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Measuring Total Face Runout

krk2573

Plastic
Joined
Oct 31, 2017
I'm new to this and could use some help.
I need to measure the runout on the face of this item.
My understanding is that the part should rotate around Datum B axis, and the height gage/indicator measures the runout on the face perpendicular to B?



2020-05-22.jpg
 
I'm new to this and could use some help.
I need to measure the runout on the face of this item.
My understanding is that the part should rotate around Datum B axis, and the height gage/indicator measures the runout on the face perpendicular to B?



View attachment 289306

The callout refers to the pitch diameter of the thread, so if you can, mount the part on a thread gage on a bench center. If you cannot mount the thread gage then an expanding mandrel may do the trick. and yes, the indicator tip is in contact with the face.
 
It might depend on any notes on the drawing. Some will use the ID bore as the datum. I did not see the size of the thread. You could find the proper size of probe for the thread and measure it. It takes a lot of work to get the probe centered in the 'V' and the helix trace right.
I use thread position gages. TRUPOS is the company of the Thread Position Gages I use. Also, the call out is Axial Run Out and not total face run out. I'd probably take three circular traces on that surface. Filter to 3 sigma. Also note I'd be using a CMM.
 
John's post does have merit. There are thread pitch position gages that are basically an expanding collet. If you could mount that on something that rotates and keep it concentric with that rotation. That would then align on the pitch of the threads. I believe that is the true functionality of the thread. Then you could rotate it and get a run out from a dial indicator.
 
Looks to me B datum is the minor Ø not the pitch.

Could be. I know some places specify it that way. As it stated in my first post, it could be called out in a note. That would then make an expanding arbor a possibility.
 
When in question as yourself why there is a spec.
Is the functional surface the thread or the minor ID?
How does the part work when assembled and what makes a difference? This one simple.
Wondering if this print inch or metric.
Bob
 
The call out of Datum B is ambiguous. It is to one side. On a casting datum it would be to that side. So, I could make the case that a trace to one side of the minor diameter is the design intent. I did measure some parts a few days ago. It was true position of a M8 thread. It id measure it ID(minor diameter) as a cylinder and inscribed filter, minor diameter with a gage pin (simulated datum), two types of thread pitch gages, fixed and expanding. I noted a large difference in position between the gage pin and cylinder trace, about .150 um. The thread pitch gages matched. I didn't go over the results though.
 








 
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