Need the scoop on tilting tables

[Nami]

Hey again guys. Almost ready to fabricate this fixture for a re-occuring part. A while back I had planned to hold a similar fixture in a vise or two, but in a thread I started back then, Mud suggested an indexer. Here's the original thread...

http://www.practicalmachinist.com/v...-material-186570.html?t=186570&highlight=nami

I'd like to set it up on a tilting table so that after all the horizontal operations I can just tilt it and do the angled bore. I've looked around, but can only find import quality tilting tables like this one...

http://metalworking.mscdirect.com/C...424Ppagenumber=1251Pjsessionid=Pmode=Pepcode=

Question is, anybody have any experience with these, or know where to find a decent/better one new or used? The one pictured is 10" x 15".

Not having much luck and am hesitant to buy this one, as someone on ebay was selling one that in his words had "only cosmetic cracks through the casting", making me suspect; LOL.

Any advice would be appreciated on tilting tables and the fixture in general. Here is my latest plan. Please slam away if it keeps me from making an expensive boat anchor.

Thanks for looking.

Burt

 

[Racer Al]

Personally, I would not depend on your user to set the angle on a tilting table repeatably.

My suggestion would be to have the part holding plate interchange over to a purpose-built, tilted base, featuring tapered pins to repeatedly locate the parts plate, which is solidly bolted to the tilted base. The tilted base should not need to be unbolted from the table during the run of parts, ensuring repeatability.

You'd have to be double darn sure there are no chips on the pins, however.

 

[Clive603]

Hmm. Those half circle base tilting tables can be a right pain to get aligned just so on the axis. Prolly hafta machine reference faces.
Why not use a simple hinged type machined to accept a spacer to set the correct angle. A couple of nearly half round grooves in the opposed faces with a nice thick spacer having matching rounded ends to slide in and set the angle should work just fine. Might need to get creative with the clamping so the job isn't fiddly. Big advantage is that all the setting surfaces are easy to wipe chips off. Make sense to add dowels / keys to the flat base so it aligned when mounted up.
I suppose you can still buy simple hinged tilting tables. Only one I've had through my hands was (lots) older than I am.

Clive

 

[gbent]

If you can't afford an A axis for your mill, make your own. Use a pair of angle plates facing each other, with bored and bushed holes for the pivot point.

For your fixture, make a cradle. For example, a piece of 1 1/2 x 6 x 10 long, and two pieces of 1 1/2 thick, 8 diameter. Have the pieces flame cut from hot rolled stock and ground both sides. Put center plugs in the rounds to fit your angle plates, and recess, bolt, and dowel the round ends to the long center piece some amount below centerline. You can make any of several styles of angular and flat locating pins or stops. The fixture can be used in both the flat as well as any angle position, and will repeat for both location and angularity far better than the Chinese rotary fixture you referenced.

The cradle method puts your work much closer to the center of rotation, so angularity errors (both absolute and repeatability) won't affect positional accuracy nearly as much.