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Stub rotary tombstone

Houndogforever

Hot Rolled
Joined
Oct 20, 2015
Location
Boring
Looking at another fixture and I would like to mount a 3-1/2" square bar extending about 8 inches out from the face of my 4th axis.
If I make a flange that will bolt to the face plate on the Sankyo rotary, how do I attach a 3-1/2" square tower onto it?
Press fit into a pocket on the face plate?
Dowel pin with some long 1/2" dia dowel pins and a couple 1/2 bolts?

Make the flange out of aluminum?
Make the the 3-1/2" bar out of aluminum? 6061 or 7075? Which is stiffer?
Or cast iron, nice chunk of 3-1/2" dura bar standing out from the flange?

The fixture is for some aluminum parts, essentially a 7" x 3/4 x 2-1/4 blade.
 
You have an RCC170 Sankyo, with a 65mm -0/+0.03mm through bore?

Take 9" of the 3.5" square stock and machine a 65mm section on the other end, just oversize so you can fit it snug with the through-bore on the Sankyo. Put an M12 thread in the center. Build a cap plug for the other end of the Sankyo and use a long bolt to attach the fixture to the faceplate.
 
Interesting. Yes, that is the rotary I have, (stalker). lol

That's a neat idea. What material would you say? 6061 or 7075?
Or mild steel? Alloy steel?
 
One-piece hardened steel ball receiver faceplate. 1.25" thick x 7.0" OD.

4" x 4" tombstone with a single ball coupler and two press fit dowels. Thru hole to actuate the coupler.
 
I would bolt it to a flange with 4 ea 3/8" or 10mm bolts and locate with 2 ea 3/8" pins about .5" into each side, which is how I hold the 6061 tailstock body to the mounting plate it sits on in the photo. I have the spindle in the yellow on one tool with no vibration issues so I have no reservations with this setup. The tailstock body is 2"x4" and the center is around 7.35" above the table so the dimensions are similar to what you are proposing. Personally, as you can see in the photo I like to support the end of long tombstones. This setup is for swapping the fixtures between ops so I can load parts while the machine is running. Now that I have two tables I don't need to do that :).


Rotary.jpg
 
That is very similar to what I'm trying to do David. Did you just use the 6061 aluminum on that fixture? I rarely use 7075 but do respect it's strength when needed.
I have a Fadal tail stock that I intend to shim to height and use to stabilize the end.
 
The light blue is the material blank standing up on edge.
Purple is the face plate and tombstone riser.
Yellow is a locating bar and dark blue pitbulls.

tombstone2.JPG
 
All my 4th axis tombstones are attached by locating in the center bore of the faceplate or the spindle nose. A dowel pin catches one of the faceplate slots or into a bolt hole in the spindle nose. I use a 3/4" stud with a stepped washer for the outboard end and a nut to hold the whole shebang together.
 
That is very similar to what I'm trying to do David. Did you just use the 6061 aluminum on that fixture? I rarely use 7075 but do respect it's strength when needed.
I have a Fadal tail stock that I intend to shim to height and use to stabilize the end.
6061 on everything I can. I don't feel the need for anything stronger, just a little more temperature stable would be nice. ALL fixutres are 6061 since I would swap them out of the machine pallet style so the spindle was running while I swapped parts, so weight mattered.
I would be thinking hard about dovetailing the bars if you are doing a lot of work. It would certainly be more stable.

Garwood, how do you handle the fixture turning in your outboard end?
 
I started this whole idea of making an adapter to hole two raptor clamps like this.
rotary 1.JPG

Then I thought, hell, I can hold 4 if I make a mini tombstone. The parts don't get machined on the top edge at all.

I was hoping the pitbulls on the edge would hold well enough and save me the $550 each for those raptors, plus eliminate the dovetail step.
 
I don't do anything little on my 4th axis (330mm Yuasa). 50 taper getting after it pretty good. I've not had good luck making tombstones or trunnions multi-piece. Turning and milling from solid seems to work the best for me. The worst has been welded steel. Damn things really sing, even real heavy plate with stiffeners wasn't that good.
 
If I had the ability to turn that from solid I might try it. But the chuck on my lathe is 5" and that's all I have. Last time I had a 50 taper it was NTSB on an old Hercules Horizontal mill.
That part above is made from 3/4 x 2 x 7.5" aluminum so not so heavy duty. lol
 








 
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