with pure single phase.
    There WAS a reason why free ,very expensive to repair spindles with correct bearings.

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    Thank you for your input John, I didnt see any suggestions so I have to ask just so I am clear, so your thoughts are:

    1. that I will be unable to manage RPM when choosing a motor and choosing wheels in advance, and also operate it within wheel specs. is that right?

    2. that I will be unable to adapt a used alternative spindle and motor setup for less cost than a good working machine and get hobby level quality out of it?

    3. that it will be impossible for me to get an acceptable hobby level quality grind using single phase, or a some 3phase residential conversion.

    4. I should abandon the idea altogether and buy a good working machine instead and scrap/sell the one I have even though I still have the residential single phase problem?

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    1 Most direct drive grinders using a 7-8 " wheel use a 3450 RPM motor.
    2 Depends on how well equipped and capable you are. Hobby level is a oxymoron as the whole idea in grinding is you are after a very accurate dimensional and smooth finish.
    3 See 2 but from personal experience going from a static converter [ie = 2 phase effectively] to a rotary converter I could see the difference in finish.
    4 If you may get more 3 phase equipment in the future set up a rotary converter otherwise VFD to get your 3 phase.All real SG's will be 3 phase.
    My first SG was a Delta hand feed and no coolant,arms get REAL tired cranking the table back and forth.
    Grinding produces heat,part grows =not to size if it is needed. Bought a B-S 6X18 2A with coolant and 2 axis power feed -life is good.
    If improving finish is your main gool belt sander and a DA to finish.
    There is a LOT to getting satisfactory results when grinding ,spindle quailty -wheel selection -and wheel dressing are 3 of the most important ones.

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    thank you John the target RPM I am after is 3600, since that is what is spec'd for the original motor. i am reasonably certain I can find wheels that will meet my needs and operate at that fixed RPM.
    I would probably use the machine 1-2 times a month to grind something in my garage. I am not making precision tools or jigs and I do not require that level of accuracy or finish. and like you said I can use secondary methods like sanding polishing to get more out of it if needed. The grinder I have does have auto features BUT I don't intend to use any of that, I will do it by hand and for the few times I will use it it wont be a problem. so that is what I mean by hobby level within that context. ok so getting back to the original request

    the problem I have is that I was unable to find a motor/spindle combo for this model, so if i want to see if I can get this thing running, I am going to have to improvise a little. I was thinking that I could abandon the direct drive approach and find an alternative precision spindle (e.g different model or mfg etc..) that would physically fit or could be adapted to fit and maybe perhaps use custom a belt drive to drive it. this would open up my options to source it and reduce cost. this is what I mean by modification. Does anyone have any advice, suggestions or experience with that type of modification?

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    modifications to take non-standard spindle will not be worth the time and effort.

    "unable to find motor/spindle combo for this model"

    unless you need to grind parts on monday, I suggest trying a bit harder to find the cartridge.

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    Quote Originally Posted by cyanidekid View Post
    modifications to take non-standard spindle will not be worth the time and effort.

    "unable to find motor/spindle combo for this model"

    unless you need to grind parts on monday, I suggest trying a bit harder to find the cartridge.
    Thank you for your thoughts, however I will ascertain for my self what my time and effort is worth toward this project, this is part of my research to make that determination, do you have any thoughts on an alternative?

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    You not only need a spindle but a way to mount conventional grinding wheels on it.
    That sort or kills the smaller E-yuck spindles that are so popular. How will you mount wheels?
    Better to search for a spindle cartridge that fits the hole and has the normal 3" taper.
    Even if well used you can replace the bearings.
    You can bush or bore the hole to use something else out of another SG but watch for length.
    You have no idea what happened to the old spindle? It moved elsewhere?
    Bob

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    Quote Originally Posted by CarbideBob View Post
    You not only need a spindle but a way to mount conventional grinding wheels on it.
    That sort or kills the smaller E-yuck spindles that are so popular. How will you mount wheels?
    Better to search for a spindle cartridge that fits the hole and has the normal 3" taper.
    Even if well used you can replace the bearings.
    You can bush or bore the hole to use something else out of another SG but watch for length.
    You have no idea what happened to the old spindle? It moved elsewhere?
    Bob
    I have been looking for alternative cartridges thanks to some others who have given my advice like Pope spindles and others that appear to fit. but I will keep in mind about the taper, thank you. the old spindle is gone, the guy I got the machine from sent it out to be rebuilt and didnt like the bill he got so he abandoned the spindle and gave me the machine, but I spent some money on transporting it to my storage. I have recently moved it to my garage. i saw some affordable spindles on ebay and craislist that may fit but no motor just the spindle and pulley for belt. this style SG normally uses a direct drive motor /spindle so if I use a pulley I will have to adapt a motor. right now just trying to get some ideas.

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    Quote Originally Posted by sherman View Post
    Thank you for your thoughts, however I will ascertain for my self what my time and effort is worth toward this project, this is part of my research to make that determination, do you have any thoughts on an alternative?
    yes, I do have thoughts on an alternative. find out where it was sent for a rebuild, and make them an offer.

    not understanding why you are convinced that you must cobble up some frankenspindle. if you really want to do that, for whatever reason, go ahead, but P-M made thousands of these, so yes, they most definitely are available.

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    Quote Originally Posted by cyanidekid View Post
    yes, I do have thoughts on an alternative. find out where it was sent for a rebuild, and make them an offer.

    not understanding why you are convinced that you must cobble up some frankenspindle. if you really want to do that, for whatever reason, go ahead, but P-M made thousands of these, so yes, they most definitely are available.
    THAT has not been my experience in the last 2 years... you make it sound as if the PM spindle style is easy to find. if that is really true then, I must be looking in the wrong places or asking the wrong questions.

    I came here for "practical" help on how to get this running, so you sound like you know something that I don't know.... then please help and share what you know because I am not finding them.

    Keep in mind it is NOT possible for me to go get the old one and I am not going to pay more than just buying a SG. The SG I have is in real nice shape minus the spindle. I really would like to bring this back to life again. SO if you were in my shoes and you wanted to get this going then what ,where and how would you go about it?

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    What is the diameter of the spindle cartridge and how is it mounted?
    Take a few pictures and post them.
    If you are determined to use an alternative spindle I may have something that would help but I need to know what you are looking for.

    Josh

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    Quote Originally Posted by sherman View Post
    THAT has not been my experience in the last 2 years... you make it sound as if the PM spindle style is easy to find. if that is really true then, I must be looking in the wrong places or asking the wrong questions.

    I came here for "practical" help on how to get this running, so you sound like you know something that I don't know.... then please help and share what you know because I am not finding them.

    Keep in mind it is NOT possible for me to go get the old one and I am not going to pay more than just buying a SG. The SG I have is in real nice shape minus the spindle. I really would like to bring this back to life again. SO if you were in my shoes and you wanted to get this going then what ,where and how would you go about it?
    It sounds as though the original may be available if you knew where. Keep in mind, a newly rebuilt spindle, with normal care, will run thousands of hours. What shape is the iron in? Does it have a good mag chuck? You may be far better off just obtaining another machine.
    FWIW, I have two Parker surface grinders, one direct drive and one belt driven. Either will do good work. Good luck


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