Lathe chuck mount for rotab - design

[kvom]

I would like to be able to move a workpiece between the lathe and rotab while keeping it in the same chuck. To that end I acquired a cutoff D1-3 spindle nose from a Monarch 10EE that was being parted out:

I also have found a set of cams and screws, so I can contemplate beginning the project. The rotab is a 8" PhaseII with a MT3 center hole. My thought is to make a mounting plate that will hold the spindle nose and locate on the center hole.

The cutoff portion of the spindle is 2-3/8" in diameter, and the ground bearing surface is in good condition.

My plan is as follows. I am posting this here to gather opinions on how it might be done better.

First, I will cut off the rest of the shaft leaving approximately 1" of spindle bearing surface. The mounting plate needs to be thicker than the length of the shaft. This plate would be ~4-5" in diameter and made of steel. I would turn it as flat as possible on my lathe and then bore a through hole to be use for locating on the rotab (call this diameter D1). Then I would widen this bore to 2-3/8" and deep enough to accommodate the spindle in a press or sliding fit. Next, I would surface grind the opposite side (that sits on the rotab) to ensure that it is parallel to the bored side.

For the table locator, I am thinking of starting with a MT3 carbon steel dead center. With the rotab center on the mill and the dead center in the hole. I would mill the protruding part to a cylinder of diameter D1 to match the spindle moun ting plate. I would actually do this operation first and bore the plate for a sliding fit.

If this all comes together, then mounting to the rotab would be straightforward: place the locating rod in the center hole and slide the plate/spindle over it, then clamp the plate to the table. Centering the rotab to the spindle could be done either using the rotab center hole or the spindle nose itself.

I would hope to get accuracy of better than .001" this way.

Thoughts?

 

[deere_x475guy]

Good luck Kvom, looks like you have it all planed out. Not sure that I can add anything that will help you out but feel free to contact me if you need to.

I use mine all the time. The rotary table now has a permanant spot on the mill and the adapter is always on it. I can use all my chucks from my lathe and....the 12" faceplate is a real plus. It has opened up a lot of options for me I didn't have before and now I don't have to buy separate chucks just for the rotary table. That's a big savings alone.

Just as an FYI I should have both the D1-4 and D1-3 completed assemblies for sale in the next 30 - 45 days. I am currently waiting on heat treat and hard anodizing quotes from local companies. After that I will probably have them available in larger sizes via special order.

They will be similar to what I have posted in my original build posted here:
http://www.homemodelenginemachinist.com/index.php?topic=5495.0

 

[CMS]

Sounds very intresting there kvom. I also like the solution that deereguy has too. I have a 6" rotary table and my lathe chucks are d1-4, would be nice to have this option of taking lathe chuck to the mill. Will stay tuned.

 

[kvom]

I received the cams for the spindle today and mounted them. Here's the collet chuck mounted on the spindle:

I did some eyeball measurement, and once finsihed will be even taller than the 3-jaw w/ soft jaws that is currently on the rotab. So this is not something to consider unless you have a fullsize knee mill. The current setup is about 11" tall, so when you add in the length of a tool (esp. a drill chuck and drill) room can run out quit fast.

OTOH, for horizontal use there is no issue.

 

[kvom]

Thanks to a friend at school, I now have some steel for a mounting plate. It's a drop of 4045 heat-treated, 5" in diameter and 3" thick. It even has a 1/2" through hole as a start point for boring.

I'll need to use carbide to mill and turn this, but according to the friend it mills "nicely".

Since the spindle shaft cuts with a file it's not hardened, so I will be able to trim to whatever length it turns out I need.

 

[kvom]

Unfortunately the base had an off-center 1/2" threaded hole. I needed to drill/bore a 2.4" hole to accept the spindle. Using the lathe at school and the largest drill bit available, I was able to get a 1.75" hole in the center, but that left half of the threaded hole in the bore.

I found a good buy of a 6" indexable boring bar at Mesa Tool, so when it arrived I made a holder from some 1.5" aluminum rod and started to bore on the lathe. Carbide doesn't like interrupted cuts, so I chipped 2 of the three edges on the insert before the job was done:

I was aiming for a press fit, but overshot .001" and had to settle for a good sliding fit instead. Before removing the piece from the chuck, I faced it again to ensure that the spindle will sit perpendicular to the top. Next, I'll take it to school and surface grind the bottom so it's parallel to the top. In principle, any work that's transfered between lathe and mill will have an accurate Z-axis.