Hello I am designing a Go/No Go fixture and the intentions of this fixture is to check the hole spacing between holes because the customer requires a specific hole pattern. The hole pattern is a simple rectangular pattern, with this in mind would a fixture using locator pins placed in the hole pattern specified by the customer be sufficient enough to use to check the required mounting pattern?
would a fixture using locator pins placed in the hole pattern specified by the customer be sufficient enough to use to check the required mounting pattern?
Maybe. Are there datums, feature modifiers like MMC, LMC, are the datums specified at MMC, LMC?
Bunch of if, and and buts here...
I apologize for the vague description. There is a Datum "A" surface that the customer shows upon which a mounting height dim of 746.3mm for one unit and 795.3mm for the other. Also a dim. of 152mm as width is given these dimensions show how two mounting plates with M10x1.5, Pem Nuts will be located. For the lower Pem Nuts a Feature Control Frame shows a position tolerance of 1mm dia. and a symbol a "S" inside a circle referencing datum "A" attached below this box a dim of 0.5mm with the same symbol of "S". I am not familiar with the "S" designation. The upper Pem Nuts a Feature Control Frame shows a position tolerance of 2mm dia. and a symbol a "S" inside a circle referencing datum "A" attached below this box a dim of 0.5mm with the same symbol of "S". I am not familiar with the "S" designation. This layout is shown as rectangular bolt pattern.
"S" probably indicates "Regardless of Feature Size", this would suggest to me that an older dimensioning and tolerancing standard is being used on the engineering drawing.
Yes, I think ~ (I have not seen the drawing) a fixture can be designed to verify relative to the minor diameters of the PEM nuts relative to the specified datum(s) feature(s).
Again, I have not seen the engineering drawing and additional dimensional and tolerance checks may be required.
Last edited by Kelly_Bramble; 01-26-2015 at 04:13 PM.
I attached a partial drawing illustrating the datum and feature control frame specified by this particular customer. My goal is to design a check fixture for establishing the mounting hole locations.2477_001.pdf
Ok, I'm of the opinion that there are insufficient datums defined, never the less...
You will need two separate go fixtures as follows:
For the two PEM nuts upper middle of the drawing Zone C-?.
Fixture 1 will simulate Datum "A" and include 2X gauge pins located and oriented to Datum A and the Basic dimensions (not shown). These pins should be sized at the minor diameter MMC size of the PEM nuts minus the location/orientation tolerance given within the upper frame of the composite feature control frame (dia. 2 at RFS). The fixture should be designed such that the pins are initially retracted (spring loaded) out of the way so that a firm and proper datum A contact can be established.
Fixture 2 would be a plate with two pins located at the basic dimensions distances from each other and sized at the Minor diameter MMC of the PEM nuts minus the tolerance given within the lower frame of the composite feature control frame.
Both check fixtures should be built at the appropriate gauging tolerances.
Additionally, a thread go, no-go gauge should be employed to verify the M10 pem nuts.
These fixtures I'm suggesting are academically not correct in that you should most correctly design the fixtures to verify locations at the pitch diameter axis of the PEM nuts. However, it is in my experience that verifying the minor diameter of the threaded features is usually adequate and much more practical.
Last edited by Kelly_Bramble; 01-29-2015 at 09:01 PM.
Thank you very much with your input.
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