Mill use for track support in rolling ball sculpture (RBS)

[markstephens]

Hi,

OK, true confessions, I'm not building an engine... yet! I do think a Sterling is in the near future, but I need to begin somewhere and so I have a beginners question whose answer will hopefully lead to a mill purchase.

I'm creating a Rolling Ball Sculpture using wood, brass and glass marbles as the media. I'm pretty good at woodworking, but very new to machining.

My router table makes for a poor mill with the use of jigs and, as you can image, it's not very accurate or easy. The photo shows what I'm attempting. On the left is the raw stock, a brass pipe 1 5/8" diameter with 1/4" walls (also shown is a 1/8" rod used as track). I use a jig with a Dremel to cut off a 1/4" thick circle. A jig on the router table mills the 1/8" holes in the ring (next photo clockwise). The ring is cut into 4ths, a small flat made on the each of these track supports and a hole drilled into, but not thru, the flat. Add some solder and you get to the picture on the bottom right.: a marble rolling on a track in dire need of a clean up!

It seems to me a small mill with a rotary table can drill the 1/8" holes. Can I drill them down the length of a pipe and then cut the rings? That would save a lot to time. In either case, is the drill bit going to flex as it is only drilling a half hole?

Is there another way to add a grove down the length of pipe to avoid any flexing of the bit?

Also, can a mill with a saw bit cut the 1/4" rings from the pipe?

So... anyone want to convince me to buy a mill!?

thanks,

mark

 

[tornitore45]

Drill bits do not drill 1/2 holes, is not like a Foster bit in wood.
End mill do what you need but a 1/8" End Mill working down a 1/2 hole is limited to may be 3/4" depth so you are not going to make several pieces before restarting the process of milling the half holes deeper.
You could fill the tube with a slug of the same metal and then drill on the dividing line between them. The plug will be expensive waste but you can rotate the plug every time just enough to place solid metal opposite to the hole to be drilled, in the end the plug will look like a bicycle sprocket with many 1/2 round teeth. Then there is the problem of parting off the rings from the tube.
Sawing them gives you a rough finish, best done on a lathe which you need anyway.

There are other way to skin this cat: Start from straight strips. Sandwich many into the vise. Mill 2 semicircular slot with a round nose end mill across all the strips. Make a bending die and bend the strips into arcs, cold or hot.

 

[MachineTom]

There are so many ways to do things, here are some thoughts. Take that tube and cut pieces 2-4" long, then slit them in half lengthwise, then quarters. Now you have 4 pieces 2-4" long, using a ball end mill 1/4" mill the slots the length of the piece, then cut into final size. Trying to mill half holes in the end of the material is a slow process.
The idea of drilling then bending, will close up the holes, and if not used with a full form fixture, you will find just crimps where the holes are, because all the bending was done at the weakest point, the holes.

 

[markstephens]

How about using a slitter to cut multiple 1/4" thick rings. Mount a ring on the rotary table. Use an an 1/8" mill end to cut the "holes" moving along the X or Y axis? If this works, anything more accurate than an end mill?

The holes on each arc are 3/4" apart on-center (my track gauge). While the balls don't give a hoot if this is off, I always strive for accuracy. It's good practice and you can always be less accurate.

mark

 

[markstephens]

ups can't delete this inadvertent posting!