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Advice on machine/ setup/ cutter needed for job

momalleyhorns

Plastic
Joined
Feb 13, 2020
I’m currently working on developing a new part and am looking for advice on how to go about making a specific feature. I do not have access to cnc and will need to do this op on a manual mill. In the attached pictures shows the two opposing channels through a rotor for a musical instrument. The channels aren’t simply straight cuts with a ball mill but curve in and out of the rotor. Hopefully that feature is apparent in the pictures. How would I cut this without a very complicated and unreliable setup? I’d rather not shop this op out because I’ve already gotten a quote and it seems steep. The o.d. Of the part is .875 in. and the diameter of the channel is .468 in. Material is c360.

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Do you have a horizontal spindle? all I can think of is setting it up on a rotary table and using a full width lollipop cutter. I don't think this is really possible in a cost effective fashion on a manual machine.
 
What is the material?

Get a 15/32 end mill and "drill" the 2 channels while the part is held in a fixture that clamps it to keep it from rotation.
 
^ What he said.

I think I'd rough it with something smaller first just to clear out the center.
I'd probably go with a 4 flute just so it doesn't bounce around too much in the interrupted cut.
 
Drill First the holes and maybe bore/ream for roundness and surface quality, Then turn to size.
 
He said they are not straight channels

I would say if those two cuts are not straight you need an indexing head. hold it in a 3 jaw, bore then rotate back and forth to get what you want

If they are straight and just look complicated, then the previous advice holds.

I think you need to clarify

If they are straight drilled vertically, then they are simple, maybe a fixture to hold them and keep the burr down
 
I’m currently working on developing a new part and am looking for advice on how to go about making a specific feature. I do not have access to cnc and will need to do this op on a manual mill. In the attached pictures shows the two opposing channels through a rotor for a musical instrument. The channels aren’t simply straight cuts with a ball mill but curve in and out of the rotor. Hopefully that feature is apparent in the pictures. How would I cut this without a very complicated and unreliable setup? I’d rather not shop this op out because I’ve already gotten a quote and it seems steep. The o.d. Of the part is .875 in. and the diameter of the channel is .468 in. Material is c360.

View attachment 278678View attachment 278679
Screen shots of solid model aren't' showing any tolerances.
 
I'm all for manual ops, but sometimes it's cheaper in the end to get someone with the right tools to bang em out. Might even be cheaper in the long run.


Maybe post a rfq in the rfq section. You might be surprised.
 
If this is a prototype, 3d print the OD's oversize, the channels to size, and fit up as needed. Good reason to buy a 3d printer??
 
Looks like a French horn rotary valve body, or some other very similar application. If indeed the 2 cutouts through the body don't follow a straight line, do they follow a known constant radius value? If so, then you COULD set up a final machining step using a rotary table and the proverbial "lollypop" cutter, but that should be done only after roughing as much material away as possible. That is assuming you don't have a radius value of 48" or so, as the radius you would be able to make with manual setups like that will be limited to machine travel envelope and where you can set up a rotary table relative to spindle. Looks like you have some 3D modeling skills, so you can figure out the max size straight path and get the stock down to something (maybe) manageable with end mills to start.
 
I rather suspect the cutouts are straight cylindrical sections and the confusion about them being odd from his first post is that he realizes he can't just lay it on its side and cross it with a ball end mill. The two drills would indeed work.

It seems like lots of the viewers and responders are really thinking in 3D and imagining a curved track like a worm hole through the part and a shape that would require the lollipop cutter. However, if it's a functioning rotary valve it's only the shape of the peripheral opening that's important. Whether the air travels straight across or follows a curved path to it's intended exit should be immaterial. And it would be nice if the OP showed up again to enlighten us.
 
He said they are not straight channels

I would say if those two cuts are not straight you need an indexing head. hold it in a 3 jaw, bore then rotate back and forth to get what you want

If they are straight and just look complicated, then the previous advice holds.

I think you need to clarify

If they are straight drilled vertically, then they are simple, maybe a fixture to hold them and keep the burr down

Yes they are not straight channels they curve in and out of the valve body. Imagine these parenthesis were the centerline of the channel: )(
 
I think you may be right. The trouble is I know parts with this feature have been made on manual machines in the past.
 
I’m currently working on developing a new part and am looking for advice on how to go about making a specific feature. I do not have access to cnc and will need to do this op on a manual mill. In the attached pictures shows the two opposing channels through a rotor for a musical instrument. The channels aren’t simply straight cuts with a ball mill but curve in and out of the rotor. Hopefully that feature is apparent in the pictures. How would I cut this without a very complicated and unreliable setup? I’d rather not shop this op out because I’ve already gotten a quote and it seems steep. The o.d. Of the part is .875 in. and the diameter of the channel is .468 in. Material is c360.

View attachment 278678View attachment 278679

Ball end mills. Stock rougher, then custom-ground finisher.

Swing arm fixture, appropriate radius off the pivot. Short as the arc needs to be, don't even need a rotab.

Could have been hand cocked, cut then pulled though with a handlever, spring, or simple pulley and weight.

It's only 360 Brass. ".... has the highest machinability of all copper alloys.."
 
Thanks everyone for the replies. Sorry if it wasn’t clear. Short of making a swing arm fixture and using an undercutting ball end mill. (This is the obvious answer but hat fixture would take time and a .468in 300 Degree undercutting end mill is a pricey custom grind.) eventually if my volume goes up I’ll do this. To “fake” that feature I’ve plunged with a ball end mill .400 in deep and then stepped over either side .250 in using the radius of the ball to give the curvature. I’m pleased with how it turned out and the repeatability of The process.
 








 
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