[How do I?] Lathe/mill A Converging, Internal Angle Deep Inside Part

You guys are reminding me of some designs I had worked out when I was in Jr. High. I studied R. Goddard's designs and had a pile of drawings for various liquid fueled rockets. At the time (I was about 12) I didn't have much in a way to actually build them, but I enjoyed the engineering even back then.


John, you're close. There is a way to make an offset bar that is even oval (sort of) with a higher vertical axis than horizontal. That way you get the clearance advantage of a smaller bar without losing all of the rigidity. If I could get to the shop, I'd post a pic of one I made (requires a fixture to make), but I'm housebound for a few weeks with a broken femur. Doc confined me to a walker, and I can't get to the shop.

Tony Wells said:

here is a way to make an offset bar that is even oval (sort of) with a higher vertical axis than horizontal.

Click to expand...

I'd like to see a drawing of that.

Tony Wells said:

but I'm housebound for a few weeks with a broken femur. Doc confined me to a walker, and I can't get to the shop.

Click to expand...

Hope you get better soon!

So, I also heard back from Robert (the second set of links I posted) and confirmed he had the tool post square with the lathe centerline, but the crossfeed at an angle. Also confirmed he had ~4in overhang on the boring bar and lots of chatter.

His solution (not sure if I'll follow this) was to use multiple large rubber bands to pull the boring head (not attached to head, but still a lever-like action) against any downforce the overhang and spinning material create. I feel like there is a better solution, even just going slower, but it's nice to confirm this method works.....