How hard is it to CNC this?

I was wondering how hard it would be to CNC this. Would I make it to size on the manual lathe first and then have the CNC mill do all the rest? Just to give an idea of the size, the OD is about 2.5 inches and the part is about 1 inch deep. I have a guy who will make the program in MasterCAM and I will set up the machine. I know this can be done (as I have seen way more complex stuff than this) but I don’t know how hard it would be. The space between the six protrusions is .134 which is pretty small. Is a 1/8" end mill that is at least 1 inch long a common thing? Thanks.

EDIT: Forgot attatchment, added now.



Sorry but due to the innovations that FIRSTers can come up with i think i have an image in my head of this. But do you have a screrenshot from inventor or a sketch of this item. A photo would help give me give you a clue on the trickiness it will take to machine on a CNC.

Other than the keyway, it should be fairly easy to CNC. The keyway would be phisically impossible to mill (unless you have a 90 degree end mill, which may not even exist), and would need to be broached.

Also the spaces between the 6 stading posts can not be milled due to you wanting them to be square. If you dont mind that space being a circular gap, it could be done. Though if it needs to be a square gap, it would have to be cut out with a saw most likely.

Edit: ok you can mill the spaces and get a circular gap then grind/sand/file it to square but i doubt it would look or act as if you did it with a saw if you want it to be square.

that is true, but you could mill it rounded and take a little time filling it out. it wouldent be TOO bad

When doing a keyway, you want to properly broach the keyway. That is so you have the correct tolerances and the key does not slide out of position or move at all.

lol thats why i do programing and nothing else
because i dont know these things…

The keyway is easy to broach. I can do that no problem.

Could you explan this a little more? I’m having a bit difficult time understanding what you mean by “circular gap” Perhaps a quick sketch? How is everyone envisioning this being held in the machine (what orientation?) I picture the axes of the holes parallel to the z axis of the machine.

this is incorrect…if you have the clearance past the spaceing going past it with a standered cutting mill bit will leave a square notch…the side profile on a round mill while spinning is a rectangle

That’s what I was thinking. Perhaps dez was envisioning this thing in a rotary chuck 4th axis which would index that part for each slot and then when it gets to the end of the slot where the big diameter portion of this part is it would be rounded in the end of the slot.

maybe…i am just glad you agree i was going insane trying to figure out what he was talking about…

btw for someone who is good with a cnc mill this souldn’t be that bad of a part

Would I face it to length, step down the diameter, and bore the (5/8 di) hole on a manual lathe first?

Facing the part on a lathe and taking down the outside diameter will make the time on the cnc mill much less than if you just put a square block of aluminum on. However, if you are using a square block you don’t need to drill any center hole in the part, the cnc can do that all for you. If you plan on taking the part down on the lathe then I would reccomend having a center hole of some size larger than 1/2 inch so your machinist can easily use a dial indicator and find the center of the part to make set up much simpler. Having the cnc mill do the center hole to exact dia. will be better than doing it on the lathe if you planned on using a drill bit, if you are using a boring bar then you will be fine making it exact, provided your lathe is true. And yes, make sure you take the keyway out of the drawing before you put it into mastercam, it does not like things like that, and it will try to cut it out if you leave it in there.

[edit] to nicely go from Inventor to Mastercam you will need to save it as a .step file, and then you can import that into Mastercam. If you have Mechanical Desktop installed, I would open to .step into there and save it as a .dwg because Mastercam seems to like them slightly more.

Hmm… this looks an awful lot like the hubs for the skyway wheels, just with a hub & keyway attached…

If thats what there intended purpose is, why not just machine a plate to mount to the existing hubs?

It is very similar to the skyway wheels but it is actually for different wheels for a different project. They are just a plain bore through plastic, no pre-existing keyway. That’s what these hubs are for. I had thought about a plate that clamps the wheel ( but have determined that since I have the resources to do a full-blown CNCed hub, I will go with that. It is kind of dificult to explain but the center section of my wheel connecting the spokes to the hub is is very thin width, only .125 at the most. Putting just bolts through that thin of plastic will not be enough to drive the wheel reliably, so the two sides of the hub would have to clamp together to drive the wheel and I’m not so sure of that because in its application, it really cannot afford to slip no matter what. This design I have shown in this thread will fully engage the wheel and fills in all the voids in the hub area which makes it very strong. Basically with this, the plastic cannot flex anywhere because it would be running into aluminum, which is contacting the next section of plastic, and so on.

EDIT: I attatched a picture of the wheel’s hub area. These void spaces are present on both sides of the wheel. One of these hubs will go on each side. The “thin plastic area” I talked about above is in these cutouts or void areas in the wheel. These cutouts have a bottom to them, and so do the ones on the other side. See, the whole wheel hub is about 2 inches thick and the cutouts are .95 deep on each side. That’s why I want to fill up those spaces with the aluminum hub.



you can actually do it on a vertical mill if you have the 1/8th inch long endmill. But you must lathe it down first and then put it in an indexing head. Then if you have the time you can rotate the piece while lowering the endmill after each rotation. Then make all the other cuts you must.

Another option would be to make it in seven pieces instead of one. I would make the “orange wedges” seperate pieces that attach to the hub with machine screws - 10-32, perhaps.