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View Full Version : Cat-Head Steadies - getting centered?



BadDog
01-19-2009, 02:27 AM
All this talk of steadies brings up a project that's been on my back burner for some time. I got a Devlieg Boring mill head (and other random bits) in a odd-trade situation (swap meet, nobody wanted to take home what they brought, so there was some weird swaps, including this one). Mainly I parted it out for some high quality shafting, some cast iron donor bits, and so on. But the main head has a MASSIVE 50 taper spindle with HUGE bearings at around 6" ID. I thought it would make a great cat head steady, but was too big for my 11" lathe. But now I have a 17x60!

So, 2 problems. One is that the casting is too long. No big deal there, I figure I'll cut it off and use one end. That depends on the bearings and how they manage pre-load. Worst case I'll cut off both ends and mate them back to back. That would be about 3-4" wide max. Heck, it would almost be like a second spindle. <shrug> That I'll work out, or it'll prove insurmountable, we'll see.

But the real question is how get the bearing(s) PERFECTLY coaxial with lathe spindle. On a normal steady, anything +/- 1/4 will likely do (ok, exaggerations, but the point is valid) due to the 3 finger adjust to locate center. But that don't work on a bearing rigid mounted in the casting. I basically need to cut the casting so that when done, it sets on the flat ways and has a good locating fit on the tail stock v-way. Not much chance for "bringing it in". You almost have to hit it right the first shot. So I've got a few ideas, yet I'm sure there are better. Here's what occurred to me.

1) Main casting in too parts. Slice off the bottom and fit to flats so main casting is vertical, and locate v-center "darn close" to correct position for axis horizontal location based on best effort measurements. Should be able to get within 0.010 or so I think. Mill key way in base for horizontal location of top, leaving top casting well tall. Locate shallow key way on top and position with trimmed down key stock. Measure error with DI in lathe spindle to quantify error. Mill off bottom of top casting and make second key way in correct location. Verify and correct again if needed. Once located, this becomes reference. Now identify vertical axis error in the same way. Carefully drop height in at least 2 steps to make sure there is no "drift" due to earlier mistakes (i.e. orientation is not "perfectly" perpendicular to the bed). Bring in vertical within a thou, then surface grind to finish. If it's a bit low, shim it up. If it drifts horizontally, grind the tongue and shim. Once dead on, bolt and taper pin.

2) Fore go the fiddly crap and just cut it "close" Use an offset key to correct horizontally, use shims or further griding to locate vertical, bolt and pin. Or, locate horizontal like a tail stock with screws. Still need shim/grind for vertical.

Then there is the co-axial issues beyond getting the center point on axis. May require tilting fore/aft, particularly relevant if 2 bearing (thick) design. Either way, seems like this is going to be a difficult setup/location given the desired start/end points.

Side Note: I also thought it might be neat to put a planetary drive from my D1-6 to the thick 2 bearing (wide) version of the "steady". That could then form the basis of a "speeder" OR a large bore spindle. Devlieg wasn't too shabby in that department, and all indications are that the spindle IS still good. The only hassle is the hardened 50 taper spindle will be a BEAR to bore through even on my big lathe (PCD maybe?). Still, neat idea. Or maybe leave the 50 taper and use it as a 50 taper horizontal boring mill, though then the table becomes an issue since the head is fixed.

Just trying to figure out what I can do with this. Too bad Evan isn't closer, he could use that head for the lathe project...

John Stevenson
01-19-2009, 04:53 AM
On mine the vertical mounting that carries the bearing is bolted to the horizontal bed mounting and the holes are slightly over size.
I held the bearing inner by the 3 jaw chuck jaws and then tightened the bolts up.

I can do pics tonight but not before.

j king
01-19-2009, 07:33 AM
baddog.

I ruffed machined everything as close as possible.I drilled and tapped for 2 3/4 bolts to go thru base into the upper bearing part of steady.As John did I opened up the clearance holes a bit.Bolted it together and set it up at the chuck.Set an indicator in chuck and swept the bearing bore in and tap it around till it is as close as you can get it to center.Then I marked the readings that the indicator read on the face of the part.If it showed .010 high I milled the base to suit.On the side ways alignment I loosened the bolts and bumped it then tighened it.Removed it and installed a dowel on the base to body split line to maintain position.That can be seen in the rear view.Clear as mud ..

Andrew_D
01-19-2009, 09:42 AM
I've been planning to do a bearing steady rest/cathead as well, but haven't found a big-ass bearing yet.
Anyway, I was planning to do a two part base. One piece to match the ways, the second to hold the bearing, then use shims between them if (when) necessary. Sort of like a tailstock base...

Andrew