Generalized solution to machining 2D complex curves by hand?

[dbb-the-bruce]

I have on more than one occasion wanted to machine a complex 2d curve profile. The most general case is a curve that has both convex and concave components. But either concave or convex non-circular curves also apply.

These are the kinds of things you would do with a pin router or following a template with a router if you were working with wood.

I have done convex curves with lots of straight cuts to approximate the curve. This works but is slow and time consuming, perhaps there is a better way?

For convex curves, I can imagine using a boring head or fly cutter and determining a number of circular cuts that would approximate the internal curve.

In both cases the result is something that will still need some hand work to smooth out or something that is approximate depending on how accurate you need to match a given curve and much fussing you are willing to do to get there.

One could also just make a long list of points to hit in order and do a painfully slow manual CNC job. I imagine that there are / were specialized machines that could do this prior to everything being CNC.

My question is: is there a general solution to this kind of task that's (relatively) efficient or some affordable or relatively easy to make shop fixture that can accomplish this?

 

[Winegrower]

My question is: is there a general solution to this kind of task that's (relatively) efficient or some affordable or relatively easy to make shop fixture that can accomplish this?

I think not.

If it’s critical, I blue and scribe a line, cut out as much as possible with whatever tool(s) work, like mill, bandsaw, drill, grinder, nibbler, etc. Then use the die filer to file as close as needed to the line. You can do extremely fine work like this.

I admire the work Clickspring does on his YouTube channel.

 

[markba633csi]

You could use a fly cutter and then some smoothing by hand for simple shapes, but it may not save you much work
For one-offs a bandsaw+filing would get you there. For thick or hard materials like steel there is always the option of drilling a series of
small holes along the outline then finishing by hand by grinding or filing. It's what they did in the olden days
-M

 

[ChazzC]

I have on more than one occasion wanted to machine a complex 2d curve profile. The most general case is a curve that has both convex and concave components. But either concave or convex non-circular curves also apply.

These are the kinds of things you would do with a pin router or following a template with a router if you were working with wood.

Based on how well carbide router bits work for corner rounding on Aluminum, a template & carbide roller bit might work if you’re not working with steel.

 

[homebrewed]

If you have a rotary table you could approximate the curve(s) you want, then finish them with hand work. Got a filing machine? Bob's yer uncle.

Maybe you can flip the work over so the curves are variations on the Z axis. For that you could use a combination of ball end cutters/whatever(s) to again approximate the curves you want.

Tilting the column and advancing the work on the X axis will generate an elliptical shape with a square end mill. I've tilted my RT and used it to machine a section of an oblate spheroid that way. Not for any particular application, just to prove to myself that it works.

I have used my 4x6 bandsaw, set up as a vertical bandsaw, to hand-cut relatively gentle curves. Another option: I recently acquired an oscillating spindle sander that probably has some metalwork in its future.

Router bits can be had in a variety of shapes. I've used them to cut Vees in aluminum, and to round the corners on my QCTP's. So far I haven't found a need to use one of my ogee router bits

Choices of approaches are heavily dependent on the particular job -- how thick the material is, type of material, etc.

 

[C-Bag]

My problem is being able to picture the exact problem. Generally speaking there is a millions ways to skin a cat and ways to adapt machines to do it. My goto rough smoothers for big chunks into compounds is my angle grinder and my big electric die grinder I’ve made stationary. The stationary die grinder has a small table so can do very fine work way faster than a die filer along with being able to fit anything from carbide router bit to abrasive and carbide burrs of different sizes along with diamond cutters and burrs. Generally I don’t do big stuff and try to not do compounds unless its sheetmetal and then I’m loaded for bear.

 

[rodm1]

A carbide burr in a mill may workout ok for finish work make shift die filler.

 

[Jimsehr]

This was done free hand on my Logan.

 

[dbb-the-bruce]

Thanks for all of the useful comments so far. Let me try to be a little clearer on the question. Most of you you got the idea.

You have a part that you want to make out of something substantial like 1" thick steel. You want / need to only mill it in X and Y. Z is simply 1". In other words, it's a 2D shape.

The shape is not square or circular for either engineering or esthetic reasons. Think of something like a crank arm or a cam disk. The point is you need to machine a shape that is not a straight line and not part of a circle.

The second point is that you want it accurate enough that need to machine away most of the material and only finish up with abrasive or files.

BTW - I've spent a good chunk of this morning looking at/for die filers. Will definitely be adding one to my collection of tools. However, in the context of this question, something like a die filer would be used after the machining only to clean up where necessary. IE. cleanup the cusps that would be left where approximate profile cuts where made.

I have an oscillating spindle sander that I've used for this but a die filer would be much easier to control and more accurate.

So, again the question is about way to mill a profile using multiple approximate cuts (straight lines or circular arcs) or any other technique but not free hand.

A rotary table would be a method to do multiple arc cuts. The tilted head is a great idea (my mill doesn't tilt though)

I'm asking here to get a conversation going and maybe hear some ideas/ways of approaching this that I haven't heard of or considered.


Thanks.

 

[francist]

If you have a shaper you have some nice options for deep pieces -- see here...

Freehand curves

I've been fooling around on another little project recently which in itself is of little consequence. But part of my design has a couple pieces that have some curves on them. I considered the usual ways I could made them, then figured I'd try free-handing them on the shaper. It can be a bit...

www.hobby-machinist.com

-frank