????Milling an oval????

[dockrat]

I would like to mill a 5"x7" oval in some 1/2" Al plate. Is it possible to do this without CNC???? If so, how would I approach it???

[Fasttrack]

How accurate does it need to be? You could construct a mechanical device to move in an oval but thats alot of work and it would have to be made sturdy.

If it doesn't need to be all that accurate, aside from torching it out, you could scribe the oval on the plate and then rig up a little guide to cut the oval. I can't seem to find it now, but someone posted a thread on how the milled an elbow in a piece of tubing by hand. Basically, the poster had rigged up a bit of bailing wire bent to point at the center of the end mill - or it could be edge in your case depending upon how you sribe your line - and then kept the pointer on the line while carefully feeding the handwheels. You could work out an approximation and do it in a series of steps as well.

All of these methods would be very time consuming, though. Curious to see what else pops up.


Edit - you could quickly make an oval cuting device for a torch or plasma cutter. That would be the quickest, albeit not the prettiest.

[mark61]

Making oval

Cut your 5" hole and then move table left or right 2" while still cutting and viola! 5x7 oval!


mark61

[Alguy]

The Machinest Workshop April/may 2002 had an article about doing elliptical items. It is bit involved article is about 11 pages. This was done on a sherline mill. The author made a sliding fixture involving a cam for use on a rotary table.. this is bit over my head as did not understand how it worked. The author Matthew j. Russel wanted to make decorative oval boxes from wood

[Dragons_fire]

if you look at drafting books, its pretty easy to make an ellipse by doing four part circles. the top and bottom would be the same size, and the sides would be the same size.. ill see if i can find it for you. if your trying to do an ordinary oval with the straight sides, mill 2 5" holes on 4" centers and then mill out the rest in between.

[dockrat]

Cut your 5" hole and then move table left or right 2" while still cutting and viola! 5x7 oval!


mark61

Mark...that isnt going to work....you would just have 2-5" overlapping circles.

I think it could be done with a series of diminishing radii from center to left and right but I would need a CAD program to find those radii and to locate the centers. Something like this I think maybe.



yes???? no????? maybe?????

[Mcgyver]

wasn't there a thread here about chucks that produced elliptical turnings? (intentionally ) or maybe it was a article in the mags.

anyway there is such a thing as chuck that somehow turns the work elliptically, you could bolt the stock to some sort of mandrel....now if someone remembers where the content was....

[aboard_epsilon]

if you cut a bar ...at say 45 degrees and then screw the alu to it then mount it in a lathe ...

and go easy ...you will get an oval .........by experimenting with different degree cuts ...you may end up with what you want...only the sides wont be square to the face .

all the best.markj

[dockrat]

I think I need to clarify what i am attempting. I want a 5x7 oval hole in a piece of AL about 10"x8". Like a picture frame.

[jacampb2]

I guess the simplest method that comes to my mind is to lay it out and chain drill it. Then hand file to the finish you desire. If it is a one off deal, this is going to probably be faster than any other manual method.

Later,
Jason

[Dragons_fire]

heres one link that says how to approximate an ellipse, http://demonstrations.wolfram.com/Dr...rclesAndLines/



and if you scroll down to Stevens method for drawing ellipses, you will get an approximation, but it would be easy to machine with a rotary table: http://www.sevenhills-h.schools.nsw....etric_draw.htm

[lazlo]

wasn't there a thread here about chucks that produced elliptical turnings?

I think you're thinking of the Machinist Workshop article that AlGuy mentioned: it was essentially on on child's sprirograph attachment bolted onto on on rotary table - very cool, but on on complicated build.

Ernie's approach seems really cool - looks like it should work, but you'd need on on spreadsheet to calculate the offset for the circles' centers.

[Evan]

An oval is not an ellipse. More to the point an ellipse is not an oval. The word oval is derived from ovum, meaning egg. It has no precise mathematical meaning as it means only "egg shaped".

The simplest way to draw an elliptical shape is to put two nails in a board (or equivalent) and place a loop of string around the nails and a pencil. Draw all the way around while keeping the string taut.

[Fasttrack]

An oval is not an ellipse. More to the point an ellipse is not an oval. The word oval is derived from ovum, meaning egg. It has no precise mathematical meaning as it means only "egg shaped".

The simplest way to draw an elliptical shape is to put two nails in a board (or equivalent) and place a loop of string around the nails and a pencil. Draw all the way around while keeping the string taut.

Yep - thats why i figured using a torch would be the easiest. With two holes and a bit of scrap metal and a few bolts you have yourself an elipse cutter. A plasma cutter will cut aluminum if you have one. Once you get it cut you can file it smooth.

[dp]

There was one hell of a nice series of posts recently that resulted in a miniature rifle. I don't know that any parts were round, but the fellow roughed them staircase fashion. That makes for a lot of filing for a very large project, but that rifle was drop-dead gorgeous when he was done.