Are most rotary tables like this?

[Larry$]

When working with the RT for a complex set of rotations, I always make up a table of positions for each operation. It saves the wear and tear on the old noggin and potential head injuries from banging my head against the wall when I screw up a part.

Me Too! I made an 11" auxiliary table with 8 slots, for my 8" Vertex to get more clamping area & clamping locations. Never even considered on clocking it. Not sure that T slots are accurate enough to matter. But then I've never made a fixture plat for it either.

 

[Manual Mac]

Wobbly, you may want to take your RT apart to understand it a little better. Pretty simple & kinda fun . Look for assembly grit inside, mine was pretty clean & oiled well.
Remember, there is a grub like screw (backlash adjustment) that has to be backed out (I didn’t see this at first) before the handle & worm assembly will pull out. Mine did anyway.
i kinda screwed up when I assembled it the first time by trying it to get all the backlash out. I got it too tight & noticed wear on it the next time I took it apart. My fault.
I now leave a bit of backlash, but I always set up turning the handwheel the same direction, so no harm, no foul.
if you have degree pointer screws (mine was riveted on) that are few degrees off, just make a longer pointer plate.
When I re-assemble mine the zero degree pointer always ends up pointing at the same degree mark, I’m not smart enough to figure out why. Probably simple? dunno.
Also the minute dial zero can be set anywhere you want it with the allan grub screws, but I’m sure you already knew that.
I have to oil all the ball oilers often while using mine. My table seems to need a lot of lube to move smooth.
Once again, I am no expert, but this works for me.
Cheers

 

[WobblyHand]

Also the minute dial zero can be set anywhere you want it with the allan grub screws, but I’m sure you already knew that.

Ahem, of course I knew that, but ahem, I seemed to have forgotten that ... duh. Thanks for reminding me! That will get some adjustment.

It seems the worm is cut at 4 degrees. So I can make the error be whatever it is, modulo 4 degrees. Freewheeling the table by one degree will not re-engage the worm. So the table could be set to 15 degrees, 11 minutes. (Choices are: -4.816, -0.816, 3.183, 7.183, 11.183, 15.183, etc. ) And maybe I can get some of that 11' out with the dial. My outer ring of holes is at 15 degree increments, so that would be close enough to work.

Boy, this has been exercising the grey cells. Going into this, didn't think making a fixture plate had this many nuances. There are some, if you want it to come out a certain way.

 

[WobblyHand]

Ok, got the 11 minutes adjusted out by rotating the outer dial. My goodness, what a mental block that was! I can adjust the pointer to 2 degrees, more requires opening the slots by 3mm or so. I can do that. Thanks for getting me over the hump! Done.

 

[wildcatter]

I dont have a RT but I saw this addressed somewhere, likely on a utube video. maybe Joe Pi . Might be worth searching his vid, unless you have it solved already.

 

[Janderso]

Thanks for the perspective. I was trying for it to not look like a disaster before I started. I do realize they do get improved and modified over time.

Well, have to come up with something manageable. There's no way I could index that many holes and not mess them up bad, if I don't stay on even numbers. Had wanted the fixture holes on 0 degrees, but they really don't have to be there. Or I could rotate the mounting holes slightly. Ok, something to think about.

Guess, the answer to my question is: yes, rotary tables do have some arbitrary offset, and it is up to the user to deal with it. And no, there is no way to clock the table. Having never had a rotary table, I did not know this.

I should add , my 10” Gorton does not line up either

 

[WobblyHand]

I should add , my 10” Gorton does not line up either

Mine does now.

Rotating the dial, plus offsetting the pointer did the trick. Until reminded by @Manual Mac, I didn't quite comprehend the dial adjustment. The hardest part of the job, was realizing what he meant. Once I figured it out, it was pretty easy to change.

One can freewheel the table to multiples of 4 degrees from your current position, with no problem. (Assuming a 90:1 drive) The worm repeats every 4 degrees. Fractions of 4 degrees are adjusted by turning the dial. The last little bit is to offset the pointer. I had to slot mine to get a little extra travel. Quite simple, as it all turned out.

 

[Larry42]

And the winner is ..... WobblyHand by a degree. Congratulations

 

[pontiac428]

So, I have a Kamaura 8" RT that I really like. Mine indexes to zero on the t-nut channels, and can be adjusted by backing out the worm gear preload spring stopper screw and adding shims to the worm shaft.

While I understand the desire to be indexed to zero on the x axis, I don't know that it matters. Just like it doesn't matter where on the x or y axis of your mill table you decide to plop down a part and go to work. All that matters is that you have your dimensions referenced to the work piece. It doesn't matter if you start a x-axis cut at 24.88325 inches, because that is what you reference to zero. Same on the rotary table, 29deg55'40" to 74deg55'40" looks the same as 45deg to the part. This is where a pad and pencil helps. It's kinda brute force compared to CNC or DRO, but mathematically, zero is wherever you say it is.

 

[WobblyHand]

So, I have a Kamaura 8" RT that I really like. Mine indexes to zero on the t-nut channels, and can be adjusted by backing out the worm gear preload spring stopper screw and adding shims to the worm shaft.

While I understand the desire to be indexed to zero on the x axis, I don't know that it matters. Just like it doesn't matter where on the x or y axis of your mill table you decide to plop down a part and go to work. All that matters is that you have your dimensions referenced to the work piece. It doesn't matter if you start a x-axis cut at 24.88325 inches, because that is what you reference to zero. Same on the rotary table, 29deg55'40" to 74deg55'40" looks the same as 45deg to the part. This is where a pad and pencil helps. It's kinda brute force compared to CNC or DRO, but mathematically, zero is wherever you say it is.

Yes, I agree. But as a new user to indexing on an RT, I really wanted to make it easier on myself to do the very first operations on the table. Later on it won't matter much. I do have a bunch of holes to make, and wanted them on easy to remember boundaries. It's a crutch, but, it's a way to start. Later, I can set the crutch aside.