Thread concentricity verification
Thread concentricity verification
(OP)
We both manufacture and purchase hydraulic manifolds which consist of SAE ports and cartridge valve cavities machined in aluminum, steel, brass, or iron. All of the ports and cavities involve a drilled or machined cavity with threads ranging from SAE #2 to #24. We are experiencing valve shifting problems with a purchased part and suspect an out of tolerance condition with the threads. The threads must be concentric to the bore within .002 and perpendicular to the surface within .001. We are looking for a reliable way to verify these tolerances. Can anyone help us out?





RE: Thread concentricity verification
- Make up some functional gages to check the bore centering and spotface perpendicularity, and provide a set to the vendor.
- Review the tolerancing on your purchased part prints to make sure that your requirements are clear, and are specified in a way that is inspectable. This is probably an application where you absolutely should be using GD&T.
Mike Halloran
Pembroke Pines, FL, USA
RE: Thread concentricity verification
RE: Thread concentricity verification
For a cartridge to fuction - "All diameters concentric within .002" is all you need.
Control the perpendicularity of the cartridge cavity elsewhere, NOT by the thread.
Checking this is another issue. You could try testing the cartridge in a different cavity. Also after removing the cartridge from the suspect cavity, look for wear marks on the nose diameter (and others) for signs of rubbing. Creating an accurate gage for this is practically impossible due to the (I'm guessing here ......) 6H thread tolerances.
The SAE spec does use the thread as Datum -A-, but perpendicular to .008" at a predefined diameter on the spotface. (not .001")
Remember...
"If you don't use your head,
your going to have to use your feet."