Centering Disc on Vertical Rotary Table?

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Odyknuck
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Re: Centering Disc on Vertical Rotary Table?

Post by Odyknuck »

Why would a manufacture make a rotary table with a center bore not concentric with the table and/or axis? That does not make sense to me.
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Charles T. McCullough
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Re: Centering Disc on Vertical Rotary Table?

Post by Charles T. McCullough »

It does make sense if the manufacturer was more interested in profit over quality.
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GlennW
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Re: Centering Disc on Vertical Rotary Table?

Post by GlennW »

Some of the high end tables have no center bore. Mine has a threaded plug in the center, so there is nothing to indicate off of.

The method that I describe uses the axis as the reference, so it makes no difference if the periphery or the bore are accurate or not.
Glenn

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

Post by Odyknuck »

I can understand why you use the method you describe with your table.
Rich_Carlstedt
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Re: Centering Disc on Vertical Rotary Table?

Post by Rich_Carlstedt »

The RT i mentioned was a 6 " craftsman ( Palmgren ) that was pretty rough when i got it
the T slot was broken in one spot ( Then i cast iron/nickel welded) and i had to grind the face
The hole was off .002" and I am not sure if it was made that way , or the metal jockey that owned it first did that.
but here is my point, do not use the mill to remachine the hole, it's not accurate enough
Remove the table from the base casting and mount it in a 4 jaw or a face plate and indicate the Radial Registration Points(RRP) on the bottom of the table . make sure the FACE of the faceplate or 4 jaw 'jaws" have no laterial runout . ( meaning plumb !)
Now every RT is different so let me explain my point. Say the table is 12". The RRP could be 11" or 8 " or 2-1/2" depends who made the RT
The 'base" has a counter-bored ring that the RRP registers against for rotary location control. generally the larger the RRP, the better, but have seen
the RRP as a 2 1/2" diameter boss in the center of the casting . The "fit" should be snug , but it may not be on low quality RT's . We had one at work that used the worm for latererally loading the table against the base C/bore ( no wonder our bolt circles were off at times )
Anyway, mount the table and indicate the RRP surface to 0-0 TIR and then bore the hole for a perfect concentric hole/table. Then while you are at it
indicate the OD of the table, it should be dead nuts, but who knows ?
If you want a taper socket , then reverse the table and you have a perfect hole to work with in boring a taper.
Rich
PS
The comment about the bolt circle error may seem meaningless for bolts/screws, but when using Dowel Pins , it's critical
mcman56
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Re: Centering Disc on Vertical Rotary Table?

Post by mcman56 »

I bought one of the cheap Chinese 8" rotary tables on Amazon. It seems OK. I have never mounted a rotary table in a vertical position and am wondering if bolting down just through the cast in holes is adequate. It seems like a clamp on the back side would be helpful but there are just some short ledges. I will be doing light cuts.
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Harold_V
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Re: Centering Disc on Vertical Rotary Table?

Post by Harold_V »

While a rear clamp might be somewhat more rigid, I suspect that you won't have any issues with the provided clamping area, especially with light cuts.
I hope the workmanship in the rotab is as good as it looks. Nice looking piece of gear!

H
Wise people talk because they have something to say. Fools talk because they have to say something.
mcman56
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Re: Centering Disc on Vertical Rotary Table?

Post by mcman56 »

I ended up using a machinable MT3 arbor for centering. It is threaded for an M20 type draw bar and I used a bolt for retention.

I thought I could use your 1" bar method for centering when vertical by moving the quill up and down but the spindle still had rotation to deal with. An edge finder found the arbor to be withing 0.001 of the rotation center so I used that.

The 8" rotary table seems OK and was just around $200 delivered. It is not too heavy but I can't see how they can be so low priced. I found a way to clamp at the back.

Thanks for all of your input.
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