A Project Quest

For some reason I haven't been following this, till I saw the project was a surface grinder. Will it be benchtop or floor standing? May I ask why the 8" wheel was chosen over a 6" or 7"? A lot of Bridgeport brand grinders used a large wheel to work envelope ratio.

Very interested in what kind of spindle you guys are going to build.
 
Jet Skis use something similar. I assume the main reason for this is to compensate for any minor misalignment between the drive motor and the table feed?
Robert
 
rwm said:
Jet Skis use something similar. I assume the main reason for this is to compensate for any minor misalignment between the drive motor and the table feed?
Robert
Click to expand...

Yes and no. While it does compensate for minor misalignment, the primary reason for this design is to provide a zero lash, mechanical quick disconnect for manual operation. If the motor was connected by a normal spring type coupling, you would have to loosen the grub screws and slide the coupling off of the shaft. In the case of a surface grinder table drive, a standard Lovejoy coupling would work, but they are not zero lash. This same design would work in applications requiring zero lash. And besides, we are hobby machinists so why buy it when you can build it?:grin:
 
Andre, it will be large enough to be either a Bench top or Free standing Andre. As for the wheel size, it's a personal choice on the part of both builders. No special reason other than that.

"Billy G and Mark"
 
Robert, misalignment is out of the question. The bottom line is, we are hoping to build a Precision Grinding Machine. It won't be state of the art but it will be damn close. LOL

"Billy G"
 
Having trouble seeing the need for a zero/low lash coupling on the table drive. There won't be any cases where the table will need to stop in a precise location that I can think of. Normally, the table runs out from under the wheel some small but arbitrary position before reversing direction.

And Bill, are you saying you are using a rack and pinion for the main table drive? I've thought about that on a few projects, but mentally can't get past the upward force by the engagement angle of the teeth. Unless the table is possibly constrained somehow or is just plain heavy enough to negate this effect. I've been under the impression that this is one reason that many of the smaller grinders use a belt drive there. No criticism intended, just sort of thinking out loud.
 
The Mag Chuck alone is close to 50 lbs. The rack at a 10 pitch 14.5 Pressure angle. This should be optimum and have no problem staying on the pinion. The pinion will have 20 teeth. At this point Tony, I believe we are OK, but that's not written in stone till I mock it up next week.

In the case for the rack lifting, you could install the rack with the teeth pointing up and the pinion on top. Pressure would then hold the table down.

Most all Surface Grinders have a rack and pinion for manual movement.

"Billy G"
 
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An advantage to rack and pinion drive over tape, cable, or belt drives is the ability to lift the table off the machine. With other drives it can be a bugger to remove the table, and when replacing you have to make sure it's tensioned correctly. I imagine a rack and pinion would be a lot simpler to manufacture as well. It's what I plan to use on my shaper project, with a further gear reduction.
 
I checked my tracking number and my mag chuck should arrive on Monday.

Bill, Are we still going with the linear bearings on the table or undecided.

I kind of liked the idea of the rack on the bottom as I wondered about pressure up lifting slightly. Even as heavy as the table is with the chuck on it, I would think we would want to avoid the possibility of lifting at all. The linear bearings would be fine as long as they are covered well. The original design only covered the rear to protect them because the wheel rotation throws most trash out the back, but I would think they should have protection on both ends. In the original design he should have made that handle bracket a cover also.
 
Hold off on the Linear Bearings Mark. I am thinking about V-Ways and Turcite B. I will know by mid week. I want to see how Turcite B works under that much weight. I'll call you tomorrow.

"Bill"
 
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