ball radius turner needed

[joebiplane]

I am looking for a radius ball turning tool to use on my emco/maier compact 8 lathe to complete a project i am working on
I am a beginner at machining so un-able to take on building one from scratch so i am looking for perhaps one that i can modify to use on my lathe or perhaps a very simple desigh ( as opposed to Steve B's beautiful design but difficult for a beginner to construct me thinks )

 

[Starlight Tools]

Joe

Keep your eyes open on Fleabay for a Holdridge Radii Cutter. I just got the 8D and it is massive, you could probably go smaller say a 3 or a 4.

There is also a fairly simple design that mounts in the boring bar holder for a QCTP. Will see if I can dig it up.

Here it is

http://hobby-machinist.com/index.php?topic=54.0 Reply #6

Walter

 

[pdentrem]

Are you turning the balls from steel or something softer?

If in brass you can actually make balls for handles for example by using the same technique as wood turning. Use the top of the tool post or some other firmly attached tool rest and use a long sturdy file that you have shaped to a point and leave the top flat and shape the ball. I have done it years ago with some trepidation but the old tool maker said to go for it and it worked. In brass or plastic the cuts are not deep and the chips fly off like a spray.

Now if it is brass or plastic it works, but for steel or gummy stuff like copper, first rough turn and then file to shape while spinning in the lathe is the best way.

 

[joebiplane]

thanks guys,
i'll try both your suggestions. Iwill be turniog 6061 aluminium I will eventually build a turner but i was hoping to be able to buy one at a reasonable price. i will need to turn a 2" to 2 1/4" ball ( actually a half ball) it is the front crancase cover of a dummy radial engine for a static display model
joe

 

[Tony Wells]

It's a crazy sounding idea, but there is a way to more or less make a sort of "tracer" with very little effort. Try this on for size:

Print or draw a full scale pattern on some typing paper or equivalent. Needs to be only half of profile, from centerline out. For a ball, just use a compass if drawing it. Use clear tape to mount it on some heavy poster board or cardboard.

Tape or affix the pattern somwhere close to the carriage, like on top of the tailstock.

With a pointy object clamped in the stem, arrange it to hover just over the paper pattern. Follow the pattern mounted on the tailstock.

This will mean manually moving in both axes while watching the "tracer". If you have a small, full radius tool, you can follow many shapes. If you want some close duplication, use a marker, or pointer the same profile as the cutting tool. You can just plunge in until you are almost on the line, then dial out and move over....repeat. Or cut into the part in Z, then dial in and repeat. Pretty soon you can do both at the same time, watching the pattern.

I'm sure this is confusing, but it's a workable method for cosmetic work. After cutting, a little file work and paper....done.

 

[billinecin]

There's a little program called Ballcut.exe that lets you plug in size of ball and desired depth of cut. It generates the needed steps, and you can print them out. Would be a whole lot of steps on size ball you're making, but wouldn't require any extra tooling except a file and emery paper. It is one of Marv Klotz's many utility programs.

I've used it on a small ball in steel. Was a lot of cuts. Didn't take much work with file and paper to create a pretty smooth ball. Biggest problem was keeping track of which step was next.

Bill

 

[Starlight Tools]

in Guy Lautard's Machinist Bedside Reader the procedure for Manual Numeric Control is layed out for doing exactly that. Etch-A-Sketch on the lathe to produce balls and other intricate shapes.

Walter

 

[MisterT]

I've got a holdridge radii cutter model 12-d. It is absolutely like new and was only used ones. All the cutters but one is still in wax. No corrosion and in orginal box. I'll make someone a smoking deal. My email is tayloraircraftservice at yahoo.

 

[TOOLMASTER]

Made a bunch just by turning the compound..

 

[jamesmelville]

Testing my posting skills and adding .02 @ the same time. Your cutting aluminum and want to TURN the radius cheaply? If it were me, I would find a 2" drill or bore the hole thru a scrap piece of steel about 3" sq. x 1/8" thick. Cut that in half. Grind a touch of clearance/relief. Clamp it in my toolholder and it will cut the radius cheaply and quickly.