When machining a rear sight base or grip cap on a milling machine to an elliptical shape, do you have a preferred method ? A formula for your DRO ? A fixture on the manual machines ?

A "one off"or a hundred? One off...eyeball...a hundred, enlist the services of a CNC

Well put Mr Weibe, I have been doing machinist work for over 50 years and still have not figured out how to mill and ellipse on a manual milling machine

A mill bastard file seems to work real well,,,, for one!

Thanks for your help guys. Eye ball or cnc was all I could come up with. So many times I find out I've been doing something the hard way when there's a much better way that I didn't know about.

I've never had to do one. What about a cherry attachment & a rotary table.

Someone will correct me I am sure, but to my knowledge there is no way to machine an ellipse manually by the numbers. A tracer using a pattern, etc, sure. There may be an odd attachment somewhere, but I doubt it. Sounds like something Deckel would make.

If you have the means of machining a radius, you can however machine a decently acceptable grip cap or similar, depending on what you have available.

I made a few stock escutcheon and at least one grip cap manually. They were not great. They took several hours to make. Not worth the time or effort in my opinion.

I don’t remember the dimensions, but as big of a radius as I could on the two long sides, tangent to a small radius on the ends.

The cadd sw I have gives two ways to make an elipse call ture and construction .

Construction is 4 arcs.

Home Shop Machinist had an article several years ago about a fixture that would do this on a manual machine. There's a lot of ingenious setups that have been long forgotten since CNC became common and affordable.

Dirt simple on a Prototrak just faking it like Rich says. Turn the ellipse into a chain of tangent arcs and just plug in the numbers.

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Home Shop Machinist had an article several years ago

I subscribed to that magazine for a number of years but I don't remember that article. I know there is a jig/fixture you can build to cut an ellipse in wood with a router but I don't think you could make that design work with a mill.

I agree there are many ingenious set ups and designs from the past that have been forgotten or unknown by this generation. There are a series of three books on that subject "The Machinist's Bedside Reader" by Guy Lautard . My copies were printed around 1993 but I think they are still available.

[URL= https://youtu.be/lP2qxxoHCSI ]video of turning oval[/URL]

Hand filed~

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Originally posted by gunmaker:
[URL= https://youtu.be/lP2qxxoHCSI ]video of turning oval[/URL]

I did not even consider turning one on the lathe, that would be a slick way to do it.

I've made a couple grip caps from round stock.
Just cutting the stock on an angle gives you an ellipse.
But you have to measure and figure for the loss of the over hanging ends.
The 'longer' the oval, the greater the loss

By the time all the sawing and filing was done. I figured I might as well just cut one out of flat stock the next time,,,which hasn't come along yet.

Maybe with a powerhacksaw for those diagonal cuts it would've seemed like a better idea. At least I can I've been there!

I think steel bar stock in oval shape(s) are sold, but you probably have to buy a ship load.

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There's a lot of ingenious setups that have been long forgotten since CNC became common and affordable.

Precisely. (pun intended) Well said, that man!

Milling an elliptical shape on a manual milling machine and rotary table. https://www.youtube.com/watch?...st=WL&index=8&t=544s

I use a rotary table.

The last one I did, I put the screw holes in the centres of the short radii, and drilled two shallow holes in the back of the piece of material, half way between the mounting holes but off-set to the sides (one either side), in my case by 14mm.

Then I made a taper bushing to fit the bore of my rotary table with a reamed hole into which I place a dowel pin. This dowel pin locates in the shallow holes. I then milled the long radii first. This way you don't even have to worry about setup angles, you just mill until the cutter stops taking away material.

I know it's not a true and mathematically-correct ellipse, but I doubt many people will know.

Thanks Peter. That would be worth trying.