Easiest way to machine diamond shape.

Hi guys,

Hoping someone on here would be able to help me out with the easiest to machine the following part. I only have manual mills and lathe to work with. This is the part that I'm trying to make, and its the diamond shaped top that I'm a bit stumbled on. How would you guys execute this part?

Thanks ahead of time!

How many facets and what angles are they? It looks like a job for an indexer and chamfer mills in a manual machine. It looks like eight facets at one angle and eight more at another angle set 22.5* from the first set.

I would make the part about 1" longer on the small side that is straight turned, and leave about .2" on the bigger side for a center drill hole. Make the diameter of the c'drill nub about .05 bigger than the cone of your c'drill hole that can be machined or ground off later. After its c'drilled chuck up on the side that's going to be the small end and turn the whole part complete from one side, make a groove deep enough at the overall length so you can make the 45° with your part off blade and compound rest, or a form tool that will fit. After you have everything turned take it to your mill with a spacer or divider, I have a spacer. Chuck on the extra stock and put a tail stock in the other end. In the spacer put an 8 pattern dummy plate(it looks like 8 flats in the pic). Cock the mill head to the 1st angle you need and verify with a bubble protractor on the quill. cut your 1st 8 flats with a wide enough end mill. then set your other angle and cut them 22.5° from the original flats. On the first 8, your spacer will click into place, the next ones it won't and you'll have to use the vernier scale if it has one or eyeball it best you can if not (my $100 cheaper than vertex elephant spacer does not have a vernier scale). After the mill work is done bring it back to the lathe and part it off. If you have to face off the nub instead of grinding you can make a short sleeve to accept the taper of your part, its steep enough to hold for a quick facing op. Just take about an inch of scrap stock(even the left over from the part will work), drill it smaller than your part and bore the taper with your compound or taper attachment till your part goes in deep enough to face it. That's how I would execute that part.

dj55b said:

Hi guys,

Hoping someone on here would be able to help me out with the easiest to machine the following part. I only have manual mills and lathe to work with. This is the part that I'm trying to make, and its the diamond shaped top that I'm a bit stumbled on. How would you guys execute this part?

Thanks ahead of time!

View attachment 71382

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I am supposing you have a spindex and that the part is maybe 3/4" diameter and 5 inches long. I ma supposing it is to be made from aluminum or a reasonably easy to machine metal and is not hardened. I am also assuming it is designed largely as a decorative item and is not to be extremely precise nor highly polished. That is a lot of supposing---it would be better to provide dimensions, material, tolerances and intended use in your original post.

I suppose this is a one-off part.

If all that supposing is more or less right, it looks like there are eight facets per row of facets (probably would have been good to say so in the original post).

First cut over size by a and inch and a half in length the metal. Center drill both ends. Turn down the end to receive the facets to 3/8 inch for a quarter inch in length to form a spigot. Place piece in spindex and use a sine plate/vise or something to set the piece off vertical enough to cut one set of eight facets. Re-position the spindex and cut the other eight facets.

Now set up to turn between centers and offset the tailstock to cut your taper. Also form a spigot on the base end of the piece after setting the tailstock back to center.

Now grasp the base spigot in a 3-jaw and use a steady bearing just proximal from the facets to turn off the spigot on the large end. Turn end for end. Use some aluminum or copper sheet to protect the large end as you grasp it in a 3-jaw. Use a steady rest bearing on the small end of the taper to part off the small-end spigot.

This should get the discussion started. But, in the future please frame your inquiry with more information so that a reasonable answer can be made without so much guessing.

Denis

I see I was typing while another member was also posting a solution.

Thanks guys for the information provided and sorry for not providing proper information. I really should have know better than that. The overall length is 8", diameter at the widest is 2.25", material is aluminum 6061. This is a one off, and its for a shift knob.

There are 8 facets on 2 different angles. The first ones (the bigger sides) of the "diamond top", those are set 25* measuring it from the length side. Then the other ones which are offset at 22.5* from the other ones are cut at 45* angles. I do not have a spindex, nor a rotary table .. Any other ways that this could work?

Tolerances can be off by about 10 thou.

Pretty tight tolerance for a cosmetic part of a shift knob. Making it for one of the guys in that thread about reading scales, who can measure to .001 with thumb and forefinger?

