Question I always wanted to ask.

sigp2101 said:
That is pretty similar to what I was thinking. Like that approach. That is sure way to center rotatable to the mill spindle. Now continuing from there, 4 jaw chuck has to be affixed to the rotatable and object's radius center trued to the center of the rotating table. This is the part I am difficulties with. Having 4 jaw chuck, that holds the part, between rotating table and part itself you just lost your reference point. Cant see it, can't access it. But you have one in the spindle of the mill if you didn't move mill table at all.
Click to expand...

I suppose you could use the same method I talked about with one little caveat, make the 1" (or whatever is appropriate) steel shaft long enough so that when it sits down in the rotab hole it is long enough to stick out of the chuck when the chuck is placed on the rotab.

So what you do is to set up the rotab just like my first post. Get it dialed in perfectly.

Now, lower the mill table and place the longer shaft back in the rotab. You can get the chuck close to center on the rotab and then once again use the indicol/dti to fine tune/center the chuck on the rotab.

Once that is done you can center the "part" you are working on using the indicol/dti setup. If the whole mess, rotab/chuck/part, gets off center because you accidently turned your X or Y (been there, done that :banghead: Hey, I was grabbing for the Z and the Y was real close...) you can always re-center everything by going off the outside of the chuck body.

Hopefully that makes some sense :eek:

-Ron
 
More I think about it more I am convinced that solid sturdy indicator bar as explained is way to go.
With this solution you can go quick and dirty or fine tune it just after as continuation of the same process.
Producing such bar accordingly to size of the equipment in each shop is right solution. This bar could be used in conjunction with dead center for roughly centering center mark to the center of the spindle that is centered to the center of the rotary table, right?:goodjob:
 
I must be missing the huge flaw to what I said that would call for, aw well never mind.

So being I'm new, tell me the huge flaw here. Seems to me checking run out from the table to the 4 jaw would center the 4 jaw. Then getting rid of the run out in the part would make the part true with everything under it. Right up to the tool. Our instructor makes a huge deal of everything being nuts on. From the table, up the vise, and so.
 
Chuck, the only thing I will say is that I can offset the chuck 1/4" and indicate a part true to the table, then the spindle.....and then cut whatever I want.
 
sigp2101 said:
More I think about it more I am convinced that solid sturdy indicator bar as explained is way to go.
With this solution you can go quick and dirty or fine tune it just after as continuation of the same process.
Producing such bar accordingly to size of the equipment in each shop is right solution. This bar could be used in conjunction with dead center for roughly centering center mark to the center of the spindle that is centered to the center of the rotary table, right?:goodjob:
Click to expand...

That sounds right. :thumbzup:


chuckorlando said:
I must be missing the huge flaw to what I said that would call for, aw well never mind.

So being I'm new, tell me the huge flaw here. Seems to me checking run out from the table to the 4 jaw would center the 4 jaw. Then getting rid of the run out in the part would make the part true with everything under it. Right up to the tool. Our instructor makes a huge deal of everything being nuts on. From the table, up the vise, and so.
Click to expand...

One error (in my opinion anyway) is indicating off the "part" to center the rotab/chuck. "Getting the run out in the part would make the part true with everything under it." would only be true for that particular part. As the part itself could be out of true or just some odd shape I would think trying to center from it wouldn't be real reliable. Another problem is that if the 4-jaw isn't centered on the rotab it might not even be possible to remove the run out with the part as the part could never be center to the rotab.

There may (and probably are) other/better ways to handle this but it makes more sense to me if a person center/squares up the work holders - rotab and chuck, so that you have a "known" point to start from.

-Ron
 
I under stand what you guys are saying. And I see how your getting to the end result. We would never indicate the roto to the spindle though. We would use the spindle to hold an tdi to run the edges for square and work up. The last thing we would even consider is the tool to part. We would square the table to head, roto to table, jaw to roto, part to jaw, and then the tool to part. At least I think we would.

Admittedly your way seems more straight forward. I'm gonna ask the teacher on monday how he might do this.

Thanks for the info fellas
 
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