question about positioning work piece on rotary table

stoneaxe · Dec 21, 2020

I could use some rotary table setup help here-

How is the work positioned on the rotary table? For example- say there is a 1" wide x 6" long bar that has to have a radius put on the end.

How do I measure to ensure the bar long axis is centered on the radial axis of the rotary table? There is no parallel surface on the table to measure to.

The only way I can think of is to find the center point of the rotary table at the pivot, subtract 1/2 the stock width, and then run the mill table in and out to get the same measurement at both ends of the stock.

Thanks for any tips!

CORONA VIRUS · Dec 21, 2020

Is the 6" bar parallel to x axis?
If so, just indicate at every 90 degrees of rotation. Maybe you should make a sketch.

eKretz · Dec 21, 2020

Treat the rotary table like a lathe chuck and use an indicator to set the part relative to the table's axis of rotation.

stoneaxe · Dec 21, 2020

eKretz said:
Treat the rotary table like a lathe chuck and use an indicator to set the part relative to the table's axis of rotation.

I do not understand this.
The idea is to mill an arc on the end of a bar clamped flat on the rotary table. So the bar has to be on exact radial axis of the rotary table, so the arc cut on the part is even. Without a defined Y or X axis, supplied by the mill table movement, I can't see what surface to indicate off of.

Is your example like setting up a face plate in the lathe, and using a indicator mounted on the cross-slide to check alignment of the part on the faceplate?

Without the fixed linear axis supplied by the crosslide (on a lathe)or the mill table axis, how would the part be axially aligned on the rotary table? From what point would the measuring take place?

CarlBoyd · Dec 21, 2020

stoneaxe said:
I do not understand this.
The idea is to mill an arc on the end of a bar clamped flat on the rotary table. So the bar has to be on exact radial axis of the rotary table, so the arc cut on the part is even. Without a defined Y or X axis, supplied by the mill table movement, I can't see what surface to indicate off of.

Is your example like setting up a face plate in the lathe, and using a indicator mounted on the cross-slide to check alignment of the part on the faceplate?

Without the fixed linear axis supplied by the crosslide (on a lathe)or the mill table axis, how would the part be axially aligned on the rotary table? From what point would the measuring take place?

I'll give it a shot.

1) clamp the bar on the table as close as you can by eye, end and 2 sides 1/2 " from the center of the table
2) rotate the table so the long axis of the bar is parallel to table movement , bye eye
3) with a dial indicator of the spindle or main frame, rotate the table until the bar is exactly parallel to table movement
4) rotating the table back an forth 180 degrees move the bar until the dial indicator says the 2 sides are the same distance away
the center of the bar is now directly over the center of rotation of the table
5) rotate the table 90 degrees and move the bar until the end has the same indicator reading
the sides of the bar and the end of the bar are now the same distance from the center of rotation of the table, 1/2"

double check 3,4,5 until you don't need to make adjustments

Do you now understand?

Merry Chrisztmass
CarlBoyd

metalmaster1 · Dec 21, 2020

Simplified Rotary Table Setup. Tool Demonstration #1 - YouTube

johnoder · Dec 21, 2020

Worked for me making this

stoneaxe · Dec 21, 2020

CarlBoyd said:
I'll give it a shot.

1) clamp the bar on the table as close as you can by eye, end and 2 sides 1/2 " from the center of the table
2) rotate the table so the long axis of the bar is parallel to table movement , bye eye
3) with a dial indicator of the spindle or main frame, rotate the table until the bar is exactly parallel to table movement
4) rotating the table back an forth 180 degrees move the bar until the dial indicator says the 2 sides are the same distance away
the center of the bar is now directly over the center of rotation of the table
5) rotate the table 90 degrees and move the bar until the end has the same indicator reading
the sides of the bar and the end of the bar are now the same distance from the center of rotation of the table, 1/2"

double check 3,4,5 until you don't need to make adjustments

Do you now understand?

Merry Chrisztmass
CarlBoyd

Yes-

Thanks.

Red James · Dec 22, 2020

And when you get tired of all this horsing around, you will understand one of the true blessings of cnc mills.

trevj · Dec 22, 2020

stoneaxe said:
I could use some rotary table setup help here-

How is the work positioned on the rotary table? For example- say there is a 1" wide x 6" long bar that has to have a radius put on the end.

How do I measure to ensure the bar long axis is centered on the radial axis of the rotary table? There is no parallel surface on the table to measure to.

The only way I can think of is to find the center point of the rotary table at the pivot, subtract 1/2 the stock width, and then run the mill table in and out to get the same measurement at both ends of the stock.

Thanks for any tips!

If you have the RT centered under the spindle, set the dials (or preferably, the DRO) at Zero Zero.

