Machinists! Technical question for you all.

[MattMunson]

I'm working on a sonic screwdriver, and I've figured out how I'm going to make everything, save for one detail.

Strike that, i've figure it out, but my intuition tells me there's a better way than what I've got planned.

Here's the part I'm talking about:

This is the head of the screwdriver. See the rectangular shapes that run up and down?? On the outside of the square, rounded-corners hole?? Those rectangles are part of the original stock. Not glued on. The diameter of the space in between the slats is less than the outer diameter measure at the slats.

It's sort of an exaggerated pommel from the luke ROTJ saber.

So the question is, how does one do that?? My first instinct was to lathe down to the OD of the slats, then put the stock on a mill and take it down to the appropriate diameter. But you'd have to do a ton of passes with the mill, rotating it a little bit each time. And then you'd have to go in and sand it smooth.

Seems like there's a better way to do it. For those of you that have done Luke ROTJ sabers, please chime in.

 

[Matsuo]

Seems like there's a better way to do it. For those of you that have done Luke ROTJ sabers, please chime in.

Yes...it's called a CNC lathe with live tooling...

The lathe turns the outside dimension and detail you need as any lathe would then the piece would be 'clocked' in position for the longitudinal cuts and a mill would come down and do those cuts, the lathe would automatically be able to clock itself for each cut...pretty nifty...

To do it by hand you would have to have an indexing tool in your manual mill, that you mount the finished 'lathed' part in and milled out the longitudinal cuts by hand...

Kenny could answer better than I can though.

M

 

[MattMunson]

To do it by hand you would have to have an indexing tool in your manual mill, that you mount the finished 'lathed' part in and milled out the longitudinal cuts by hand

Thanks! Thats' pretty much what I was considering. I dont' have access to CNC equipment, so it sounds like that's the route I'll be going.

 

[wamser_e]

Thanks! Thats' pretty much what I was considering. I dont' have access to CNC equipment, so it sounds like that's the route I'll be going.

It can be done with a rotary table mounted vertical on a mill(acting like a lathe chuck). I made a phaser emitter ring that way to upgrade my AA phaser.

From the looks of it, you'll have to mill it first, then put in on the lathe to bevel/finish pass the ends. As an additional note, it almost looks like they used a dove tail mill bit to do those long slats as the grooves appear to cut into the rectangular parts a bit.

Here is what a dovetail bit looks like:
http://www.ares-server.com/Ares/Ares.asp?MerchantID=RET01229&Action=Catalog&Type=Product&ID=82772

Ed

 

[MattMunson]

wammy, thanks for bringing that up. I spotted that earlier today when I was looking at the visual dictionary. They have a sort of 3/4 head on view that shows it better. Good catch.

 

[nickytea]

Matt,
It looks to me like they just ground a conicle shape into a keyway cutter and then simply did four passes with an indexer mounted on a mill. Any decent tool grinder could do the cutter for you. Anyway, thats how I planned on doing it. Do you have any dimensions to share?

 

[MattMunson]

Matt,
It looks to me like they just ground a conicle shape into a keyway cutter and then simply did four passes with an indexer mounted on a mill.

All I hear is "Blah blah blah blah blah" I've only been machining for about a year now, and I'm unfamiliar with those things you mention. I just did some googling, and now have a better idea, but it's still not clear to me how you could get that effect using a keyway cutter. Those seem to be for cutting a slot on the inside of a tube????

I dont' have any dimensions or drawings yet, but I'll post them when I get them finished. No worries.

 

[JBReplicas]

It'd be quite simple on a 4th axis held in a chuck, oh id love to have a go at that but my boss wouldnt be so keen, its a matter or programming your tool path and simply indexing it round at each angle to repeat all 4 sides

 

[MattMunson]

Strike that. I did some more looking around and found out how a keyway cutter works. YES, that makes perfect sense. That would save me a ton of time. It's not quite clear to me how a keyway cutter tool gets mounted, or even what it gets mounted on, but I understand the basic concept now. Thanks for the tip. tha'ts GOT to be how they did it.

 

[MattMunson]

I'm still a little fuzzy on what gets mounted where. I can visualize it if you're doing the key cutting on the inside of a tube, because I can see where you'd mount the cutter on the lathe. But where would you mount it if cutting on the OD of a dowel???

 

[MattMunson]

Never mind. Just TOTALLY got it figured out. I'll mount the stock in the chuck, and load the keyway cutter into the tool clamp. I can adjust the tool clamp in any direction, so I can get it into position. I then move it back and forth along the X axis to make the cut, getting a tad deeper with each pass. Brilliant. Now I just need to get my drorings done and have a shop grind the cutter to the proper shape.

I don't have an indexer, so I'll have to eyeball it, but I think I can manage.

AWESOME! and thanks.

Still, the keyway cutter won't be able to do the dovetail cut. NOtice the slats have a tiny undercut to them. I don't see how a keyway cutter can do that unless you do the cut in one pass, which I don't think is possible.

 

[wamser_e]

If you go the keyway cutter route, you would still have to go back with the dovetail cutter to get the undercut effect. afaik

 

[obi1kenny]

Let's assume you don't have an indexer or rotary head of any find. You can do these milling operations in a vise too. Just clamp the round material in for the first side, once you have taken all your cuts you can take it out and turn it 90 deg, as I am assuming you want to go with 4 equal cuts like the photo, or was that just a reference. Anyhow, once you turn it 90 degs, it will line up perfectly as you had already cut a flat/groove on one side and the jaw of the vise will make it line up straight. Or turn it 180 degs, and place the flat/groove you jsut cut on the base of the vise and it will also line up square. This will work for any even number of flats or grooves you want to cut, if it's and odd number then you will just need to eyeball it, and that is pretty easy to do as well.

And yes, if it's a true dove tail then it was probably done in one pass. Which is easy to do in aluminum. Or 2 or more passes with a smaller dove tail bit.

also, you could always just give me a call or take a nice drive down here to the central valley.

 

[obi1kenny]

If you go the keyway cutter route, you would still have to go back with the dovetail cutter to get the undercut effect. afaik

Yeah, use both tools. Use the keyway cutter tool to rough out the shape then go back and use the dove tail cutter as a finishing step.

 

[nickytea]

Matt,
For the keyway aproach I would recommend using a mill. Just put your stock into an indexer and index it after each pass. Now, who has some dimensions to share?