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4

Yet Another Ball Turner

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f350ca

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#1
Been at this off and on for a while, have it to the point that there's something worth posting.
Liked the look of the ball turners that use a boring head for the adjusting mechanism. In true not for profit and needed the challenge I decided to build the mechanism from scratch, or in this case cast iron as I was all out of scratch.
Had a piece of scrap cast iron that looked like there might be a tool hiding in it.
Was given a beautiful little boring head from a jig borer. I thought the locking mechanism for the dovetails was elegant so blatantly stole the design.

KIMG0448.jpg

KIMG0450.jpg



Cheated and cut the dovetails on the mill rather than the shaper, mostly because I need a better vice for it. Interesting note. I cut the male section first using two 3/8 dowels to measure the size as I always do. That went fine. Used .005 shim stock to hold the clamping section open while I cut the female part. The measurement between the dowels that I took off the CAD drawing wasn't even close. Still can't figure where the error is. If I take the distance across the dowels from the male dove tail and subtract the diameter of the two dowels that should be the inside measure, but that doesn't seam to work either. So in true hacker fashion I just snuck up on the fit and it worked.

Greg
 

f350ca

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#3
Stole some time today and made the tool holder. It gives the tool a 15 deg clearance angle, not sure its necessary on a curved surface, we'll see.
Broke the edges with a rounding over bit. If you set the cutter up along the fixed jaw of the vice, you can rotate the part to that jaw to do the 4 edges.
KIMG0451.jpg

KIMG0454.jpg

Greg
 

f350ca

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#4
Found some time to do a little more today,
Made the adjusting screw. Wanted to use an allen wrench to adjust it but haven't tried building a rotary broach yet so cheated. Bored the end of the screw and silver soldered the head of a cap screw in.
Haven't decided if I'll add divisions or not, the thread is 20 tpi so 0.05 change in radius per turn.
KIMG0455.jpg

Had a tool holder blank that was large enough to bore for the rotating shaft. Made from mystery metal that loved to work harden. Was a bear to thread for the height adjusting screw.

KIMG0456.jpg

Not sure if I'll get time tomorrow or not, have to go and trouble shoot the shut down solenoid on a diesel running a rotary compressor.

Thanks for watching

Greg
 

f350ca

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#5
Pretty much finished it up today. Could sand the cast iron a bit to blend the milling marks, and may cold blue some of the steel parts. Will cold blueing work on cast iron?

Assembled.
KIMG0463.jpg

Of coarse the first ball to turn was for the handle. Didn't have a long enough piece of aluminum so it came out a little short on the bottom and a divot from a previous hole. Thats the finish I got with the cutter, an odd sized, about 7/16 round HSS piece ground back on about a 15 degree angle.

Tried a 1 1/2 steel one, (mystery metal, a bent pin from a hydraulic cylinder I think). Was getting chatter with it. Expect the problem is the 3/8 the bolt I cut for a mandrel. A bit of emery paper took care of that.

KIMG0462.jpg

Thanks for watching.

Greg
 

Silverbullet

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#6
Looks good , did you incorporate any stops on the rotation or cutting distance?' I like beefy build . That should help on finish and chatter.
 

f350ca

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#7
Looks good , did you incorporate any stops on the rotation or cutting distance?' I like beefy build . That should help on finish and chatter.
Had thought about making rotation stops but decided they weren't worth the time. As it turns out, the cylindrical cutter seams to just skate on the mounting stud and going over centre on the outboard end does nothing. The mass does seam to dampen vibrations. Now need to come up with a stiff mandrel, maybe carbide lol

Greg
 
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