need advice on modifying a Parker majestic grinder

[sherman]

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.

[Harold_V]

If you hope to achieve acceptable results (a grind without choppiness), you aren't going to be successful unless you invest in the proper spindle and motor. Surface grinding can be troublesome, as the slightest deviation from flatness displays as waves in the resulting finish. Even switching to a single phase motor from a three phase motor generally results in a serious degradation of finish, due to the pulsations of single phase, which translate in to the finish.

Bearings of high precision are also a requirement, assuming finish is a consideration.

Now you see why the grinder was free. It's entirely possible a replacement spindle and motor was cost prohibitive.

H

Edit.

A mention of RPM.
Grinding wheels are designed to operate at a given speed. If you use the wrong speed motor (it most likely should be 3,600 rpm), the performance of the wheels you choose will be disappointing. Running a wheel slower than its design speed results in a wheel that behaves too soft. The vast majority of wheels used on a grinder like this are 7" diameter, and, typically, have a 1¼" arbor hole. Thickness varies, but ½" wheels are the norm. These wheels mount on removable hubs on most grinders, so wheels can be exchanged without having to be dismounted. That's common for cutter grinders, although not so much with surface grinders. Both use the same wheels.

[sherman]

thank you Harold 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. I can use secondary methods like sanding polishing to get more out of it if needed. so that is what I mean by hobby level within that context. ok so 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 perhaps use custom a belt drive to drive it. but i am open to other ideas. 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?

[GlennW]

I have a PM 2Z and it is a multi speed spindle using a serpentine type belt like this one.

Parker.jpg (11.23 KiB) Viewed 2180 times

I just got home, but can post more images next week when I'm back at my shop.