Debugged a function to mill a cone

That would seem to be a better task for a lathe... perhaps you should try a pyramid... with stone detail... and stairs... kinda Myan... a real g-code project...

Well, I am getting ready to make a particular sprocket.

Ignoramus8984 fired this volley in news:dbudnUSRx9l7FtLRnZ2dnUVZ snipped-for-privacy@giganews.com:

Just particular in its general nature, or spectacularly "particular" as to precision?

LLoyd

I need to copy a sprocket from an old motorcycle for a friend of mine. It has a conical hub.

How about modifying that to mill a projecting cone to fit it? As long as you have the cone generation capability -- just add a switch option to define whether it is male or female. (In other words -- generalize the program as much as possible.)

And then test the two against each other -- even in wax.

Hmm ... what happens if you make it larger at the bottom? It would need a ball end mill which is more of a ball -- not just the bottom half of the mill. And you would need to be able to tell it what the diameter of the shank above the ball was so it could predict interference.

Of course, with such a mill -- you would have a lot of deflection with a larger diameter cutting section and a skinny shank. They probably don't make those for metals anyway. :-)

Oh yes -- do you also have the ability to specify conventional or climb milling? If so -- do the heavy work in conventional, and the finish cuts in climb which makes a cleaner surface (especially in aluminum. :-)

Understood.

Enjoy, DoN.

That would be the next program. But it is not really the same.

Ideally I would like to find a way to mill any pocket given by a reasonably friendly predicate function p( x, y, z );

I do not really need that

sure

Seems like an awfully convoluted way to make funnels to transfer all those leftover chemicals to smaller containers.

Ignoramus8984 fired this volley in news:rY-dnTc1PtfTDtLRnZ2dnUVZ snipped-for-privacy@giganews.com:

My first two questions would be: "Is the hub conical simply as a casting/forging expediency?", and (if it's tapered on the i.d.) "could I cut that with a tapered reamer instead of milling the hole?"

LLoyd

No, it is tapered so that the sprocket would lock on the hub.

It is from some old Indian motorcycle. I am not a motorcycle guy and have no knowledge or interest in them. But my friend does. This is perhaps a 90 year old sprocket that needs to be reproduced. I would guess that the angle on it is not standard.

Hey Iggy,

In a machine/tool shop, they would probably do the "cone"as you have done so far, leaving a few thou for finish, then on a Deckel SO (or similar) would make a tapered carbide cutter, possibly just grind a "D" type (or even 2 or 4 flutes) to the angle required and then use that cutter and do the finish circular interpolation using it to give a "finish" surface.

As this sounds like a kinda small workpiece, or at least if the "hole" is less than 2 inches, you might even try using a smallish grinding stone/wheel cut to the correct angle and chucked in a Dremel clamped to the quill or spindle of the Bridgeport. A "high-speed" attachment for a mill is a handy thing to have anyway.

Take care.

Brian Lawson, Bothwell, Ontario.

ps....are you thinking of attending IMTS2010 at the McCormick? It's on from September 13 to 18. I might go for one or two days.

Lemme know if you are interested.

If the taper can be accurately measured, it can be accurately milled with a ball end mill. I am not really pretending that I know what I am doing, but to me the big issue is whether we can measure the taper with the required degree of accuracy.

We can always test the fit with Prussian blue or something.

I milled some cones yesterday (in wax), with a ball mill.

My procedure for milling a cone involves, first, roughing out of the area, and second, doing many circular passes through the material. The number of passes depends on my parameter fine_finish_zstep.

I milled a cone that was 1 inch deep, and was 1.2 inches diameter on top and 0.6 inches at the bottom.

For fine_finish_step I picked 0.01, so my mill did 100 passes, with a

The result was smooth as if it was turned on a lathe.

Roughing out was relatively quick. I had to stand by with a vacuum to remove wax chips.

Finishing took quite a while, since I selected a slow feed speed. About 15 minutes IIRC. It was boring (as in "not fun"), so I went inside and watched it via the netcam.

If I get time to go, definitely.

I am pretty sure it is a front sprocket. Whatever you can find out, will be most gratefully appreciated.

The surface finish of tapered fittings is rather critical. Would you try to ball mill and R8 collet? Material and heat treat also come into play for something like this.

Ignoramus6705 fired this volley in news:CuydnXGpC7xa3s3RnZ2dnUVZ snipped-for-privacy@giganews.com:

Heh! That's funny, because it's what I do, too.

I have a wireless IP camera that I've set up with a weighted base.

Sometimes it's watching the mill. Sometimes it's outside next to the barbeque watching the thermometers!

That last one is especially nice, because I can check on it all night long without having to trek out to the smoker.

LLoyd

I've never seen a rear sprocket that had a tapered seat, but never know with vintage stuff. However have seen dirt bikes with tapered countershaft instead of splines. These are very precise tapers, and I question the ability of a mill to interpolate a sufficiently accurate taper just in terms of the angle, let alone getting a surface finish that will do the job. Husqvarna dirt bikes of the 70's for one, used ground tapers. These could be a real bitch to remove.

Is Iggy just roughing out the taper so it can be more easily ground? Or trying to generate a finished and functional taper? If it's for something really rare and not to be ridden or ridden only very gently on rare occasion, maybe an interpolated taper might hold up. But it would be wise to consider the possibility of munging up the shaft taper on a part that might be very hard to come by.

I am assuming front sprocket here as again, have never seen a rear sprocket seating on a taper.

Jon

Ok, REAL vintage. Ask what year and model, my dad rode and raced Indians for years. Is it a front or rear sprocket? I'll ask what he knows (remembers?) about the fit of this taper.

Jon

I did not know that. Now I'm going to have to run out to the shop and do some experiments to see. If it's a big enough difference I am going to have to double the number of MOPs for almost every job when I am laying it out.

Sounds a bit like overkill. As much as I like to make something I think I would just buy funnels for transferring all those leftover chemicals to smaller containers.