huangyhg

gd&t for radius (fillet)
hi,
please guide me in giving gd&t to a radius (fillet). i have attached a ppt which explains my problem.
we have the interference problem when the male and female flanges are manufactured to the worst case.
thanks

i have once again attached the file in pdf format.
thanks,
i have once again attached the file in pdf format.

you don't tell us if the r0.1 on the female part is worst case, but assuming it is, normal design practice would be not to have an inside radius exceed the size of a mating outside radius.
you have already determined that your inside radius should be r 0.13-0.17 to work.
you can apply position tolerance and mmc (bonus tolerance) to the mating diameter (dia 21.32-21.45)that radially locates the male radius, but not to the radius itself. that requires that you relate this diametral feature to a diametral datum (od or bore) and that the diametral size and position tolerance is sized to not exceed the limits of the mating part, whose dimensions are not specified on your sketch.
bottom line, your radius is too big.
if this were my design, i would change the male side to a straight line instead of the 12.5° angle and use a lead-in chamfer. size it to the desired fit and use your mating faces to hold contact. if you rely on the taper, then chances are you will bottom out on the taper before your mating flat faces meet.
they i would use an undercut on the male side, where the radius is at, to allow any build up of dirt or shavings to accumulate when the two parts are mated together.
assuming that you can't do the above, then i would undersize your radius on the male part and use a max callout on the radius a few thousandths under what is the actual max before they bottom out.
so your radius callout would be something like r0.15 max should suffice.
1. actually, your female flange should be male and the male flange should be female, in order to prevent any confusion i will use your terms.
2. since your female part won't be changed, so you may use your cad software to define a new radius outline with basic dimension based on female flange, this new outline feature is a profile.
then, you may use profile tolerance to control the interference between them by :
*to choose unilateral inside tolerance for female part.
*to choose unilateral outside tolerance for male part.
seasonlee

thanks for the reply. please see the attached file for my reply.
thank you

i have once again uploaded the pdf.
the reason for again uploading the file is last time the uploaded file name had specials character so it will not open.
thanks,
why not just continue the angled edge of the male side past the mating face and create an undercut then come back out with enough material for a mating face? this way you eliminate the possible interference in the corner and you have a place for debris to gather when the two parts are mated.
you state that the flange is an industry standard. i presume the female flange is to that standard. if the standard give the same dimensions that you have, then possibly the design intent is to have the interference to create a seal. check the standard to see if there is any surface finish requirements to make the radii good sealing surfaces. also check on if in the "best" case there is or is not an interference.
peter stockhausen
senior design analyst (checker)
infotech aerospace services
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