Countersink Dia. Size

[[Mi...]]

Hi All,

What is the best was to capture the counter sink dia. size on a radial part?

The call out is .501Ø X 100°

I am currently capturing the cone and a space point and doing a cone addition to get the dia. Is this the best way/ accurate way to capture this callout?

Regards,

Screenshot 2021-09-21 101029.png

[[Cl...]]

This should help.

viewtopic.php?f=13&t=3136

[[Mi...]]

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Thanks Clarke,

I did this method and it worked great. Unfortunately for them the part is still kicking out.

Regards,

[[Cl...]]

I have recieved a lot of help from some very smart people in this
forum. If I can return that help to someone else I'm happy to do so.

[[Ma...]]

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You are lucky to have CAD model, so you know exactly what designer want.
So part is still bad? What is wrong and do you know how it is machined?

[[Mi...]]

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Yeah the customer supplied a CAD model but made some changes to the print and didn't change the model.

The part is being machined on a 5 axis. There are 8 radial hole with .501 X 100° c'sinks equally spaced. It started off with 6 of the 8 c'sink diameters being undersized. They made some comp adjustments but they were still kicking out. Now they are holding onto the part differently in the machine and only 2 of 8 are kicking out. I believe this is due to the jaws holding the part and throwing it out of round when machining. But what do I know I'm just a CMM guy.

[[Ma...]]

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Well i am just machinist with 13y of exp. but now i am sitting and programming cmm for 2y exp. until today.

Can i know tolerance for diameter? If part is thin, then claws can do some problems. What about main outer diameter of part?
Diameter of c'sink will change with it.

[[Mi...]]

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[[Ma...]]

Well that's awfull tolerance. With that angle every .001 on main outer radius will be .00238 for c'sink diameter.
What tolerance is for outer diameter of part?
I don't know why you are using 100° c'sink - in EU we are using 90° ( same as screws ) - but that's just another standards used.

At machining they should implement variable to program to consider thickness of wall ( manually measure with caliper ).

[[Mi...]]

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± .005 on the outer main

[[Ja...]]

Just got a call back from our customer on this part. Apparently, per ASME Y14.5-2018, 4.5.13, we are supposed to measure at the minor diameter of the countersink (see pics below).

My question is, how do we achieve this?

We need to measure in the direction of the blue arrow, not the red.
Here is the section from ASME Y14.5-2018, 4.5.13, Figure 4-38

[[Ch...]]

I think there's a few ways.

I've seen this in Y14.5, I don't think I've ever had to measure it though.

You could:
1) Measure the cone/c'sink below the curved portion area for an X/Y center for an alignment (or use the thru hole but that assumes they are on co-incident).
2) Measure the "curved surface" and intersect.
3) Change alignment of this intersection to cone center, and also change it to a polar feature that has a R,A,H instead of X,Y,Z.
4) Construct/get minimum coordinate (radial point) of the intersection / polar feature.
5) Create a theoretical perfect circle at the nominal minor diameter intersection; inside this theoretical feature use a formula for the actual diameter that is 2x the min coordinate. Now you can report a "diameter" feature with the proper size.

Good luck, let us know how you make out. I will try to make a CAD of this and test this theory out as well.

Thanks, happy measuring !

[[Je...]]

1 - Measure the OD
2 - Measure the Cone
2a - Strategy - minimum 4 line scans. 2 of which must be at horizontal 90/-90 (perpendicular to outer cylinder axis) + any added scanning you wish.
2b - Constrain vector
3 - Create a 3d Line
3a - Recall from feature points
3b - Right click on Cone > Open
3c - Select ONE of the line scans
4 - Repeat step 3 for other line scan
5 - Intersect each 3d Line with outer cylinder as SHELL - 2x
6 - Report distance between points.

Chamfer diameter should always be reported at its smallest point. The rational way to view this is if you put a counter-sink screw of that size in the counter-sink, it should sit flush-to-below surface

[[Ch...]]

I would go with Jeff's recommendation - as he is a tremendous wealth of knowledge.

My only concern is what if they use a minimum 4 line scan vs. 2x 360°+ paths on the cone, what if those 4 places do not capture the minimal radial area ? With a Csink so small , its probably not really that critical..

Just thinking ...

[[Je...]]

Great point Chris,

The concern is I have seen cones not create an intersection using the shell method, I agree that this method would give a more robust result. The caveat is the intersection creation issue.

To do this would require using a theoretical plane to create 2 3d-Lines in the same manner. The planes Z origin (assuming cylinder is standing upright as in the picture) would be a getActual([coneName]).z

I tend to use helical scans in cones. 3 revs (~1100°) minimum. If it is a countersink or a chamfer and the feature angle (not cone angle) is not of critical importance, constrain the vector to improve calculation and evaluation. This becomes even more relevant as the evaluation length vs diameter ratio increases.

[[Ja...]]

Jeff,
I will give your method a try. Talking to my QE, Mike Kelly (OP), we are doing to 2D lines using the center of the thru hole for the Z value, and then doing an intersection (shell) to the cylinder of the OD. That looks to be reporting the correct size. We are still a few weeks away from getting the parts back from our customer to rework, but we have some leftovers in inventory we will be modifying shortly, and we will see how it works out.

[[Je...]]

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Great! One of the things to keep in mind is that on cylindrical parts with thin walls, sometimes an enlarged countersink will affect the location or length of the thru hole (as in wipe it out entirely). This is why I suggest using the getActual of the cone and applying a constraint to the vector.

Ive measured parts that utilized a stackup sufficient to wipe the thru bore right out of the part, leaving only a countersink and the part still be conforming.

[[Gr...]]

Hello The way I have been doing that part is to make a reference plane four points in a square around the counter sink. Then measure cone . Note cone angle . Create an ellipse by intersecting the cone with the reference plane. record the short axis to meet ASME definition . Lather rinse repeat .