[cobrakai]

I'm making my first part with my mill and it's a pretty diverse part. It has everything including contouring, deep pockets, drilling, chamfering and tapping. I think it's a good way to learn how to use the machine and CAM software.

So far, I did one side of the part. I did the steps progressively so I wouldn't be taking cuts that are too aggressive. I also drilled the bores to 1/2" first to allow chips to fall out and left .005" all around for a nice finishing pass. The depth of the pocket is 1.3" so I set my tools only as long as they needed to be. Still the flutes were not that long and you can see some lines where the mill shank was rubbing.

Based on this picture, does that surface finish look decent? Can I get it better? I took off the last .005 climb milling with a 1/4" 3fl end mill at .25 DOC, 3200rpm, 20ipm. I cannot actually feel any ridges, but I can see the little ripples.
Attachment 201174

Anyway here's my question:
Now I need to flip the part over to do the rest of it, which is basically facing off the top, finishing a couple holes, chamfering, etc. What is the best way in general to do this? As you can see, I have stock that prevents me from indicating the part itself. Am I supposed to indicate the corner of the vise and then push the part into the corner? What about indicating the Z height?

My concern is that this has to be absolutely perfect or else the contouring I do will not match with the existing curves and there will be a ledge. Any pro tips for doing this? Seems like it's such a common thing that no one bothers explaining it.

Thanks!!

[Khalid]

Practice on wood.

[SCzEngrgGroup]

Your odds of flipping that part and *exactly* matching the profiling are about zero. It will almost certainly end up being off by several thou at least in places. All you can do is reference to the machined surfaces of the part, and hope for the best.

Regards,
Ray L.

[sansbury]

If the stock is precisely milled square then you can indicate the edges after flipping. You could also use a vise stop to locate it repeatably. You could also mill the outer sides individually rather than profiling them. You could also make a fixture plate that precisely locates the flipped part by features and indicate the fixture.

Or just buy a longer endmill....

[zero_divide]

What we do is machine half of the part.
Then flip it over and indicate either outside walls or a hole.
When indicating this way you can get within a thou easy.

Flipping in vise never very accurate. Unless part is indicated after.

[cobrakai]

What I'm seeing is I should try to avoid flipping the part if possible, except for maybe a facing operation. If I want to do something more complex I need to fixture it.

I was thinking I was missing some kind of trick!

[Geof]

....I was thinking I was missing some kind of trick!

I am not sure if it is a trick but what I do is machine custom soft jaws in the vise to hold the exterior of the shape.

You have a contoured outer profile so the jaws need a matching inner profile. There is no need for indicating the part held in the custom jaws because the work zero for machining the jaws is the work zero that is used for machining the part held in the jaws.

[WOTDesigns]

It's not hard at all. Several good suggestions already, but the easy fast way I would do for one part is to square the block first and use a corner of the block as datum. Flip and then reference the same corner as the datum for the bottom. Its as accurate as the machine your making it on.

If I was doing 10 I would add $12 to the quote for the Aluminum soft jaws I would machine to match the top and flip th into that.

Brian
WOT Designs

[cobrakai]

I like the soft jaws idea, if you're making many copies. It makes it real easy to just throw in and press go.

The stock I am using is not square so I can't go indicating off the stock because it means nothing compared to the machined part.

My plan, as of now, is to indicate my vise, then use parallels to help align the part to the left. Since I didn't machine the stock, and the edgefinder can't physically reach the part yet, I can't think of a better way..

[WOTDesigns]

I use a 5 axis work stop for stuff like this too since you can set it, Place a squared block up against it with X amount of pressure. Lock the vise. Indicate the block. Now remove it and slide your part into it with X amount of pressure and you are within a thou (I have tested and use that frequently) very repeatable as long as you apply a reasonable amount of force.

You can do the same basic thing with a 123 block against the sides of the vise jaw. My production parts have 8 thin pieces vertically in the vise and I just indicate the edge of the vise, the slide the parts towards a 123 block pushed against the outside of the jaws and close the vise. Done. Easy. Close. Fast.

Brian
WOT Designs

[Moggot]

My plan, as of now, is to indicate my vise, then use parallels to help align the part to the left. Since I didn't machine the stock, and the edgefinder can't physically reach the part yet, I can't think of a better way..

What you're describing is a common way to do this sort of thing. It's good practice to square your stock first whether your aligning it against the vice or indicating off it. Just take your time when you flip it- are you sure you've got it in the right orientation? I've screwed that up more times than I'd like to admit.

In order to run both sides of a part in one program I set up two CS's; 55 and 56, each located at a corner of the stationary vise jaw. You can use the same corner or, like me, two separate corners. The only real difference is how you need to flip the part. In my work the first side is done under g55 by aligning a machined face with the left corner of the vise. I'll flip the part and align the same face against the right side of the vise where g56 is located for the remainder of the program. I reserve 54 for 'normal' programs, so I don't have to worry about finding 55 and 56 again unless I move the vise for some reason.

If you take care in setting things up you can get within a couple thou or so using nothing fancier than a edge finder and parallel. Indicating against stock itself is better but this has the advantage of being faster and quasi permanent. It's sort of the solution between fixture plates/soft jaws and indicating the part.