Subtract Command?

[Big Red]

MyPart.PDF

Two questions...

1) Please tell me how to inspect the 2.809 diameter on the CMM. This diameter is from the center of the .168 Radius on both sides of the relief.

Should I measure .168 radius on one side, then .168 radius 180 degrees from that, then report the distance between the two radii? Is it that simple?

2) How should I go about checking the 3.020 diameter on the CMM? It looks like this diameter is at the intersection of the .168 rad and the .153 rad. I've never programmed a feature where two radii intersect. Do I have to measure twice (at 180 degrees apart) then report the distance between two intersect points?

I will recieve the parts next week and I'm trying to prepare as they will be very anxious to get this checked quickly.

Thank you in advance.
3.7 MR3

[John Riggins]

I don't envy you.
The 3.020 dim looks like comparator or video inspection to me.
About the 2.809:
Yes, you could do it the way you describe. Probably measure the .168 4x at least to get a reading on roundness.

[cmmguy]

[ATTACH]1729[/ATTACH]

Two questions...

1) Please tell me how to inspect the 2.809 diameter on the CMM. This diameter is from the center of the .168 Radius on both sides of the relief.

Should I measure .168 radius on one side, then .168 radius 180 degrees from that, then report the distance between the two radii? Is it that simple?

Measure the .168 radius is four sections and construct the diameter from their centers.

2) How should I go about checking the 3.020 diameter on the CMM? It looks like this diameter is at the intersection of the .168 rad and the .153 rad. I've never programmed a feature where two radii intersect. Do I have to measure twice (at 180 degrees apart) then report the distance between two intersect points?

I will recieve the parts next week and I'm trying to prepare as they will be very anxious to get this checked quickly.

Thank you in advance.
3.7 MR3

Looks like this diameter actually has a small part of it to hit. It would take a small diameter styli

[#2#]

[ATTACH]1729[/ATTACH]

Two questions...

1) Please tell me how to inspect the 2.809 diameter on the CMM. This diameter is from the center of the .168 Radius on both sides of the relief.

Should I measure .168 radius on one side, then .168 radius 180 degrees from that, then report the distance between the two radii? Is it that simple?

I agree with the others.

2) How should I go about checking the 3.020 diameter on the CMM? It looks like this diameter is at the intersection of the .168 rad and the .153 rad. I've never programmed a feature where two radii intersect. Do I have to measure twice (at 180 degrees apart) then report the distance between two intersect points?

I think comparitor on this as well. I think I tried intersecting circles on the cmm once and it wasn't as easy as it should be.

[inspector212]

What they said.

[Wingman]

In addition to all the above, tell the Engineer to get his head out of his **** and dimension the thing on real surfaces whenever possible.
To be honest, I would probably report the 2.089 as SET and take radial points for the 0.168 form SET Gage Locations (4 or 6 points diametrally opposed about on the C/L of the Actual surface). Report the 0.168 as MIN and MAX along with the 2.089 as SET (perfect) and Hand that to the Engineer and say there you go.
But, what the others say is the way to go. Less confrontational to be sure. I just like handing silly stuff back to Engineers!

[Paul F. Jackson]

I wouldn't measure the undercut at all given the information shown. Are the parameters (dia 2.809, R .168, and .826) basic dimensions? Is there a general profile tolerance or is there a title block tolerance? If you did attempt to measure it could you determine whether it was good or bad?

[Addison Wood]

I would not attempt to do this on a CMM given the tolerances and geometry. I would either section a part or take an impression ( we use Densply Caulk Reprosil Regular Body) and section that then use an optical comparitor.

[Underspec]

You got the radii locations already given to you. From centerline take 1/2 of 2.809 and go down .826 for your radii location. From there qualify the radii with polar radii locations of points. Take those qualified radii center points and dimension distance, or do it 4x and contruct a circle in the (z) workplane.

[Wingman]

Definitely a hard gage is your best bet as shown. First thing - Datum A is the Threads, right? How are you going to set Datum A?
Also, sectioned part with Comparator will not give you runout. I would seriously talk to the powers first about a hard gage (functional gage) quote.

All the advice you have to this point though is good stuff showing several ways to tackle issues like this.
My 2 cents.

[Tested]

"2) How should I go about checking the 3.020 diameter on the CMM? It looks like this diameter is at the intersection of the .168 rad and the .153 rad. I've never programmed a feature where two radii intersect. Do I have to measure twice (at 180 degrees apart) then report the distance between two intersect points?"

This does not appear to me to be a intersection. i see it as a small straight wall coming up off that radii. I say that because of the cross hairs at 1.002 ±.005. You should be able to just check it as a auto circle at a given heigth up from the 1.002.