Freehand turning

[Johnwa]

Here’s an interesting take on a freehand turning device.
https://eccentricengineering.com.au/index.php?option=com_content&view=article&id=47&Itemid=56

 

[John Conroy]

Very cool, thanks for posting the link.

 

[Tom O]

thats interesting

 

[PeterT]

I saw that on the model engineering forum. I can think of a few applications including my radial project. I had to make 5 intake nozzles with kind of a venturi bell mouth shape. Another example is maybe my nose case which has a elliptical-ish section that doesn't lend itself to a Radii tool. I was thinking of making a 2D template, line it up under the blank & it acts as a shape stop for the cutter base. Just taking light progressive cuts. Hopefully I'll only be making one nose cases so I ended up generating a table of X-Y intercept coordinates. After roughing the 'steps' it gets filed & smoothed. But its a longer process. A gadget like that might be better for these 'analog' cnc applications, not just freehand ornamental work. Just watch the fingers LOL.

 

[Bofobo]

Ive watched Chris on the Youtube channel Clickspring do actual freehand turning at 3:30 in this video is an example

 

[PeterT]

Ya the Clickspring freehand method is essentially how I did my venturi's by eye, although I have yet to make a proper steady bar or whatever you call it. But if the curvy shape has to conform to something semi-accurately, then 100% freehand gets a bit iffy. You would have to hold up a template or something I guess to compare progress or something like that.

The Eccentric method is also an ornamental/freehand, but it has the capability of being something more precise & repeatable with just a 2D template, kind of like a 1:1 pantograph follower principle. But I have to figure how to make a good base plate datum, that's an integral feature.

 

[Bofobo]

Looks like a better option than a ball turner on the compound for sure.

 

[PeterT]

ya the ball turner takes a bit of time to set up properly, both in terms of tool radius & positioned to the work. I'm talking for close tolerance dimensions. But there also can be some substantial cutting forces in the operation especially with steel & that's why the frame is pretty heavy duty, the axle fits are quite snug & a big long lever handle to traverse the tool with control. Even though its typically shallow cuts, its pretty much the same cutting forces involved as our carriage & cross slide which has a lot of stability & rigidity. Simple round-overs & chamfers with hand files & de-burring tools I do all the time, but I'd be a bit careful with my fingers close to the action end of these freehand profiling tools. All it would take is an inadvertent dig-in & tools go flying.

 

[Bofobo]

It would be not much different than a wood lathe i suspect, A smaller tool than a 12"x1/2"x1" steel cutting tool with a 12" handle and i do not suggest trying to round a square with it in the same way but I would use any of the methods myself. Though i would rather build this contraption than a ball turner, i have aspirations to make a chess set and consistency is desirable. although i seen a video recently, i cannot remember who's, but they used a dial indicator on the compound to create consistant repeatable representations of a radius mounted (i believe on the bed) in a manner similar to a duplicator attachment for a wood lathe. My eyes are crossing looking for it to share unfortunately

 

[NGrimberg]

Thanks for sharing an interesting link.