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Question for owners of Haas Pneumatic (8 or 12") tailstocks; does the shaft stay straight?

GiroDyno

Cast Iron
Joined
Apr 19, 2021
Location
PNW
I'm trying to design a rotary fixture for flipping a range of parts that vary from 10-16" OD x .75-1.5" thick.
Thinking a big "double-V" shaped block mounted to the rotary would provide contact on two points 120* apart and a self-centering/leveling function. I'd need a tailstock to support the far end (probably with a few doweled positions to allow the 2.5" stroke to cover the range of diameters) also with a V-block that would hopefully provide the same self-leveling function but that is assuming that the tailstock shaft stays straight and doesn't rotate at all...

Something maybe along these lines:
1674588660763.png
I've never seen one of these tailstocks, I'm curious if this would be feasible in real world circumstances... Anybody with one of these units have any idea how much I could expect the shaft to move? In other words: How much will the part to rock about the rotary axis or droop/lift from the table end to the tailstock?

Material is cast iron (parts have been machined on all faces by this point) but the cutting loads are already light (40% max spindle on Haas VF#SS machines). Being able to cut both sides of these in one setup would still be a huge throughput gain even if we slowed our cycle down by 30% to accommodate a fixture that wasn't rock solid.
 
OK that was kind of a dumb way to ask the question because the tailstock support needs to be able to spin to allow the rotary to move...
But I still need to know if it can spin, and how much because I need it to either spin totally freely and be able to lock the V-block in the "flat" position, or I need to know if it only has a few .001* of float in which case I need to add a bearing to my V-block.
 
Are your contact points just lines on a vee? I think you'll need more contact to get the rigidity you need out of that setup for brake rotor milling.

Your vee angles could grip on the chamfers if the angles match. That would be better.

Sorry, don't know if Haas tailstock Rams spin. I bet they're fixed.
 
The Haas tailstock I have is fixed. I use a small drop of oil like one would on a dead center on a lathe, or one can use white lead? I think that’s what they used to recommend back then, or was it whale oil?
 
I'm 110% positive there will need to be change/finessing of this design. I don't have a rotary or any hardware for this, I'm just trying to get the idea out of my head and see if it seems do-able once everything is drawn up to scale.
There are radiused corners on the top and bottom faces of the discs which will distribute the load a little bit, but the idea is to use the V to self-center/level in Z and Y (as shown) which kind of requires minimal contact. TBH I'd be surprised if this didn't hold them more firmly (if not flat) than the mag-chucks we currently use.

And really I'm hoping this can be installed on a Brother R650 so I wouldn't be relying on a Haas tailstock long term, but for now we run these on VFs and so that's likely the rotary table/tailstock combo I'd end up getting for my first stab at this setup.
 
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The Haas tailstock I have is fixed. I use a small drop of oil like one would on a dead center on a lathe, or one can use white lead? I think that’s what they used to recommend back then, or was it whale oil?
Like FIXED fixed, or does it have a noticeable amount of rotational play?
I need these level +/-.0025 across the 10-16" span. I'm sure I could use the probe to check and comp the rotary axis and reduce the error but it needs to be pretty tight to start with.
 
Like FIXED fixed, or does it have a noticeable amount of rotational play?
I need these level +/-.0025 across the 10-16" span. I'm sure I could use the probe to check and comp the rotary axis and reduce the error but it needs to be pretty tight to start with.
It has the same amount of play a lathe tailstock has. You can slightly rotated it back and forth.
 
Not sure about the 8 or 12 inchers but with my 5 inch one, there is really no measurable "drop" from full in to full out.
And no measurable slop as far as "rotational" is concerned.
The movable shaft is keyed on the top, inside the casting. With a Dowel under the name plate on the top. So it would be the "slop' between the key way and the dowel.
If that helps.
 
Thanks for the info guys.
I have to cover such a "large" range in parts that I'm not sure if I'd be better off with a 2.5" stroke tailstock and maybe 3 quick change positions for it, or just put a fixed tailstock on rails and use one big cylinder to cover the range...
Making something from scratch would be nice because I could add some actuated pins to lock out the driven end after it flips between machining positions :scratchchin:
 








 
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