Put a known diameter stub in the mill chuck. Move off Zero by half the diameter of the stub, and half the width of the part. Set the work against the edge of the stub, clamp a parallel down beside it.
Use an indicator to dial the parallel bar true to an axis, rotating the table to adjust.

This sets you on the center of your work (center of work is over center of axis of rotation of RT). You now also have a reference to the axiis of the mill table movement.

Now swing your stub around using the dials or DRO, to use it to measure the distance you need the end of the part to be past the Zero/Zero point for the Radius you want.
Clamp your part.
Install a cutter , and remember to account for the radius of that.

Done.

gbent · Dec 22, 2020

Layout the center of the arc on your part. Pick up the center of rotation of the table with your spindle. Put a wiggler in the spindle and center the arc location under the wiggler. If you have the need to align the workpiece with the quadrant of the rotary table, put keys in the tee slots and use spacers to put the workpiece in the correct position. Planer gages work great for this.

You can also use the distances the tee slots are from the centerline of rotation and use spacers for one or both directions.

Either of these methods will get you close. The need to refine the location depends on whether you are working to tens or tenths of thousandths.

Bill D · Dec 23, 2020

You also have to locate the arc center point at the correct distance from one end or the other of the bar so I think gbent's method does both in one step. Make a slug that goes into the rt's center hole and is a straight round bar sticking up. Set the rt on the mill and grab the stub in the collet. Then clamp it down. This centers the rt under the collet axis. Make sure to keep the bar up off the Rt surface so you do not cut into the rt.
Bil lD

CORONA VIRUS · Dec 23, 2020

stoneaxe said:
I do not understand this.
The idea is to mill an arc on the end of a bar clamped flat on the rotary table. So the bar has to be on exact radial axis of the rotary table, so the arc cut on the part is even. Without a defined Y or X axis, supplied by the mill table movement, I can't see what surface to indicate off of.

Is your example like setting up a face plate in the lathe, and using a indicator mounted on the cross-slide to check alignment of the part on the faceplate?

Without the fixed linear axis supplied by the crosslide (on a lathe)or the mill table axis, how would the part be axially aligned on the rotary table? From what point would the measuring take place?

We do not understand because you have not provided a sketch of what you mean.

CarbideBob · Dec 23, 2020

Three questions.
Full end rad or corner rad?
Side(s) and end to finish size already or is there stock on one, both or all three?
Part in vice on table or clamped to the table?
We just put a pin in the collet and shove the part against it but knowing the above would make it easier to show pictures of the how. You make your own offset axis on the table.
A larger rad we allow 10-15 minutes from start to end on a job routing, if the rad is standard in a collet size a different method using vee block and 3-5 minutes tops.
Expected results within a thou or two on rad size and position.

If the part is raked or twisted up top in a compound vice and the sides at zero with stock , say a 5x7 toolholder, this gets more complicated math wise than a flat setup to get to size and correct nose rad.
I do not like scribed lines for a center.
How close this scribe and how close to hit it as a zero? Too many errors for me but if .010 is good then I can see it as being efficient and a very good way to go.
I do blue and scribe things a lot. They tell me if I way pucked up the math or zeros. A safety check and sure as heck has saved me from doing wrong when I have forgot an offset. Oh shit, half the endmill. :wall:

Bob

onecut · Dec 24, 2020

Most of ways mentioned will work.I also like to roughly mark the first one off.Mark the center of your end radius off.Its easier if you clock the center of your R/Table in.So either put a plug in the hole in the center of R/T. Or clock the hole central.When you have clocked the table in .Zero both your dials in.Thats your x/y and R/T dial.Put something in spindle with point and raise table so your pointed object drops/lines up with the center of your required end arc.If its critical check with DTI

Forestgnome · Dec 27, 2020

metalmaster1 said:
Simplified Rotary Table Setup. Tool Demonstration #1 - YouTube

Joe Pie has several good videos on rotary table setups.

440rr71 · Dec 27, 2020

If your rotaty table, ie rotab does not have a plate mounted to it, do it. Get a chunk of aluminum at least 1 inch thick. When mounted mill a circle in the center. Now you have a perfectly concentric circle to pick up. Put the table on zero degrees. Get a couple of dowel pins. If your bar is 1 inch dial off half inch plus 1/2 dia of your pins.Install 2 pins,slip fit. Using this method and 3 pins, you can fixture most anything on a rotab quickly. 2 pins for the X and 1 pin as a stop for the Y. Hope this helps.

stoneaxe · Dec 28, 2020

Thank you all for the set-up advice- it is slowly making its way into my brain...

See, the totally obvious is what had eluded me-
If the end of the part, or any portion of the part centerline, is centered under the spindle, by default, it has to be on a radial axis.

now all I need is an anti gravity device- dang that rotary is heavy!

question about positioning work piece on rotary table

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