A Project Quest

It is hard to think about an improvement without even knowing the original design. The sprocket and chain idea gave me a thought but not sure how hard it would be to implement on the original design and any other changes that have already been decided.
 
Thanks for the replies to my question. I knew (but forgot) about the lift off requirement (or 'desire') but I was thinking more along the lines of zero backlash. Ball screws seem to be the most precision drive method. But you're right about SGs being messy and ball screws probably wouldn't be zero tolerance for very long.

I think someone mentions a guide roller earlier. Maybe this could be put on the back side of the pinion somehow to negate the lift factor. More thinking aloud.
 
The rack location on any lighter duty Grinders I have seen is located under the table. The rack is on the non-movable part of the table assembly. The pinion on the movable part. Sound familiar? This puts the pinion on top. No lift. This is the reason you need to lift the table off. We plan to put the rack on the front edge of the moving Mag Chuck. The lift off feature is not that important. This is why Open linear Bearings on round rails is the preferred set-up at this time. Again, this is not written in stone.

"Bill and Mark"
 
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Bill, as I picture that in my mind, the issue is the same. The force generated, however minuscule it may be in reality, is the same no matter which is on top. I see that as the same, except now you are also lifting the spinner, shaft, and pinion along with the support bearings/blocks that the pinion shaft rides in.

Maybe I'm imagining it wrong, but I can't see the difference in lifting forces with that arrangement. I'm studying on Johns suggestion regarding the exact tooth design to translate most of the force lengthwise and very little upward. I think backlash is immaterial in this application, so that should be used to your advantage if possible. I am beginning to see a sort of dovetail rack with a stem/ball shaped pinion gear so that as soon as it engages, it is actually pulling the table down. The only caveat being the ball must be smaller in diameter than the narrow opening of the dovetail pattern on the rack so the lift off can be effected.................still studying on it. Multiple simultaneous engagement during lift-off is the stopping point for me right now.
 
Ok. since have no idea on how this was designed, and have not used anything similar to this since about 1977, have just watched and learn. But on some of the items I think there is ways to do things.
1. The rack and pinion. One way to keep the lift out of it is to put the rack and pinion under the table and attach the table to the rack with pins. Build a solid rack and Pinion that way any play is in it, and free from the table, Use pins that can slide up and down through the ends of the Rack thus not transferring the lift to the table, yet the table can be easily removed. It does not have to be pins, it can be some sort of latching systems etc. as long as it will allow the rack to move any up and down without transfer to the table. Almost like was being talked about with the chain drive system.
My problem with the chain drive system, is that at the end of the cutting stroke it may let the table go back if there is much slack in the chain. Thus bumping against the wheel like it was trying to go the wrong direction. Of course if you have to much play in the rack and pinion system you could have the same problems. but that can be set by tooth depth etc.
Just what I am thinking but it may not help as I do not know how the design has the current rack and pinion set up. My idea may take a bit more work to put in.
 
Hmm, Ken, use socket shoulder screws as pins, once the heads are turned down to below the pin diameter? Thread them into the bottom of the table. I like that. Let the rack float on the pins vertically but be held in place linearly. Might be a little unwieldy removing the table and realigning the pins coming back down, but there may be a slick solution to that too.
 
kvt said:
Ok. since have no idea on how this was designed, and have not used anything similar to this since about 1977, have just watched and learn. But on some of the items I think there is ways to do things.
1. The rack and pinion. One way to keep the lift out of it is to put the rack and pinion under the table and attach the table to the rack with pins. Build a solid rack and Pinion that way any play is in it, and free from the table, Use pins that can slide up and down through the ends of the Rack thus not transferring the lift to the table, yet the table can be easily removed. It does not have to be pins, it can be some sort of latching systems etc. as long as it will allow the rack to move any up and down without transfer to the table. Almost like was being talked about with the chain drive system.
My problem with the chain drive system, is that at the end of the cutting stroke it may let the table go back if there is much slack in the chain. Thus bumping against the wheel like it was trying to go the wrong direction. Of course if you have to much play in the rack and pinion system you could have the same problems. but that can be set by tooth depth etc.
Just what I am thinking but it may not help as I do not know how the design has the current rack and pinion set up. My idea may take a bit more work to put in.
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There's no reason for there to be any slack in the chain. Also, as I mentioned, you could use a timing belt rather than a chain: same principle.
 
Has any thought been considered towards cable drive? All you need is a cable mounted at both ends, and the "pinion gear" used on the rack and pinion setup would just be a shaft with a cross hole. No table lift, very simple, and 1/8" braided steel cable has a very high tensile strength and is dirt cheap.
 
Guys, I have the little Sanford bench top surface grinder with a 4X6 mag chuck. The whole table and chuck maybe weights 30lbs and it is rack and pinion drive and has some backlash. The table does not lift during use. My grinder can hold 0.0002” corner to corner. I would design your grinder with more concern over the grinding swarf getting into moving parts than the table lifting. The manufacture recommends taking the table off every week to clean the bed. I think a linear bearing translation system would be grinding grit problematic. Just my 3cents…Dave.
 
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