Home Built Surface Grinder

Thanks for posting that Toni. I had not noticed but it will move. Mine takes a fair amount of pressure but then again I took mine apart. :eek: Don't do that! Took me an hour and a half to get the balls back in. I'm thinking maybe an adjustable tension clamp on the back of the crank.
 
I think that will work. Wenn you grab it like I did in the video and you rest the tip of your thumb on the crank it is very hard to move.
 
Another option I’m gonna try is replacing the thread rod with a fine thread. I think this will solve the problem + will be much easier to to fine adjustments.
 
Toni - you mention fine adjustment with screw thread vs the ball thread you've got. How many turns to cm (or inch) does your ball screw have? I went with a 1/2"X20TPI screw for that reason. That gives .050" per round of screw. I see your problem with the ball screw - that table does need to lock in place so it doesn't move while grinding.
 
Toni: Thanks for checking, that's about .166" per turn. With the ball screw it makes a smooth easy adjust, but as ya'll found (before I ordered one of those) there needs to be a way to lock into place.
 
To solve locking it in place I think you could fabricate a locking system on the side. Is the slot on the side like a T slot? If it is, #5 would be a locking lever. 1-4 just attach it to the sliding block.


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KnuckleDownKnives said:
To solve locking it in place I think you could fabricate a locking system on the side. Is the slot on the side like a T slot? If it is, #5 would be a locking lever. 1-4 just attach it to the sliding block.


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The problem is, the way I've seen these used is you take a pass, advance the table, repeat. Locking and unlocking for every pass would seem to be a real pain.
 
My simple solution is sandwiching o-rings between the crank and end plate. I used several to fill the bearing recess and one inside another to get the right diameter around the shaft. Squeeze the crank on with a clamp and tighten the set screws. I tried to move it by putting an Irwin squeeze clamp on it and it will not move unless you turn the crank.
 
Done except locking levers and grinding in the chuck. By far not perfect but done.
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I feel like the last guy picked in gym class. My rail and table have been delayed due to the chinese new year. Parts are supposed to ship this week. Great looking builds so far. My 13 year old son is excited as well, since he is doing a science fair project on hardness numbers with different quenchants. He wants to use the SGA to surface his coupons. I'm tearing up hear just thinking about it....
 
I'm really not happy the ball screw guide rail. When grinding it has enough play in a cross twisting motion that at the end of the slide rail there is more than 1/4" play toward the belt. If I can't find a work around, I'll have to change it to something different. Very annoying!
 
Jesse Latham said:
I'm really not happy the ball screw guide rail. When grinding it has enough play in a cross twisting motion that at the end of the slide rail there is more than 1/4" play toward the belt. If I can't find a work around, I'll have to change it to something different. Very annoying!
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Wow, that sounds like a lot of slop. It would seem like a ball screw guide rail like that were supposed to hold a lot tighter tolerances.

I had a little side to side slop in my guide rail (the smaller one) before I lapped it. But even that one didn't give me more than 0.1mm (0.004") play across the 400mm chuck.
 
currenthill said:
It would seem like a ball screw guide rail like that were supposed to hold a lot tighter tolerances.
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I thought so too. The forward and back motion of the ball screw is very tight. So if you're just pushing or pulling it's ok. But not for the twist from one end of the chuck to the other. And of course if it twists sideways it has to be twisting up and down also. I've a work around in mind and will post it if it works.
 
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