【转帖】questions on connector cut ou

yang686526

questions on connector cut out
i鈥檓 looking at a bracket that has a couple of mating pairs of d type connectors that mount to it.  the location of the cut outs in the bracket isn鈥檛 too important but the size/shape of the cut-outs, and the holes associated to the cut-outs are more critical.  see attached sketch.
i鈥檓 thinking this is an ideal case for composite profile like asme y14.5m-1994 fig 6-25 for the cut-out.  however, i鈥檓 not over confident on then relating my holes to follow the cut-out.  i found a similar example in some training material from gary whitmire but my cut out is a lot more complex and i don鈥檛 fully understand the datum structure regarding use of d-e rather than d|e.
q1: which of the hole feature control frames in my sketch makes more sense or is there another better way.
q2: where symmetrical i鈥檝e given overall dimensions for the cutout, like you would for a simple slot.  however some of the examples around here that my previous checker did have additional dimensions to relate the overalls to the 鈥榗enter鈥? e.g. a .656 dimension from the center to one of the holes and similar for the width and height of the slot.  are these extra dimensions really needed?
(please note i haven't properly calculated the values of the positional tolerances yet, i probably should have made them the same for the sketch.)
thanks.
kenat, probably the least qualified checker you'll ever meet...
kenat,
   your specification looks okay to me, although it is a little complicated.  i take it your datum_d is the outside quadrant of your radii.
   i think you can make the drawing views simpler.  apply positional tolerances to the jack screw holes with respect to the main drawing datums.  apply the profile tolerance all around the big hole, showing the boundary outside.  this makes your nominal dimensions the mmc.  all you need to do is make sure your d-sub poke out through the hole when it is located by the jack screws.
   on main drawing views, i tend to dimension to one of the jack screws.  on my detail view, i can use the jack screw as a datum.  unless your d-sub is fixed to a printed circult board, its location is not nearly as critical as the location of the pattern elements to each other.  you can buy d-sub hole punches, so there is a way a fabricator can take advantage of well prepared drawings.
   your form obviously is symmetric, and you cannot measure from a centreline, anyway.  i think you are right to leave of the centring dimensions of the jack screw holes.
                         jhg
thanks drawoh,.
i take it with your proposed scheme the profile fcf would also refer back to the main drawing datums.
in this case how do you propose to take advantage of the fact that the connector cutouts positions can vary a lot with respect to the main drawing datums but that that the shape/size of the cutouts and the position of the holes reletive to them must be more more closely controlled?
i've updated my sketch to show what i understand of your proposal.
kenat, probably the least qualified checker you'll ever meet...
if you can could you include the a|b|c datum features in your sketch so i can get clearer understanding.  off the cuff, i'm thinking fig. 6-19 in conjunction with fig 5-28, the kicker would be declaring the two hole pattern as a datum as well and position the cutout wrt it.  although that might be to much for what you need.  this is just a knee jerk until i see what else you've got going here.
i think your original print was good except that i would have repeated all the datums in frtz of the composite profile tolerance. also, don't forget to add the "all around" circle to the elbow of the leader line.
i don't understand the alternative method that you show on your drawing at all. i've always understood that type of callout to apply to axes or planar features but have never seen it used like this before. i'm curious to know how that method even works.
as for your second question; if you position the hole pattern relative to d and e and show no dimension from center of d to the center of the hole and from the center of e to the center of the hole then the dimension is an implied zero and thus "centered". you don't have to add dimensions to show it centered.
powerhound, gdtp t-0419
production supervisor
inventor 2008
mastercam x2
smartcam 11.1
ssg, u.s. army
taji, iraq oif ii
kenat,
check out the march tip on the tec-ease website that i frequently refer to. it directly addresses your second question.
powerhound, gdtp t-0419
production supervisor
inventor 2008
mastercam x2
smartcam 11.1
ssg, u.s. army
taji, iraq oif ii
xplicator, i looked at those figures.  i'm not sure 6-19 actually achieves what i want, in fact it's almost opposite.  if i understand correctly it has a relatively lose profile and then puts a tighter position.  i effectively want the opposite, relatively tight profile to control size & shape but looser position.  i don't see what you're referring to on 5-28.
powerhound, i looked more closely at 6.5.9 after what you put about the lower profile size/form/orientation refinement control and i'm tempted to think i don't necessarily need to add them as i'm not too concerned about orientation to a & b.  however, the fact i'd put this already was more by luck then understanding, having looked at it again i better understand it and will think some more about adding them.  given that d & e are derived from the cutout itself i don鈥檛 think having loose orientation of the cut-out will negatively effect the location of the holes relative to the cut out, but please correct me if i鈥檓 wrong.  thanks for prompting me to take another look.
i realized the all around symbol was missing after i posted the sketch, thanks for reminding me though.  
i was lost by the second option on the fcf for the holes too, it didn't make sense to me in this application but i thought maybe i was missing something.  i know there's a couple of errors in the material i was looking at, maybe that's one of them.
on my second question what you, drawoh and tec-ease say confirmed my understanding of things.  i was doubting myself because the other drawings were done by someone who really knows their stuff and if he'd put it i was thinking maybe i was missing something.
attached, is updated sketch again with the all around symbol & datums a & b shown.  c is the far side face of the tab that the cut outs are in, so is normal to them.  it鈥檚 slightly higher resolution so hopefully clearer where leaders/dim lines are going to (i鈥檝e cramped it up to keep the file size down, on the drawing it鈥檚 more spread out).
kenat, probably the least qualified checker you'll ever meet...
kenat,
  the reason i would have repeated the datums in the lower portion of the composite profile fcf is not as much for orientation as it was to maintain a smooth profile. as it is the profile would have to be perp to c within .010 but the profile itself can still wander within .050 of the true profile. for example the vertical line across the top of the cutout can still wander + and - .025 from the true profile, making for a potentially jagged line. if this is not a concern then never mind.
  something i just noticed about the print is the feature that makes up datum d. it is comprised of 2 tangent points on the arcs. it might be better to make datum d the .875 dimension instead...just an observation.
powerhound, gdtp t-0419
production supervisor
inventor 2008
mastercam x2
smartcam 11.1
ssg, u.s. army
taji, iraq oif ii
powerhound, are you sure about the profile still being able to wander the .05 rather than .01 effectively wrt istself (not quite the right terminology i suppose sorry)?  i'm looking at 6.5.9 and especially at figure 6-25 and that isn't my understanding of it.
you'd be more likely to know than i but i don't see it matching what the standard says or figures show.
kenat, probably the least qualified checker you'll ever meet...
regarding the implied symmetry tolerances that powerhound and kenat mention. the march tec-ease tip does clarify that a dimension off a centerline isn't needed but the tolerance definitely is.
i often get drawings where the designer assumes symmetry on a linear feature dimensioned with a 卤 tolerance and shown symmetrical to a feature centerline, but without giving  either a gd&t tolerance or a toleranced dimension to the centerline. as i understand the tec-ease tip, you need one or the other.  agree or disagree?
if you're not using appropriate gd & t to apply the tolerance then yeah, i'd say you need a dimension to center it.
the examples i was looking at (cca faceplates if that rings a bell ron) had both gd&t and centering (basic) dimensions.
however my main concern now is that i'm using the composite profile properly and that my holes are following it.
kenat, probably the least qualified checker you'll ever meet...