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pntrbl
04-20-2007, 09:08 AM
I'll be needing to build an elaborate and versatile ball turning tool of the type I've been seeing here someday, but that's a mill and skills down the road from where I'm at now. Meanwhile, I'd like to at least rough-in a radius I can file smooth on the heads of some bolts I'm making.

Would it be OK to use my compound as the pivot?

My Logan has a circular dovetail under the compound that gets clamped by setscrews against pins that are angled to match the dovetail. I'll just pretend they're little gibs ......

Sounds like a recipe for chatter tho. lol. I dunno.

To hold a bit I've got some 1.5" wide by 1/2" thick bar stock I'll weld into a "L". One side bolted to the compound and the other to hold the bit at the right height.

Which begs the next set of questions. Have I read along here that you can use an old HSS drill bit for a cutting tool? If so, how? Do you grind one flute off? Lose both flutes and just use the shank? Anybody got a pic before I break the tip offa something and hit myself in the head? Not having the ability to drill a square hole for conventional bits a round bit is something I can mount up.

Thanx for any opinions and advice.

SP

sch
04-20-2007, 10:29 AM
Square HSS bits are not so expensive that recycling drillbits
is necessary. It is straightforward to use a carbide or diamond
scribe to trace out a radius on a HSS square bit and grind and
relieve until the curve is satisfactory. For 1/2" bit sizes it can
take awhile to grind away the metal but it works, and by pivoting
the bit around through only a small angle you can cut most of a
sphere.

SGW
04-20-2007, 11:32 AM
Sure, use the compound as the pivot. It won't be great, but it's a classic way of turning a radius when you don't have anything better.

As for toolbits...anything you can get to work.

BadDog
04-20-2007, 01:50 PM
Never tried using a drill bit as an OD turning tool, but good drills make great boring bars.

Some folks swing the compound, I think Evan posted that he does, no idea how well it will work with the Logan implementation.

Somebody (mklotz on here?) had a sphere interpolation program. It basically gave you coordinates to cut a series of ODs that closely approximates a sphere, you then file off the steps. May have been an Excel file? Search should turn it up.

mklotz
04-20-2007, 03:00 PM
Somebody (mklotz on here?) had a sphere interpolation program. It basically gave you coordinates to cut a series of ODs that closely approximates a sphere, you then file off the steps. May have been an Excel file? Search should turn it up.

Look for BALLCUT.ZIP on my page.

jimsehr
04-20-2007, 10:57 PM
Use a radius gage and grind the radius as close as you can . Then you can make a lapping mixture out of grinding grit and oil. Next turn the radius size you want then apply a little grit to turned radius dia. and with lathe turning at a slow speed you can lap radius to size. It takes a steady hand and you have to eyeball tool clearance. But I've done it many times. It goes pretty fast once you get the hang of it. Be sure to cover ways with a rag to protect them from grit. The pic shows a radius tool for I inch ball I lapped . I am holding it in a vice grip so I can take the pic.
jimsehr

http://i86.photobucket.com/albums/k106/jims_03/toollapped.jpg

cybor462
04-28-2007, 01:18 AM
I saw a real easy tool that mounts on the compound. It was on another's shop page. I downloaded the plans. Let me find them and I will post them. My son wants me to make him a new shifter knob. I will be making it soon.