MIL-DTL-83513 Connector Dimensioning Inconsistency

[Transient1]

Has anyone noticed that for D-sub miniature connectors (in my case a 9-pin connector) if the connectors are each hard mounted that according to the dimensioning of the connectors it is impossible to gaurantee 100% fit. I am dealing with the case of one box plugging into another box.

According to 83513, the maximum flange to flange distance for a mated connector is 0.216''. The largest flange to connector face distance is .198'' (0.195+/-.003''). These are the bounds then for mating connectors. If the connectors are greater than 0.216'' then you cannot consider the connectors fully mated. If the connectors flange to flange distance is less than 0.198 then there is a potential that the two boxes cannot fit together.

This leads to a nominal connector spacing of 0.207''+/-.009 in flange to flange. However, each flange is 0.093+/-.005''. Therefore, if you assumed that you have perfectly machined mounting surfaces with zero tolerances the connectors spacing between flange faces can still vary 0.010''. I find it hard to believe that this was never addressed. So that leads me to two conclusions:

(1) I'm thinking about something wrong.
or
(2) D-sub connectors are never meant to be hard mounted on both sides. If so can someone point out where in the mil standards that is stated.

If there is a better forum for this question please point that out to me as well. Thanks for your assistance.

These mil standards are readily available on the internet at:

http://www.dscc.dla.mil/Programs/MilSpec/listdocs.asp?BasicDoc=MIL-DTL-83513

 

[itsmoked]

I am not following your description very well as I am much more visual oriented then most.(even after sketching your description)

Do you realize that the connectors don't care about the 0.010" of pin insertion difference since they engage, generally, a lot more than that? Often the pins or the sockets actually float.

I have designed in about 150 D-subs and have never had any problems with mating with the exception of mixing brands and styles like plastic into metal. Sometimes that leaves you with slightly odd looking mate-ups that perhaps don't look fully seated but electrically are.

I have on occasion had to get the connectors in question and actually mess with them and mate them to see what's happening. At this point I'd be doing that.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Transient1]

I can't upload pictures at work or else I'd send a sketch. I talked with DSCC and it seems for my application the mil standard as it is just isn't good enough, and so we'll specify a new source control document.

My basic point is that according to mil 83513 documents two connectors which are mounted to independent surfaces (not fastened to each other) cannot be shown to always meet the mil requirements for flange to flange spacing based on the tolerances inherent in the part. It requires two connectors that are at there maximum dimensions for two dimensions. I would imagine that is a pretty rare occurence. On top of that it would only be noticed during assembly when the space between connectors is larger than the specified 0.216'' and I imagine that you still have a pretty decent connection at 0.217'' so it would hardly be noticeable.