1 inch cube,7/8 ball, 3/4 windows

[jimsehr]

I made this cube today. Many thanks to Lane for telling me how. And Lane it's all done on a 11 inch Logan, an old Bridgeport and hand ground tools.
Jim Sehr

[lazlo]

Nice job Jim!

[Bill Pace]

Can sure see Lanes influence, looks just like his..... and, THATS a compliment!

So, how long did it take to finish yours?

[japcas]

Nice looking work jimsehr. Do you have any setup pictures or machining pics? I'm sure I'm not the only one who would like to see them. Give us the run down on how you did it. Inquiring minds want to know. I've got some ideas on this project, would like to see if I'm on track.

[lazlo]

Knowing how much Lane hates to type, here are his instructions on how to build the "Ball in the Box" (lightly edited for readability).
I'm hoping to have time to try it this weekend

Well here is how I did mine. Square up a 1 inch block of aluminum in the mill. Using a stop on a mill vice get over the center of block and machine a .7500" diameter flat bottom hole. The depth must be held .0625" deep for machining in the lathe later. This hole diameter and depth is repeated on all faces.

Next grind a boring bar out of a Rex 95 (T-15) tool bit with a perfect 7/16" radius on the end face, and grind away excess material until the back of the bar is the center of the radius and the very front has a whisker edge that will reach around toward the front edge of ball. It helps to have 7/8" ball to use as a gauge while grinding the tool, and remember you have to reach in and around a 3/4" diameter hole without touching it.

Now set up a toolmaker's grinding vise in a face plate on the lathe, and put a side stop on the vise. Clamp the cube in the vise against the stop and indicate the 3/4" hole true by moving the vise around and clamp good and tight. Now you should be able to index each face of the cube and all should run true. Check before you start machining or the ball wont come out right.

Now set up the boring tool. That takes some finagling. Remember the back edge of tool must finish on center of the ball and the tool cutting edge must be on the center line of lathe. You will be plunge cutting a radial face. Slow speed and lots of cutting oil. You will need indicators set on the carriage, crossslide and compound: that is 3 indicators. Once the first face is done just repeat to all indicator readings on each index of cube. The front whisker on the tool touches first and does most of the cutting so be careful. Remember 5 more times to go. When the back of the tool just makes the first scratch on the bottom of the .093" deep flat bottom hole, that is where you start measuring from to know how deep to go.

When the ball is finished with all 6 faces cut it will be suspend by 4, 3-sided needle points which you cut off with wire cutters. Put the cube back in the mill and square out the 3/4" in holes to 3/4 square: use a 3/32" or smaller end mill to keep from touching the ball. When you're done, lightly file the 4 specks left on ball. Now you have a ball in a box.

[Bill in Ky]

Very nice work!

[RetiredFAE]

Very nice work indeed! I have read and understood most of Lanes instructions, but I am having trouble visualizing the lathe tool bit that has to be ground to make the ball. Any chance you could post a picture or two of the bit you used?
Thanks!

Steve

[jimsehr]

Lazlo, Bill, & retiredfae thanks for the compliments .
Bill Pace Hard to say how much time it took as I made a collet to hold 1 inch
square piece. Then found that part would pull out of collet because of the
cutting forces forming the radius. So I used the collet to mill the 3/4 square windows. Then I made a fixture to hold the cube. The fixture fits into a 1.125
5c collet. The 1 inch blocks are held to about .001 square so that depth of radius could be held very close. I made a total of 4 different tools before I was happy with the radius. I took a bar of 7/8 dia stock and after hand grinding hss tool as close as I could , I lapped the radius by using some grinding grit mixed with oil as a lapping compound. By turning the 7/8 dia bar in the lathe and lapping till I could see cutting edge was lapped true. Also gave tool some positive top rake.Then I set the radius on the end of the 7/8 bar and checked it before I cut the cubes. Also slit the 1 inch square collet on my saw.So I had to make a fixture to do that. Notice it has 4 slits. Broke first radius tool as part pulled out of collet.
Right in the middle of this project I found out my wife had lung cancer. And was rushed to hospital. She is doing well and the docs think they got it all. japcas, I'll post some more pics next post. I'll go out and take some now. Jim Sehr

[Your Old Dog]

Neato! But it makes my head hurt just thinking about the prospects of making one myself !! Maybe I'll make a few of them after I've mastered the fine art of cutting threads

[japcas]

Jimsehr, thanks for the explanation and the pics. I'd like to make one of these to go with the little 3/4 inch cube that I made. It has a smaller cube in it. One with a ball would be really cool to go with it, and I wouldn't mind the challenge. Also, I hope your wife gets well. Take care.

[jimsehr]

ball in cube

more pics. Sure slow on dial up.

[jimsehr]

ball in cube

Hope this makes the process clear. If not email me. I have more pics if anyone wants them.
Jim Sehr

[RetiredFAE]

Hi Jim. First off, I am very sorry to hear about your wife. Will keep both of you in our thoughts and prayers for a speedy, complete recovery. Second. Great pictures! They cleared up the design of the lathe tool bit for me completely. It looks like what I had it pictured in my minds eye, just a bit more robust. I had envisioned the "whisker" end being much more flimsy. And I like the collet and fixture idea too. Great idea and nicely executed design. Thanks again for the pictures.

[jimsehr]

cube

Lazlo
I think Lane made a mistake in his instructions when he said to bore all sides
.093 deep by .75 dia. I think he meant to say bore .0625 deep by .75 dia.
As this is the first step people might not check it till it is to late.

Also if you look at the my pic of 7/8 bar with the radius on the end and see the grey area on od behind the radius that is where I lapped the radius tool cutting edge. After tool is lapped you have to tap it around and check with a radius gage to get it right. Once it's right mark your dial.

Jim Sehr

[lazlo]

I think Lane made a mistake in his instructions when he said to bore all sides .093 deep by .75 dia. I think he meant to say bore .0625 deep by .75 dia.

Yep, a 1" cube - a 7/8" sphere = 1/8" / 2 = 0.0625" cube thickness on each face.
Thanks Jim -- I edited Lane's instructions on the first page.