Perpendicularity Punched Hole

[Bob Pierce]

I am working with square tubing having a wall thickness of .065". The designer has place a profile call out on a square shaped punched hole to datum A. After discussion, he is wanting perpendicularity to the surface in an attemp to monitor tool wear. I am not sure if this is possible on such a small surface. I am going to get started using sample surface hits and predetermined depths. Create a feature set of the points and dimension profile. Does anyone have comments as to this idea?

[Matthew D. Hoedeman]

You will not be able to use surface sample hits & different depths of touch, when ever you use a surface sample hit for a feature, it WILL project the measured data into the surface it sampled, so you will not get any different 'depth' between the features. You will probably have to use RELATIVE MEASURE to get what you are looking for. You define additional touches at NEW nominals (ie deeper into the hole) and it will measure them IN RELATIONSHIP to the one that takes the surface sample.

[Bob Pierce]

Thanks for relative measure tip.
If perpendicularity is our concern, couldnt the datum be dropped and dimension form only?

[Matthew D. Hoedeman]

Well, what I would do, in this case, is program the square slot (assuming you have that ability, I think CAD++ is required) with 3 surface sample hits, then set the depth as shallow as possible to stay on the edge of the shear. Then, program a few more of those square slots, with NO surface sample hits and with a NEGATIVE stock thickness equal the the extra depth you want each one to be from the first, but NOT beyond the shear of the pierce hole. Each of the extra slots will be measured relative to the original slot. IN ADDITION to that, you will have to do some HAND editing of the extra slot features, basically, the SURFACE vectors of them (to get the results of the surfrace sample hits). However, you must stay out of the breag of the pierce since that will not give you any good data.

At this point, you should probably bring this info up with the guy who told you to do this. The shear is the ONLY viable measurement area you can use in the hole. If you are only getting 0.020" of shear and the rest is break, then you are pretty much screwed for getting good perp numbers from this hole. As for a perp value telling him tool wear, I think he is barking up the wrong tree. The size of the hole should give him tool wear on the pierce punch, not the perp to surface.

[Wingman]

With PERP you must use a Datum Feature. The face will be your datuim feature.

First, I think the measurement is problematic for at least two reasons. The .065" wall is not much surface area for one. But it also means the surface is not real solid and reporting perpendicularity to it could be an issue. For example, try capturing 3 or 4 different surfaces / features on the face around the hole. Measure one about 1mm or so from the corners (4 hit plane) measure another about 10 mm out from corners. Measure a third about 20mm out form corners. Then see how parallel they are to each other. This will give you an indication of how true your Datum Surface is.
Treat the 4 sides individually. Define them as planes and sample them (I would use Auto Feature to make the nominals of each point exact. You could use Auto Points and construct a plane). Report them Perp to Face individually. If you need individual point data you can turn text on.

However, I agree with Matt. Perp isn't going to tell you much about tool wear.

HTH,
Bill

[inspector212]

I think the engineer was thinking form and not orientation. Checking orientation of a feature in a sheet metal part to the surface the feature is on is useless. Give the engineer form of the feature to the surface. This will tell you tool ware. Take a number of vector points and construct a set out of them(or scan it) and report the profile of the set. Include the analysis in a screen capture.

[Bob Pierce]

I will be reporting as inspector 212 has suggested. I convinced the Eng perp to surface is not good. And will not say alot concerning tool wear. I will be taking some additional square slot measurements at various depths to study for tool wear.
thanks everyone.