I don't personally think that 10 thou is that tight of a tolerance at all. Most of the things that I work with is 1 thou tolerance, so 10 thou is plenty to deal with But yes realistically, it can be more, but if I can machine it within tighter tolerance, I'll do so

If you have a dividing head, use that.

If not I'd suggest do it in the lathe the following way..

Grab a toolpost holder for your lathe and take the tool out, or use a non q/release post with no tool in it.

Set it up so that is square with the compound slide..

Using a set square or some item that will give you a center across each end diameter to work form, and divide the end diameters to the desired amounts, equally so that you can then mark out the divisions down the length of the piece.

G-clamp (or whatever) the piece in/against the tool post or holder and set the compound slide to the angle you want, put some class of endmill in your chuck and mill out the flats using the cross slide.

Do the taper afterwards because you left enough material to chuck it up after the flats get done, however you might need to do the taper first, and set your toolholder to the required offset...
Use the marks you put down the length of the work to line up with some reference point on the toolpost to get equality (lol), so you can turn it to the next section more easily.

Experiment with some other piece of scrap till perfected, till you get the method down pat, and go.

Make more than one, sell the rest on fleabay or some where........

Just my 2 cents.......

BTW 10 thou is 1/4 mm, try to achieve the best tolerances you can, because with facets they need to be quite equal in size and spacing or you can see the sloppyness really easily because each facet visually acts as a refrence point in the minds eye for the next facet to it......so 10 thou will look like you filed it out with blunt woodaxe., probably.........and if you are 10 thou out one side that is 20 thou of/on the facet next to it, most likely. so bear that in mind also.......good luck....

dj55b said:

Thanks guys for the information provided and sorry for not providing proper information. I really should have know better than that. The overall length is 8", diameter at the widest is 2.25", material is aluminum 6061. This is a one off, and its for a shift knob.

There are 8 facets on 2 different angles. The first ones (the bigger sides) of the "diamond top", those are set 25* measuring it from the length side. Then the other ones which are offset at 22.5* from the other ones are cut at 45* angles. I do not have a spindex, nor a rotary table .. Any other ways that this could work?

Tolerances can be off by about 10 thou.

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If you have a miracle point you can do this part in some small V-Blocks, you still leave it long and have the nub for the c'drill, but just don't taper anything. Clamp it in the V-Blocks, you may want to set up a stop on the other end. make your first cut, put your miracle point on tap a punch mark then un-clamp and rotate 45°, then after the last cut rotate 22.5° for the 1st other angle then 45° for the rest. then after the mill work take it to the lathe and finish the taper and grooves and cut it to length.

If you don't have a miracle point you can do the same thing with a bubble protractor leveling on each flat that you cut or you can make some reference flats on an area that will be tapered so you can have a good wide surface to place your protractor on.

FFS! it's a bloody gear shift handle

Take your pick from these, charge em 100 bucks and call it good.

HANDLES / KNOBS / SCREW CLAMPS, KNOB HANDLES :: Carr Lane Manufacturing Co.

Limy Sami said:

FFS! it's a bloody gear shift handle

Take your pick from these, charge em 100 bucks and call it good.

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Tsk, Sami, it has to be "billet" or it won't be cool.


Rex

If you don't have some sort of indexer this will be a big PITA to make accurately. Outsource it to someone with a rotary table, and the inclination (pun intended) to do finickly 1-off work.

Regards.

Mike

Thanks guys for the added information. I may be looking at acquiring more tooling from the looks of it. I like the challenge of doing weird things, and I'm sure I can find plenty of other uses for a rotary table or a spindex.

Limy Sami said:

FFS! it's a bloody gear shift handle

Take your pick from these, charge em 100 bucks and call it good.

HANDLES / KNOBS / SCREW CLAMPS, KNOB HANDLES :: Carr Lane Manufacturing Co.

Click to expand...

Can't make life that easy I like the challenge. This shift knob I'm actually giving away. I did a contest on "create your own shift knob" as a prize, and this is what the guy had liked. Its different, and yes I may do more of them later on if all is successful.

bjorn toulouse said:

Tsk, Sami, it has to be "billet" or it won't be cool.


Rex

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In my old Land Rover truck I had a wooden file handle on the gear lever and the car kids thought it was about the coolest ever.

now's your opportunity to buy an indexer and some tools, sheesh.

OR, you could FILE it if you were a true old school craftsman. :P

or you make some tool steel "grills" and gnaw on it? that's all the rage these days, I hear.