Centering Disc on Vertical Rotary Table?

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mcman56
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Centering Disc on Vertical Rotary Table?

Post by mcman56 »

I just purchased a Chinese rotary table with MT 3 taper at the center. I have a project that will require using it vertically with a disc bolted to the center. If the center of the table was not tapered, I could simply make an arbor to go through the center of the disc and table to align plus clamp together. Is there any easy way do do this with the MT 3 taper? All I can think of is mounting the rotary table horizontally, aligning to spindle, mounting disc to table, align to spindle, clamp in place and then mount assembly vertically. I would also have to space the rotary table above the mill table when horizontal to access a center bolt if I camp with center bolt. It seems there should be an easier way.

Maybe a short piece of MT3 tapered shaft could be bolted to rotary table from bottom and then an arbor could be used on top to locate and clamp to short tapered shaft. Can you turn an MT3 shaft accurately enough for a purpose like this?
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Bill Shields
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Re: Centering Disc on Vertical Rotary Table?

Post by Bill Shields »

You can purchase MT3 tails with cylindrical tops.

You can use these to find center, then tap them out.

Shars.com has many varieties available
Too many things going on to bother listing them.
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GlennW
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Re: Centering Disc on Vertical Ro

Post by GlennW »

Some rotary tables have no center bore, and others that do may not coincide with the rotary axis.

Roughly center the table under the spindle.

Zero the rotary table and then clamp a piece of 1" round bar about an inch long to the rotary table about an inch or two from center at the 3:00 position.

Step 1 Now place a DTI in the spindle and rotate the spindle by hand to sweep the inner edge of the round bar. Zero the DTI.

Step 2 Rotate the rotary table 180 degrees (to 9:00) and then rotate the spindle and sweep the round bar again. Move the X axis 1/2 the error and zero the DTI again.

Step 3 Now move the rotary table 90 degrees (to 6:00) and sweep the round bar again. Adjust the Y axis until the DTI reads zero.

Step 4 Now do the same at 12:00.

If you can go around again and the DTI needle remains on zero in all four positions, your rotary table axis is perfectly aligned with the spindle axis.

You may have to repeat the procedure to eliminate all error and get the DTI needle to remain on zero.

Once the rotary table is zeroed under the spindle, you can check the center bore of the rotary table to see if it is coaxial with the center of rotation, or center your part on the rotary table using a DTI.

I hope that makes sense, as the only thing I find worse than trying to explain how to do something is having to type to do so... :) Easier done than said!
Glenn

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Odyknuck
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Re: Centering Disc on Vertical Rotary Table?

Post by Odyknuck »

My Rotary table has an MT2 and as stated above I had several MT2 drill chuck adapters on hand and used one in the table. I taped the bottom of the MT2 and hold it in the table with a button head Allen. Then I just use an indicator to center the table and done. My table is only 6" in diameter, when I need to do a larger piece I would make a plate that drops down over the MT2 straight shank and bolt it down with "T" nuts.
Example attached:
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mcman56
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Re: Centering Disc on Vertical Rotary Table?

Post by mcman56 »

"You can purchase MT3 tails with cylindrical tops"
Is there another name for these? I'm not finding them. I do have a couple of MT3 dead centers but they are rough turned between MT3 and cone on end.

GlennW - Yes, the text is hard to follow. Would Odyknuck's picture be basically what your are describing?

Thanks
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rmac
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Re: Centering Disc on Vertical Rotary Table?

Post by rmac »

Would the following steps work?

1. Mount the rotary table vertically as you need it to do the work.

2. Bolt the disk to the rotary table so that it's snug but can still be moved around.

3. Set up a dial test indicator so that it rides against the edge of the disk.

4. Adjust (tap, tap, tap) the position of the disk on the rotary table until the DTI doesn't move as you rotate the rotary table.

5. Tighten the bolt(s) holding the disk to the rotary table.

6. Check that nothing moved in Step 5 and make adjustments if it did.

This seems to me like a more direct way to get where you need to be than aligning both the rotary table and the disk to the spindle.

-- Russell Mac
ChipMaker4130
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Re: Centering Disc on Vertical Rotary Table?

Post by ChipMaker4130 »

Mine came that way too. I bored it straight through to 1". Much more handy that way.
10 Wheeler Rob
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Re: Centering Disc on Vertical Rotary Table?

Post by 10 Wheeler Rob »

I have one that has the MT taper, I use MT arbor that I put. I centerdrilled the end and use center finder that has the tapered tip on it to center the table. Is quick and easy to and accurate enough for my needs.

Rob
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GlennW
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Re: Centering Disc on Vertical Rotary Table?

Post by GlennW »

mcman56 wrote: Fri Mar 03, 2023 6:16 pm GlennW - Yes, the text is hard to follow. Would Odyknuck's picture be basically what your are describing?
I edited it a bit. Just follow the steps.
Glenn

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GlennW
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Re: Centering Disc on Vertical Rotary Table?

Post by GlennW »

rmac wrote: Fri Mar 03, 2023 6:52 pmThis seems to me like a more direct way to get where you need to be than aligning both the rotary table and the disk to the spindle.
The method that I described allows you to accurately zero your dials (or DRO) at the center of rotation if other features need to be accurately placed.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
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rmac
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Re: Centering Disc on Vertical Rotary Table?

Post by rmac »

GlennW wrote: Fri Mar 03, 2023 11:01 pm
rmac wrote: Fri Mar 03, 2023 6:52 pmThis seems to me like a more direct way to get where you need to be than aligning both the rotary table and the disk to the spindle.
The method that I described allows you to accurately zero your dials (or DRO) at the center of rotation if other features need to be accurately placed.
Good point!

From the original question, though, I got the impression that mcman56 was going to immediately remount the rotary table vertically after he had the disk centered on the rotary table. If that's true, then the relation between the rotary table and the spindle would be immediately lost, and there's no reason I can see to temporarily mount the rotary horizontally in the first place.

-- Russell Mac
mcman56
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Re: Centering Disc on Vertical Rotary Table?

Post by mcman56 »

If I am reading this correctly, Glenn's method would work with the table horizontal and vertical. If horizontal you sweep the bar by rotating the spindle. If vertical, you could sweep the bar by moving the spindle up and down. (I am assuming the round bar is clamped to the table such that it sticks out away from the table.) Assuming the table is vertical, can you simply use the outside edge of the rotary table to square it to the mill table?

I did find an arbor this is called out as MT3 to M20. There is a ring before the thread, I wonder if that is true to the MT3.

Dan
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