Perpendicular Measurement?

[[Ia...]]

My thought for measureing P5 in the drawing was to do a Perpendicular between the Centre of the part and the Cut Out Plane. This however is saying that the plane is 0.050" closer to the centre than nominal.
Is there a better way to measure P5 in the drawing?

[[De...]]

First off, the biggest problem with small features like that and measuring to C/L is the inability to determine rotation. A small amount of rotational error in the face being measured causes a substantial amount of error in the measurement to C/L since the feature being used for C/L does not establish a rotational alignment on its own.

One method would be to create a symmetry construction using the two opposing planes of the cutout, then make a 3D Line from the C/L of the bore to the Symmetry Construction. Finally measure from the face to the Line.

That said, it depends on if the feature is related to the others or not, if so you should probably make a geometry best fit of all related features in order to establish a common point of rotation then measure in relation to that so you are measuring all the slots to one common rotational alignment - it really is dependent on how it is drawn on the print, however from a purely mechanical standpoint, I would expect the cutouts are likely related to one another rotationally.

[[Ia...]]

Thank you for the reply Derek.
I am using the hole in the part at the bottom of the drawing for my rotational index. All of the cut outs and tabs were cut from a WEDM, and that hole was burned out in the same set up so that it could be used to relocate if we ever need to set it up again. All of the cut outs are relative to one another, and the index hole.

[[Ia...]]

Here is another example.
When I ask for the X location relative to the centre bore I get 0.7429".
When I ask for depth perpendicular to the centre bore, I get 0.7432"
I know that both are out of spec, but which is the best measurement to go with?

[[De...]]

It's really hard to say without being able to evaluate the data / part and look at the program, you have two things that could be contributing to the error you are seeing. You could have a size issue or a location issue, or a combination of the two.

In this situation I would do a couple of things to see what was going on.

To start with I would check the width of the slot using gage blocks or at the very least calipers. This is an easy method that will let you verify the size the slot actually is. This is a good sanity check that lets you see if your numbers are at least close. Using gage blocks provides a physical check that is completely independent of location.

I think the next thing I would be looking at would be to check the position of the hole itself in relation to the slots. I would create a line to the center of the slot as I mentioned in my earlier post and check what the rotational error was between that and a a line between the bore and the hole you are using for a rotational alignment.

Between these two things you should be able to start seeing where the error is coming from. If the slots are all off rotation to the rotational clocking feature, then this will cause some variation in your size check because the sides of the slots will be slightly angled to the nominal centerline created from your clocking feature.

I often find in situations like this it is a good idea to make a centerline from the slot as I mentioned in my previous post, then use that to make a check of the width of the slot independent of rotation. If that is still yielding results that do not match size blocks you might look to see if the slot is out of square with the face of the part.