Order of operations and general approach question on this small part

[ssdesigner]

The photos attached are a 3D printed version of a part that I need to make out of aluminum. The part is a custom scope mount for a small movie prop.

The radius cuts are 1" and 1/2" diameters. The other sides of this thing are perfectly flat. It measures 1.250" x .750" x .375"

My initial thought was to drill out the 1" and 1/2" holes first, but that will make it a very difficult part to clamp down as I shape the other sides.

For reference, I am working with the LMS 3990 mill.

Thanks in advance for the advice!

 

[mmcmdl]

Leave it long and mount it in vise standing up . You could use an end mill to plunge , or use a boring head for the radiis . Not sure what tooling you have on hand .

 

[ssdesigner]

Leave it long and mount it in vise standing up . You could use an end mill to plunge , or use a boring head for the radiis . Not sure what tooling you have on hand .

I don't have a 1" end mill or a boring head, but I'm totally fine getting either. Do you think a 4 flute end mill would be the easier operation?

 

[woodchucker]

Like Dave said, longer handle. You could also bore the radius on a lathe if you have a 4 jaw.

 

[GrifterGuru]

If it were me...

1) Square up the stock
2) Machine to length
3) Mark and drill the through holes, counterbore if/where required.
4) create smaller radius
5) create larger radius

I would also consider the use of sacraficial stepped blocks (like a split cradle) to hold the part whilst machining the larger radius so as to both support it as well as protect the vice jaws.

 

[ssdesigner]

No 4 jaw yet for the lathe. It’s on my list to get at some point.

Leaning toward the end mill as my method of action on this. I have some bar stock that would work great size wise. Just wondering now if hogging off that much aluminum would be better suited for a 2 or 4 flute end mill? I have to purchase one either way since my biggest is only 3/4”

 

[Flyinfool]

The best order of operations will depend on what tooling you have or will have available.
Boring head?
1" end mill? and a way to hold it in your machine?
1" ball end mill?
1/2" end mill
1/2" ball end mill?

How big is the chunk of stock that you have?

As for holding a part with a weird shape. I have 3d printed holding fixtures for small oddly shaped parts.

A 1" end mill might cost close to the same as a boring head. And most hobby machines (I am not familiar with your specific machine.) will not hold a 1" end mill. The End mill will only cut 1 inch Dia the boring head can cut any dia up to its max size. The boring head will be much more useful in the future.
2 flute will be better for rapid material removal but 4 flute will leave a better finish. I do not think your machine is big enough to maximize the material removal capability of either a 2 or 4 flute 1" end mill.

 

[woodchucker]

That's a big cut for a mini mill.
I suspect 4 flutes will do the job better, but I don't know.
You are probably going to have to drill down rather than side mill it (just my opinion). if you drill down, you don't go to your mark all at once. You drill short of it, and then move over to remove more and more until you hit your mark. For the 1" you won't need a center cutting end mill.
But for the 1/2 You may.

 

[ssdesigner]

That's a big cut for a mini mill.
I suspect 4 flutes will do the job better, but I don't know.
You are probably going to have to drill down rather than side mill it (just my opinion). if you drill down, you don't go to your mark all at once. You drill short of it, and then move over to remove more and more until you hit your mark. For the 1" you won't need a center cutting end mill.
But for the 1/2 You may.

Thanks for that info. My end mill set (goes up to 3/4” as I mentioned) are all center cutting.

I’ll pick up a 1” center cutting end mill. I will need that going forward for another project.

 

[mmcmdl]

I’ll pick up a 1” center cutting end mill. I will need that going forward for another project.

They have 1" end mills with reduced shanks ya know . Personally I would go with a 2 flute , but that's just my .02 cents worth .

Couple ball end mills could be used also .